What is the Best Way to Install a Thermocouple?

Because start-up techs do the initial training and the installing of the thermocouples, the proper technique is often misplaced or forgotten. The start-up of the equipment is a whirlwind of problem solving tons of technical information including machine configuration, operation, formulation, maintenance, etc. There is so much information it is hard to absorb in a few short days.

The thermocouple consists of:

  • A two pronged probe
  • A threaded housing
  • Threaded compression fittings

The thermocouple installation takes three steps:

  1. The threaded housing is threaded into a bushing on the side of the compression chamber.
  2. The probe is then checked for proper length.
  3. The compression fitting is tightened to lock the probe at the proper depth; Determined by looking in the compression chambers and seeing where the end of the probe is in relation to the probe port hole.
  4. The end of the probe should not extend into the compression chamber. It should be flush or slightly recessed (1/32″) with the port hole.

Why is this important? If the probe extends into the chamber, the friction from the product moving over and around it will shorten the life of the thermocouple. Likewise, if the probe is recessed into the port hole too far, it can become covered with product and give a low reading.

I like to do it by covering the port hole with a finger and inserting the probe. I do this until I can feel it on my finger. Then, I tighten the compression fitting, and the chamber is ready to go back on the extruder.

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