ISSN 1453 – 7303 “HIDRAULICA” (No. 2/2014) Magazine... · 2019-09-11 · Dorel STOICA 48 - 52...

ISSN 1453 – 7303 “HIDRAULICA” (No. 2/2014) Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics

CONTENTS

• EDITORIAL Gabriela MATACHE

5 - 6

• THEORETICAL AND EXPERIMENTAL CHARACTERIZATION OF HANDLING OF LOADS AN AUTOMATED SYSTEM USING VACUUM TECHNOLOGY

Richard CASTRO, João NETO, Cleber IZIDORO, Anderson SPACEK, Osvaldo ANDO JUNIOR

7 - 16

• ABC ANALYSIS, MODEL FOR CLASSIFYING INVENTORY Marin RUSĂNESCU

17 - 20

• EXPERIMENTAL DETERMINATION OF THE ASPHALT ROAD PROFILE IRREGULARITIES

David Alexandru-Dorin, Voicu Gheorghe, Dutu Mihaela Florentina, Cujbescu Dan

21 - 24

• DETERMINING THE STEP RESPONSE FOR A PNEUMATIC CYLINDER POSITIONING SYSTEM

Radu RADOI, Marian BLEJAN, Iulian DUTU, Gheorghe SOVAIALA, Ioan PAVEL

25 - 31

• CONTRIBUTION TO HYDRAULIC TURBINES DRAFT TUBE DESIGN Mircea BARGLAZAN, Ilare BORDEASU

32 - 38

• FORMING ECO-RESPONSIBLE BEHAVIOR OF FUTURE ENGINEERS BASED ON THE STUDY OF CARBON FOOTPRINT

Olimpia GHERMEC, Cristian GHERMEC

39 - 43

• THE IMPACT OF THE MINING ACTIVITY ON THE ECONOMIC SECTOR, HUMAN HEALTH AND ENVIRONMENT

Oana DAVID, Maria Valia MIHAI, Sanda MAIDUC (OSICEANU)

44 - 47

• SOME CONSIDERATIONS ABOUT THE STUDY OF PARTICLES MOTION ON THE CONICAL SIEVES

Dorel STOICA

48 - 52

• CAVITATION EROSION RESISTANCE OF AMPCO 45 BRONZE WITH HEAT TREATMENTS

Ilare BORDEASU, Mircea Octavian POPOVICIU, Ion MITELEA, Lavinia Madalina MICU, Octavian Victor OANCA, C-tin BORDEASU, Laura Cornelia SALCIANU, Cristian GHERA

53 - 61

• EXPERIMENTAL TESTING IN DYNAMIC REGIME OF HIGH PRESSURE PNEUMATIC ACTUATORS

Ionel NITA, Iulian–Cezar GIRLEANU,Sava ANGHEL, Alexandru MARINESCU

62 - 72

3


MANAGER OF PUBLICATION

- PhD. Eng.Petrin DRUMEA - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

CHIEF EDITOR - PhD.Eng. Gabriela MATACHE - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

EXECUTIVE EDITORS

- Valentin MIROIU - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

- Ana-Maria POPESCU - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

SPECIALIZED REVIEWERS - PhD. Eng. Heinrich THEISSEN – Scientific Director of Institute for Fluid Power Drives and Controls IFAS,

Aachen - Germany

- Prof. PhD. Eng. Henryk CHROSTOWSKI – Wroclaw University of Technology, Poland

- Prof. PhD. Eng. Pavel MACH – Czech Technical University in Prague, Czech Republic

- Prof. PhD. Eng.Alexandru MARIN – POLITEHNICA University of Bucharest, Romania

- Assoc.Prof. PhD. Eng. Constantin RANEA – POLITEHNICA University of Bucharest, Romania

- Lecturer PhD.Eng. Andrei DRUMEA – POLITEHNICA University of Bucharest, Romania

- PhD.Eng. Ion PIRNA - General Manager - National Institute Of Research - Development for Machines and

Installations Designed to Agriculture and Food Industry – INMA, Bucharest- Romania

- PhD.Eng. Gabriela MATACHE - Hydraulics & Pneumatics Research Institute in Bucharest, Romania

- Lecturer PhD.Eng. Lucian MARCU - Technical University of Cluj Napoca, ROMANIA

- PhD.Eng.Corneliu CRISTESCU - Hydraulics & Pneumatics Research Institute in Bucharest, Romania

- Prof.PhD.Eng. Dan OPRUTA - Technical University of Cluj Napoca, ROMANIA

Published by: Hydraulics & Pneumatics Research Institute, Bucharest-Romania Address: 14 Cuţitul de Argint, district 4, Bucharest, cod 040557, ROMANIA Phone: +40 21 336 39 90; +40 21 336 39 91 ; Fax:+40 21 337 30 40 ; E-mail: [email protected] Web: www.ihp.ro with support of: National Professional Association of Hydraulics and Pneumatics in Romania - FLUIDAS E-mail: [email protected] Web: www.fluidas.ro HIDRAULICA Magazine is indexed in the international databases:

HIDRAULICA Magazine is indexed in the Romanian Editorial Platform:

ISSN 1453 – 7303; ISSN – L 1453 – 7303

4


EDITORIAL RECUNOASTEREA NEPUTINTEI DE A SCHIMBA Rezultate asteptate...sau nu. Traim de mai bine de 1 an intr-o asteptare continua a unor rezultate la competitia proiectelor de cercetare. Iata a venit si clipa mult asteptata. Jocurile de culise au fost in cele din urma finalizate. Proiecte ce „trebuiau” sa se califice s-au calificat. Punctele lipsa au fost acordate in evaluarea in panel. Proiecte ce au fost punctate prea mult in prima faza au fost depunctate pentru a face loc proiectelor „favorite”. Ajung sa ma intreb incotro se indreapta cercetarea romaneasca, ajung sa-mi para rau ca am ales aceasta cale foarte anevoioasa, urmata doar de persoane ce cred cu adevarat in idealurile lor. Am crezut intotdeauna in faptul ca avand coerenta si respect fata de aceste idealuri voi obtine si succes. Cred ca succesul construieste succes iar calitate aduce calitate. Insa ceea ce se intampla astazi cu

Dr.ing. Gabriela MATACHE REDACTOR SEF

cercetarea romaneasca, punctul in care a ajuns recunoasterea cercetatorului roman, ma face sa nu-mi mai doresc sa fac parte din aceasta categorie ajunsa la pragul subzistentei, alaturi ce-i drept de alte categorii precum profesori si medici. Dictionarele nu ne ajuta foarte mult cand vine vorba despre definirea conceptului de cercetare, limitandu-se, normal, la definirea lingvistica a termenului si folosirea sa. Astfel, (DEX) activitatea de cercetare ar fi "producerea de noi cunostinte, care pot fi noi numai daca sunt recunoscute ca atare pe plan international. In caz contrar, nu poate fi vorba de o activitate de cercetare, ci de documentare" Sunt insa definitii empirice, perfect adevarate, dar, din pacate, reprezinta doar descrieri ale fenomentului, nu si explicatiile ale sale. Imi doresc sa ajung in acele timpuri in care oamenii de valoare sa fie apreciati si lasati sa-si duca la bun sfarsit munca, in conditii decente si fara grija zilei de maine. Sa iasa din cercetarea romaneasca produse ce vor putea fi apreciate si introduse in fabricatie in industria autohtona. Dar de unde fabricatie, de unde industrie? Am vazut cum pe parcursul celor 20 de ani petrecuti in cercetarea au disparut rand pe rand toate fabricile, am vazut cum rand pe rand cercetatorii devin..vanzatorii „cercetarilor” aduse din afara, am vazut cum tinerii care promiteau o cariera stralucitoare sunt „indrumati„ cu succes catre centrele de cercetare din afara tarii sa creeze astfel produsele ce se intorc in tara sub forma produselor cu eticheta UE si nu in ultimul rand am vazut cum am devenit doar o piata de desfacere pentru tot ce produc marile puteri ale lumii cu „creiere romanesti”. Toate acestea ma duc cu gandul la o intamplare ce am citit-o nu demult intr-o revista, neintelegand atunci jocul de cuvinte dar acum acestea sunt foarte reale. In timpul concursului pentru titlul de Miss America, din 1994, reprezentanta statului Alabama a primit o tema grea, fiind Intrebata daca ar vrea sa traiasca vesnic. Raspunsul pe care l-a dat este delicios: “Nu as trai vesnic pentru ca nu ar trebui sa traim vesnic, pentru ca daca am fi facuti sa traim vesnic, atunci am trai vesnic, dar nu putem trai vesnic si de aceea nu as trai vesnic”. Nu stiu ce credeti voi, insa eu una m-am bucurat atunci cand am citit, sa fie in urma cu 10 ani ca ca frumoasa sudista nu raspundea de finantarea programelor de cercetare! Dar iata cum dupa 10 ani avem la conducerea Cercetarii Romanesti...”frumoasele noastre sudiste” care nu doresc promovarea adevaratei cercetari ci doar a intereselor pe care eu nu le pot intelege.

5


EDITORIAL ADMITTING NOT BEING ABLE TO MAKE A CHANGE

The results we have been waiting for... or not. We are living for more than one year in a continuous waiting for the results in the competition of research projects. Here is the long awaited moment. Backstage games were finally completed. Projects which "had to" qualify were qualified. The missing points were awarded during assessment in panel. Projects which were scored too high in the first phase were downgraded to make room for the "favorite" projects. It makes me wonder where to the Romanian research is going; it makes me feel sorry I chose this very laborious path, followed only by people who truly believe in their ideals. I always thought that with consistency and respect for these ideals I will also obtain success. I believe that success builds success and quality brings quality.

Ph.D.Eng. Gabriela MATACHE

EDITOR IN CHIEF

But what is happening today with the Romanian research, the point reached in recognition of the Romanian researcher, it makes me no longer want to be part of this group arrived at the threshold of subsistence, alongside, that's right, with other categories such as teachers and doctors. Dictionaries do not help very much when it comes to the definition of the concept of research, being limited, normally, to the linguistic definition of the term and its usage. Thus, (acc. to DEX) the research activity would be "generating new knowledge, which can be new only if it is recognized as such at international level. Otherwise, one cannot talk about a research activity, but documentation". However, these are empirical definitions, perfectly true, still unfortunately they are only descriptions of the phenomenon, not its explanation. I want to live in those times when valuable people would be appreciated and allowed to carry out their work, in decent conditions and carefree about tomorrow; those times when from Romanian research would emerge products that would be appreciated and put into production in the domestic industry. But where is the production, where is the industry? I've witnessed during my 20 years in research all the factories disappearing one by one, I've witnessed one by one the researchers becoming... dealers of "research" brought from outside, I've witnessed young people promising a bright career being successfully "guided" towards research centers outside Romania thus to create products which return home as EU labeled products, and last but not least I've witnessed us becoming only an outlet for everything that the major world powers produce by means of "Romanian brains". All this makes me think of a story I read not so long ago in a magazine, then not understanding the play on words but now they are very real. In the contest for the title of Miss America 1994, Alabama state representative received a heavy duty when asked if she wants to live forever. The answer that she gave is delicious: “I would not live forever because we should not live forever, because if we were made to live forever, then we would live forever, but we cannot live forever and therefore I would not live forever”. I do not know what you think about it, but I was glad when I read it, could it be 10 years ago, that the beautiful Southern girl was not in charge with funding research programmes! But here is how after 10 years at the helm of Romanian Research we have...”our beautiful Southern girls” who do not want to promote real research but only interests that I cannot understand.

6


THEORETICAL AND EXPERIMENTAL CHARACTERIZATION OF HANDLING OF LOADS AN AUTOMATED SYSTEM USING

VACUUM TECHNOLOGY

Prof. MSc. Richard CASTRO1, Prof. MSc. João NETO2, Prof. Cleber IZIDORO3, Prof. MSc. Anderson SPACEK4, Prof. MSc. Osvaldo ANDO JUNIOR5

1,2,3,4,5 School of Engineering, Department of Mechanical Engineering and Automation, Faculty SATC, Criciúma, SC (Brazil), Laboratory Automation and Simulation of Hydraulic and Pneumatic Systems – LASPHI

Abstract: The two most common techniques used for fixation and of parts and materials in the industry are mechanical clutches and pneumatic suction cups. These have different characteristics, but generally perform the same function with respect to the displacement of material. The suction cups are noted for being great elasticity, being the best choice when the goal is to arrest or transport brittle materials, for example glass. The purpose of this work is to carry out some tests for lifting ideal parameters for the selection of the handling system loads by using a vacuum suction technology, automotive intended for industrial processes. In these assays will be evaluated first five physical aspects: the optional suction cup material, the air pressure system, roughness and weight of the materials to be handled and the level of vacuum generated by the system. In this work a data acquisition board will be implemented with the integration of the PIC microcontroller family, which will receive information via an analog signal from the pressure transducer, and make it available in an LCD display in order to pressure the system monitor. Keywords: Handling System Loads, Suction Cups, Vacuum and Roughness.

1. Introduction

Currently the handling loads systems are indispensable in automated processes, because they provide the more flexibility and greater productivity. One of the techniques used in the industry is the materials handling by suction cups, which have the characteristic of not damaging the parts to be handled. This important characteristic for materials fragile, such as glass, by requires specific care and handling of them. Although tough and rugged, the glass is also a brittle material and may break altogether from a simple crack in one of its surfaces. For this reason, advanced technologies of control and manipulation are essential to prevent falls and impacts during transport. In any industrial process, operating conditions are subject to variation over time, the level of liquid in a tank, the pressure in a vessel, the flow of a fluid, all of these conditions can vary. Currently there is a wide variety of equipment to help in the control and monitoring of processes, which together may constitute chains control single or multiple, adapted to numerous control problems and a large number of types of processes [1]. One of the parameters that directly contribute the behavior of handlers for suckers is the roughness of the parts. It plays an important role in mechanical components behavior and consisting of the set of irregularities, that is, small protrusions and recesses which characterize the surface, influencing the quality of slippage, wear resistance, surface resistance offered by the flow of fluids and lubricants, quality of grip that the structure offers the protective layers, corrosion resistance and also on the seal [2]. In this work we will use two parameters for measuring roughness, Ra and Rz, as they are the most widespread due to its simplicity in processing surface roughness tester and also by the type of process requirement, as in the case of the suction cups. The parameter Ra is the most well-known, accepted and used worldwide, is used in virtually all manufacturing processes and all conventional measuring equipment texture (surface roughness tester) has it as an option [3].

7


The suction cups, in turn, and to resist large deformations during handling or handling, have several advantages compared to the fastening systems by claws. Among them is the highest speed of operation which increases productivity, ease and quickness in repairs, aspect that reduces downtime for maintenance and low cost of acquisition and installation of components [4]. Select the type of material and size of the cups for an application is essential in any vacuum system. Through calculations of forces involved in the application can determine the optimal size of the suction cup, but the data obtained from these calculations are theoretical and specifications for each application needs results through practical tests [5]. Some parameters should be evaluated for the correct sizing of a sucker as mass, force, acceleration and friction coefficient. For applications in irregular sheets, defective surface or sudden movements, it is interesting to use an additional safety coeficient. In this context, the article presents some representative for pre-selection of pneumatic components for vacuum technology based on Venturi technique, through the generation of vacuum valves results. This technique consists of passing compressed air through a tube mounted in a bore within which causes a constriction to the flow of air. The air flowing through the tubes increases as a function of the flow generated by the restriction orifice. The increase in acceleration of the air flow causes a considerable pressure drop in the throttling region by causing the action occurs on the suction cups. 2. ExperimentaI Development

For the tests, two bodies of evidence were selected as shown in Fig.1. The glass like material was chosen because of relying on specific precautions for handling and transport, creating the need to make the system as reliable as possible manipulation. Both specimens have the same dimensions, these being 95 x 95 mm by 3 mm thick and weigh 0.120 kg respectively. Due to the low weight provided by the specimens for the tests, were added the same steel splints to meet the load requirement. After the selection of specimens, roughness measurements were performed through a surface roughness tester, selecting parameters and filter suited for the surfaces. In order to avoid measurement errors caused by the influence of external events such as dirt or imperfections of the material itself, the specimen was previously washed with chain water and subsequently cleaned with ethanol before each measurement. To provide greater security to the study, three tests each parameter of roughness (Ra and Rz) were performed at three different locations each specimen twelve tests were performed.

Fig.1. Specimens: (a) plain glass (b) roughened glass and measurement of surface roughness

Specimen (a) Ra (µm) Rz (µm) Measure 1 0,01 0,20 Measure 2 0,01 0,20 Measure 3 0,01 0,10 Average 0,01 0,17

Standard deviation 0,00 0,06

Specimen (b) Ra (µm) Rz (µm) Measure 1 11,57 49,81 Measure 2 13,51 51,92 Measure 3 13,41 51,97 Average 12,83 51,23

Standard deviation 1,09 1,23

a

b

Plain

Roughened

8


To study the characterization of surfaces that influence the efficiency of the vacuum process was developed a prototype for the LASPHI simulating the actual working conditions of the method of freight transportation. The prototype has a construction with two pneumatic actuators to perform the movements in the X and Y axis, pneumatic valves for the exchange of motion actuators, valve generating vacuum by Venturi principle, a PLC and other safety devices Fig.2 (a). The manipulation method adopted consisted of: vertically move the pneumatic actuator (A) to the specimen, generating a vacuum to keep the specimen caught in the suction, return to the starting point pair then move the pneumatic actuator (B) to the end of full travel with horizontal movement. Then again trigger the actuator (A) and cut the compressed air supply to the generating vacuum valve, releasing the specimen to return the two actuators to its starting point, as shown in Fig.2 (b).

Fig.2. Module tests: (a) prototype for handling and (b) mechatronic devices

Tests conducted on the bench were intended to measure and evaluate some physical parameters necessary for the proper functioning of a vacuum handling system, based on theoretical values mentioned in the course of this work. The following parameters were adopted as optimal labor standards in the tests (Tab. I). In Fig.2 (c) we can also observe that a mechanical vacuum gauge was used for the characterization of the value generated in the vacuum of the suction chamber, indicating the action of 0 to -1 bar, in which it was necessary to collect data manually.

Tab.I. Parameters adopted in the tests

Parameters Value Unit. Operating Pressure 7 bar Level of vacuum generation valve 70 % Force lifting of horizontal suction cups 22,4 N Perfect weight of the specimen (a)

0,708 kg

Perfect weight of the specimen (b)

0,354 kg

In order to the evaluate the best operating condition of the system, some parameters have been purposely altered, such as pressure (4 - 7 bar), the surface of displaced materials (smooth and rough) and the weight of the loads added to specimens (theoretical weight, 100% up).

2.1. Vacuum system applied

In this work the windy flat type and three types of rubber for its design, all with 20 mm diameter were used (Fig.3). These falls into three rubber components: natural: highlights by excellent elasticity and high tensile strength; nitrile: it has huge resistance to oil and oil products and silicone: exceptional resistance to high temperatures.

a b

Horizontal displacement

Actuator A

Actuator B

Vertical displacement

Specimen Vacuum gauge c

CLP, safety devices

9


Fig.3. Model and types of suction cups used

In testing, the generating vacuum valve (Fig. 4) that works by the Venturi principle was used, where the vacuum is generated using compressed air (positive pressure). Below is presented their main characteristics (Tab. II):

Tab. II. Technical data generating vacuum valve

Generating characteristics valve Value Unit. Operating pressure 1 to 10 bar Operating temperature -10 to 80 ºC Vacuum (varies with the inlet pressure) 0 - 660 mmHg Flow 20 l/min Venturi orifice diameter 0.7 mm

Fig.4. Valve used in the tests.

According to the manufacturer's catalog, this valve operates with 100% vacuum level to a pressure of 10 bar, this means that we have a vacuum level of 70% to our tests, whereas pressure of 7 bar will use as the default. Underscoring that the diameter of the pipe must be dimensioned in relation to the Venturi orifice, which in our case corresponds to a pipe of 4 mm.

2.2. Calculation of the displacement

For the tests was selected valve vacuum that produces 70 % vacuum level at a pressure of 7 bar According to data found in the manual and the suction cup flat type having 20 mm in diameter, was chosen this way the theoretical resultant force will be 22.4 N, according to the manufacturer. The acceleration values were calculated using the values found by measurements carried during preliminary tests with the displacement of pneumatic actuators. To test the effect, was used of stroke cylinder with 270 mm due to the fact make the movements of the worst-case handling system was used for this. These measurements were performed numerous times with the aim of reaching the most reliable possible value. Below the main equation 1 used is presented. In the calculations we used a safety factor 2 to specimen (a) that has the smooth surface characteristic and a safety factor 3 related to the specimen (b) having the characteristic of rough surface, as indicated in the catalog Parker [6].

Silicone Natural Nitrílica

10


. .sg aF mµ

+=

(1)

m – Weight [kg] F – Force lifting [N] – (suction cups in the horizontal position motion) g – Acceleration of gravity [m/s2] a – Acceleration of motion [m/s2] s – Safety Factor [---] µ – Coefficient of friction [0.5] – (empirical value related to the glass, according to FESTO). Calculating the acceleration of the movement and considering the use of a suction cups 20 mm, is found the weight values for each type of specimen. The specimen (a) and (b), was reached at a value of 0.513 and 0.342 kg respectively. 2.3. Monitoring of air pressure

The system used in the data acquisition process was composed by a Microchip PIC microcontroller family. This system has the function to convert the analog signal from the pressure transducer into a digital signal to be viewed on an LCD screen. In this research the LCD display function was to show in real time the current system pressure as shown in Fig.5 (a) e (b).

Fig.5. Acquisition of pressure. (a) Pressure transducer and (b) liquid crystal display

Giving emphasis to the pressure control to ensure the manipulation strength and interpretation of pressure data was required to integrate a microcontroller reading. However, as it has not been possible to integrate the microcontroller in the action of some event on the prototype, it was used only to compare the gauge reading of mechanical principle. To read the display in this manner was used RA0 to the analog input of the analog read signal provided by the transducer and the pin (PORT A) necessary for exchanging data eat the LCD screen, as shown in Fig.6 (a). For reading the analog signal from the pressure transducer whose output signal corresponding to a level of 4-20 mA current four 1K resistors were used in parallel, resulting in a resistance of 250 ohms in series between the power source and thereby generating a voltage drop that will eventually be read and converted to a digital signal by the microcontroller. The microcontroller used in this study is manufactured by Microchip Technology Inc. ® and has the following features: flash memory for instructions (program memory) with 14 bits/word – PIC 16F877A model. The program was developed in assembly or C programming language [7] and was only restricted in effecting the reading of an external analog signal from a pressure transducer, converts it into a digital signal and make it available on an LCD screen with order to monitor the system pressure. Thus at the beginning of the programming device to the LCD library that is already available to the developer within the development environment for programming and enabled the devices A/D converter is included, allowing the interaction of the two components (Fig.6 b).

a b

11


Fig.6. Pressure monitoring: (a) Hardware development platform and (b) Programming Platform 3. Analysis of Results

The following tables IV, V and VI express the results obtained during tests of manipulation, and the terms used in the field of analysis of the tables were set this way:

• Bad: The suction cup will not hold the sample, the same or dropped during handling. • Critical: the sample has not fallen during handling, however, is a sash very close to the bad. • Ideal: security level and all tests in this range, the system was stable and showed no change.

3.1. Suction cups of Silicone

Silicone rubber has a chemical structure consisting primarily of silicon and oxygen (Si-O), this structural formation is that justifies the broad range of temperatures and seal the excellent mechanical strength properties. These results can be seen in the results shown in Tab.III.

Tab. III. Results of tests done with the suction cup silicone

Pressure Specimen (a) - slick

Specimen (b) - rough

0.5 kg 1 kg 0.350 kg 0.7 kg Vacuum/Analysis Vacuum/Analysis

Vacuum/Analysis Vacuum/Analysis

4 bar -0.22bar/Bad -0.22bar/Bad -0.20bar/Bad -0.20bar/Bad 5 bar -0.30bar/Critical -0.30bar/Critical -0.28bar/Critical

-0.28bar/Critical

6 bar -0.36bar/Ideal -0.36bar/Ideal -0.32bar/Ideal -0.32bar/Ideal 7 bar -0.34bar/Ideal -0.34bar/Ideal -0.38bar/Ideal -0.38bar/Ideal

With these tests it was possible to show graphically with Fig.7 (a) the results obtained with manipulation of the slick glass and Fig.7 (b) with rough glass, using the silicone suction cup which was subjected to variations in pressure and manipulated load.

Fig.7. Vacuum suction cup with silicone: (a) slick glass and (b) rough glass

Transducer

a b

a b 12


The results revealed that there was a high vacuum level in relation to the increased pressure, but this variation were the same even when the weight of material handled reached twice the recommended theoretical load, with the statement that the vacuum level is directly related with the level of pressure. It could be observed that the system with working pressures below 5 bar, did not achieve satisfactory results in any of the tests, making this unacceptable level of pressure to the handling system with these characteristics. Regarding the results of cargo handled, we obtained acceptance with two of pressure levels considered optimal (6 and 7 bar), and these results are very satisfactory, noting that the burden of higher weight has twice the theoretical load recommended. With these results we can emphasize that the implementation of a vacuum handling system without conducting preliminary tests that confront theoretical data with super practical tend to scale the system in general, causing unnecessary expenses. The results showed that just as there was a high vacuum level in relation to the increased level of pressure, and this amount has remained the same for both handling charges, but the system behaved differently in achieving the movement manipulation, and the tests performed on the roughened glass surface reached only a range of ideal pressure (7 bar), which also becomes satisfactory when referred to the difference of the manipulated loads, comprising at twice the recommended load theoretical. 3.2. Suction cups of natural rubber

By infrared spectroscopy, the spectrum found that the material used is a polymer with a polybutadiene characteristics and polymethylmethacrylate respectively with polybutadiene, the natural rubber compound. This material has characteristics of high elasticity, flexibility, resistance to abrasion and impact, having easy adhesion to fabrics and steel. However, this material (natural rubber) did not show a good performance regarding the tests performed with cut glass (Tab.IV), considering the same test conditions of the previous test.

Tab.IV. Results of tests done with the suction cup natural rubber

Fig.8 shows the results of pressure levels (5 and 6 bar) which are related of the values of the degree vacuum and loading manipulated referring to the suction cups natural rubber and glass slick surface according to Tab.IV. Therefore, it is proven the accuracy of the tests and somehow identifies optimal parameters so that the vacuum handling system works within a safety range.

Fig.8. Levels of vacuum handling system

Pressure Specimen (a) - slick Specimen (b) - rough 0.5 kg 1 kg 0.350 kg 0.7 kg


Vacuum/Analysis Vacuum/Analysis 4 bar -0,20bar/bad -0,20bar/bad -0,17bar/bad -0,17bar/bad 5 bar -0,30bar/critical -0,30bar/critical -0,22bar/bad -0,22bar/bad 6 bar -0,36bar/ideal -0,36bar/ideal -0,28bar/critical -0,28bar/bad 7 bar -0,39bar/ideal -0,39bar/ideal -0,30bar/ideal -0,30bar/critical

Carga

Vácuo gerado (-0.30 bar)

5 bar 6 bar

Carga

Vácuo gerado (-0.36 bar)

13


It is remarkable the difference between the vacuum level when the system undergoes a pressure variation. Fig.9 (a) and (b) shows the graph the results obtained with natural rubber suction cup with slick glass and rough glass.

Fig.9. Vacuum suction cup with natural rubber: (a) slick glass and (b) rough glass The results showed that in this case there was also a high vacuum level in relation to the pressure increase, and this change has remained the same, even when the weight of the material handled reached twice the recommended theoretical load. Regarding the manipulated load, had the same results related to silicone suction cup, but the theoretical load raising and increase sizing two pressure levels were rated as ideal bar on 6 and 7, that is, very satisfactory results for the increase sizing reaches twice the recommended load. With these values we can assign good features of the natural rubber suction cup compared to silicone, it had the same behavior in equal working conditions related to the slick glass, regarding the application the measurement of the roughness and weight manipulated the two have ideal working conditions, however the factor that must be analyzed to choose the correct suction cup, associated with their individual characteristics influencing the final results. The results Fig.9 (b) showed which were varying levels of pressure and weight of the load. The results showed that there was a similarly high level of vacuum in relation to the increased pressure level, and this value remains the same for both handling loads. The system behaved differently in achieving the manipulation of which motions with increasing load of the glass rough surface results did not achieve any desired level of work, or for handling of the glass with this feature eliminates the possibilities of applying these parameters for loads above the recommended theoretical, making real the theoretical foundations used for handling system with these characteristics.

3.3. Suction cups of nitrile rubber

By infrared spectroscopy, the spectrum found that the material used is a polymer with characteristics of acrylonitrile and butadiene respectively nitrile compound (Ni). This material has characteristics that provide a good balance between resistance at low temperature (between -10°C and -50°C) with oil and solvents. Such combined with a good resistance to abrasion features make the nitrile rubber recommended for a variety of applications, particularly in locations that provide contamination part by oil or solvent. In Tab.V mentions the tests performed with the nitrile rubber suction cup which was subjected to the same tests that the silicone suction cup.

a b

14


Tab. V. Results of tests done with the suction cup nitrile rubber

Pressure Specimen (a) - slick

Specimen (b) - rough

0.5 kg 1 kg 0.350 kg 0.7 kg Vacuum/Analysis Vacuum/Analysis


4 bar -0,20bar/Bad -0,20bar/Bad -0,17bar/Bad -0,17bar/Bad 5 bar -0,30bar/Critical -0,30bar/Bad -0,22bar/Bad -0,22bar/Bad 6 bar -0,36bar/Ideal -0,36bar/Critical -0,28bar/Critical -0,28bar/Bad 7 bar -0,39bar/Ideal -0,39bar/Ideal -0,30bar/Ideal -0,30bar/Critical

Fig.10 shows the results obtained with the nitrile rubber suction cup, which was subjected to

handling glass slick and the specimen with a rough surface, but with different loads and pressures.

Fig.10. Vacuum suction cup with nitrile rubber: (a) slick glass and (b) rough glass In the Fig. 10 (a) the results showed that in this case, there was still a high vacuum level relative to increased pressure in all tests, but this change was similar when the same weight of material handled reached twice the recommended theoretical load. Regarding the charge of theoretical survey had two pressure levels classified as ideal and the load increment had only one ideal level of pressure, and those results also become satisfactory when reminded that the greatest burden is twice the theoretical load. In the manipulation of flat glass noted that sucker nitrile showed the same results regarding suction silicone and natural rubber with scaled theoretical load, and your choice will also depend on where it will be exposed. In the Fig. 10 (b) the results showed that there was a high vacuum level in relation to the increased level of pressure, and this amount has remained the same for both handling charges, but the system behaved differently in achieving the movements handling and that with increasing load the roughened glass surface, the results did not achieve any desired level of work, to handling of the glass with this feature eliminates the possibilities of applying these parameters to loads above the recommended theoretically, making real the theoretical foundations used in the tests. With these results it was observed that the suction cup silicone has chemical characteristics that increase their level of sealing in relation to other tested, being clear that the level of this vacuum in their tests was higher than that of other vacuum suction cups, even when handled rough glass surface with twice the recommended load. Tab.VI presents the working ranges of the suction cup who presented the best results regarding the handling of slick and rough glass, the optimal parameters in relation to the work pressure, vacuum level generated and load handled with slick and rough glass.

Tab.VI. Classification of results in relation to the slick glass and rough

Materials Pressure Vaccum Slick glass (0.5 kg)

Slick glass (1 kg)

Silicone 6 e 7 bar -0.36 a -0.40 bar Ok Ok Natural 6 e 7 bar -0.36 a -0.39 bar Ok Ok Nitrile 6 e 7 bar -0.36 a -0.39 bar Ok Ok

a b

15


Materials Pressure Vaccum Rough glass (0.350 kg)

Rough glass (0.700 kg)

Silicone 7 bar -0.38 bar Ok Ok Natural 7 bar -0.30 bar Ok Adeverse Nitrile 7 bar -0.30 bar Ok Adeverse

4. Final Consideration

According to the practical realization of the tests it was observed that the roughness of the material directly influences the performance of a handling system that uses vacuum technology , seen as the roughened glass had a mean Ra equivalent to 12.83 µm. Tests have shown that the results obtained with the specimen slick texture better had a utilization as the load capacity and the level of the working pressure, but the three suction cups had positive results with of this type, however, for the handling of glass rough texture the suction cup natural and nitrile failed to perform well when they exceeded the recommended theoretical loads. In the results it was observed that the vacuum level behaved differently in relation to the change of the pressure level and the surface of each sample. The material obtained had a surface roughness values lower vacuum level as compared to the slick surface of the material even under conditions in which the pressure level remained the same. It was also the vacuum level generated between the suction cup and the material influenced the capacity of cargo handled, as in the case of silicone suction cup that was the one that achieved positive results in all tests. This result shows that the key to be evaluated in a vacuum handling system parameter is the vacuum level generated between the suction cup and the piece, ie, for this type of roughness noted that to occur for the safe handling of the specimens system should produce a degree of vacuum less than -0.38 bar. The three suction cups showed similar regarding handling of glass with a smooth surface by manipulation of the perceived double theoretical capacity results found. According to this we can say that the three types of materials suckers are able to operate in systems with these characteristics, since the optimal choice will depend on the environment that this suction cups will be exposed considering that each has a characteristic that can influence better results as its durability and productivity. The results obtained with the manipulation of the rough surface of the material revealed that the suction cup silicone was the only one able to execute the tests with the two charges and establish optimum settings for the system, while the other two could only handle the theoretical value determined.

REFERENCES

[1] R. M. Castro, M. O. Borba, J. M. Neto, G. B. SOUZA, L. C. C. Cavaler. Automation to Assistance with Disabilities of Motion Activities in the Laboratory Pneumatic Systems. In: ICBL - Interactive Computer aided Blended Learning, 2013, Florianopolis. ICBL 2013 - Interactive Computer aided Blended Learning, 2013. v. 5. p. 375-379.

[2] R. M, Castro. Avaliação das Propriedades de Superfície e do Comportamento ao Desgaste Abrasivo em Hastes de Cilindros Hidráulicos Revestidas pelos Processos HVOF e Cromo Duro Eletrodepositado. Dissertação de Mestrado, UFRGS - Universidade Federal do Rio Grande do Sul - Porto Alegre, RS. 2012. 115p.

[3] C. Andretta. Brunimento para Recuperação das Camisas de Pistão dos Motores de Combustão Interna. Dissertação de Mestrado. Universidade Estadual de Campinas. Campinas: São Paulo, 2001. 112p.

[4] [4] F. T. Degasperi. Contribuições para Análise, Cálculo e Modelagem de Sistemas de Vácuo, Tese de Doutorado, Faculdade de Engenharia Elétrica e de Computação, Campinas, Universidade de São Paulo, 2006.

[5] A. Bezerianos, R. Balakrishnan. The Vacuum: Facilitating the Manipulation of Distant Objects. Department of Computer Science University of Toronto. CHI 2005 – Conference on Human Factors in Computing System. Portland, Oregon USA, p. 361 – 370 2005.

[6] PARKER Training. Apostila de Treinamento em Pneumática. Tecnologia Pneumática Industrial - M1001-1 BR. Parker Hannifin Ind. e Com. Ltda, Divisão Automation. 2001, 187p.

[7] D. J. SOUZA. Desbravando o PIC: ampliado e atualizado para PIC16F628A. Ed. Érica, 12ªed. São Paulo, SP, 2005. 272p.

16


ABC ANALYSIS, MODEL FOR CLASSIFYING INVENTORY

Marin Rusănescu1

1 Valplast Industry Bucharest, [email protected] Abstract: In this paper, I present a method of control of the inventories, the ABC analysis, a very popular method to classify the inventories, a method based on the Law’s Pareto or the principle 80/20. Keywords: ABC analysis, inventories, classification

1. Introduction

Inventory classification using ABC analysis proved to be a highly successful method, it becoming popular due to the practical implications, helping managers to easily identify items on which they could turn their attention to creating a surplus value, I mean the articles of Class B and C or just those in the class that represented the bulk and stars stock. This method is now present because of the possibilities they offer policies concentrating on the best products.

2. ABC ANALYSIS Bloomberg et al [1] showed the existence of two models for classifying stocks i.e. ABC analysis and critical value analysis. ABC analysis is a method of inventory control based on a principle discovered by Vilfredo Pareto statistically, a nineteenth-century Italian economist, a principle known as the law of Pareto, who observed that 20% of the Italian population owned 80% of land used, and [2]. Pareto later discovered that other phenomena and processes of nature; the economy had the same distribution, [2]. Pareto's law is stated thus, [2]: „ In many projects 20% of the total effort produces 80% of the total result”. Pareto’s Law has the following situations that were reported [2]: •„ 20 % of customers generate 80% of turnover • 20% of products make 80% of turnover • 20% of possibilities to make faults in production are responsible for 80% of product defects • 80% of the decisions are made in 20% of the time in a meeting • 20 % of products make 80% of profit • 20 % of employees account for 80% of the time absent • 80 % of results are achievable in 20% of working time if strategic time planning is used • the best 80% of sellers are responsible for 80% of the profit of a firm • 20% of the goods in a stock sum up to 80% of the stock worth • 80% of the requests for stocked articles are on only 20% of the goods • 80 % of the costs or losses of a business are caused by 20% of the problems”.

17


Arthur, [2], says that 80/20 is justified only by observation, i.e. empirically observe that it applies to many software projects: 20 % of these 80 % of these modules consume resources modules contribute errors modules consume execution time errors consume repair costs enhancements consume adaptive maintenance costs tools experience tool usage. ABC Analysis is a „method of tiered inventory or supplier valuation that divides inventory/suppliers into categories based on cost per unit and quantity held in stock or turned over a period of time” and “allows different inventory/supplier management techniques to be applied to different segments of the inventory/suppliers in order to increase revenue and decrease costs. In terms of a Pareto Analysis, it separated the critical few from the trivial many. "A" Category items generally represent approximately 15%-20% of an overall inventory by item, but represent 80% of value of an inventory. By paying attention close attention in real-time to the optimization of these items in inventory, a great positive impact is possible with minimal increase in inventory management costs. "B" Category items represent 30%-35% of inventory items by item type, and about 15% of the value. These items can generally be managed through period inventory and should be managed with a formal inventory system. "C" Category items represent 50% of actual items but only 5% of the inventory value. Most organizations can afford a relatively relaxed inventory process surrounding these items”, [3]. ABC analysis is „ An analysis of a range of items that have different levels of significance and should be handled or controlled differently. It is a form of Pareto analysis in which the items (such as activities, customers, documents, inventory items, sales territories) are grouped into three categories (A, B, and C) in order of their estimated importance. 'A' items are very important, 'B' items are important, 'C' items are marginally important. For example, the best customers who yield highest revenue are given the 'A' rating, are usually serviced by the sales manager, and receive most attention. 'B' and 'C' customers warrant progressively less attention and are serviced accordingly”, [4]. ABC analysis means classify the sub-projects in classes A, B and C in order of decreasing yields which class A has projects with the highest efficiency , class B has projects with medium yield and class C projects with contains low-yield projects, as follows:„ Class A: subprojects with relative low costs returning an over proportional yield, i.e. the relatively few subprojects in this class should return a very high yield with low expense Class B: subprojects with at least average ratio of yield to cost. Yields of projects in this class should be at least direct proportional to costs. Class C: the rest of the subprojects, i.e. these subprojects generate low profit on high costs”, [2]. ABC classification „allows an organization to separate stock keeping units (SKUs) into three groups: A, the most important; B, important; and C, the least important. The purpose of classifying items into groups is to establish appropriate levels of control over each item”, [5]. The items are classified using the annual use value, which is the product of annual demand and the average unit price, [6]. Inventory items are „ordered descendingly with respect to their annual dollar usage values”, [5]. According to this classification, items are subject to a different control. Thus, „Class A inventory items require cautious inventory control because they represent a large percentage of the total dollar value of the inventory. This state requires certain demand forecasts and detailed record keeping. Class C inventory items should receive a flexible control. Class B items should have a control effort that lies between A and C”, [5].

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http://www.businessdictionary.com/definition/analysis.html

http://www.businessdictionary.com/definition/range.html

http://www.businessdictionary.com/definition/item.html

http://www.businessdictionary.com/definition/form.html

http://www.businessdictionary.com/definition/Pareto-analysis.html

http://www.businessdictionary.com/definition/activity.html

http://www.businessdictionary.com/definition/customer.html

http://www.businessdictionary.com/definition/documents.html

http://www.businessdictionary.com/definition/inventory.html

http://www.businessdictionary.com/definition/sales-territory.html

http://www.businessdictionary.com/definition/order.html

http://www.businessdictionary.com/definition/estimate.html

http://www.businessdictionary.com/definition/yield.html

http://www.businessdictionary.com/definition/revenue.html

http://www.businessdictionary.com/definition/rating.html

http://www.businessdictionary.com/definition/sales.html

http://www.businessdictionary.com/definition/manager.html

http://www.businessdictionary.com/definition/receive.html

http://www.businessdictionary.com/definition/warrant.html


ABC analysis is done in six basic steps, [3]: „1. Identify the objective for the analysis. Determine success criteria. An ABC analysis can accomplish one of two primary goals: to reduce procurement costs or to increase cash flow by having the right items available for production or direct to customer sales. 2 Collect data on the inventory under analysis. The most common data, generally available from standard accounting already in place, is annual spend per item. This can be in terms of raw purchase dollars, or weighted cost including all ordering costs and carrying costs, if those can be readily calculated. 3. Sort inventory in decreasing order of impact. From most to least, rank orders each inventory item by cost. 4. Calculate accumulated impact. Using a spreadsheet tool, calculate the cumulative impact of the list of inventory items by dividing item annual cost by total inventory annual spend, then adding that amount to the cumulative total of percentage spent. 5. Divide inventory into buy classes. This may not be a precise 80/20 characterization. Take a holistic view and do not concern yourself with an exact 80/20 rule. The goal is to find areas where renegotiating contracts, consolidating vendors, changing strategic sourcing methodology, or implementing e procurement may deliver significant savings or ensure in-stock availability of high-volume items. 6. Analyze classes and make appropriate decisions. The key to this step is follow-up and tracking. Once strategic cost management is in place based on categories, periodic review is critical to monitoring the success or failure of the decisions.” For the determination of the borders of classes A, B, C have been proposed various methods, for the class A the proposals range from 5% to 33%, and for class B from 15% to 33%, and for class C from 25%to 50%, using many practical cases the so-called Lorenz curve, where the x axis is cumulative costs, and on the y axis are cumulative yields projects, [2]. An example is the Lorenz curve below, which shows the size of land owned by firms vs. total number of farms, where both axes are in units of percent, [2].

Fig. 1 Lorenz curve of land area usage in South Africa, [2]

19

http://www.purchasing-procurement-center.com/strategic-sourcing-methodology.html

http://www.purchasing-procurement-center.com/strategic-sourcing-methodology.html

http://www.purchasing-procurement-center.com/strategic-cost-management.html


Classification of items in groups A, B, C in ABC analysis was done using a single general criterion, frequently being that the total annual dollar value, but because it was recognized that the traditional ABC analysis has a serious drawback, because using a single criterion can generate significant financial loss problems, for example, articles for class C or class a big delivery prone to obsolescence can cause large financial losses due to possible disruption of production or creation of large stocks were ABC proposed classification based on multiple criteria, such as delivery time, criticality shortage of stock on an item, obsolescence rate, scarcity, substitutability, order an item size and other important criteria to consider which criteria can provide a comprehensive management control, [5].

3. Conclusions In this paper we present a method for classification of stocks, namely ABC analysis. This method is very useful both from the theoretical point of view but also from a practical standpoint. Has many uses and can be used initially to the classification of stocks, and suppliers, and projects, and by analogy we can extend the method to other fields of knowledge. Yet the most important use is in inventory management. REFERENCES [1] Bloomberg, D. , J. , Lemay , S. , Hanna , J. , B. , (2002) Logistics. Prentice Hall . New Jersey. USA. [2] Ultsch, A., (2002) Proof of Pareto’s 80/20 Law and Precise Limits for ABC-Analysis Technical Report 2002/c DataBionics Reseach Group University of Marburg 35032 Marburg/Lahn Germany [3] http://www.purchasing-procurement-center.com/abc-analysis.html [4] http://www.businessdictionary.com/definition/ABC-analysis.html [5] Keskin , G., A., și Ozkan, C., (2013) Multiple Criteria ABC Analysis with FCM Clustering Hindawi Publishing Corporation Journal of Industrial Engineering Volume 2013, Article ID 827274, 7 pages http://dx.doi.org/10.1155/2013/827274 [6] Ramanathan, R., (2006) ABC inventory classification with multiplecriteria using weighted linear optimization , Computers and Operations Research, vol. 33, no. 3, pp. 695–700, 2006

20


EXPERIMENTAL DETERMINATION OF THE ASPHALT ROAD PROFILE IRREGULARITIES

PhD. Stud. Eng. David Alexandru-Dorin, Prof. PhD. Eng. Voicu Gheorghe,

PhD. Eng Dutu Mihaela Florentina, PhD. Stud. Eng. Cujbescu Dan National Institute of Research - Development for Machines and Installations Designed to Agriculture and Food Industry INMA, Bucharest University “POLITEHNICA” of Bucharest - Faculty of Mechanical Engineering and Mechatronics - Faculty of Biotechnical Systems Engineering -

ABSTRACT

Determination of terrain profile is important when studying the model, the vibration on the mobil agricultural unit that occur in the vertical plane of symmetry due to vertical movement (bouncing or vertical oscillations) and rotations around the transverse axis passing through the center of gravity (pitching oscillations). This paper presents a methodology for the experimental determination of the road profile irregularities. It was considered that the irregularities profile is sinusoidal and were determined the height and length

1. INTRODUCTION

Irregularities in the terrain profile, which has a random character, influence the aggregate fluctuations and sometimes may impose diferent speed. When driving on bumpy terrain with a speed greater than a limited value, due to oscillations, the driven wheel may lose contact with the ground. The road surface profile is characterized by the following sizes (Figure 1):

• l - irregularities length ; • h0 - irregularities height ;

Fig.1. Dimensions that characterize the road profile [1]

2. METHODOLOGY It may be considered the land profile irregularities are sinusoidal. In this case the profile equation is:

ℎ = ℎ0 ∙ sin 𝜔 ∙ 𝑡 (1) where:

lvπ

ω2

= (2)

where: v – is the speed of the aggregate, [m/s].

To determine the terrain profile irregularities that will study the vibrations of the tractor – equipment for deep soil loosening aggregate using a graduated scale length 4 m, two supports, a level and a

21


ruler. Place the ruler on the supports, check its horizontal position with a level and then, with the roulette, measure the height of irregularities of 100 to 100 mm (figure 2).

Fig.2. Determination of terrain profile irregularities

On a length of 10 m on a asphalt road we made n = 100 determinations of the distance h measured from the horizontal ruler to the ground. From the set of measured values the gross errors h* must be removed by using Romanovski test [2], [3]. To do this we have to calculate the empirical standard deviation s for the n -1 assuming that the measurement results are not affected by gross errors, using the relation:

∑−

=

−−

=1

1

2)(2

1 n

imi xx

ns (3)

Knowing the average values hm for the n -1 remaining values after removing the value h*, suspected to be affected by gross errors, calculate the ratio:

tx x

s=

−*

(4)

For a confidence level of P=0.95 and n = 100 number of experiments to determine the critical value t (n, P) = 1.994 [2],[3]. If: t > t (n, P) (5) we will remove the value h* to be free of gross errors,with a level of confidence P. In the set of measured values we did not identify values affected by gross errors.

. Fig.3.. Distance h measured from the horizontal ruler to the asphalt road

Table .1 shows the measured values of h and the irregularities height h0 = h – hm where hm = 69.82 cm is the average of the measured variables.

65

66

67

68

69

70

71

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 Mea

sure

d di

stan

ce h

[cm

]

Road leangh[m]

22


Table 1. The profile of the asphalt road irregularities

Nr. h [cm]

h0 [cm]

Nr. h [cm]

h0 [cm]

Nr. h [cm]

h0 [cm]

Nr. h [cm]

h0 [cm]

1 68 -1.82 26 70 0.18 51 69.5 -0.32 76 70.5 0.68 2 67.5 -2.32 27 70 0.18 52 70 0.18 77 70.5 0.68 3 67.5 -2.32 28 70.5 0.68 53 70.5 0.68 78 70 0.18 4 69 -0.82 29 70.5 0.68 54 70.5 0.68 79 69.5 -0.32 5 69 -0.82 30 70.5 0.68 55 70.5 0.68 80 69 -0.82 6 69.5 -0.32 31 70 0.18 56 70.5 0.68 81 68 -1.82 7 69.5 -0.32 32 70 0.18 57 70.5 0.68 82 67.5 -2.32 8 70 0.18 33 69.5 -0.32 58 70.5 0.68 83 67 -2.82 9 70 0.18 34 69 -0.82 59 70 0.18 84 66.5 -3.32 10 69.5 -0.32 35 68.5 -1.32 60 69.5 -0.32 85 66.5 -3.32 11 69 -0.82 36 67 -2.82 61 68.5 -1.32 86 66.5 -3.32 12 68 -1.82 37 66.5 -3.32 62 67 -2.82 87 66.5 -3.32 13 67.5 -2.32 38 66.5 -3.32 63 67 -2.82 88 67 -2.82 14 67.5 -2.32 39 66.5 -3.32 64 67 -2.82 89 68 -1.82 15 67 -2.82 40 66.5 -3.32 65 67 -2.82 90 69 -0.82 16 66 -3.82 41 66.5 -3.32 66 67 -2.82 91 70 0.18 17 66 -3.82 42 66.5 -3.32 67 67 -2.82 92 70.5 0.68 18 66 -3.82 43 67 -2.82 68 67 -2.82 93 70.5 0.68 19 66 -3.82 44 67 -2.82 69 67.5 -2.32 94 70.5 0.68 20 66.5 -3.32 45 67.5 -2.32 70 68 -1.82 95 70 0.18 21 66.5 -3.32 46 67.5 -2.32 71 69 -0.82 96 69 -0.82 22 67 -2.82 47 67.5 -2.32 72 70 0.18 97 68 -1.82 23 67 -2.82 48 68 -1.82 73 70.5 0.68 98 67 -2.82 24 68 -1.82 49 68 -1.82 74 70.5 0.68 99 68 -1.82 25 69 -0.82 50 69 -0.82 75 70.5 0.68 100 69 -0.82

With the data in Table 1 we represented graphically the variation of the distance measured from the horizontal to the road irregularities based on the length of the road

Figure 4 shows the the variation the asphalt road height irregularities based on the length of the road

Fig.4. Height h0 of the asphalt road irregularities

Half-profile road bumps irregularities are calculated with: i11 L-+= ii Ll (6)

-5

-4

-3

-2

-1

0

1

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

irreg

ular

ities

hei

ght

h 0 [c

m]

Road leanght[m]

23


where: iL - is the measured distance from the origin of the path length to the point i where the irregularities height is equal to zero. There were obtained 11 values shown in Table 2.

Table 2. Semi-length irregularities values

Nr. Li [m] l1i [m] Nr. Li [m] l1i [m] 0 0.7 - 6 7.1 1.2 1 0.9 0.2 7 7.7 0.6 2 2.45 1.55 8 8.9 1.2 3 3.1 0.65 9 9.45 0.55 4 5.1 2 10 10 0.55 5 5.9 0.8

The true value of the height and length of the field irregularities is determined as the average values of the measured values. The real value for the two measured variables is:

ml

mh94,001669,0

1

0

==

(7)

The asphalt road surface profile is characterized by the following sizes: • l = 1.88 m irregularities length; • h0 = 16.69 mm irregularities height.

3. CONCLUSIONS

• Approximation of the irregularities in the terrain profile with a sinusoidal function is recomended to study vibrations for a mobil agricultural unit ;

• The number of measured values depends on the accuracy of approximating the height and length of the irregularities and level of confidence of their determinants

• The method presented is simple, requires no expensive equipment and high qualified personnel to perform measurements for road profiles.

REFERENCES [1] Ghiulai C., Vasiliu Ch., Vehicle dynamics, Didactic and Pedagogic Publishing, Bucharest, 1975 [2] Ioan Paunescu, Ladislau David, Basics of Biotechnical experimental research, Printech, 1999 [3] Rumsiski Z.L., Mathematical processing of the experimental data, Technical Publishing House, 1974

24


DETERMINING THE STEP RESPONSE FOR A PNEUMATIC CYLINDER POSITIONING SYSTEM

Radu RADOI1, Marian BLEJAN2, Iulian DUTU3, Gheorghe SOVAIALA4, Ioan PAVEL5

1 INOE 2000 - IHP, [email protected];2 INOE 2000 - IHP, [email protected];3

INOE 2000 - IHP, [email protected];4 INOE 2000 – IHP, [email protected];

INOE 2000 – IHP, [email protected] 5

Abstract: Linear pneumatic actuators are used to provide linear motion for medical, automotive, laboratory and robotics applications or in industrial aplications such as chemical and petrochemical industries, oil refineries, drilling industries, food industries for sorting and packaging lines, paper industries, etc. These actuators must be reliable and accurate to ensure proper and without disruption functioning of the installations they belong to. Applications they belong to sometimes require a high dynamics. In order to determine the performance of an actuator for a specific application or if it is intended to achieve a high dynamics by using new designs or new materials there are necessary experiments. The paper presents an experimental stand which allows for dynamic testing of pneumatic actuators.

Keywords: pneumatic, cylinder, step signal, positioning, incremental transducer, converter, controller

1. Introduction

Linear pneumatic actuators are used to provide linear motion for medical, automotive, laboratory, and robotics applications or in industrial aplications such as chemical and petrochemical industries, oil refineries, drilling industries, food industries for sorting and packaging lines, paper industries, etc. These actuators must be reliable and accurate to ensure proper and without disruption functioning of the installations they belong to. Applications they belong to sometimes require a high dynamics. The paper presents the development of a stand which allows experimentations to determine the performance of an actuator for a specific application or if it is intended to achieve a high dynamics by using new designs or new materials.

2. Description of the testing system

The stand is made of two identical pneumatic cylinders with rods connected oppositely by means of a force transducer. Pneumatic cylinders are mounted in a closed frame, on which the other devices within the stand structure are installed. These other component devices are: the pressure regulator, the pneumatic proportional directional control valve, pressure transducers and the throttle check valve which helps create a load type pneumatic spring using the cylinder located oppositely to the one controlled by the proportional directional control valve. Pneumatic diagram of the testing system (Fig. 1) includes compressor 1, relief valve 2, limiting the load pressure of the air tank 4, air filter 3, pressure regulator 5, setting the working pressure in the system, manometer 6 allowing visualization of pressure that has been adjusted. The positioning system which is to be tested consists of proportional directional valve 7, controlling pneumatic cylinder 8, equipped with displacement incremental encoder 9. To view the evolution of pressure values in the pneumatic cylinder chambers there wewre provided pressure transducers 10. On the exhaust ports of

25


the proportional directional control valve there were installed two silencers 11. Cylinder 14, by means of which a load type pneumatic spring is created, has been connected to the actuator cylinder by means of a force transducer 13. At the outlets of the load cylinder there have been installed two throttle check valves 12, allowing to create load only in the opposite direction in regard to the movement of the actuation cylinder. In the diagram can also be found signal converter 15, PID controller 16, USB-6218 data acquisition board 17 and computer 18 equipped with data acquisition software.

Fig. 1 Pneumatic and data acquisition diagram of the system

3. Data acquisition system

To generate control signals and to acquire signals from the transducers and from the PID regulator there has been used a data acquisition board made by National Instruments. Sine wave incremental encoder (9) incorporated in Festo DNCI-32-200-P-A pneumatic cylinder provides relative values. In order to capture the signal from this encoder with the meters on the acquisition board, there has been developed a module for conversion of sin and cos signals (Fig. 2) supplied by it into TTL signal, a type of signal that can be registered by the meters on the USB – 6218 acquisition board.

Fig 2 Encoder signal from sin channel of Festo DNCI pneumatic cylinder

26


Fig. 3 Block diagram for signal acquisition from incremental encoder

In figure 4 can be seen the diagram developed with two operational amplifiers included in the capsule of an integrated circuit type MCP602. The assembly is powered at 5V DC, and it has terminals located on sides for connecting the cable from the encoder (sin and cos signals, and also the 5V power supply of the encoder), while at the other end it has terminals for connection to the meter of the acquisition board.

a. Diagram of the signal converter b. The printed circuit board

Fig. 4 Signal converter developed with MCP602 containing 2 CMOS Op Amps Impulses recorded by the meter of the acquisition board have been processed using the application developed in LabVIEW and converted into a signal of 0 ... 10 V voltage, which was applied to the PID controller as a positioning signal of the pneumatic cylinder – actual value. The setpoint signal has also been generated within the range 0 ... 10 V, manually or as a step signal using a block for simulation of a rectangular signal.

Fig. 5 Control signal of Festo proportional directional control valve type MPYE

27


According to the theory, the output signal of the PID controller is made of the sum of the terms proportional, integral and derivative.

The output signal of the PID controller has been scaled from the range -10÷10 V to 5 ±5V, because the control signal of the proportional directional control valve is within the range 0...10 V, the 5 V voltage being the center position of the proportional pneumatic directional control valve, as in Fig. 5.

Signals recorded with the help of the data acquisition application have been the ones from the two pressure transducers (bar), from the force transducer between the cylinder rods (daN), the time elapsed (sec), control signal (%), position achieved by the pneumatic cylinder rod (mm), rod speed (mm/sec) and also the signals that PID controller works with (setpoint, actual value, error, PID output) in volts.

4. Test results

We have carried out several tests during which the parameters Kp and Ki have been varied, aiming that the system to respond quickly and be steady.

Fig. 6 Aspect during tests

The first tests were carried out without load type pneumatic spring, the throttle check valves being fully open. The pressure adjusted at the installation regulator has been of 7 bars. To power the transducers there has been used a 24 V laboratory power source. In figure 7 can be seen graphs of the control signal within the range 30÷70% of the total stroke of the cylinder, PID gains being Kp=7, Ki=5. It can be seen that the answer has a large overshoot and the tendency to get into oscillation.

In Fig. 8 is shown the evolution of PID controller signals, also for the test without load, where it can be noticed at the end of the test stationary error of 2.2 %.

28


Fig. 7 Test under no load (Kp=7, Ki=5)

Fig. 8 Signals of the PID controller at testing under no load (Kp=7, Ki=5)

29


At tests with load type pneumatic spring, the pneumatic throttle check valves at the load cylinder have been completely closed. In figure 9 we present the diagrams of the pressure transducers of the two chambers of the pneumatic cylinder under actuation, and diagrams of the force transducer located between the two rods of the cylinders. For the test presented PID gains have been Kp=6, Ki=5. In figure 9 it can be seen that in a direction the force measured is greater, which is due to the difference in areas between the piston sides.

Fig. 9

Fig. 10

30


In figure 10 can be seen the graphs of control signal in the range 10÷90 % and the graph of response of the positioning cylinder rod. Because of the load the system can not accurately track the control signal, there being a stationary error of 10 % that can also be seen in Fig. 11, which shows variation of the signals from the PID controller.

Fig. 11

5. Conclusions

This system enables us to test the response to step signal for a pneumatic cylinder positioning system.

The system enables the tuning of the PID controller in order to obtain an optimal response of the system.

By means of the data acquisition system there can be displayed variation of the signals of interest, and these signals can be registered for further processing.

REFERENCES

[1] M. Avram, V. Banu, C. Bucsan, D. Duminica, V Gheorghe, L. Bogatu, “Mechatronic approaches of pneumatic positioning units“, Proceedings – HERVEX 2009”, ISSN 1454-8003; pp.167-171,

[2] M. Comes, P. Drumea, A. Mirea, G. Matache, Intelligent servohydraulic device for the control of the motion – 24th International Spring Seminar on Electronics Technology ISSE 2001 [3] M. Comes, A. Drumea, A. Mirea, I Enache. , Electronic module for servo hydraulic system with frequency control, MTM 2001, Romania [4] C. Cristescu, P. Beca, G. Vranceanu, D. Dobrin, M. Neacsu, C. Cristescu, “Instalatie pneumatica de

actionare sistem de pozitionare-orientare piesa pentru sistemele tehnologice moderne de prelucrare” Caciulata, Romania; 7-9 November, 2007, “Proceedings - HERVEX”, ISSN 1454-8003; pp. 300-304

[5] http://www.festo.com/cat/ro_ro/data/doc_engb/PDF/EN/MPYE_EN.PDF.

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http://www.festo.com/cat/ro_ro/data/doc_engb/PDF/EN/MPYE_EN.PDF


CONTRIBUTION TO HYDRAULIC TURBINES DRAFT TUBE DESIGN Prof.univ.dr.ing. Mircea BARGLAZAN1, Prof.univ.dr.ing. Ilare BORDEASU2

1 “Politehnica” University of Timisoara, [email protected] 2 “Politehnica” University of Timisoara, [email protected]

Abstract: The paper is devoted to parametric design of reaction hydraulic turbines draft tube. Knowing the hydraulic turbine runner data and location there are determined the draft tube length, cross sections geometry and shape. The efficiency ( recovery coefficient ) of this divergent special pipe in function of geometric and kinematic parameters is established. The analytical formulas obtained are useful for design and local hydrodynamic flow numerical analysis. The obtained design formulas fits for power plants with one or small number of hydro-units or for micro-power-plants.

Keywords: hydraulic turbines, draft tube, geometric and hydrodynamic parameters, draft tube design and optimization

1. Introduction

Draft tube is an important part of the Francis and Kaplan hydraulic turbines. It’s roles are to recover the exit hydraulic energy of the water from the runner and to install the hydraulic turbines in an convenient position ( from economical and non-cavitational point of view). Researches about hydrodynamic flow in draft tubes are present in the last IAHR Symposiums and Conferences ( Beijing 1994, Valencia 1996, Singapore 1998, North Carolina 22000, Lausanne 2002, Stuttgart 2003,..,Timişoara 2010). A lot of books and articles ( authors like N. Kovalev, S. Granovschi, J. Raabe, ed. R. Krishna, J. Giesecke, A. Bărglăzan, and reviews like Trudî VIGM ) give design statistical data and empirical dimensions about draft tube geometry and operation.

List of symbols

D – diameter of draft tube cross section, L- length of the draft tube, h – highness of draft tube diffuser, l – breadth of the draft tube diffuser, α- angle of the draft tube divergence, Δz / D – draft tube relative deepness, β - elbow angle, R – elbow curvature radius, Hs- suction head of the hydraulic turbine, a – runner vertical height in respect of draft tube entrance, b - draft tube exit depth in respect of the tail water level, Δ A / L – gradient of cross section area along the draft tube, v – mean axial velocity of the flow in the draft tube, HT – hydraulic turbine head, Q – rate of flow, p – pressure,

2. Draft tube parameters

The draft tube is a special divergent pipe in which it is necessary to maintain the attached flow inside in order to obtain a good hydrodynamic efficiency. Taking into account the variety of the

32


draft tube parts it is introduced a compromise between its position, divergence degree and length in order to obtain an optimal operation. The draft tube design will be realized with the following assumptions:

- draft tube shape is presented in Fig. 1, and its geometry fits to hydro-plants with one or small number of hydro-units. - divergence gradient of the draft tube cross sections area is constant inside the cone,

elbow and diffuser but different between these parts.

The draft tube geometry and hydrodynamics is considered in the frame of the following parameters:

- the optimal divergence angle of the cone , α1, is accepted from [3] and equal with:

α1 = 6º…8º (1)

- the divergence angle of three faces of the diffuser ( in accord with Fig. 1 ), α3 ,

3 1α α= (2)

- The draft tube deepness, n, the most important parameter after [4] is:

33


1

2...4znD∆

= = (3)

The “n” value is an indirect function of the hydraulic turbine suction head and the local conditions for the position of the hydro-plant. Its value is determined from a technical-economical problem.

A first estimation, from figure 1 dimensions chain and relation (3):

4

1

sH b a hnD

+ − += (4)

Here Hs is evaluated form rel. (8), approximately b = 1 <m> and a first guess is:

h4 = D1 (5)

Nowadays smaller values for “n” are usually used. The draft tube elbow makes the transition from vertical flow to horizontal flow and the change from a circular cross section to a rectangular section. The degree of cross section distortion, Y, is defined:

3

2

0,5hYD

= (6)

- the curvature angle of the elbow, β, is usually 90º but can be also greater.

The flow velocities ratio from exit to entrance of the draft tube, B, is established in function of the estimated performances attended from the hydraulic turbine. So:

4

1

1 1...4 5

vBv

= = (7)

- the suction head of the hydraulic turbine, Hs after [1] is:

at vsi T

sT

p p HgH

H

σρ−

− ⋅⋅= (8)

Knowing the atmospheric pressure, pat, the saturation pressure of the water vapour, pvs, which is a function of liquid temperature, the critical cavitation coefficient of the hydraulic turbine, σi , and the turbine head, HT, the suction head is possible to be calculated. Other variants of draft tubes like one with a leg inside the diffuser and/or unsymmetrical diffuser are easy adapted to the above conditions and developments.3. Draft tube parameters calculus

The length of the draft tube is:

12 23 34dtL L L L= + + (9)

From Fig. 1 the cone length, L12, is determined through the relation:

312 2

hz L R∆ = + + (10)

34


considering also

12 1 12 1 1

1

1 2 ( )2 ( )1 (2 ) ( )

n tgD D L tg Dw Y tg

ααα

+ ⋅ ⋅= + ⋅ ⋅ = ⋅

+ ⋅ + ⋅ (11)

and with relations ( 3) and (4) results:

( ) ( )12 11

21 2

Yn wL D

w Y tg α

− + = ⋅+ ⋅ + ⋅

(12)

The cone cross section gradient, x, is:

2 221 2 1

12 124A D Dx

L Lπ∆ −

= = ⋅ (13)

The mean elbow length, L23, has the formula :

123 1

1

1 2 ( )1 (2 ) ( )

n tgL R w Dw Y tg

αβ βα

+ ⋅ ⋅= ⋅ = ⋅ ⋅ ⋅

+ ⋅ + ⋅ (14)

Obtained from the curvature radius:

R = w·D2 (15)

Often value is w = 1.

The divergence degree, x , calculated with the help of relation (13) results:

( )( )

( ) ( )1

1 11

12

1 2

Yn w tgx tg D

w Y tg

απ α

α

+ + + ⋅ = ⋅ ⋅ ⋅+ ⋅ + ⋅

(16)

The diffuser entrance height “h3”, after relations (3), (10) and (12):

13 1

1

1 2 ( )1 (2 ) ( )

n tgh Y Dw Y tg

αα

+ ⋅ ⋅= ⋅ ⋅

+ ⋅ + ⋅ (17)

Following the indication from [8] the diffuser length is recommended to be:

L34 = (4. . .5)·D1 for radial-axial hydraulic turbines and

L34 = (4…4,5 )·D1 for axial hydraulic turbines.

In the Case Study ( chapter 6 ) the diffuser length is equal with:

L34 = 5·D1 (18)

35


The diffuser exit dimensions are “h4”:

( )4 3 34 3h h L tg α= + ⋅ (19)

And “l4” from continuity equation between the cross sections 1 and 4:

21

444

DlB h

π ⋅=

⋅ ⋅ (20)

The diffuser entrance breadth is:

( )3 4 34 32l l L tg α= − ⋅ ⋅ (21)

So all the parameters of the draft tube are determined. As an application see the Case study results in Table 1.

4. Draft tube efficiency calculus

The efficiency ( recovery coefficient ) formula:

( )2 21 4

21

2 dtdt

v v g hv

η− − ⋅ ⋅

= (22)

expresses this quality criteria as a dependence from entrance axial velocity, v1 ,exit velocity, v4 , and the hydraulic losses, hdt , of the draft tube. Entrance velocity is a function of hydraulic turbine runner and rate of flow. Exit velocity from the draft tube is accepted v4 = 1...2,5 <m/s> in order to obtain high recovery coefficient [8]. The draft tube losses are composed from the con losses, hc , the elbow losses, he ,and the diffuser losses, hd . So:

hdt = hc + he + hd (23)

Using formulas given in [3], [5] and [24]:

- the cone losses are:

( ) ( )24 2 4 2

1,2512 1 1 1 21

1 2 2 2

1 3,2 18 sin 2c

D D D vh tgD D D g

λ αα

= ⋅ − + ⋅ ⋅ − + ⋅ ⋅ ⋅

(24)

- the elbow losses may be approximated:

2' ' '

2m

e evh a b c

gς= ⋅ ⋅ ⋅ ⋅

⋅ (25)

with the loss coefficient ςe = 0,73 : for R/D2 = w =1 corresponds a’ = 0,3 ; for β = π / 2 , b’ = 1 and for l3 / b3 = 2 , c’ =0,4.

36


The mean velocity of the flow, vm:

2 3

2mv vv +

= (26)

and from rate of flow definition:

2 22

4 QvDπ⋅

=⋅

(27)

respectively

33 3

Qvl h

=⋅

(28)

The diffuser losses, considering the conical approximation for its geometry, is:

( ) ( )

2 2 2 21,2534 3 3 3 3 3 3 4

33 4 4 4 4 4 4

1 3,2 18 sin 2d

l h l h l h vh tgl h l h l h g

λ αα

⋅ ⋅ ⋅ = ⋅ − + ⋅ ⋅ − + ⋅ ⋅ ⋅ ⋅ ⋅ ⋅

(29)

For numerical calculus

0412 34 1 3

12 2 2

2 1 1 2

1 2 1 2 3 3

2

3 3 3 322

4 4 1 2

; 0,02 ; 6 ;

1; 12 4

4

m

v Bv

vv D D Dv D v D l h

l h l hDBl h D D

λ λ α α

π

π

= = = = =

⋅= = ⋅ ⋅ + ⋅ ⋅

⋅ ⋅ ⋅= ⋅ ⋅ ⋅ ⋅

(30)

The results are given in Table 2 With these data it is possible to establish the draft tube recovery degree.

5. Cavitation verification

Knowing all the before mentioned data it is possible to verify the hydro-unit ( vertical ) position is correct from cavitation point of view in respect of the tail water level.

312 42 s

hb L R a H h= + + + − − (31)

If the condition of the hydraulic turbine good operation : b = 1 <m> is not fulfilled there are one of the next possibilities : to modify “n” or “L12”, eventually “R” or “β “ or “α3”.

37


6 . Case study Table 1

β = 90º ; B = 1 / 5 ; w = 1 α1 6º ( 0,1047 rad ) 10º ( 0,1745 rad ) n 2 4 2 4 Y 0,5 0,7 0,5 0,7 0,5 0,7 0,5 0,7

D2 / D1 1,1248 1,1064 1,4578 1,4339 1,1836 1,1553 1,6730 1,6331 L12 / D1 0,5939 0,5063 2,1778 2,0640 0,5206 0,4404 1,9087 1,7954 L23 / D1 1,7669 1,7380 2,2899 2,2524 1,8591 1,8147 2,6280 2,5652 x / D1 0,3508 0,3478 0,4058 0,4018 0,6047 0,5969 0,7402 0,7292 h3 / D1 0,5624 0,7745 0,7289 1,0037 0,5918 0,8087 0,8365 1,1431 l3 / D1 2,5587 2,7579 2,0780 1,5170 2,4637 1,8923 1,8322 1,3025

L34 / D1 5 5 5 5 5 5 5 5 h4 / D1 1,0879 1,3 1,2544 1,5292 1,1173 1,3342 1,362 1,6686 l4 / D1 3,6097 3,0207 3,129 2,568 3,1547 2,9433 2,8832 2,3535

If some of the restrictions of the results aren’t fulfilled a possibility is to modify “B”. Table 2

B ηdt w = 1 β = π / 2 n = 2 Y = 0,5 α1 = 6º L34 = 5·D1

1/5 0,8813 1/6 0,8964 1/7 0,9055 1/8 0,9114 1/9 0,9154 1/10 0,9183

7. Conclusions

The draft tube parameters permit to characterize in an unique analytical mode this hydraulic turbine element. There was established formulas like : (10), (11), (15), (17), (18), (19), (21),(24) and ( 25) which enables to calculate the geometrical parameters of the draft tube.With the relation (29) it is possible to maximize the draft tube recovery coefficient knowing the cost of draft tube erection. Despite the flow inside the draft tube is far of being uniform but more and more irregular during the evolution in the draft tube, the method developed in the issue is a good start – in the assumed hypothesis – for design and analysis of the draft tube. These results - obtained by case study chapter – are the base for local flow analysis through numerical methods for turbulent streams.

References

[1] A, Bărglăzan, Maşini hidraulice, ed. I.P. Timişoara, vol.1,vol. II, 1952. [2] M. Bărglăzan, Turbine hidraulice şi trasmisii hidrodinamice, ed. Politehnica Tmş. 2000 [3] B. Nekrassov, Cours d’hydraulique, ed. Langue Etrangeres, Moscou, 1980. [4] P. Henry, Turbomachines hydrauliques, Press Polytechniques Lausanne, 1992. [5] P. G. Chiselev, Indreptar pentru calcule hidraulice, ed. Energetica, Bucureşti, 1953. [6] J. Raabe, Hydropower, VDI Verlag, Dusseldorf, 1986. [7] V. V. Barlit, Ghidravliceschie turbinî, Izd. Vîşcia şcola, Kiev, 1977. [8] ed. R. Krishna, Hydraulic Design of Hydraulic Machinery, Avebury, Aldershot, 1997. [9] J. Giesecke, ..,Wasserkraftanlagen, Springer, Heidelberg, 2009. [10] N. M. Şciapov, Vîgodneişaia dlina otsasîvaiuşcei trubî ghidroturbin, Trudî VIGM XXIII, Maşghiz, Moscva, 1959. [11] I. E. Idelcic, Îndrumător pentru calculul rezistenţelor hidraulice, ed. Tehnică, Bucureşti, 1984. [12] N. N. Kovalev, Ghidroturbinî, Izd. Maşinostroenie, Leningrad, 1971 [13] L. Ia. Bronstein, .., Spravocinic constructora ghidroturbin, Izd. Maşinostroenie, Leningrad, 1971. [14] S. Granovschi, .., Construcţii i rasciot ghidroturbin, Izd. Maşinostroene, Leningrad, 1971

38


FORMING ECO-RESPONSIBLE BEHAVIOR OF FUTURE ENGINEERS BASED ON THE STUDY OF CARBON FOOTPRINT

Ph. D. Eng. Olimpia GHERMEC*, Ph. D. Eng. Cristian GHERMEC*

*University of Craiova, Faculty of Mechanics, Department of Engineering and Management of the Technological Systems, Drobeta Turnu Severin, Romania, [email protected]

Abstract: One of the major problems of humanity is represented by the climatic changes caused by the anthropogenic impact on the environment. Calculating carbon footprint for an activity or for a process is important in the conscious action of fighting global warming by reducing the emission of GHG. Studying carbon footprint (individual, for system or for activity) by the students from the technical education puts them in the situation to analyze the relationship between the environment and their own activity on the one hand and on the other hand of industrial processes and activities, from the point of view of GHG emission. Keywords: carbon footprint, global warming, greenhouse gases emissions

1. Introduction

Scientific research in the field have shown both the causes, linked especially with greenhouse gases (GHG), and the strategies which must be applied in order to prevent the process of global warming as the main vector of the climatic changes [2]. Successfully applying the strategies in the domain requires the awareness of the entire society which can be made through cultivation, training and education. The Law on National Education from January 5, 2011, stipulates at article 4: ‘The education and the training of children, youngsters and adults have as main finality forming skills which are understood as a multifunctional and transferable assembly of knowledge, abilities and skills necessary for… employment and for participating at the functioning and the development of a sustainable economy.’ In this context, the skills developed during the training programs of an engineer, regardless of his/her specialty must also have in view the sustainable usage of resources, eco-friendly technological processes, sustainable production, ecological design, sustainable consume and the life cycle of products.

2. The concept of carbon footprint

A carbon footprint has historically been defined as ‘the total set of greenhouse gas (GHG) emissions caused by an organization, event, product or person.’ However, a more practicable definition has been suggested, and namely : ‘A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest.’ [3]. The carbon footprint expresses greenhouse gases by converting them into an equivalent amount of carbon dioxide (CO2 equivalent or CO2e), based on the relative global warming impact of each gas. The standardized definition of this parameter can be found in the ISO 14064-1: 2012 standard [7].

3. The calculus and the interpretation of carbon footprint The calculus of carbon footprint, as it is suggested by the definition, can be made both in personal or familial domain and in all fields of activity: enterprise, company, corporation, authority or

39


institution [5]. Engineers activate in all these domains. Depending on the domain and the study program, they master in technical superior education professional and transversal skills which can ensure a successful career and mobility on the labor market. Due to the fact that sustainable development has become a worldwide priority both in economic and social areas, the technical university curricula should deepen this subject, especially because the industry and the services have such an important anthropogenic impact [8]. 3.1. The usage of the case study in calculating carbon footprint In order to pass from general to particular and given the life and professional experience of students, the first application in calculating carbon footprint is recommended to be the individual or familiar calculus. In this regard there can be accessed on – line programs which require from the student pieces of information regarding the structure of the family, the endowments of the house and the degree of comfort established individually or with the family, the manner of spending the free time or the holidays etc. The student is thus made knowledgeable in a series of pieces of information regarding household consumption, the consumption of electricity and the consumption of fuel for transport. It is preferable that this study be realized for a period of 1 year. 3.2. Phases in the calculation of carbon footprint of a productive activity This study can be realized in the period of student practice in different industrial organizations. The period for which the calculus is effectuated is indicated to be of one year. In order to form the ability of calculating carbon footprint, for the beginning processes or activities with reduced complexity are chosen, which eases the data interpretation and the establishing of a coherent action plan in order to decrease the emission of CO2e. Step 1. Establishing the field of study For the results to be accurate, in a first phase a limitation of the field of study should be realized. In this regard, there can be made an approach based on the process with which the students are familiar from ISO 9001:2008 Standard - Quality management systems - Requirements: ‘An activity or set of activities using resources, and managed in order to enable the transformation of inputs into outputs, can be considered as a process. Often the output from one process directly forms the input to the next’. For the same purpose, environment aspects with impact from the point of view of GHG will be established thus applying the knowledge gained from the study of the International Standard for Environmental Management Systems EN ISO 14001:2004. The process selected as being relevant for the study will be added with the emissions of equivalent CO2. Step 2. Calculating the emissions of CO2e 2.1. Establishing the types of GHG emissions GHG emissions are classified as [7]: a) Direct GHG emissions which are specific to the processed which release GHG into the atmosphere; b) Indirect energetic GHG emissions from the process of generating imported electricity, heat of steam consumed; c) Other indirect GHG emissions: coming from the production of purchased raw materials or of basic materials, employee transport and which are generated in the usage phase or the final phase of the life cycle of products and services. Given the complexity of the field and in order to apply the acquired experience during the case study, emissions will be calculated for categories b, respectively c. 2.2. Selecting the methodology of quantification For the categories of emissions analyzed it is chosen the calculus method based upon the quantities consumed for the analyzed process. For indirect energetic GHG emissions from the process of generating imported electricity, heat of steam consumed: based upon the 2006/32/EC Directive from April 5, 2006 regarding the energetic efficiency at final users and the energetic services, from annex II, it is established the energetic amount of the fuels which are selected for final usage based upon the conversion table (table 1). Students can create their own work documents or to use the following model, in which kWh was selected as measurement unit.

40


In the category of other indirect GHG emissions (c) are usually enlisted those coming from the automobile park of the organization, being taken into consideration their route in km of those which are useful for the process. Table 1. The conversion of the type of fuel in kWh

Type of fuel Consumed quantity Units Units x Conversion factor

( kWh per unit) Total kWh

Natural gas kg m3 x 13.1 kWh/kg 7.85 kWh/m Liquefied petroleum gas (LPG) kg L x 12.78 kWh/ kg 7.65 kWh/L

Coal kg x 6.65 kWh/kg Associated petroleum gas (APG) kg L x 11.75 kWh/kg 9.87 kWh/L Wood, moisture 25% kg x 3.83 kWh/kg Wood pellets/ Wood briquettes kg x 4.67 kWh/kg

TOTAL (Source: www.iuses.eu/materiali/ro/.../Exercitiu_complex_pe_energie) 2.3. The quantification of GHG emissions For the category of indirect energetic emissions (b) the entry data are obtained either from the bills sent for the respective fuels or from the material or energetic balance of the respective activity. For the quantification of the CO2 emission, the consumption is amplified with the respective emission factor (table 2). For the category of other indirect GHG emissions, the route in km is multiplied by the value of CO2 emissions from the Certificate of Registration of the Vehicle or with the value resulted from consulting, for example, the site http://www.servicii-inmatriculare.ro/emisii-co2-calculator/. Table 2. Quantifying indirect GHG emissions

Type of energy Energy

consumption, kWh

x Emission factors Emissions CO2,

kg/kWh CO2e,

kg/kWh CO2, kg

CO2e, kg

Electricity from National Electro-Energy System x 0.5108 0.5387 Natural gas x 0.2019 0.2178 Liquefied petroleum gas (LPG) x 0.2271 0.2440 Coal x 0.3459 0.3470 Associated petroleum gas (APG) x 0.2786 0.2800 Other fuels x

TOTAL (Source: www.iuses.eu/materiali/ro/.../Exercitiu_complex_pe_energie) 4. Results and discussion The obtained results will be compared with the values from specialty literature in order to appreciate the length the measures to reduce carbon footprint should have had [1]. The target should take into consideration the commitment of Romania to reduce greenhouse gases at the level of 2020 with a percentage of 20% as compared with the level of emissions in 1990 [6]. The first measures can emerge from the deduction of the consumption of electric energy on consumers and its pie chart type representation.

41


The proposals will be synthesized according to table 3. Measures will relate to different types of uses of thermal or electricity power. The measures to reduce carbon footprint must be in correlation with the dynamic of the process and must be within the limits of economic efficiency. Table 3. Proposals to reduce carbon footprint

5. The eco – responsibility of future engineers with the aid of carbon footprint Studying carbon footprint (individual, for system or activity) by the students from technical education puts them in the situation to analyze the relationship between the environment and their own activity on the one hand and on the other hand of industrial processes and activities, from the point of view of GHG emissions. The study of the influence of GHG on the process of global warming and processing a sufficient amount of data regarding the sources that generate GHG emissions leads to an approach through knowledge, understanding, explanation and interpretation of this phenomenon. Using methods, techniques and instruments of investigation and application that are specific to carbon footprint results in the rise of the awareness of the role that the engineer plays in the process to fight climatic changes. The proposals of measures to reduce carbon footprint must be the result of a brainstorming debate thus ensuring the participation to the individual professional development. Students ought to be encouraged to apply innovative solutions [4]. Principles as ‘the polluter pays principle’ or ‘extended producer responsibility’ are better understood and at the same

Type of energy Usage

Proposed measures Economy %

Saved energy,

kWh

CO2 prevented,

kg

Thermal

Heating Modernization industrial ventilation systems 25 Improvement of the thermal isolation of the buildings 10

Assemblage of windows with double glass 5 Assemblage of an isolating adherent tape at doors 10

Assemblage of devices to close entrance doors 5

............

Electricity

Lighting and Equipments Replacing the incandescence lamps with fluorescent lamps 15

Turning off interior lights during the night 5 Closing the monitors of the computers when they are not used 2

Putting the computers in ‘sleep’ mode when they are not used 2

Control office lighting with timers and motion sensors 5

......... Consumption of hot water

Assemblage of solar panels 30 .........

42


time increase the personal responsibility in approaching scientific problems which are current and of perspective. In this process a major role is held by the university teacher who coordinates such a study because he/she must have skills in the field of environmental protection in industry.

6. Conclusions

Calculating carbon footprint for an activity or a process is important in the conscious action of fighting global warming by reducing GHG emissions. In order to be relevant, carbon footprint is calculated periodically, preferably at intervals of one year. The measures to reduce carbon footprint must be adapted to the analyzed process and their effect must be quantified. For future engineers this is an application which reflects the anthropogenic climate change through the emissions of GHG which can be quantified in CO2e. The coordinator of this study accommodates the students with data collecting regarding the schedule and the planning of production, the control of the consumption of raw materials, of materials and of energy. Using methods, techniques and instruments of investigation and application which are specific to carbon footprint lead to the awareness of the role the engineer plays in the process of fighting climatic changes.

REFERENCES

[1] I., Purica, C., Uzlău, S., Dinu, “Impact assessment to reduce emissions of greenhouse gases on the Romanian economy using technological relationships and interdependencies between branches “, Economical Publishing House, Bucharest, 2012

[2] A., Aichele, G., Felbermayr, „Kyoto and the carbon footprint of nations”, „Journal of Environmental Economics and Management”, ISSN: 0095-0696, Volume 63, Issue 3, 2012, pp 336–354

[3] P., Konieczny, R., Dobrucka, E., Mroczek, “Using carbon footprint to evaluate environmental issues of food transportation”, “LogForum” 9 (1), pp. 3-10, 2013, http://www.logforum.net/vol9/issue1/no1

[4] F., Negoescu, E., Axinte, Gh., Nagîţ, A., Iosub, „Innovative solutions creates environmental advantages”, „Environmental Engineering and Management Journal”, 8, 2009, pp. 1191 – 1197 [5] D., Pandey, M., Agrawal, J. S., Pandey, “Carbon footprint: current methods of estimation”, “Environmental

Monitoring and Assessment” ISSN: 0167-6369, 178, pp.135–160, 2011 [6] C.E., Report from the Commission to the European Parliament and the Council. Progress towards

achieving the Kyoto and EU 2020 objectives, Bruxelles, 2013 [7] EN ISO 14064-1:2012 Greenhouse gases - Part 1: Specification with guidance at the organization level

for quantification and reporting of greenhouse gas emissions and removals [8] http://www.rare.fr/cahiers_observation_GES/index.html, Territorial Energy Climate Tools-RARE-ADEME,

Introduction to the practice of observation of greenhouse gases, Technical Manual No.1, 2011

43


THE IMPACT OF THE MINING ACTIVITY ON THE ECONOMIC SECTOR, HUMAN HEALTH AND ENVIRONMENT

Lecturer PhD.Ec. Oana DAVID1, PhD.Ec. Maria Valia MIHAI2, PhD.Ec. Sanda MAIDUC (OSICEANU)3 1 University Politehnica of Bucharest, [email protected] 2 Petroleum-Gas University of Ploiesti, [email protected] 3 University Politehnica of Bucharest, [email protected]

Abstract: It is estimated that the EU's energy mix will still rely heavily on fossil fuels, including coal, and the countries of Central and Eastern Europe, coal will be the main pillar of energy security, even to the year 2035. Therefore, this paper aims to capture the efforts made by the Romanian state in an attempt to streamline existing coal mines and close them those that were no longer profitable, showing the impact of the economic sectors in terms of the economic, social and natural.

Keywords: dust, coal, occupational disease, environmental degradation, environmental restoration.

1. Introduction

Everything started a long time ago for many areas in Romania that used to hold coal deposits. Back then, there was a hill that turned later into a coal mine and, after many years of exploitation, it reached the shape of a valley. This deposit has had a significant meaning for that area, having both an advantage and also a disadvantage. On the one hand, mining has brought employment in the area, thus contributing to the development of this area from an economic perspective but, on the other hand, it has damaged the environment and the health of the residents. Among the areas in Romania that used to and still have coal deposits are Valea Jiului (Petrila, Uricani, Paroseni, Aninoasa, Lonea, Livezeni, Vulcan, Lupeni), county of Brasov (Codlea), county of Covasna (Bodos, Baraolt), county of Bacau (Comanesti), county of Arges (Cotesti) etc. Of all these mines, the following are still operating: Valea Jiului - Petrila (until the end of 2015), Uricani and Paroseni (until the end of 2017), Lonea, Livezeni, Lupeni, Vulcan. The others have been closed, such as Comanesti (county of Bacau) in 2005, Mina 1 Mai in Codlea (Brasov County) in 1961, Bodos and Baraolt Mines in the county of Covasna, Cotesti Mine in the Arges County in 2002. In Copsa Mica, lampblack has been produced for years on end, made from charcoal and used in the rubber processing, manufacturing the printing ink and some black paints. As a consequence of this economic activity, both the environment and the people were contaminated and harmed. In time, the coal mines have been depleted from their resources, a reason for which the mining activity has required a significant financial aid from the Romanian Government. Similarly, these areas have been confronted with a surging number of unemployed people, an increase in the poverty level of the residents. The health condition of those people has worsened and many profession-related diseases have emerged, due to this economic activity.

2. Content paper

The closing of the mines has triggered a considerable damage to the environment. In some areas, though, this operation has been done via environment-friendly methods, which means that the vicinities of the mine are clean and not polluted with toxic waste. This has been possible by a World Bank project that had the mining villages overcome their condition.

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The main purpose was to close the mines, thus having a minimum impact upon the environment. Finances have also been provided for improving the infrastructure and the services for the former mine workers and their families and for creating more employment places. The general objective of the Government Strategy for the mining sector 2004-2010 was to turn the mining industry into a lucrative sector and to support the economic increase, as well as a durable existence in the mining regions in Romania, with the purpose to assist the economic integration of Romania into the EU. The mining strategy approved by the Government in April 2004 aimed to wipe out all the subsidies granted to the state mines of minerals and metals until 2007 and for the coal mines until 2010. A number of over 20 mines were successfully closed between 2005 and 2010. Their closing affected circa 650,000 people, who were later helped with services of professional conversion and programs of creating employment. Due to its nature, the entire mining activity triggers multiple and various negative effects on the environment, such as:

– Changes in the landscape, manifested by the degradation of the scenery and relocation of the households and of the industrial objectives in the exploitation areas;

– Occupancy of large areas of land for the exploitation activity, stockpiling, storage of the useful mineral substances, industrial equipment, access roads, etc, surfaces that thus became useless for other purposes, for long periods of time;

– Degradation of the land, by vertical and horizontal slides of the surface and the drifting of the dumps and of the drainers, leading to serious accidents;

– Contamination of the surface running waters and of the ground waters; – The hydrodynamic imbalance of the underground waters; – Negative influences on the atmosphere, flora and fauna in the area; – The chemical pollution of the land that can lead to its loss of fertility; – Noises, vibrations and radiations spread in the environment, with a strongly unfavorable

action; The impact of the mining industry upon the environment can be described in a nutshell, via the following features that are relevant for this economic branch:

– The mining projects should include stipulations regarding the preservation of the biodiversity;

– The reduction to minimum of the derived waste, from production and consumption, which will contribute to the prevention of generating waste and to the reuse, recycling and transformation of the waste into products;

– Improvement of the recycling process and of the reuse of water and other natural resources;

– The implementation of the European legislative framework at the national level for the mining industry with the purpose to design the storage equipment, of decantation and management of waste, of closing, post-closing and reparation of the abandoned mining sites, so that they will have an ignorable risk for the public health, environment and also a low social and environment effect during the operation and after closing.

The exploitation of the coal deposits has also a significant impact upon the health of the people working and living in the areas of these deposits. The mining activity leads to the ground pollution, of the water and to building residues in the atmosphere. The air pollution has harmful effects upon health, from minor breathing symptoms for short periods of time to increasing of mortality and morbidity (mainly in breathing), in association with longer episodes of a higher or sustained exposure to this contamination. To prevent the decay due to the exposure of the population to various pollutants in the atmosphere, prophylaxis is the key. To this purpose, there should be focused on maintaining the concentration of the toxic substances in the environment under the maximum admitted value, in accordance with the current legal norms. The respiratory system is the most vulnerable to the pollutants in the atmosphere and to the toxic stimuli in the air (allergens and the cold air). The breathing apparatus comprises superior airways (nose, pharynges and larynges) and inferior airways (trachea, bronchi and the lung alveoli). The trachea, the bronchi and the lungs are intrathoracic internal organs that have a direct

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communication with the atmosphere and the exterior world, due to their tubular shape, and they are exposed to the action of the existent pollutants in the air. The most frequent maladies of the respiratory system, triggered by the atmosphere pollution, are coughing and bronchoconstriction, tracheitis, bronchitis, asthma, chronic obstructive lung disease, pulmonary abscess, pneumonias and bronchopneumonia, pneumoconiosis and lung tumors. While considering the chronic effects of the irritant atmosphere pollutants, they need to be looked at from the perspective of long-term exposure (5-10 years) at relatively high concentrations. The pathology due to the atmosphere pollution holds an important place in the evaluation of the impact upon the health condition. It is unavoidable and absolutely normal to have the health of the population depend on the quality of the environment factors (air, water and ground), which indirectly or directly affect the human health. The air pollution is a major factor in triggering such disorders. The irritating ability of the powders in suspension increases when there are other disturbing pollutants for breathing in the air (SO2 and NO2, thus having the synergistic effect manifested between SO2 – powders in suspension and NO2 – powders in suspension. In the areas that register higher admitted limits of concentration (the powders in suspension, mainly the ones with micron and sub-micron dimensions), the respiratory system of the children is firstly affected, by leading to pneumonias, bronchitis, asthma or emphysema; their eyes can be irritated (conjunctivitis) and so can their skin. These powders are able to reach the respiratory apparatus to the alveolar level, where there are no specialized mechanisms to dispose of them. The soluble particles will be directly absorbed into the circulation and the indissoluble ones are embedded in the macrophage, responsible with the chronic inflammation, associated with the release of intracellular mediators of the inflammation that will raise the blood viscosity and the coagulability, thus making it possible for vascular accidents or decompensation of preexistent cardiac insufficiencies. The agents in the particles as carbon, coming from coal burning, have been posing a problem in the air pollution for many hundreds of years. The air pollution parameter that is the closest linked to the increase in the decay or mortality rate is the concentration of breathable particles. The atmosphere pollution based on powders has a stronger effect upon the human health than the one directly derived from the polluting gases. According to the definition provided by the World Health Organization, ‚the professional diseases are affections whose specific etiological agents are present at the employment place, associated with certain industrial processes or with the performance of certain professions’. The concept of ‚professional disease’ involves the existence of a causality relation between the risk factors present in the work process and their effect, visible in the emergence of the disease. In Romania, the ‚professional disease’ represents the affection that derives from performing a certain job or profession, caused by toxic factors (physical, chemical or biological), particular to the employment place, as well as by the overstressing of various organs or body systems during the work process. The social impact of the mining activity can lead to the following:

• Increasing the production costs, due to the compulsoriness to provide further conditions of work safety and healthy and environment protection;

• High social vulnerability, from the mono-industrial nature of the area, of the degradation in the financial situation and downsizing, where is no other real economic alternative;

• The dependence of the production on the operation of the thermal power stations; • The lack of a regulated price, close to the production cost; • The lack of funds for an extensive development of the exploitation; • Slim chances of providing the investment demand for the capitalization of the viable mines,

during the present organization system. The mining industry must bring a significant contribution via rents, royalties and other transparent payment methods, to a fair distribution among the earnings of the companies, the local authorities and of the Romanian state. The promotion of the internal resources in the national economic circuit has been one of the items on the Agenda G20. To this perspective, the strengthening of the fiscal regime in the mining sector

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and of the related fiscal policies can build a platform of durable income for the local and national economic growth. The mining activities subscribe to the durable development provided that they generate appropriate and reasonable income. The officials of the mining industry and the state have to cooperate for a strong and balanced fiscal regime, as well as for a good management of the financial resources, required to guarantee long-term benefits.

3. Conclusions

The recent capacity of energy generation for trapping and storing the carbon helps with reaching the objectives of climate protection and supply security. Similarly, the latest emergent technologies of capitalizing the coal deposits (the underground distillation, the methane in the coal layer, etc) can change the significance of the coal in the energetic mix. A modern, efficient and a highly lucrative company has to adopt the most adequate knowledge and technologies, use the best practices and most modern management methods, in order to maximize the economic benefits from the exploitation of a mineral substance, for all the interested parties, including in the ecological reconstruction of the areas affected by mining activities. The supporting of the economic environment in order to lessen the effects of the economic critical situation and to sustainable develop the current economic operators and also to assist with establishing new ones, all these fall into the jurisdiction of the local and central administrations. The work accidents and the professional diseases have a negative impact on all the elements involved in the work system: the worker, the work duty, the production means and the labor environment. In the context of the work process, the human can be perceived from two angles: of a human being and of a worker. Every angle is associated with a series of specific values and features, such as life, health, the anatomical and functional integrity, the creative and affective ability, the work capacity, skills and knowledge. The work accidents and the professional diseases have repercussions on both categories of values, and the consequences are visible in multiple plans:

• psycho-physiological: pain, stress, inability to work, disability, etc; • economic: reduction in the efficiency of the individual work; • financial: income lowering, expenses for medical care.

The direct consequence is the non-fulfillment of the work duties or their untimely (especially for the work accidents), as well as improper performance (for some professional diseases, unless the temporary work inability stage has been reached).

REFERENCES

[1] Fodor D., Baican G., “Impactul industriei miniere asupra mediului”, Publisher Infomin, Deva, 2001; [2] Onica I., “Impactul exploatarii zacamintelor de substante minerale utile asupra mediului”, Publisher

Universitas, Petrosani, 2001; [3] Fodor D., “ Impactul activitatii miniere asupra mediului”, Bulletin AGIR No.3/2006; [4] The Mining Law No.85/2003, updated on 1 January 2012, implemented by rule published in the Monitorul

Oficial I No.772 of 04.11.2003; [5] Popa R.G., Dragut Gh., “Studiu privind efectele pulberilor rezultate din activitatea depozitului de carbune

Rosiuta, asupra populatiei din zona”, Annals of “Constantin Brancusi” University from Targu Jiu, Engineering Series, No.2/2011.

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SOME CONSIDERATIONS ABOUT THE STUDY OF PARTICLES MOTION ON THE CONICAL SIEVES

Dorel STOICA1

1) University Politehnica Bucharest, Biotechnical Faculty of Engineering, Splaiul Independentei, 313, Bucharest, Romania [email protected]

Keywords: conical sieve, oscillation amplitude, vibration parameters, the vibration spectra Abstract. In this paper, the oscillation amplitude is determined by the influence of vibration of conical sieve with experimental measurements for both experimental stand. In order to determine the influence of vibration amplitude oscillations on the grid tapered experimental determinations were performed for both the experimental stand idle and when driving in pregnancy. The amplitude of oscillation was changed by changing the length of the arm fastened to the screen and the proper positioning of the main drive mechanism so that the oscillation is conducted in a direction tangential to the screen, at a distance R (radius of the driving arm in a radial direction of the circle having mesh cone base). With the help of the purchase made and the program developed in LabVIEW were purchased vibration signals to the four accelerometers placed on the surface of the separating grid. Two accelerometers acquires the signal in the direction of the arm, and the other two in a direction perpendicular to the arm about the drive shaft.

Introduction Vibratory movement is applied in practice in many fields, both for the transport of granular and powder products, or even in the form of pieces, as well as to complete the separation process. In addition, the vibratory motion is used to evenly supply the material of the various separation equipment and process, as is the case for the equipment of the harvesting and processing of agricultural products, [4, 6, 8] If machinery for agricultural products, oscillating body of work, its vibratory motion is achieved by switching to a rigid or elastic mechanism with the characteristics prescribed periodic motion, [5, 7] The amplitude and frequency of the working depends on the kinematics of the driving mechanism. Crank mechanism is the most common drive mechanism kinematic vibrating machinery.

Materials and methods

Separation conical surface is made of perforated sheet meal with circular holes diameter φ 4,2 mm and cone diameter at base φ 430 mm. The steel cables diameter is φ 1,5 mm. The acting mechanism provides mostly an alternating circular motion of which amplitude can be measured to the edge of the sieve on both sides of the equilibrium position of oscillation. At this point an arm of length d is connected to the acting mechanism (horizontal oscillating circular saw). The acting mechanism consists of an alternating current electric engine with a power of 710W and a worm-wheel drive with oscillating crank lever acting system. This one has the control button eccentrically disposed on the worm wheel of the transmission mechanism.

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mailto:[email protected]


The oscillating crank lever stroke of the acting system is of 16mm. The slider arm is joined by a spherical joint on the arm stiffened with the sieve and it is laid on radial direction to the base circle of the cone. Scheme of experimental installations is shown in Figure 1.

Figure 1. Experimental stand

The experimental equipment is provided with the possibility to set the oscillating motion parameters namely the oscillation frequency F, and the oscillation amplitude Ai. Oscillation frequency can be changed from the electric motor by varying the electric current parameters. The oscillation amplitude can be modified by changing the position of acting mechanism in relation to the radial arm of the sieve, joined one to the other by a spherical joint, [1]. By the eccentric tangential positioning of the arm joint of acting mechanism to the conical sieve, it develops almost circular oscillations towards the vertical axis of the cone. This motion is assumed to be oscillatory, because the vertical axis of the sieve (its center) was not constrained to move in the direction of the arm joined with the sieve (placed radial at the base circle of the cone). The designed and experimentally developed equipment was used both to determine the vibratory motions of the separation surface (as an agricultural products processing element) and to estimate the material movement on the sieve and the separation and seed crops sorting process efficiency, [3]. Experimental stand is provided with the ability to set parameters, namely the oscillating movement of the oscillation frequency, oscillation amplitude F and Ai. Oscillation frequency can be changed from the electric motor by varying the electric current parameters and the oscillation amplitude can be changed by changing the position of arrangement of the drive mechanism in relation to the radial arm of the sieve. For experimental determinations was used as a chain composed of the following devices: card National Instruments data acquisition, four 4508B Brüel & Kjær accelerometers with magnetic fastening and metal clip, computer software Labview data acquisition and processing; radial arm jointly sieve about the possibility of four-point swing arm ram to obtain four different values of oscillation amplitude, single-phase electric motor speed control can offset and worm gear drive system with swing and slide, To achieve the four measurements used accelerometers were placed two by two diametrically opposed to the center of the filter being able to determine both the direction tangential vibration and the radial direction. Measurements were made both idle and full load for the two directions, both radially (accelerometers 4 and 2), as well as the tangential direction (accelerometers 1 and 3) as shown in the way of settlement accelerometers shown in Figure 2. Four accelerometers were connected to data acquisition card through a computer set with printer for plotting graphs acquired signals.

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Fig.2. Positioning accelerometers Before each sample were appropriately modified kinematic parameters of the oscillating sieve namely that the oscillation frequency of the oscillation amplitude. Signal acquisition was done through LabVIEW, [3], data acquisition was performed before the program structure by which the purchase was made and signal processing. Results and discussions Oscillation amplitude was modified by altering the length of the arm reinforced with mesh and proper positioning of the main drive mechanism, so that oscillations are driven in a direction tangential to the screen at a distance d (radius of the actuator arm radial direction with the circle base of the cone filter).

With the acquisition system developed and the program developed in Labview, vibration signals were acquired at four accelerometers positioned on the dividing surface of the screen. Two accelerometers buy signal on the arm, the other two, in a direction perpendicular to the arm about the drive shaft. Measurements at idle were performed only for the oscillation frequency f2 = 8.6 Hz, three arm lengths of the filter, while the full load measurements were performed with rapeseed three oscillation frequencies (f1 = 4.1 Hz, f2 = 8.6 Hz, f3 = 13.1 Hz) and three different lengths of arm filter (d1 = 480 mm, d2 = 460 mm, d3 = 420 mm). Based on the analysis of acceleration signals acquired and presented table 1 sinusoidal oscillations variation is found for the four accelerometers. This is profoundly visible accelerometer mounted near a site that acquires signal arm tangential direction (perpendicular to the mean position of oscillation of the arm mesh). For idling, amplitude purchased the oscillation frequency f2 = 8.6 Hz, is inversely proportional value with mesh arm length d Thus the accelerometer 1, the amplitude of oscillation reaches maximum acceleration, order of 100 m/s2, the overall oscillation type sinusoidal with minor disturbances related to elastic suspension system and own vibration sieve. The arm length increases, the acceleration amplitude of the filter decreases to below 50 m/s2 at an arm length of 480 mm with deeper overall vibration disturbance superimposed oscillation.

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Table 1. Analysis of acceleration signals

Table 2. Load variation acceleration filter F2 = 8.6 Hz frequency for three different lengths of arm drive

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At the accelerometer 3 signal acquiring all three of the tangential direction (perpendicular to the arm mesh) but found a greater distance from the point of operation, general oscillation, although it is obvious sinusoidal type, is not as pronounced as the accelerometer 1, being more flattened, but in this case, acceleration amplitude of oscillation, decreases with increasing arm length filter, the average value of about 100 to below 50 m/s2 m/s2 for arm length of 420 mm. It also notes the existence of interference oscillations caused by factors other than printed oscillation mechanism. At 2 and 4 accelerometers that acquires signal radial direction (ie parallel to the arm mesh) located at about the same distance from the point of operation, sinusoidal oscillations general are not as visible as the 1 and 3 accelerometers and vibration disturbance are more pronounced.

CONCLUSION Conditioning technologies are quite different when it comes to the final destination of seeds under some specific operations are present in the flow conditioning technology and new ones may be added depending on the physico-mechanical properties of seeds and special needs conditioning. Separation of mixtures of seed foreign bodies is based on differences in physical characteristics of seeds and foreign material (size, aerodynamic properties, coefficient of friction, elastic properties, shape, density, color, etc). Separation surface oscillations is characterized by its basic parameters: oscillation frequency and oscillation amplitude, must be considered and other parameters relating both to process and the characteristics of the material to be machined: the angle of the site coefficients friction, optimal speed and speed limit imposed screening passes through interactions between particles, interactions with surfaces sifting energy consumption in processing, size and shape hole separation. REFERENCES

1. Magheţi I., Voiculescu L. – Elemente de mecanică aplicată, Editura Printech, Bucureşti, 2000 2. Voinea R., Voiculescu D. – Vibraţii mecanice; I.P., Bucureşti: 1979 3. Dumitrache I., Dumitriu S., ş.a. – Automatizări electronice; Editura Didactică şi Pedagogică, Bucureşti,

1993. 4. Stoica D. Contribuţii la studiul fenomenelor vibratorii privind utilajele din domeniul prelucrării produselor

agricole (Teza de doctorat, 2011) 5. Voicu Gh., Stoica D., Ungureanu N. - Influence of oscillation frequency of a sieve on the screening

process for a conical sieve with oscillatory circular motion, lucrare acceptată şi în curs de publicare în Journal of Agricultural Science and Technology, ISSN 1939-1250, USA June. 2011, Volume 5, No.2 (Serial No.27)

6. Voicu Gh., Stoica D., Ungureanu N., Plosceanu B., Workflow and on the efficiency of a conical suspended sieve with swinging movement, Proceedings of 3rd International Conference „Research people and actual tasks on multidiciplinary sciences”, Lozenec, Bulgaria, 2011;

7. Stoica Dorel, Rusanescu Carmen Otilia, Research On The Influence Of Vibration Frequencyon A Conical Sieve Suspended – Metalurgia International,vlo.XVIII (2013), nr.3, ISSN 1582 – 2214, pp 84-86, Bucuresti,

8. STOICA Dorel, VOICU Gheorghe, RUSĂNESCU Carmen Otilia - Influence of vibration amplitude oscillations on the conical sieve suspended, Univesity og Agricultural Sciences And Veterinary Medicine Cluj Napoca “The 11TH International Symposium Prospects for the 3RD Millennium Agriculture”, Print ISSN 1843-5246; 27-29 septembrie 2012, pp 173- 177, Electronic ISSN 1843-5386

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CAVITATION EROSION RESISTANCE OF AMPCO 45 BRONZE WITH HEAT TREATMENTS

Prof.univ.dr.ing. Ilare BORDEASU1, Prof.univ.dr.ing. Mircea Octavian POPOVICIU2, Prof.univ.dr.ing. Ion MITELEA3, Asist.dr.ing. Lavinia Madalina MICU4,

Dr.ing. Octavian Victor OANCA5, Ing. C-tin BORDEASU6, Drd.ing.Laura Cornelia SALCIANU7, Drd.ing. Cristian GHERA8

1 “Politehnica” University of Timisoara, [email protected] 2 Academy of Romanian Scientists, Timisoara Branch, [email protected] 3“Politehnica” University of Timisoara, [email protected] 4“Politehnica” University of Timisoara, [email protected] 5“Politehnica” University of Timisoara, [email protected] 6“Politehnica” University of Timisoara, [email protected] 7“Politehnica” University of Timisoara, [email protected] 8“Politehnica” University of Timisoara, [email protected]

Abstract: Cavitation erosion of ship propellers is a great inconvenient for maritime transportation. The use of proper alloys and heat treatments can increase the life of these pieces. In the paper is analyzed the effect of such a heat treatment upon the bronze AMPCO 45, used in the past especially for aircraft bearings, valve spindles and wear rings. Paper analyzes if it can be also applied for ship propellers, a field in which outside corrosion it appear also cavitation. In order to increase the hardness of this material a special heat treatment was applied. AMPCO 45 with and without heat treatment was subjected to vibratory cavitation erosion in the T2 device in the Cavitation Laboratory of Timisoara Polytechnic University. The final evaluation was realized through comparisons with the bronze CuNiAl- III RNR, used on a large scale for manufacturing ship propellers. Finally, it was demonstrated that AMPCO 45 has excellent properties from the cavitation erosion point of view.

Keywords: cavitation erosion, bronze, volume heat treatment, hardness, cavitation mean depth erosion, cavitation mean depth erosion rate

1. Introduction (Arial, 11pt, Bold)

For increasing the cavitation erosion resistance frequently is used heat treatment, for the entire mass of the machine detail. This procedure increases all the mechanical characteristics and especially the hardness. On the other hand, Garcia and Hammitt [4] established that the increase of hardness is a key factor for fighting with cavitation erosion. Consequently the present paper analyzes the case of the bronze AMPCO 45. Using an appropriate heat treatment the HV3 hardness of this material was increased with 20.64%. Afterwards this material was carefully examined in the laboratory station T2 form the point of view of the resistance to cavitation and the results were compared with those of the bronze CuNiAl – III RNR a material frequently used for manufacturing ship propellers. Comparing the curves MDER(t) in the stable zone of erosions resulted that untreated AMPCO 45 is 1.8 times weaker than CuNiAl- III RNR but after the heat treatment the resistance to cavitation erosion of AMPCO 45 became 1.2 times better than CuNiAl – III RNR.

2. Researched material and applied heat treatment

The tested material is a bronze with CuNiAlFeMn with the commercial name AMPCO 45. The detailed chemical composition is [13]: Al 10%, Ni 5%, Fe 2,5 %, Mn 1,0 %, others 0.5%, balance Cu and the following mechanical properties [13]: tensile strength Rm=814 MPa, yield point 517

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MPa; Rockwell hardness HRB30= 98; Fatigue limit (100,000,000 cycles) 262 MPa, Density ρ = 7,53 g/cm3. The detailed heat treatment is given in Fig. 1 and consists in heating at 890°C followed by cooling in water and a second heating at 520° C followed by cooling in air

Fig.1 Heat treatment diagram

The hardness measurements after the heat treatment are presented in Table1 and show important increases in comparison with the untreated material.

Table 1 Hardness HV3

AMPCO 45 heat treated AMPCO M45 original state Depth [µm] HV3 Mean

HV3 Depth [µm] HV3 Mean

HV3 161 294

298

145 265

247

159 301 148 254 159 301 149 251 159 301 148 254 159 300 155 232

158,5 300 152 241 1161 293 152 241 165 293 143 238

152 241 146 261

Taking into account the mean of the measured values it results an increase of the hardness HV3 with 20.64%.

3. Cavitation erosion tests

The tests were obtained in the T2 vibratory device with piezoelectric crystal [10], [11], respecting the prescriptions of the Standard ASTM G32-2010 [8]. There were subjected to cavitation three specimens and for the characteristic curves it is used the mean value of these three specimens [1]. In Figure 2 are presented the measured values for the three tested specimens, the curve for mean values computed with the exponential equation [2], [5], [12] and its tolerance interval for a probability of 0.99. As can be seen the scatter is very small which means that the heat treated material is very homogenized. Table 2 give some numerical data.

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Fig. 2 Measured values, mean curve and its tolerance interval for 0.99 probability

Table 2 Values of statistic parameters after 165 minutes of exposure Measured mean depth erosion [µm] 6,208

Maximum value from the tolerance interval [µm] 7,366

Minimum value from the tolerance interval [µm] 5,05

Standard error of estimation (syx) [µm] ±0,386

3.1. Cavitation erosion specific curves and parameters

Figure 3 present the experimental results both for mean depth erosion (MDE) and for mean depth erosion rate (MDER). The curves for the mean values are traced with the exponential equation shown in the diagrams.

a) b)

Fig.3 Cavitation erosion characteristic curves: a) Mean depths erosion against time

b) Mean depth erosion rate against time

Figure 3a show a very good estimation for all measured points. From figure 3b result a good estimation only for the interval 90-165 minutes, especially the initial points show outstanding values of the erosion rate. This situation can be explained from the definition of the derivative. In the upper

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part of Fig. 3a there are presented also photographs of the specimen surfaces subjected to cavitation.

3.2. Experimental results analyze

The measured points scatter in Fig. 3 can be explained as follows: in the initial period, less than 10 minutes the sharp roughness crests, which are weak points, are easy eliminated and the erosion rate is very great. In the interval 45-90 minutes the destructive cavitation energy is consumed mostly to create cracks and dislocations of the material and the erosion rate is not very great [1], [3], [7]. After 90 minutes of exposure the situation is somehow stabilized the crack formation and the expelling of particles are approximate equal, the difference between the maximum erosion rate (0,041 µm/min) and the final erosion rate (0,037 µm/min) is not significant.

3.3. Investigations of the eroded microstructure

It is well known that binary Cu-Al alloy under 9.4% of Al have a single-phase structure, constituted by the solid solution α of Al dissolved in Cu. When the stability limit is exceeded, in conformity with equilibrium diagram Cu-Al [6], in the structure appear the phase β, which is a solid solution of Cu3Al. If the aluminum content of the alloy increase it will be e constituted, at room temperature, by the phase α and the eutectoid α + γ΄ (γ΄ is the compound Cu32Al19). In industrial cooling conditions, the eutectoid is formed also for bronzes with 6-8 % Al. The supplementary alloying with Ni, Fe, Mn, etc. reduce the maximum solubility of aluminum in copper and the eutectoid line will be translated to smaller concentrations in Al and to more reduced temperatures. The existence of the eutectoid transformation makes this alloy susceptible to hardening through quenching heat treatment followed by ageing through dispersion (Fig. 1). During the heating faze, the eutectoid α + γ΄ is transformed in faze β, and through sudden cooling is released a transformation, without diffusion, forming a martensite structure. The final heat treatment operation, which is an ageing, determines a hardening through dispersion by the effect of partial martensite decomposition and by precipitating minute chemical combination (fig. 4). The reduced roughness (fig.5) together with a uniform and minute erosion of the area exposed to cavitation (Table 3 and Fig. 9) demonstrates the high efficiency of the applied heat treatment. The EDX analyzes (Fig. 10-12) show that only in the central zone of the specimen occur a small reduction of the concentration in aluminum, explainable through the pronounced expelling of phases of compounds with copper and iron. Figures 8-10 show the excavation process of the bronze structure, with caverns of various dimensions, depending on the position of eroded area.

a) 350x b)1050x

Fig.4 Microscopic images of the heat treated bronze structure

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Table 3 Microscopic images after different cavitation exposure (x150)

0 minutes

30 minutes

90 minutes

165 minutes

Fig.5 Measured roughness after 165 minutes of cavitation exposure - ZEISS SURF COM 2000 SD3

Fig. 6 The zones microscopic analyzed

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A C

Fig. 7 The cavitation eroded surface (165 minutes) - digital microscopy A- Central zone; C – External limit of the eroded zone

A B C

Fig. 8 Cross section through the eroded area at the end of cavitation exposure (165 minutes) Digital Microscopy - HIROX 1300 apparatus

A- Central zone; B- Limit of eroded zone; C- External ring, without erosions

A B C

Fig. 9 Images of the zones specified in figure 6

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a) b)

c)

Fig. 10 SEM microscopy and EDX spectroscopy, Central zone A

a) b)

c)

Fig. 11 –passing over zone B

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a) b)

c)

Fig. 12 SEM microscopy and EDX spectroscopy, -external zone C

4. Comparisons with reference materials

A reliable evaluation of the heat treated AMPCO 45 bronze can be obtained through comparisons of the characteristic curves with those of the marine bronze CuNiAl III-RNR (with excellent cavitation erosion) and recommended by the Standards RNR [9] and ICEPRONAV for manufacturing ship propellers [1].

a) b)

Fig.13 Cavitation erosions characteristic curves a) Mean depth erosion against time

b) Mean depth erosion rate against time

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Figure 13 presents the cavitation erosion behavior of three bronzes CuNiAl III-RNR (curve 1), AMPCO 45 without treatments (curve 2) and AMPCO 45 heat treated (curve 3). The curves in Fig. 14a show the great increase of the cavitation erosion resistance for the treated AMPCO 45 which become better than CuNiAl- III RNR. The evolution of the curves MDER(t) with reduced maximum values and the tendency to stable erosions near the maximum value are characteristic with good and excellent cavitation erosion [1], [3]. Taking into account the values of the erosion rate in the stable zone (Fig. 14 b) results that untreated AMPCO 45 is 1.8 times weaker than CuNiAl – III RNR. After the heat treatment the resistance to cavitation erosion of AMPCO 45 became 1.2 times better than CuNiAl- III RNR.

5. CONCLUSIONS

The applied heat treatment for the bronze AMPCO 45 conducted to an exceptional increase of the cavitation erosion qualities. The resistance becomes better that that of the bronze CuNiAl – III RNR and recommend this material even for manufacturing the ship propellers. The determined tolerance interval shows that the regression equation is correct and representative. The differences between the mean depth erosions for all the three specimens are smaller than the tolerance interval. It means that the tested material is uniform in different points. This feature remains for the whole extension of the exposure time. Measurements of the hardness for the material in the genuine state and for the heat treated show an increase of the later with 20.6%. This increase explains in great extent the excellent behavior of the heat treated AMPCO 45 to cavitation erosion. The measured roughness of the eroded surface does not reveled sharp crests. This is also an explanation for the good behavior to cavitation erosion.

REFERENCES

[1] I. Bordeaşu, „Eroziunea cavitaţională a materialelor”, Editura Politehnica, Timişoara, 2006 [2] L. Edwin, A. Frances, W. Margaret, „Statistics Manual”, Dover Publications, Inc. New York, 2010 [3] J.P. Franc, a.o, „La Cavitation, Mecanismes phisiques et aspects industriels”, Press Universitaires de GRENOBLE, 1995 [4] R. Garcia, F.G. Hammitt, R.E. Nystrom, „Corelation of cavitation damage with other material and fluid properties, Erosion by Cavitation or Impingement”, ASTM, STP 408 Atlantic City, 1960 [5] A.D. Jurchela, „Cercetări asupa eroziunii produse prin cavitaţie vibratorie la oţelurile inoxidabile cu conţinut constant în crom şi variabil de nichel”, Teza de doctorat, Timişoara, 2012 [6] I. Mitelea, „Studiul metalelor”, Litografia Institutului Politehnic”Traian Vuia” Timisoara, 1983 [7] A. Thiruvengadam, H.S. Preiser, „On testing materials for cavitation damage resistence”, Report. 233 – 3, 1963. [8] *** „Standard method of vibratory cavitation erosion test”, ASTM, Standard G32-10, 2010 [9] *** „Registrul Naval Roman, Reguli pentru clasificarea şi construcţia navelor maritime”, Vol. V, Bucureşti, 1986 [10] I. Bordeaşu, M.O. Popoviciu, “Cavitation Erosion Resistance for a Set of Stainless Steels Having 10 % Nickel and Variable Chromium Concentrations”, “HIDRAULICA” (No. 1/2013), Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics, ISSN 1453 – 7303, pp.79-85 [11] I. Bordeaşu, M.O. Popoviciu, M. Sava, “Stainless Steel Cold-Work Hardening Through Cavitation”, “HIDRAULICA” (No. 2/2013) Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics, ISSN 1453 – 7303, pp.54-59 [12] I. Bordeasu, M.O. Popoviciu, C-tin Patrascoiu, V. Bălăsoiu, „An Analytical Model for the Cavitation Erosion Characteristic Curves”, Scientific Buletin “Politehnica” University of Timisoara, Transaction of Mechanics, Tom 49(63), Timisoara, ISSN:1224-6077, 2004, p.253-258 [13] ***http://www.ampcometal.com/common/datasheets/us/A45_EX_E US.pdf

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EXPERIMENTAL TESTING IN DYNAMIC REGIME OF HIGH PRESSURE

PNEUMATIC ACTUATORS

Dipl.eng. Ionel NITA*, PhD.st.eng. Iulian–Cezar GIRLEANU*, Dipl.eng. Sava ANGHEL*, Dipl.eng. Alexandru MARINESCU*

*Hydraulics & Pneumatics Research Institute, Bucharest-ROMANIA Abstract This article aims to present specific procedural issues related to testing in dynamic regime of pneumatic drive systems with high pressure (max. 40 bar) actuators, methodologies used in the testing activity conducted in the Laboratory of Pneumatics at INOE 2000-IHP Bucharest. Dynamic test procedures referred to in this article are: a)- testing the performance characteristics of the high-pressure actuator b)- testing the dynamic adjustability of high pressure actuators system c)- testing the dynamic stability of high pressure actuators system. [1]

1. Introduction

Pneumatic servo systems and their constituent parts are pneumatic equipment working in automatic mode, which can be analyzed in two aspects:

a) Static – when in their functioning a parameter changes, the others being considered either constant or negligible. In experimental pneumatics, using the law of perfect gases is specific to the analysis of this type of functioning.

b) Dynamic – when in their functioning (at least) an external parameter changes, being performed real-time control of the system. [1]

2. STRUCTURE OF PNEUMATIC SYSTEMS WITH HIGH PRESSURE ACTUATORS

(4.0Mpa) Pneumatic actuator systems are complex process systems which, mainly, consist of the following parts:

• The operative part with pneumatic drive (linear or rotary motor); • The control part, which provides adjustment and control of the output parameters of the

mechanical system or servomechanisms; • The system for monitoring the translation (using transducers and sensors); • The electronic system for control of movements (the control unit). [2] [4]

In the case of actuators working at high pressure (max. 40 bar), there are known two representative construction types: [8]

a) Pneumatic drive system with linear actuator for high pressure with intensifier stage

This differs in terms of construction from the standard model by: • It has two pneumatic working chambers: one for low pressure (below 10bar) and the other for

high pressure (which can generate up to 40 bar); • Their pneumatic drives are analog; • By the amplification process there can be multiplied the pressure (force, torque) or the flow

(linear or rotational speed) at a given power; • The intensifier stage can be made in several constructive types (intensification by pison or

membrane). [5]

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Fig.2 Simplified representative diagram of a pneumatic drive system with linear actuator for

high pressure with intensifier stage

The structure of this diagram is the following: MP - the actuator itself; M1 and M2 - input-output gauges of the equipment to be tested; DC1 and DC2 - directional throttles; B1 and B2 - 4:1 pressure amplifiers; DP- proportional pneumatic valve; D - mass flow meter; GPA – air preparation unit; SS1 and SS2- check valves This diagram operates at the stage 1 (medium pressure) with the pressure inside the network, and at the stage 2 (high pressure) with air pressure amplified at the maximum 4:1 (up to 40 bar); • Components of the stage 1 are standard construction; the ones of the stage 2 are of special construction and resistant up to 40 bar. • The compressor is standard construction.

b) Pneumatic drive system with linear actuator for high pressure without intensifier

stage [5]

Fig.3 Representative diagram of a pneumatic drive system with linear actuator for high pressure without intensifier stage

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The structure of this diagram is the following: MP- the actuator itself; M1 and M2 - input-output gauges of the equipment to be tested; RP1 and RP2 – pressure relays; DP1 and DP2- pneumatic control 3/2 pneumatic valves; SE1 and SE2 – quick exhaust valves; SP1 and SP2- pressure regulators; SS1 and SS2 – check valves.

• All components are of special construction and resistant up to 50 bar; • There shall not be used high-pressure servo components; • The servo components control the 50 bar (low or medium pressure) valves; • The compressor must generate high pressure (special construction); • This diagram works with one pressure stage (high pressure); • Controls work at medium pressure.

3. THE PROCEDURE FOR TESTING THE DYNAMIC BEHAVIOUR OF A PNEUMATIC (SERVO)-EQUIPMENT. PARTICULARITIES OF THE BEHAVIOUR OF ACTUATORS UNDER MEDIUM AND HIGH PRESSURE. The block diagram for testing a pneumatic actuator is the following: [4]

Fig.3 3.1 The technique of dynamic control of pressure in pneumatic actuator systems. Specific parameters

Pneumatic devices used for this purpose are the pneumatic regulators and valves (usually proportional). [6] Among them, pneumatic pressure regulators are the most used ones, in operations in which pressure is the disturbing factor. They cover the entire range of switching operations in terms

Power supply

Ammeter

Servo equipment

Data acquisition system

displacement transducer

Force transducer

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of frequency: ranging from extremely fast switching to values which are to be updated immediately, with short term overpressure, to slow transitions with precise displacement of loads (Fig. 3. 1). [9]

Fig. 3.1

a) Open loop pressure control

For many simple applications, the clear mechanical interrelation between the controlled pressure and the surface area is sufficient to adjust the output value (the force) with sufficient accuracy (Fig. 3.1a). [9]

Fig. 3.1a

b) Closed loop pressure control

For very precise control tasks, however, it is necessary to register directly the controlled variable and to override the pressure control with a force controller, for instance Fig. 3.1b. [9]

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Fig. 3.1b

c) Adjustability of pressure in dynamic working processes. Their definition parameters (Fig. 3.1c). [10]

Dynamic stability of a pneumatic system is defined, in the case of adjustability, by the following characteristics, which must be determined experimentally: linearity, hysteresis, rated flow, repeatability and the dynamics of switching cycles - In the case of pressure, these characteristics vary with the size of the load to be switched, related to the maximum capable force of the actuator to be tested.

• Linearity This value is the maximum deviation of the characteristic determined from the ideal, linear relation between the set value and the pressure at the output. Positive assessment criterion in this case is a Δp as small as possible.

a-Linearity

b- Repeatability

c- Hysteresis

d- Dynamics Fig.3.1c

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• Repeatability The secondary pressure deviation range, in the case of repeatedly adjusting a value. For an imposed controlling pressure p1, positive assessment criterion in this case is a p2 as close as possible to p1.

• Hysteresis The highest pressure drop for the same control point, ascending and descending, throughout the adjustment range. The assessment criterion is expressed the same as at the linearity.

Fig. 3.1.d

• Dynamics of pressure switching

Pressure transit over time from controlled output as a result of the sudden change in the adjustment point. The assessment criterion is expressed by a size as small as possible in rapid pressure change p max when switching from 0 to p [bar] in a very short period of time t [msec].

• Rated flow as default parameter in the evolution of the dynamic behavior of a pneumatic system

The amount of air that a valve can provide at the outlet depends on the primary pressure and the pressure required at the outlet. It is the control parameter dependent on the working pressure, considering the law of perfect gases pV / RT =ct. 3.2- Techniques for controlling the pressure of the compressed air in the dynamic working regime [5] a)- By pneumatic shutters This method offers the following working options: - pilot control - direct control - high dynamics control.

Pilot control w – controlled value

Direct control

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Fig. 3. 2a

u/p – pressure sensor 1 – inlet 2 – outlet 3 – atmosphere

Fig. 3. 2b

High dynamics control

Fig. 3. 2c

a) Direct control (by shutter valve)

The shutter valve underlies the control technology of electro pneumatics. The valve is insensitive to contamination due to the relatively large crossing section and the seal with soft lining.

b) Indirect control by pilot operated valves In this type of control pressure is applied to a volume using pilot operated valves (Fig. 3. 2a). The pressure in the pilot operates the valve until reaching a balance between the control pressure and the output pressure, and this is performed through the dynamic effect of pressures on the membrane. Inside the control valves working in accordance with this principle the outlet pressure is always measured, thus achieving electronic offset for interferences from the mechanical elements of the valve. If the valve is controlled by pilot valves, the device is ideal for static conditions. As the pilot valve should switch several times for each control process, when the adjusted values are constantly changing, this would result in a large number of operations and high wear. This effect is removed when using proportional valves as pilot valves.

c) Direct control by proportional electromagnet

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In this type of direct control, the force for adjusting the valve seat is provided directly by a proportional electromagnet. The pressure is measured at the output and conveyed to the electronic devices, making it possible to control the current level and, as a result, opening of the valve. By direct control, inertia and hysteresis can be avoided in the mechanical transfer parts. The accuracy of adjustment depends, in fact, only on the quality of the pressure sensor used. Thus much larger dynamic performance can be made with the smallest deviation of the adjustment. Also, an adjustment of the valve seat almost without wear provides the best precondition for a control element used in processes with continuous change.

d) High dynamics control For this type of control two 2/2 valves are used instead of a single 3/2 valve. In addition to the opportunity for increased circulation of air by a large valve, another advantage of this type of control is given by its dynamic characteristics. Exhaust and vent valves can be controlled directly and independently of each other. This drive principle is ideal for dynamic processes.

4 THE DIAGRAM OF THE STAND FOR TESTS ON THE DYNAMIC BEHAVIOR OF A

PNEUMATIC SERVO EQUIPMENT WITH ACTUATORS (THE TEST STAND) [5]

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Fig 4. The test stand [5] 5 CLASSIFICATION OF TESTS FOR DETERMINATION OF PRESSURE INFLUENCE ON

THE DYNAMIC BEHAVIOUR OF PNEUMATIC SYSTEMS [2] [5]

# Class of tests Symbol of test parameters Method of determination 0 1 2 3 TESTS ON THE CHARACTERISTICS OF THE ACTUATOR 1 Maximum working pressure pn ( bar) Monitoring of FESTO

system 2 Control pressure pc (bar) Monitoring of FESTO

system 3 Maximum working flow Q (mc/h) Monitoring of FESTO

system 4 Stroke of the actuator (mm) Mechanical measurement 5 Control current (mA) Electrical measurement 6 Maximum working frequency Hz Electrical measurement TESTS ON THE DYNAMIC ADJUSTABILITY OF THE SYSTEM a) Characteristics of adjustment in current 7 Current-frequency characteristic I=f(ν); Elevation of curve 8 Current-load characteristic I=f(F); Elevation of curve b) Characteristics of adjustment in frequency 9 Adjustability depending on the work

load R=f(F); Elevation of curve

10 Adjustability depending on the frequency

R=f(ν). Elevation of curve

TESTS ON THE DYNAMIC STABILITY OF THE SYSTEM 11 Characteristics of step signal response t i=time lag, in ms; ts=override

time, in ms; σ= override, for s=1/2 c; and s=1/1 c;

Elevation of curve

12 Characteristics of sine wave signal response (in amplitude).

Mitigation amplitude-frequency; offset- frequency.

Elevation of curve (Bode diagram);

OTHER TESTS Are conducted depending on the above results, if necessary.

6 CONCLUSIONS The main conclusions resulting from testing the systems with high pressure pneumatic actuators are the following: • It is found that at pressure below 16 bar (low and medium pressure) operation of the servo system with actuators depends on the variation of both load F and the working temperature T, the working agent being compressible; • It is found that at pressure above 16 bar (above 30 bar – high pressure) operation of the servo system with actuators depends only on the variation of load F, and the influence of the working temperature T, being insignificant, the working agent being virtually incompressible; • It is found that the parameters that influence the dynamics of the actuator are: Size and geometry of the drive system chambers; Type of sealing elements and mobile assembly, which can develop very large forces; Size of servo valve; Length of the pressure-supply system (of pipes and connecting

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elements); Value to be developed by the actuator (force, positioning accuracy and speed); Area of the supply pressure (medium or high); The parameters mentioned have a nonlinear influence that can affect system performance.

Fig.6[5] REFERENCES A) 1 – Avram M: “Acţionări hidraulice şi pneumatice - Echipamente şi sisteme clasice şi mecatronice”, Editura Universitară – Bucureşti, 2005; 2 - Belforte, Bertetto, Mazza: “Pneumatico - curso completo”, Editura Techniche nueve, Milano, 2004; 3 – Banu, Demian: “Motoare pneumatice liniare si rotative”, Editura Tehnică, Bucureşti, 1994; 4 - Banu, Stanescu Atodiroaiei, Gaburici: “Sisteme de automatizare pneumatice”, Editura Tehnică, 1997; 5-Matache G; Nita I. Visan A-Studii, metodologii şi mijloace de cercetare avansată privind comportamentul sistemelor de acţionare pneumatică utilizând actuatori de medie şi înaltă presiune, în vederea îmbunătăţirii performanţelor dinamice şi energetice-Studii le teoretico experimentale din seria de lucrari Nucleu 2009-2014, INOE 2000-IHP Bucuresti 6 - Mihaita, Gheorghe, s.a: “Mecatronica –Principii şi Aplicaţii”, Editura AGIR, 2007; 7 - SMC Divizia Europa: ”European Best Pneumatics”, SMC România, 2006; 8 - Pneumatische Division Kaeser Universitat: “High pressure And Free-oil Pneumatische Technologies”, Verlag gmbH. Munich , 2005; 9 - Farroresy C, Veladocchia M - “Posizionatore pneumatics con controlo – Oleodinanica & Pneumatica” (articol pentru Mecatronics Conference, Italy ,1997) - Universita di Torino; 10- Academia de Ştiinte Tehnice din România, Popescu A., Stefanoiu, s.a: “Automatică industrială - Reglarea şi optimizarea sistemelor”, Editura AGIR, 2006; 11 - Janocha: “Neue Aktuatoren-Procedings”, Verlag gmbH. Berlin 1998 B) INTERNET References 1 -http://www.sciencedirect.com/: Pneumatic drive positioning and force servosystems; 2- [email protected] –Articles about pneumatic actuator systems and their static and dynamic control; 3- [email protected] - Articles about pneumatic actuator systems and their static and dynamic control; 4 - www.robotics.mcmaster.ca : Pneumatic drive positioning and force servosystems;

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http://[email protected]/

http://[email protected]/

http://www.robotics.mcmaster.ca/


5 - www.sauer&son.com – Equipment at high and extreme pressures; 6 - univagora.ro. pneumatic systems; 7 - www.burow.cr.uk –Simulation of servopneumatic systems.

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mailto:[email protected]

http://www.burow.cr.uk/

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