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Category: Thermowells

So What Is A Thermowell, Anyway?

Thermowells come in many different lengths and materials

Thermowells are a lot like hazardous material suits for thermometers.

You know? The big white or yellow suits that virus hunters use in a “hot zone” or nuclear engineers use to keep their skin from glowing when they turn off the lights.


In other words, thermowells keep the bad stuff away from the thermometer so that it has a long and happy service life.

Installed in a permanent position before the process begins, thermowells are usually one-piece designs which act as a second skin for thermometers.

The thermowell transfers the heat or cold from the medium being tested via a hollow tube which the thermometer fits into. The tube is closed at one end and the temperature testing equipment is inserted and removed from the other.

In many cases, a thermometer can be secured inside the thermowell with a threaded end.


Anything that might do damage to them. A thermometer may bend over time due to stresses from high velocity flows or warp because of high pressure.

And depending on the medium, the temperature testing equipment can corrode or erode over time. If, for instance, the material being tested contains phosphoric or sulfurous acids, then you may want a thermowell made of Stainless Steel 316, as they stand up to corrosion better than other metals, including those often used to make thermometers.

The thermometer is screwed into the thermowell with the stem extending down this tube.

Likewise, if the material being tested has fine particulates suspended in it, the movement of those particulates might wear away at the thermometer.


Actually, thermowells have another function other than the hazmat suit. You can also see them as the gloves that historians use when touching delicate old paper, when the oil on their hands could damage something important.

Thermowells help eliminate contamination of the materials being measured by keeping the temperature testing equipment from ever touching it.

That means that the thermowell allows the user to service or replace a thermometer without disturbing the process, pressure or temperature.

We offer thermowells in Stainless Steel 304Stainless Steel 316, as well as heavy duty Stainless Steel 316 models. They are all one-piece construction and made to fit thermometers with 1/4” diameter stems.