Aniruddha Medhi

8/6/2019 Aniruddha Medhi

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CROSS COUNTRY GAS TRANSPORTATION LINES

Submitted By

ANIRUDDHA MEDHI

College of Engineering

University of Petroleum & Energy Studies

Dehradun

April, 2011.


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CROSS COUNTRY GAS TRANSPORTATION LINES

A thesis submitted in partial fulfillment of the requirements for the Degree of

Master of Technology

(Pipeline Engineering)

By

ANIRUDDHA MEDHI

Under the guidance of

Mr. ADARSH.K.ARYA

Assistant Professor

UPES (Dehradun)

Approved by

Dr. Sri Hari

Dean, College of Engineering

University of Petroleum and Energy Studies

Dehradun

April, 2011


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CERTIFICATE

This is to certify that the work contained in this thesis titled Cross Country

Gas Transportation Lines has been carried out by Aniruddha Medhi under

my supervision and has not been submitted elsewhere for a degree.

Mr. ADARSH.K.ARYA

Assistant Professor

UPES (Dehradun)

Date:-


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ACKNOWLEDGEMENT

This is to acknowledge with thanks the help, gratitude and support that I have

received during the final report from the management of University of

Petroleum and Energy Studies.

I wish to express my profound sense of gratitude and sincere regards to Mr

Adarsh.K.Arya, Assistant Professor, College of Engineering, UPES, who has

helped me immensely with his ingenious ideas and valuable guidance without

which the completion of this thesis would have been impossible. Mere wordscannot express what I owe to him.

I feel immense delight to acknowledge Dr. Shri Hari, Dean, College of

Engineering, UPES Dehradun, for his help and kind support throughout this

work.

I am very much thankful to Mr. B.C. Bora (Ex Chairman,ONGC) for his

extended help to me for this project.

Above all, I express my whole-hearted regards to my parents whose blessings

and boundless patience has kept my moral high during the course of my study.

ANIRUDDHA MEDHI


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ABSTRACT

Cross-country pipeline transport for Natural Gas seems to be the most preferred convenient

economical & reliable method. The intrinsic properties of natural gas and its increasing

industrial /commercial importance have resulted in greater movement of natural gas through

the pipelines.

For the M.Tech final semester project titled Cross-Country Gas Transportation Lines, I

have joined as a Project Trainee in PUNJ LLOYD. I was in the Head Office in Gurgaon for

15 days for studying and understanding the scope and various activities regarding the project.

I have started my training from 20th

of January 2011 in HO, Gurgaon and then shifted to one

of their Gas Pipeline Project site (Dahej-Vijaypur Pipeline-II) in Vadodara for further

training and getting the actual idea of Gas Pipeline Construction.

This project is on the construction activites involved with a 48-inch cross-country gas

pipeline (610 km) based on the estimated demand of 78 MMSCMD. The pipeline starts at

Dahej (Gujarat) to Vijaypur (Madhya Pradesh).

It also includes the study of the basics terms and equations used in the design of a Cross

Country Gas Pipeline.


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CONTENTS

Topics Page no

Chapter1 Introduction 01-01

Chapter 2 Basics of Pipeline 02-04

2.1 Specific Gravity 02

2.2 Viscosity 02

2.3 Compressibility Factor 03

2.4 Design Factor 03

Chapter 3 Flow Equations 05-12

3.1General Flow Equation 053.2Gas Velocity 063.3Reynolds Number 073.4Friction Factor 083.5Transmission Factor 083.6Pressure required to transport 083.7Hydraulic Pressure Gradient 093.8Colebrook-White Equation 103.9Weymouth Equation 113.10 Panhandle A Equation 113.11 Panhandle B Equation 12


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Chapter 4 Project Details of a Cross Country Gas Pipeline 13-15

4.1Project Details 134.2

Scope of Work 14

4.3Free Issue Material 15Chapter 5 Construction Activities of a Gas Pipeline 16-43

5.1 Pre-Construction Activities 16

5.2 Construction Activities 16

5.3 Post-Construction Activities 17

5.1.1 Reconnaissance Survey 18

5.1.2 Detailed Engineering Survey 18

5.2.1 Front-End Activities 19

5.2.1.1 Clearing & Grading of ROW 19

5.2.1.2 Hauling & Stringing 20

5.2.1.3 Trenching 21

5.2.1.4 Bending 23

5.2.1.5 Welding 24

5.2.1.6 Radiography 29

5.2.1.7 Joint-Coating 29

5.2.1.8 Holiday Testing 33


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5.2.1.9 Lowering 33

5.2.1.10 Backfilling 35

5.2.2 Back End Construction Activities 35-42

5.2.2.1 Tie-Ins 35

5.2.2.2 Crossings 36

5.2.2.3 Horizontal Directional Drilling (HDD) 36

5.2.2.4 Hydro testing 40

5.2.2.5 Valve Installation 41

5.2.2.6 Marker Installation 41

5.2.2.7 Documentation 41

5.2.2.8 Site Restoration 42

Chapter 6 Observations 43

Chapter 7 Suggestions and Conclusions 44

BIBLIOGRAPHY 45


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LIST OF FIGURES

Figure no with name Page no

FIGURE 3.1 Steady Flow in Gas Pipeline 06

FIGURE 3.2 Hydraulic Pressure Gradient for Uniform Flow 09

FIGURE 3.3 Hydraulic Pressure Gradient for Deliveries & Injections 10

FIGURE 4.1 Route Map of DVPL Up gradation 14

FIGURE 5.1 Clearing & Grading of ROW 19

FIGURE 5.2 Hauling of Pipes 20

FIGURE 5.3 Stringing 21

FIGURE 5.4 Trenching 21

FIGURE 5.5 Rock Breaking during Trenching 22

FIGURE 5.6 Bended Pipe 24

FIGURE 5.7 Bending Machine 24

FIGURE 5.8 Mainline Welding 25

FIGURE 5.9 Various Activities of Welding 27-29

FIGURE 5.10 Joint-Coating 30

FIGURE 5.11 Various Steps involved in Coating 31-32

FIGURE 5.12 Holiday Testing 33


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FIGURE 5.13 Lowering 34

FIGURE 5.14 Tie-Ins 36

FIGURE 5.15 Steps in HDD 37

FIGURE 5.16 Reamers 38

FIGURE 5.17 HDD Machine 39

LIST OF TABLES

Table no with name Page no

TABLE 2.1 Location class & its Design Factor 03

TABLE 3.1 Pipe Internal Roughness 10


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CHAPTER 1

INTRODUCTION

Cross-Country Pipeline has been in use for transportation of water, petroleum liquids and

gases for the last 70-80 years in the developed countries. In India, cross-country pipelines

have been installed and operated for the past 25-30 years, especially water supply pipelines.

A cross-country pipeline (CCP) can be underground, submarine or aboveground.

The conventional mode of transportation of fluids before the advent of cross-country pipeline

was by sea, rail or road transport. These modes are still in use. However, wherever bulk

transportation on a continuous basis between two fixed locations is required, a cross-country

pipeline is the most economical mode.

The reason is that the transportation by cross-country pipeline is continuous and so it reduces

the quantity to be transported, to a manageable level. The cross-country pipeline

transportation reduces the risks since the quantity is small and are generally provided with

safety devices.

Cross-country pipeline transport for Natural Gas seems to be the most preferred convenient

economical & reliable method. The intrinsic properties of natural gas and its increasing

industrial /commercial importance have resulted in greater movement of natural gas through

the pipelines. These pipelines are often referred as highways of natural gas transmission.

Natural Gas is transported at high pressure in the pipeline at pressures anywhere between 30

~ 100 bar. This reduces the volume of natural gas being transported, as well as providing

propellant force to move the Natural Gas, through the pipeline.

A 48-inch cross-country gas pipeline (610 km) is being proposed based on the estimated

demand of 78 MMSCMD. The pipeline starts at Dahej (Gujarat) to Vijaypur (Madhya

Pradesh). Natural gas have customers on both ends of pipeline, the producers and processors

that input gas into the pipeline and the consumers and local distribution companies that take

gas out of the pipeline. Hence Supervisory Control & Data Acquisition (SCADA) system for

electronic monitoring of pipeline is done for the entire stretch of pipeline from the control

station.


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CHAPTER 2

BASICS OF GAS PIPELINE

There are some very important terms associated with gas pipelines which we should be aware

of. These terms are very essential for designing a gas pipeline.

2.1 Specific Gravity:-

Specific gravity of gas, sometimes called gravity, is a measure of how heavy the gas is

compared to air at a particular temperature. It might also be called Relative Density, called as

the ratio of the gas to the density of the air. Because specific gravity is a ratio, it is a

dimensionless quantity.

G =

Since natural gas consists of several gases (methane, ethane, etc.), the molecular weight Mg

referred to as the apparent molecular weight of the gas mixture. When the molecular weight

and the percentage or mole fractions of individual components of natural gas mixture are

know, we can calculate the molecular weight of the gas mixture by using a weighted average

method. Thus, a natural gas mixture consisting of 90% methane, 8% ethane, and 2% propane

will have a specific gravity of

G =0.91+0.082+(0.023)

29

Where M1, M2, and M3 are the molecular weights of methane, ethane, and propane,

respectively, and 29 represents the molecular weight of air.

2.2 Viscosity:-

The Viscosity of a fluid represents its resistance to flow. The higher the viscosity, the more

difficult it is to flow. Lower viscosity fluids flow easily in pipes and causes less pressure

drop. Even though gas viscosity is a smaller as compared to liquids, it has an important

function in determining the type of flow in pipelines.


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2.3 Compressibility Factor:-

The compressibility factor is a measure of how close a real gas is to an ideal gas. The

compressibility factor is defined as the ratio of the gas volume at a given temperature and

pressure to the volume the gas would occupy if it were an ideal gas at the same temperature

and pressure. The compressibility factor is a dimensionless number close to 1.00 and is a

function of the gas gravity, gas temperature, gas pressure, and the critical properties of gas.

In a gas pipeline, the pressure varies along the length of the pipeline. The compressibility

factor Z also varies and must therefore be for an average pressure at any location on the

pipeline. If two points along the pipeline are at pressures P1, and P2, the following formula is

used for a more accurate value of the average pressure:

Pavg =2

3[(P1

3-P2

3)/(P1

2-P2

2)]

2.4 Design Factor:-

Design factor can be determined by using class location table provided in ASME 31.8

Location Class Design Factor F

Location Class 1, Division 1 0.80Location Class 1, Division 2 0.72

Location Class 2 0.60



Table 2.1- Location class and its Design Factor

2.4.1 Location Class 1: A location class 1 is any one mile section that has 10 or fewer

building intended for human occupancy. A location class 1 is intended to reflect areas such as

wastelands, deserts and mountains, grazing land, farmland, and sparsely populated areas.

2.4.2 Location Class 2: A location Class 2 is any one mile section that has more than 10 and

less than 46 buildings intended for human occupancy. A location class 2 is intended to reflect

areas where the degree of population is intermediate between Location class 1 and location

class 3 such as fringe areas around cities and towns, industrial areas, ranch or industrial

estates etc.


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2.4.3 Location Class 3: A location class 3 is any one mile section that has 46 or morebuilding intended for human occupancy expect when a location class 4 prevails.

A location class 3 is intended for areas such as suburban housing development,

shopping centers, residential areas, industrial areas and other populated areas and

other populated areas not meeting location class 4 requirements.

2.4.4 Location Class 4: A location class 4 includes areas where multi-storey buildingsare prevalent and where traffic is heavy or dense and where there may be

numerous other utilities.


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CHAPTER 3

FLOW EQUATIONS

Several equation are available that relate the gas flow rate with gas flow rate with gas

properties, pipe diameter and length, and upstream and downstream pressure. These

equations are listed as follows:

1. General Flow equation.2. Colebrook-White equation.3. Modified Colebrook-White equation.4. Weymouth equation.5. Panhandle A equation.6. Panhandle B equation.

3.1 General Flow equation:-

The most common form of this equation in U.S. Customary (USCS) of units is given in terms

of the pipe diameter, gas properties, pressure, temperatures, and flow rate as follows.

Q = 38.77 (Tb/Pb)[(P12-e

sP2

2)/(GTfLeZ)]

0.5D

2.5(USCS Units )

Where

Q = Gas flow rate, measured at standard condition, ft3/day (SCFD)

F = Transmission Factor, G = Gas Gravity (air =1),

Pb = Base pressure, Pisa, Tb =Base temperature,oR (460+

oF),

P1 = Upstream Pressure, Pisa, P2 = Downstream Pressure, Pisa,

Tf =Average gas flowing temperature,oR (460+

oF),

Z = Gas Compressibility factor at the flowing temperature, dimensionless


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D = Pipe inside diameter, inch,

Le = Equivalent length of pipe segment, mile Le = L (es-1)/s

The equivalent length Le and the term es

take into account the elevation difference between

the upstream and downstream ends of the pipe segment. The parameter s depends upon the

gas gravity, gas compressibility factor, the flowing temperature, and the elevation difference.

Upon examining the General flow equation, we see that for a pipe segment of length L and

diameter D, the gas flow rate Q (at standard conditions) depends on several factors. Q

depends on gas properties represented by gravity G and the compressibility factor Z. If Gas

gravity is increased (heavier gas), then the flow rate will decrease. Similarly, as the

compressibility factor Z increases, the flow rate will decrease. Also, as the gas flowing

temperature Tfincreases throughput will decrease. Thus, the hotter the gas, the lower the flow

rate will be. Therefore, to increase the flow rate, it helps to keeps the gas temperature low.

The impact of pipe length and inside diameter is also clear.

Figure 3.1- Steady flow in gas pipeline.

3.2 Gas Velocity:

The velocity of gas flow in a pipeline represents the speed at which the gas molecules move

from one point to another. Unlike a liquid pipeline, due to compressibility, the gas velocity

depends upon the pressure and hence will vary along the pipeline even if the pipe diameter is

constant. The highest velocity will be at the downstream end, where the pressure is the least.

Correspondingly, the least velocity will be at the upstream end, where the pressure is higher.

The gas velocity at any point in a pipeline is given by

u = 0.002122(Qb/D2)(Pb/Tb)(ZT/P)


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Where

u = Upstream gas velocity, ft/sec D = Pipe inside diameter, inch

Qb = Gas flow rate, measured at standard conditions, ft3/day

Pb = Base pressure, Pisa P = Upstream pressure, Pisa

Tb = Base Temperature,oR (460+

oF) T = Upstream gas temperature,

oR (460+

oF)

3.3 Reynolds Number of Flow:-

An important parameter in flow of fluids in a pipe is the non dimensional term Reynolds

number. The Reynolds number is used to characterize the type of flow in a pipe, such as

laminar, turbulent, or critical flow. It is also used to calculate the friction factor in pipe flow.

The Reynolds number is a function of the gas flow rate, pipe inside diameter, and the gas

density and viscosity and is calculated from the following equation:

Re = 0.0004778(Pb/Tb)(GQ/D) (USCS Units )

Where

Pb = Base pressure, Pisa Tb = Base temperature,oR (460+

oF)

G = Specific gravity of gas (air =1.0) D = Pipe inside diameter, in

Q = Gas flow rate, Standard ft3 /day (SCFD) = Viscosity of gas, lb/ft-s

Laminar flow occurs in a pipeline when the Reynolds number is below a value ofapproximately 2000. Turbulent flow occurs when the Reynolds number is greater than 4000.

For Reynolds numbers between 2000 and 4000, the flow is undefined and is referred to as

critical flow.

Thus, for laminar flow, Re2000

for turbulent flow, Re> 4000

for critical flow , Re>2000 and 4000


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Most natural gas pipelines operate in the turbulent flow region. Therefore, the Reynolds

number is greater than 4000. Turbulent flow is further divided into three known as smooth

pipe flow, fully rough pipe flow, and transition flow.

3.4 Friction Factor:-

In order to calculate the pressure drop in a pipeline at a given flow rate, the term friction

factor is used which is a dimensionless parameter that depends upon the Reynolds number of

flow.

1

= - 2 log1o(

3.7

+2.51

) for Re >4000

Where

f= Friction factor e= Absolute pipe roughness

Re = Reynolds no of flow, dimensionless D = Pipe inside diameter, in

3.5 Transmission Factor:-

The transmission factor F is considered the opposite of the friction factor f, whereas the

friction factor indicates how difficult it is to move a certain quantity of gas through a

pipeline, the transmission factor is a direct measure of how much gas can be transported

through the pipeline. As the friction factor increases, the transmission factor decreases and

therefore the gas flow rate also decreases. Conversely the higher the transmission factor the

lower friction factor and therefore the higher the flow rate will be. The transmission factor F

is related to the friction f as follows:

F =2

3.6 Pressure required to transport:-

In the flow of incompressible fluids such as water the pressure required to transport a

specified volume of fluid from point A to point B will consist of the following components:

1. Frictional component2. Elevation component3. Pipe delivery pressure


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In addition in some cases where the pipeline elevation differences are drastic, we must also

take into account the minimum pressure in a pipeline such that vaporization of liquid does not

occur. The latter results in two phase flow in the pipeline which causes higher pressure drop

and therefore more pumping power requirement in addition to possible damage to pumping

equipment.

3.7 Hydraulic Pressure Gradient:-

The hydraulic pressure gradient is a graphical representation of the gas pressure along the

pipeline. The horizontal axis shows the direction along the pipeline starting at the upstream

end. The vertical axis depicts the pipeline pressures.

Since pressure in a gas pipeline is nonlinear compared to liquid pipelines, the hydraulic

gradient for a gas pipeline appears to be a slightly curved line instead of a straight line. The

slope of the hydraulic pressure at any point represents the pressure loss due to friction per

unit length of pipe; this slope is more pronounced as we move toward the downstream end of

the pipeline, since the pressure drop is larger toward the end of the pipeline. If the flow rate

through the pipeline is a constant value and pipe size is uniform throughout, the hydraulic

gradient appears to be a slightly curved line. If there are intermediate deliveries or injections

along the pipeline, the hydraulic gradient will be a series of broken lines. A similar brokenhydraulic gradient can also be seen in the case of a pipeline with variable pipe diameters and

wall thickness, even if the flow rate is constant. Unlike liquid pipelines, the breaks in

hydraulic pressure gradient are not as conspicuous in gas pipelines.

Figure 3.2


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Figure 3.3

3.8 Colebrook-White Equation:-

The Colebrook-White equation, sometimes referred to simply as the Colebrook equation, is a

relationship between the friction factor and the Reynolds number, pipe roughness and inside

diameter of pipe. The following form of the Colebrook equation is used to calculate the

friction factor in gas pipelines in turbulent flow.

1

= - 2 log1o(

3.7

+2.51

) for Re >4000

Where

f= Friction factor e= Absolute pipe roughness

Re = Reynolds no of flow, dimensionless D = Pipe inside diameter, in

Table 3.1- Pipe Internal Roughness.


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3.9 Weymouth equation:-

The Weymouth equation is used for high pressure, high flow rate and large diameter gas

gathering systems. This formula directly calculates the flow rate through pipeline for given

values of gas gravity, compressibility, inlet and outlet pressures, pipe diameter and length. In

USCS units, the Weymouth equation is stated as follows:

Where

The Weymouth transmission factor in USCS units is: .

3.10 Panhandle A equation:-

The Panhandle A Equation was developed for use in natural gas pipelines, incorporating an

efficiency factor for Reynolds numbers in the range of 5 to 11 million. In this equation, the

pipe roughness is not used. The general form of the Panhandle A equation is expressed in

USCS units as follows:

Where


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By comparing the Panhandle A equation with the General Flow equation, we can calculate an

equivalent transmission factor in USCS units as follows:

3.11 Panhandle B equation:-

The Panhandle B equation, also known as the revised Panhandle equation, is used large

diameter, high pressure transmission lines. In fully turbulent flow, it is found to be accurate for

values of Reynolds number in the range of 4 to 40 million. This equation in USCS units is as

follows:

Where

The equivalent transmission factor for the Panhandle B equation in USCSis given by:


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CHAPTER 4

PROJECT DETAILS OF A CROSS-COUNTRY GAS PIPELINE

4.1 Project Details:-

Name of the project: Dahej-Vijaypur Gas Pipeline Up-gradation Project.

Contractor: Punj Lloyd Limited.

Client: GAIL (INDIA) Limited.

Consultant: Suez Tractebel Engineering India Private Limited.

Location: Dahej (Gujarat) to Vijaypur (Madhya Pradesh).

Pipeline Length & Size:610 KM & 48.

Capacity: 78 MMSCMD.

Dahej-Vijaypur Gas Pipeline Up-gradation Project is named as DVPL-II. The whole project

is divided into total of five spreads which is undertaken by three contractors i.e. Punj Lloyd

Ltd, Corrtech International Private Ltd, Fernas International Private Ltd.

Among all these Spread, this spread 1 is undertaken by Punj Lloyd Limited. It covers

approximately 145 Kms and it is from Dahej to Jhabua (near Bodeli). This spread consists of

six SV (Valve Stations), one Dispatch Terminal & one Intermediate Pigging Station. It has

two dump yards one is at 46 Km at Samili starting from Dahej i.e. 0 Km and another is at 135

Km at Waghodia of Vadodara District. In this spread it is found that there are 128 crossings

i.e. river, pond, highway & railway crossings.

The Project Office is located at village named Valan near Palej Ta. Karjan Dist, Vadodara.

Along with project office the camp is also located where the welders qualification test is

done.

The project duration is of 12 months including one month for commissioning of gas.


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Figure 4.1- Route map of DVPL Up gradation.

4.2 Scope of Work:-

Laying, Testing & Commisioning of approximately 145 Km long, 48 Pipeline and

associated facilities including the following:

Supply of free materials (other than free issue). Construction / QA-QC/ HSE. Pipelaying work ( survey, clearing of ROU, grading, stringing, bending, welding,

trenching, lowering, crossings, Tie-in, backfilling, site restoration, etc.)

NDT and Destructive testing. HDD Laying of OFC & HDPE ducts. Hydro- testing, dewatering, drying & pre-comissioning

Comissioning & Gas-In.


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Construction of gas stations (Scraper launching / Dispatch / Receiving / IP / SVs)and associated Mechanical, Civil, Electrical & Instrumentation works.

All consumables Ball Valves (below 8) Globe and Check Valves Fittings (below 16) Flanges (below 16) Assorted pipes (below 16) Induction bends Coating material Instrumentation Items Electrical Equipments OFC HDPE

4.3 Free Issue Materials:-

Coated / Bare line Pipes Ball Valves (above 8) Fittings (above 16) Flanges (above 16) Casing pipes Metering Skid Scrapper launcher/ receiver Insulating joints (all sizes)


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CHAPTER 5

CONSTRUCTION ACTIVITIES OF A CROSS-COUNTRY GAS PIPELINE

Any large scale Cross-Country Gas Pipeline project involve multitude of activities, which

may be broadly classified into the following categories:

5.1 Pre-Construction Activities:-

- Reconnaissance survey- Detailed Engineering survey- Permits & clearances from various statutory authorities.- Acquisition of R.O.W in accordance with P&MP Act.- Permanent acquisitions of land for pump stations, repeater stations, block valves.

5.2 Construction Activities:-

Construction Activities can be broadly classified as below:

5.2.1 Front End Activities:-

- Opening of ROW- Clearing and grading- Hauling and stringing- Trenching- Bending- Welding & Radiography- Joint coating- Lowering- Back filling


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5.2.2 Back End Activities:-

- Tie-ins- Crossings- Hydro testing- Valves installation- Final cleanup and restoration- Installation of pipeline markers- Documentation

5.3 Post-Construction Activities:-

- Caliper survey- Line preservation- Cathodic Protection- Commissioning


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5.1.1 Reconnaissance Survey:-

The main objectives of this survey are

- To establish the pipeline route- To avoid populated areas, forest and mining areas- To keep the number of crossings to a minimum- To ensure easy approachability to the ROW- Utilization of existing ROW if any.

5.1.2 Detailed Engineering Survey:-This survey includes

- Route Survey- Ground Profile Survey- Crossing Details- Collection of hydrological data- Collection of data on the type of terrain, soil and crop pattern- Soil Resistivity Survey

5.1.3 Acquisition of R.O.W in accordance with P&MP Act.:-- Positioning of land acquisition personnel's and notification of Competent Authority- Preparation and Notification of land schedule under section 3 (i) of P&MP Act- Serving of Notice under section 3 (i) to land owners- Hearing of objections from land owners- Preparation and notification of schedule under section 6 (i) of P&MP Act- Award and disbursement of compensation- Land compensation @ of 10% of land cost- Crop compensation

Standing crops

Presumptive crops

- Preparation of notification for termination operation in respect of the lands andnotification of the same under Rule IV of the Petroleum Pipeline (Acquisition of

Right of User in land) Rules, 1963.


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5.2.1 Front end Construction Activities:-5.2.1.1 Clearing and Grading of ROW

- Stacking of ROW.- Marking of ROW boundaries.- Clearing of trees, bushes, farm crops, undergrowth and routes, electrical and

telephone poles falling within the 18 M width of ROW.

- Grading of ROW sufficient to be consistent with the maximum permitted pipebending radius.

- Providing ramps, diversion at road crossings, hume pipe culverts for maintainingwater flow across the ROW.

- Width of R.O.W is 25 M.- Pipeline occupies a small area balance for movement of equipment and machinery.- Rail tracks, highways, roads, canals, and embankment of canals not to be disturbed

during clearing and grading.

Figure 5.1- Clearing & Grading of ROW.


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5.2.1.2Hauling and Stringing of pipesDefinition: Once the construction rights-of-way have been cleared sufficiently to

allow construction equipment to gain access, sections of pipe are laid out along the

rights-of-way. This process is called 'stringing' the pipe.

- Transportation of pipe from stockpile/storage yard and arranging them along R.O.Wis done.

- Extreme care is exercised during loading and unloading.- Rough handling is avoided as it may gouge or dent a pipe.- Coated pipes require extra-ordinary precautions.- Stringing to be done in such a manner that the pipes are readily accessible but do not

obstruct the movement of equipment and personnel.

- In rocky areas, pipe stringing shall be done after rock trenching.- Stringing shall not be done for more than 10 km ahead of trenching.- Pipes of special grades or wall thickness shall be strung at the required specific

locations.

Figure 5.2- Hauling of pipes.


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Figure 5.3- Stringing.

5.2.1.3TrenchingDefinition: After stringing the pipe sections in place, a trench is dug along the rights-

of-way alongside the pipe sections. Topsoil is often removed from the work area and

stockpiled separately to be used in site restoration.

- The pipeline shall be laid at a distance of 5 mtr. from one edge of the ROW.- Stacking of trench line.- The width of the trench shall be equal to the pipe diameter plus 400 mm.- The depth of the trench shall be equal to diameter of the pipe plus 1 mtr.- Extra width and depth shall be provided in rocky terrain.- Stripping of the top soil upto 30 cm of the trench and storing separately.- Suitable crossing for passage of men, equipment, cattle etc. shall be provided.

Figure 5.4- Trenching.


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- Sometimes rocks may come in the trench route. The thickness of rock to be removedis less than 500 mm then it is done by rock breaker (attached to the excavator).

Figure 5.5- Rock breaking during Trenching.


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5.2.1.4BendingDefinition: A bending machine is used in the field to make slight bends in individual

sections of the pipe to account for changes in the pipeline route and to conform to the

topography.

- Bending of pipe is required to negotiate changes in vertical and horizontal alignmentof the pipeline.

- Bending procedure has to be approved before bending of pipes.- Cold field bends shall only be used- The radius of bends shall be limited to 40 D for pipes upto 18 dia and to 60 D for

pipes of 20 and above.

- Weld seams to be kept in the plane passing through the neutral axis of bending.- Tangents of minimum 2 M length to be left at both ends of the pipe.


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- Check for ovality, thinning, wrinkles and buckles.- Calibrated indicator gives operator check point to prevent over bending.- Checking is carried out with inclinometer.

Figure 5.6- Bended Pipe.

Figure 5.7- Pipe Bending Machine.

5.2.1.5WeldingAfter the pipes have been stringed, the main-line welding is carried out. An open

space is selected for making the pipe section and the number of pipes will depend

upon the length of that particular site where the tie-in joints will be made. The length

of a single pipe section is tried to make maximum so as to minimize the number of

tie-in welding (thus minimizing the total welding time).


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- Welding procedure specification has to be prepared for approval of the procedure andqualification of the welders as per API 1104.

- Internal line up clamp shall be used for proper alignment of joint.

Figure 5.8- Mainline Welding.

Steps in Main-line welding:

1.

Bevel cleaning:It is done with help of wire grinding and its purpose is to remove any foreign material

or rust from the bevel.

2. Alignment of Pipes:This is the operation of bringing two pipes together. With the help of internal clamp a

second pipe is brought into alignment with the first one. This is a manual clamp

whose operation is controlled with a handle coming out of the free end of the second

pipe.

The seams of the adjacent pipes are kept in such a way that they are at least 30 away

from the vertical plane (at least 60 away from each other). This is done so as to

facilitate weld joints. The seams shall not be kept at the lower side because the

possibility of corrosion and erosion are maximum throughout the seam.


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3. Preheating:This is an important operation that plays a vital role in determining the weld quality.

Since the pipe comes from a distant place and comes across different temperature

conditions it becomes necessary to preheat the pipe that removes some of the possible

residual stresses and avoids sudden rise in temperature while welding.

4. Root-Gap:After the preheating the root gap is provided. It facilitates the proper penetration of

the root pass.

5. Hammering:Hammering is done with help of a brass hammer to detect ovality in the pipes.

Purpose of using brass hammer is to avoid making dents on the pipe surface (since

brass is softer than steel).

6. Root-Pass:The whole quality of the weld jont depends upon root pass so this is done by the

specialist welders. This is a downhill operation. Current used is 90-130 Amps.

Electrode used for this operation is E6010 type (3.2 mm).

7. Root- Grinding:After the root pass root grinding is done to remove slag as well as to give bevel for the

hot pass. This must be done within 3 minutes of the root pass.

8. Hot-Pass:This is done at a current around 110-140 Amps. The electrode used is E8010 (4 mm).

Hot pass must be completed within 5 minutes from the root pass.

9. Slag-Removal:After the hot pass the slags are removed by wire brushing. A shining face would

indicate proper slag removal.


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10. Filler Pass and Capping:Filler and capping are multiple pass operation. Filler has three steps F1, F2 & F3.

Electrode used is E8010 (4.8 mm).

Capping is again wire brushed and left with shining face; start point of the capping

pass is grounded to an even surface.

11.Weld-Joint Numbering:After completion of the welding process record of various welders has been kept and

marked on the pipe itself for future reference.

Following diagrams show different activities of the main-line welding:-

Bevel cleaningAlignment of pipes

PreheatingRoot-Gap


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Hammering

Root-Pass

Root Grinding Hot-Pass

Slag Removal

Filler pass and Capping


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Weld joint Numbering

Figure 5.9- Various activities of Welding

Two welding machines are connected in series so that two welders can perform the welding

operation simultaneously.

All main-line weldings are done by the contractors as per the API 1104 specification. Any

doubtful joints are then made to undergo radiographic testing; the NDT has been caried out

by the NDT team.

5.2.1.6Radiography:- Radiographic inspection is carried out by using X-rays.- Visual inspection of all welds shall be carried out by qualified welding engineer

having minimum qualification of Level - II certification.

- All joints at the following locations shall be radiographed.Initial 1 km.

At cased road / rail, submerged crossings,

Tie-ins (including golden tie-ins)

Marshy areas.

Valves and insulating couplings

20% of balance mainline joints(100% here)

5.2.1.7Joint-coating:The main pipe coating is 3LPE (Three Layer Polyethylene) coating. Field-coating is applied

to the welded areas at the ends of the pipe sections to prevent corrosion.


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- 250 mm on either side of the pipe is left un-coated in the coating yard to facilitatewelding.

- The width of the sleeve shall depend upon the cut back length provided in the yardcoated pipe.

- Heat shrinkable sleeves are used for coating welded joints.- Pipe surface is sand blasted to SA-21/2 specification.- Sand blasted area is heated upto 600C and epoxy primary is applied on the surface.- The sleeve is wrapped around and then shrunk on the joint using a propane/ LPG

torch.

- Air bubbles trapped are removed using hand rollers.- The integrity of the joint coating is tested by conducting peel test.

Figure 5.10- Joint coating.

Various steps involved:-

1. Sand Blasting:The flawless joints are sand blasted to shining face (SA 2.5). Sand is directed to the

joint surface with the help of a hose pipe and compressed air. 100 mm on the both

sides of the joint of the factory coating adjacent to surfaces shall be thoroughly

cleaned.


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2. Heating:The sand blasted surface is heated with gas flames by two operators. It must go up to

70-80 C. the line coating edge is prepared with a 30 chamfer to provide a smooth

transition between the pipeline coating and the bare steel.

3. Apply Polymer: Then Primer A and B is mixed in the ratio of 70%:30% respectively.Then the mix is applied on the heated surface with the help of brushes.

4. Wrap the Sleeve and Covering Strap:The heat shrinkable sleeve is wrapped around the joint and a covering strap is placed

at the overlapping end of the sleeve. The thickness of the coating sleeve is 3 mm and

that of the covering strap is 2 mm.

5. Shrinking the Sleeve:Heat is applied uniformly over the sleeve and it shrinks to fit with the metal surface.

6. Rolling:Freshly applied coating is rolled properly to eject any air entrapped in between the

metal and the coat.

The following diagrams show the steps involved in coating operation:-

Sand BlastingSand Blasted Surface


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Figure 5.11- Various steps involved in Joint Coating.

Heating and Chamfering Applying Primer

Sleeve and StrapShrinking sleeve

RollingFinishing


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5.2.1.8Holiday Testing:This is done with the help of holiday machine. This is done to detect any damage in the

coating before lowering. Before the lowering operation the whole pipe section has to be

checked for any irregularities or disbondment in the coating. This operation is known as

holiday detection. The instrument with which it is done is called Jeep or Holiday

Detector. A beep in the Jeep gives indication of irregularity at that point/position.The flaw

must be removed (coating repaired) again checked for holiday and then only the lowering is

allowed.

Figure 5.12- Holiday Testing.

5.2.1.9Lowering:- Ditch to be free from rock, hard clods, welding rods or objects that may damage

the pipe

- Pipe to be handled using non-abrasive lowering belts to avoid coating damage.- Sufficient number of side booms to be deployed for lifting the pipe to ensure safe

operation without overstressing the pipe.

- Trench to be rectified so that bends fit the ditch in a satisfactory manner.- Padding (min 4) to be done in rocky areas.- Usually the section of 1.2 km can be lowered in a day.


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Figure 5.13- Lowering.


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The process of connecting the un-connected sections of the pipeline is defined us tie-

in operation.

Figure 5.14- Tie-ins.

5.2.2.2Crossings:Type of Crossings

1. Open Cut : Roads, and minor water courses.2. Cased : Railways, National & State Highways.3. Submerged crossings : Major Rivers.4. Horizontal Directional Drilling : Perennial Rivers & Canals.

5.2.2.3 Horizontal Directional Drilling (HDD):-

- method of laying pipeline without trenches- usually done in river crossings, canal crossings etc.- main instruments used are drilling equipment and pipe thruster and soil.


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Working Steps involved in H.D.D are:

- PILOT DRILLING:

- PRE-REAMING:

- PULLBACK:

Figure 5.15- Steps in HDD.


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REAMER AND DRILL PIPE:

Figure 5.16- Reamers


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Figure 5.17- HDD Machine.


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5.2.2.4Hydrotesting:Definition: The purpose of a hydrostatic pressure test is to eliminate any defect that

might threaten the pipeline's ability to sustain its maximum operating pressure, or to

determine that no defects exist.

- Hydrostatic pressure testing consists of filling the pipeline with water and raising theinternal pressure to a specified level above the intended operating pressure. Critical

defects that cannot withstand the pressure will fail.

- Upon detection of failures, the defects are repaired or the affected section of thepipeline is replaced and the test resumed until the pipeline "passes".

-

Inline Inspection (ILI) technologies are also used that permit the identification ofspecific types of defects, such as corrosion. But because not all lines can be inspected

with ILI tools and because of the need to find types of defects that are not currently

detected by ILI technology, hydrostatic testing is an accepted method for

demonstrating the fitness of a pipeline segment for service.

Hydrotesting may be done either section wise before lowering in or between two

successive valve stations just before commissioning. Difficulties with the sectional

Hydrotesting is that after testing the section has to be filled with standard fluids along

with corrosion inhibitor which may raise the cost.

Parameters for choosing test sections:

- Availability of water- Suitable place for disposal- Ground profile- Logistics

Test procedure

- Air cleaning the pipeline to clear of all debris and muck- Gauging- Water filling with corrosion inhibitor- Thermal stabilization- Pressurization


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- Evaluation and acceptance5.2.2.5Valve Installation:

- Block valves are either Hand operated or Motor operated.- Mainline isolation valves are provided at an approx. interval of 25 to 35 km.

depending upon the size of the line.

- Isolation valves are provided on either side of major rivers.- Tapings for pig signaler and pressure transmitters are provided at the valve locations

for monitoring the pressure, temperature and moment of pig.

5.2.2.6Marker Installation:- ROU Boundary Markers- Warning Markers- Kilometer Markers & Direction Markers- Warning Markers are installed at National and State highway crossings, railway

crossings, water crossings, other road crossings, Valve station etc.

5.2.2.7Documentation:- Daily log book- Separate register for each activity- Pipe Book- Welding inspection report- Radiographic inspection report- Tie-in charts-

Pipe damage register- Equipment & manpower mobilization report- Hydrostatic testing register- Claims register

Due to deviations

Due to change in work plan

Damage to pipes etc.


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5.2.2.8Site Restoration:Definition: The construction right-of-way is restored as closely as possible to its

original condition. Depending on the location and circumstances, this could involve:

- Smoothing the construction area.- Replacing topsoil.- Applying fertilizer and grass seed.- In hilly areas, erosion-prevention measures such as interceptor dikes - which are small

earthen mounds constructed across the right-of-way to divert water - are installed.

- Stone or timber materials known as riprap" is also sometimes installed along streamsand wetlands to stabilize soils and retain habitat following construction.

Some of the important Codes to know for Mainline Construction:

API-5L : Specifications for line pipes.

API-1102 : Steel pipeline crossings.

API-1104 : Welding of pipeline & related facilities.

ASME B31.4 : Pipeline transportation systems for liquid

hydrocarbons and other liquids.

API 1110 : Pressure testing of liquid petroleum pipelines.

OISD 141 : Design and construction requirements for cross

country hydrocarbon pipelines.

ASME B31.8 : Gas transmission & distribution piping systems.


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CHAPTER 6

OBSERVATIONS

The various observations are:-

- Construction schedule :10 months for Mechanical completion and 1 months for gas In- Controlled Rock blasting.- Pipeline is laid at a clearance of 6 m from existing pipeline ( except at river and

Special crossings.)

- Most of the pipeline crossings is by Open cut, except one HDD (Narmada Canal)- Line pipe Material grade is API 5L X 70 or X 80 or combination.- The station construction would be in X70 grade pipes with X 70 grade fittings.- Number of Hot bends is significantly higher than conventional pipeline as the

Pipeline is being laid in common ROU.

- Additional ROU width to be acquired by GAIL isDahej To Vemar : 10 Meters

Vemar to Vijaipur : 18meters

- Lack of experienced of X 80 welding (manual and semi-automatic)- Availability of Automatic welders for X-80 grade Line pipes- Availability of AUT and UT Operators for X-80 grade line pipes.- Necessity to conduct Field cold bending test to determine max. angle achievable.- Line pipe hot bend manufacturer to assess their capacity to fabricate

Induction bends with X80 material (LSAW/HSAW).- Farmers creating problem related to land acquisition.- As a result problem faced by GAIL in acquiring the land and submitting the ROU to

Punj Lloyd to further proceed.

- Imperfect mobilization of funds.- Improper planning.- Delay in the project by a larger time period.


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CHAPTER 7

SUGGESTIONS & CONCLUSIONS

The contractual start date was : 19th

August 2009

The contractual completion date was : 18th

August 2010

EOT : 18th

March 2011

Current stage of the project:

- ROU Hand Over : 101.36 KM (Total 145.437 KM)- Welding : 85.00 KM- Lowering : 61.00 KM- Hydro Testing : 11.76 KM- Cased Crossing : 30 Nos (Total 45 Nos)- River Crossing : 01 Nos (Total 03 Nos)- HDD : 01 Nos- Station work : Is in Progress.

Suggestions:

- Proper planning should be carried out to avoid delays.

-

Should have adequate manpower.

- Make sure that experienced welders are available.

- Easy availability of AUT & UT operators.

- Proper co-ordination between the contractors and the workers.

- Timely acquisition of ROU.


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BIBLIOGRAPHY

1. Menon E. Shashi. Gas Pipeline Hydraulics. Published in 2005 by CRC Press, Taylor& Francis Group, LLC.

2. ASME B31.8- 1995 Edition, New York. GasTransmission and Distribution PipingSystems.

3. Mr. S.R. Bhaskar. (2009, August 12th) Indian Oil Corporation Limited.Pipeline Construction- An OverviewPresentation.

4. Scope of Work (SOW) provided by Punj Lloyd.5. Construction Manual and Documents provided by Punj Lloyd.

Aniruddha Medhi

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