© 2007 Conax Technologies Temperature Sensors. © 2007 Conax Technologies Temperature Sensor Types...

© 2007 Conax Technologies

Temperature Sensors


Temperature Sensor Types

• Conax manufactures two types of sensors:– Thermocouples– RTD’s


Comparison of Sensor Types

Thermocouple RTD

Advantages

• Self powered• Simple, rugged• Inexpensive• Wide variety• Wide temperature range

• Most stable• Most accurate• More linear than a thermocouple

Disadvantages

• Non-linear• Reference junction required• Least stable• Least sensitive

• Expensive• Current source required• Self heating


Principle of Operation for RTDs

Materials of Construction

• Most common material is PLATINUM because of its linearity, repeatability and useable temperature

• Other RTD materials include nickel and copper

RTDs based on electrical resistance changes through a materials which is proportional to a change in temperature

Resistance increases with increasing temperature.


RTD Element Construction

• Hand fabricated• Highest operating temperature

• Most common at Conax• Good in vibration

• Mass produced• Least expensive

• Low operating temperature• Largest resistance for size

Alumina Oxide‘Shell’

Alumina Oxide‘Substrate’

Platinum FilmLaser Etched

Wire WoundWire Wound Thin Film


RTD Lead Wire Configuration

Catalog Description - RTD43W3-SS25-T5AL-12.00”


Common RTD Probe Constructions

RTD

“Compacted Construction”

ERTD

“Powder Filled Tubewell Construction” (Bare Leadwires Strung Thru Preformed MgO Insulators)

Can’t be Bent!

MRTD

“Powder Filled Tubewell Construction”(Teflon Insulated Wires Connected Directly to Element)

Limited to < 400°F


Sheath Materials

Catalog Description - RTD43W3-SS25-T5AL-12.00”

Refer to Catalog 5005

Physically protects and mechanically supports the leadwires and insulatorsfrom contamination from the process media

Must be compatible with theprocess media and withinternal components

Cost is a consideration

Sheath material may limitconstruction method


RTD Time Response

0 1 2 3 4 5 6 7 8

.250 RTD

.187 RTD

.125 RTD

.187 U

.125 U

.187 G

.062 U

.125 G

.062 G

Pro

be

Co

nfi

gu

rati

on

Time (Seconds)

THERMOCOUPLE RESPONSE TIMES SHOWN FOR REFERENCE

Approximate Conversion Factors

Still Air

20X

Air (10 ft/sec)

4X

Water (15ft/sec)

.25X

Typical Response Times(Based on 63.2% Change - Still Water)


Principle of Operation for Thermocouples

All Thermocouples have a unique‘Seebeck Coefficient’

When wires of two different materials are joined at one end and placed in a temperature gradient, a thermoelectric voltage is

observed.

A thermocouple is not a point measurement .

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Thermocouples

Temperature – Millivolt Graph for Thermocouples ISA SYMBOL

T Copper vs. ConstantanE Chromel vs. ConstantanJ Iron vs. ConstantanK Chromel vs. AlumelN Nicrosil vs. Nisil G* Tungsten vs. Tungsten(W) 26% Rhenium D* Tungsten/3% Rhenium vs.(W3) Tungsten/25% Rhenium C* Tungsten/5% Rhenium vs. (W5) Tungsten/26% Rhenium R Platinum/13% Rhodium vs. PlatinumS Platinum/10% Rhodium vs. PlatinumB Platinum/30% Rhodium vs. Platinum 6% Rhodium

Bas

e M

etal

Ref

ract

ory

M

etal

Pre

cio

us

Met

al

Bel

ow

230

0 °

FA

bo

ve 2

300

° F


Thermocouple Calibrations

Catalog Description – K-SS25-U-T5AL-12.00”

Refer

to C

atal

og 500

5


Thermocouple Limits of Error

Refer

to C

atal

og 500

5


Thermocouple Construction

Catalog Description – KK-SS25-U-T5AL-12.00”

“G” Grounded

“U”Ungrounded

“B”

Bare Tip

Two Common Methods of Manufacturing

Compacted Construction

MIMS (Mineral Insulated Metal Sheathed)

Typical of Base Metal Thermocouples

Tubewell Construction

Typical of High Temp (Platinum and Refractory Metal ) Thermocouples

Three Common Tip Configurations


Thermocouple Ungrounded Junctions

• Advantages– Circuit is isolated from ground– Generally more reliable– Problems with insulation can easily be detected

• Disadvantages– Slightly slower response time– Junctions are difficult to fabricate in small

diameter probes (<= .040”)


Thermocouples

0 1 2 3 4 5 6 7 8

.250 RTD

.187 RTD

.125 RTD

.187 U

.125 U

.187 G

.062 U

.125 G

.062 G

Pro

be

Co

nfi

gu

rati

on

Time (Seconds)

RTD RESPONSE TIMES SHOWN FOR REFERENCE

Typical Response Times(Based on 63.2% Change - Still Water)

Approximate Conversion Factors

Still Air

20X

Air (10 ft/sec)

4X

Water (15ft/sec)

.25X


Compacted Design Construction(Typical of Base Metal Thermocouples)

NO INSULATOR CALLOUT FOR COMPACTED THERMOCOUPLE CONSTRUCTION (MgO)!!

Catalog Description – KK-SS25-U-T5AL-12.00”

Typical Dimensions

Sheath Wall - 10% (min) of Probe OD

Thermoelements

2-Wire - 15% (min) of Probe OD

4-Wire - 12% (min) of Probe OD


Tubewell Design Constructions(Typical of High Temperature Thermocouples)

Note: Can’t be bent

Catalog Description – S24-AL25-AL-U-T1-12.00”Refer to Catalog 6008

Wire AWGInsulator Material

Cold End Seal(300°F Rated)

Leadwire

Sheath

Single PieceAlumina Insulator

Welded Tip

Thermoelements


Specifying Catalog Sensor Assemblies

Catalog #5005 + Price List Sensor Configurator-OR-


Specifying Catalog Sensor Assemblies

• Use Sensor Configurator for all standard catalog configurations

• Use Catalog #5005 + Price List for all non-standard catalog configurations

– Specials

– High temp sensors

• Future plans include expanding functionality of Sensor Configurator to produce all sensor designs


Termination Styles


Spring Load Assemblies


Temperature Transmitters


Why Transmitters?

• Used to amplify & condition the very small signals generated by process sensors.

• The standard 4-20 mA signal is a high level signal not easily affected by outside noise such as that generated by large electric motors or other strong magnetic fields.

• The current signal versus a voltage signal makes the transmitted signal insensitive to the series resistance of the transmission and permits any number of recorders, controllers and indicators to be series connected without upsetting its calibration.

• Eliminates the need for long runs of expensive, shielded T/C extension wire back to a control room. For RTDs with three-wire circuits, proper resistance balance is critical and, when long extension wire runs are used, accuracy is typically reduced.


Temperature Transmitters

Hockey Puck DIN Rail

SMART/HART SMART PC Programmable


General Features

• All Models are DC powered

• All Models are custom set for the customer’s desired temperature range - or are fully programmable

– A feature that fits well with the Conax Buffalo Technologies philosophy of custom products

• Delivery is typically one to two weeks

– Coincides with our sensor assembly lead times


Thermowells&

Pipewells


Threaded ThermowellThreaded Thermowell


ANSI Flanged ThermowellANSI Flanged Thermowell


PipewellsPipewells


Thermowell-Only Thermowell-Only Description FormatDescription Format

TW,.50-260S-U5.00-S316TW,.50-260S-U5.00-S316


Temperature Sensors

Applications


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©2006Conax Buffalo Technologies 2300 Walden Avenue, Buffalo, New York 14225 USA 800-223-2389 716-684-4500 e-mail: [email protected]

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RTD Assemblies

Thermocouple Assemblies

High Temp Thermocouples

Thermowells and Pipewells

Transmitters and Controllers


Mounting Methods

Termination Styles

Applications Case Studies

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CEMENT KILN SENSOR STANDS UPTO HIGHLY ABRASIVE, HIGHVIBRATION ENVIRONMENT

Industry: Cement Kiln Manufacture

Application: Measurement of temperature inside a rotating kiln, operating temperature 330°C, and stressed by continuous high vibration. The material being processed is nickel laterite ore, an irregular crushed stone approximately 6" in diameter, with a high moisture content. This material is very abrasive.

Customer Requirement: This application needed a thermocouple assembly rugged enough to measure ore temperature in a very abrasive, high vibration kiln environment..

Conax Buffalo Design Solution:A Type K thermocouple made of 8 AWG wire and beaded with two-hole alumina insulators. The 8 AWG Type K thermocouple is placed in a 0.50" Schedule 40 446 SST pipewell to protect the sensing junction. A 3.00" OD x 1.50" ID heat resistant alloy grade HT outer protective pipewell, welded to a 5.25" OD 310 SST flange, houses the 0.50" Schedule 40 446 SST pipewell assembly. The outer grade HT pipewell is coated with a 0.05" thick Nickel/Chrome/Boron coating for the first 3" to provide extra abrasion resistance.

Benefits of Using Conax Buffalo Sensor:The Conax design allowed the customer to provide temperature monitoring of the product in an area that was previously thought to be too harsh for a thermocouple. To date, these sensors have been in service more than 36 months without failure.




©2007Conax Technologies 2300 Walden Avenue, Buffalo, New York 14225 USA 800-223-2389 716-684-4500 e-mail: [email protected]






Fiber Optic Sealing


Accessories



RTD Assemblies






Mounting Methods

Termination Styles


Application Case Studies

Industry: Pharmaceutical Application: Eye Drop Production

Customer RequirementThe production of eye drops requires periodic sterilization of the bottle filling station with careful monitoring of the steam used for sterilization. The bottle filling station uses 20 nozzles to fill a progressive line of plastic bottles. Periodically, the nozzles are lowered into the sterilization chambers located directly below the station. Here the nozzles are exposed to steam to sterilize them. In this SIP (sterilize in place) application, the environment to be measured consists of 80°C purified water followed by 123°C clean steam at 20 psi for 30 minutes. The customer had to ensure that the sterilization process kept the equipment at 123°C for 30 consecutive minutes. The customer was experiencing problems with the accuracy of the temperature readings. They approached their local Conax representative to see if we could correct their problem.

Conax Buffalo Design SolutionUpon investigation, Conax engineers quickly realized that the problem was due to the insertion depth of the sensor element. The customer’s probe used a wirewound RTD element. Because of the construction of a wirewound element and the way the customer had located the probe into the steam flow, the element was not far enough into the stream to give a correct reading.

Conax solved the problem by providing a probe with a thin film RTD element. With a thin film element, the tube is created first, then the element is placed and the tube is filled with Al203 powder around the element. The entire assembly is then sealed with a potting compound. This process allows the element to be placed at the very end of the probe. In an application such as this one, with very little space allowed for probe immersion, the thin-film style probe assures superior accuracy in the temperature readings.

Notice the very small immersion length of the probe into the steam stream. Very little of the wirewound RTD element on the left was actually immersed in the steam. The thin film element can be fully immersed into the measurement area.




©2007Conax Technologies 2300 Walden Avenue, Buffalo, New York 14225 USA 800-223-2389 716-684-4500 e-mail: [email protected]






Fiber Optic Sealing


Accessories



RTD Assemblies






Mounting Methods

Termination Styles


Application Case StudiesIndustry: Emergency Services Application: Fire Rescue Training

Customer RequirementNot all applications for Conax products are industrial in nature. In this situation, the customer needed to replace thermocouples in a device designed to simulate a fire rescue situation. This Fire Rescue Training Center is located on a college campus in New York State and operated in conjunction with local police and fire agencies. As part of their training facilities, the Center uses numerous 12’ x 12’ burner grids to simulate a fire at a crash site of an airplane or some other large equipment. The grids contain rocks similar to lava rock. The burners within the rock are fired by liquid propane. Each grid uses three thermocouples to monitor the temperature of the fire. By controlling the temperature, the Center is able to emulate the circumstances a fire fighter would face at various types of fire emergencies.

Conax SolutionThe Center recently revised their grid structure and in the process damaged 80 of the Type K thermocouples. Since the grids are spread over a relatively large area (for example, the circumference of an airplane crash area), the thermocouple lengths vary from 12’ to 60’, 3/16” diameter, with an Inconel sheath and 20’ of Teflon-insulated leads.










Fiber Optic Sealing


Accessories




RTD Assemblies






Mounting Methods

Termination Styles



RTD SENSOR ENSURES COLD STORAGEIndustry: Liquid and Liquified Gas Storage Tank Manufacture

Application: Monitoring of internal temperatures to -200° C in large liquid ammonia, liquid nitrogen, liquid oxygen and liquified natural gas (LNG) storage tanks.

Customer Requirement: The customer has three tank monitoring options:

Option 1. The tank is filled with liquid nitrogen to pre-cool the tank structure prior to filling with the final product. This prevents rapid cool-down and possible structural damage. Sensors are installed in the insulation-filled annulus area of the double-walled storage tanks.

Option 2. Sensors are installed in the bottom of the insulation-filled annulus area of the double-walled storage tanks to detect leaks.

Option 3. Some storage tank designs require constant monitoring of the tank liquid.

The customer required an RTD sensor assembly capable of immersion in a cryogenic fluid, with a terminal lug for direct attachment to a 0.25" bolt. Leadwire lengths vary from 119 ft. to 279 ft.

Conax Buffalo Design Solution:Conax provided a Type T4 RTD sensor assembly with stainless steel braided leadwire to provide the mechanical strength needed to withstand liquid motion forces inside the storage tank. A 3..50" – long stainless steel barrel encapsulates the RTD element and provides a means to bolt onto a 0.25" stud. The wire is mechanically crimped within the SST barrel with an internal Teflon boot for the cryogenic service. A Conax Buffalo MHM5-040-B12-T seals the leads exiting the storage tank.

Conax Buffalo and local sales representatives worked closely with the customer's engineering group to develop sensor designs and specification data sheets.










Fiber Optic Sealing


Accessories




RTD Assemblies






Mounting Methods

Termination Styles



HEAVY DUTY PIPE CLAMP THERMOCOUPLE STANDS UP TO FIELD ABUSE

Industry: Cryogenics

Application: Liquid Nitrogen Tanks

Customer Requirement:This manufacturer of liquid nitrogen tanks was using a conventional pipe clamp thermocouple to measure pipe temperature externally. The conventional pipe clamp, however, is not very rugged in its design, and the clamps were not holding up to normal physical abuse in the field. They wanted to know if Conax could provide something super heavy duty and almost unbreakable.

Conax Buffalo Design Solution: Conax responded with a severe duty cast iron pipe clamp thermocouple. The pipe fitting consists of an enamel-painted cast iron body with a zinc-plated, heat-treated carbon steel U-bolt and nuts to hold the saddle to the pipe. The body provides a 1/2 NPT port. Conax uses a spring-loaded (CSLW) mounting getting to maintain secure contact of thermocouple with the pipe.

This design is available in other sizes and with any Conax termination head (shown with T8E explosion-proof head).










Fiber Optic Sealing


Accessories




RTD Assemblies






Mounting Methods

Termination Styles



Industry: Oil Refining

Application: Fluid Catalytic Cracker Unit

Customer Requirement:Catalytic cracking converts heavy oils into wide boiling range material that can then be further refined by distillation. The catalyst is in the form of very small spherical particles that act as a fluid when aerated. The particles create a highly abrasive atmosphere.

This customer used a stellite coated temperature probe to monitor the catalytic process. Temperatures range from 500° to 1000°F (260° to 538°C). Due to damage caused by the highly abrasive flow, the probe needed to be replaced monthly. This procedure required three men in asbestos suits to pull out the hot probe. A Conax Buffalo sales representative called on the customer, and as a result, the customer asked if Conax Buffalo could provide a longer-lasting probe to reduce the frequency of probe replacement.

Conax Buffalo Design Solution:Conax Buffalo designed a temperature sensor assembly very similar to what the customer was using but welded a customized Conax fitting to the end of the pipe to mount an SASIC (Hexoloy) protection tube.

Hexoloy is one of the hardest high performance materials available, second only to diamond. Hexoloy is unaffected by most chemicals up to its operating temperature of 3000°F (1650°C).

The unit can be rotated 180° to expose a "fresh" side of the hexoloy tubewell to the catalyst flow, thereby doubling the operating life.










Fiber Optic Sealing


Accessories




RTD Assemblies






Mounting Methods

Termination Styles



MONITORING TEMPERATURE IN LARGE AUTOCLAVE

Industry: Building Block Manufacture

Customer Requirement: The customer needed to monitor product temperature during the curing stage of a building block manufacturing process. The blocks are made from waste ash obtained from coal-fired power stations. The waste ash is compressed into blocks roughly 18"x6"x9", then autoclaved. The finished blocks are used to build the non-load-bearing inner wall of houses and commercial buildings. The outer walls are then constructed from standard brick.

During the curing process, the raw blocks are loaded onto carts placed on running rollers inside large autoclaves, 13ft. In diameter and 160ft. long. These operate at 250°F (121°C) and 200 psi. The sensors needed to be installed through the sides of the cart to measure temperature during the process. The assemblies required long lead lengths (up to 200 ft.).

Conax Buffalo Design Solution:Because of the temperature and steamy conditions encountered in an autoclave, a normal Epoxy filled T3 termination would not be adequate. Conax Buffalo designed a flexible Type K Teflon-jacketed cable with stranded conductors. The assembly was fitted with an MHC gland with an integral tubewell to house the isolated junction. An MHM gland was used at a port in the side of the autoclave to seal the cables as they exit the chamber. The MHM gland seals up to eight sensor pairs.


Domestic Competition

• Minco

• Pyromation

• Watlow Gordon

• Omega

• Rosemount


Where Have We Been Successful

In General • Gaining opportunities with customers who

associate with Conax sealing technology• Custom Applications• Expanding sales with existing customers• Customers having problems with present

supplier– Quality– Delivery concerns


Where Have We Been Successful

Specialty Application and Industry Successes• Power Generation Applications

– OEM’s- GE, Siemens, etc– Utilities/Power Plants– Resellers

• High Temperature Thermocouple Applications (Type R, S, B, and C)– Semiconductor-chip manufacturing and chip equipment

manufacturers– Vacuum furnace OEM’s and users (Heat Treating)– Glass processing


Thank you!

© 2007 Conax Technologies Temperature Sensors. © 2007 Conax Technologies Temperature Sensor Types...

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