How to Weld an RTD

Resistance temperature detectors, or RTDs, are a type of thermometer that uses electrical resistance in metal surfaces to detect a change in surface temperature. RTDs are used in applications where temperatures need to remain constant for safety reasons, such as food and medical supply storage as well as factories and refineries that use heaters, boilers and furnaces. They are attached to pipes, tanks or vats with the use of a metal weld pad. RTDs are welded with the use of an arc welder and a fillet weld technique.

Things You'll Need

• Welding face shield
• Heat resistant welding gloves
• Welding apron
• Clamp
• Arc welder

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Instructions

• 1

  Determine the position of the RTD on the metal pipe, heater or other device that you are going to weld it to. The RTD should be attached no further than 250 feet from the lead wire of the transmitter.

• 2

  Put on welding face shield, heat-resistant welding gloves and welding apron. Select the current/amperage setting for the type of electrode welding rod you are using on your arc welding machine-- a one-eighth-inch rod has a 75-amp setting, a 5-thirty-secondths-inch rod has a 22-amp setting.

• 3

  Place the electrode welding rod into the jaws of the arc welder. Attach the grounding clamp of the arc welder to the main metal piece that you are going to weld. Clamp the welding pad or protection well of the RTD to the piece it is going to be welded to -- as you clamp it down, make sure that the metal welding pad sits square against the surface of the work piece.

• 4

  Turn on your arc welder. Move the electrode rod across the surface of the work piece in an arc, as though you are going to light a match to start your arc. Hold the electrode over the center of the joint -- the area that forms a right angle where the welding pad edge is next to the work piece surface -- perpendicular to the piece, at a 45 degree angle to the weld plate of the RTD and the work piece.

• 5

  Start by making a tack weld at the end corners of the welding pad. Move the electrode over the work piece in a side-to-side motion to cover the end corners with a weld puddle -- or a bead of molten metal.

• 6

  Hold the electrode at a 45 degree angle, and starting at the end closest to you, begin to fillet weld by moving the electrode towards you. Allow the weld to make a 15 degree incline up the side of the welding pad edge as you move the electrode back and forth in a Z-shaped pattern. Cover the entire edge of the joint where the weld pad edge of the RTD meets the work piece with the weld puddle.

• 7

  Wait for the molten metal to completely cool before attaching the wires of the RTD to the sensor.