Weld Pad Temperature Sensors In Depth

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Thermometrics manufactures a full line of standard and custom weld pad RTD’s. The weld pad (tube skin) termination allows a temperature sensor to be welded directly onto piping or other metal surfaces to sense the surface temperature. Weld pads are most commonly used in fired heater tubes, refinery heater tubes, boilers and furnaces in refineries, and industrial boilers. However, they can be used in virtually any application requiring surface temperature measurement.

Weld Pad (Tube Skin) RTDs come in 4 standard configurations

•Weld Pad Sensor with Straight Transition

•Weld Pad Sensor with 45 degreeTransition

•Weld Pad Sensor with 90 degree Transition

•Weld Pad Sensor with 45 degree Sheath and Straight Transition

Weld Pad (Tube Skin) RTDs Attributes

•Heat Transfer pad with excellent temperature response

•Rugged stainless steel sheath provides excellent mechanical protection

•Replaceable element design simplifies RTD replacement.

•To replace a faulty element, you simply remove the head cover, disconnect the leads and remove the element. You then insert the new element and reconnect the leads. Your process is up and running in minutes.

Weld Pad RTD and Thermocouple sensors are commonly used in Petro-Chemical industries. These sensors are welded to pipe to provide a measurement of process temperature.

The samples shown are 100 ohm RTD sensors in a 4-wire, Flex Armor and Teflon insulated configuration. This provides an operating temperature range of -50 to 250oC. Fiberglass insulated wire is also available.The outside diameter of the sheath is .250 O.D.

The length of the tip, sheath, transition and lead wire are specified by the customer to suit the application. The lead wire can be supplied as bare wire, terminated with plugs, jacks, spade lugs, or junction boxes.

Weld Pad RTDs Can Be Customized To Your Application

The temperature sensor can be configured to your dimensional requirements or it may be purchased off the shelf with a 1.0″ by 1.0″ weld pad, (.125″ thickness), 4″ sheath length and 36″ of stainless steel protected fiberglass lead wires.

These temperature sensors configurations can be manufactured as RTD’s, Thermistors, Thermocouples.Common types include; 100, 500 and 1000 ohm RTD temperature sensors.

Weld Pad (Tube Skin) RTD Specifications

Platinum 100 Ohm, .00385 Alpha
Temperature Range – 50oC to 400°C
DIN Class B, ± .12% ohms at 0°C Celsius
= .3 ohms + (.005 ohms x (temperature) )

Temperature versus Resistance relationship for the range – 200°C to 0°C

RT = R0 [ 1 + At + Bt² + C ( t – 100oC) t³ ]

Temperature versus Resistance relationship for the range 0°C to 850°C

RT = R0 (1 + At + Bt² )

Coefficients

A = 3.908 02 x10 ^-3oC^-1
B = -5.802 x 10 ^-7oC^-2
C = -4.273 50 X 10 ^-12oC^-4