How to install Thermowell?

Thermowell is a crucial instrument to measure temperature in the process industry. They provide encapsulation and protect the sensor from direct contact with process fluid in the pipeline, tank etc., All this with allowing the sensor inside the thermowell to measure temperature more accurately.

Thermowell Installation:

  • The thermowell shall be installed as close as possible to the place where the temperature is to be measured.

  • A thermowell with ample extension length shall be used when the tubing is covered with insulation.

Immersion length of thermowell:

  • In the pipe or vessel, thermowells should be inserted so that the entire temperature-sensitive part of the measuring element is projected into the medium to be measured.

  • The thermowell would require the device to extend at least one inch beyond the length of its temperature-sensitive area into the medium for liquid calculation.

  • For gases, the thermowell should be able to immerse the element three or more inches beyond its reactive range.


There are three types of mounting methods for installing thermowell:

  • Perpendicular to the pipe: The perpendicular mounting will be more restrictive for a given size because the thermowell must not touch the far wall of the pipe.

  • In the pipe elbow: In elbow mounting, the thermowell protrudes into the pipe’s exact center line, and the thermowell is in the pipe’s directional flow area

  • At 45° angle to the pipe: An angle mount generally gives the thermowell additional space.

Flow velocity effect:

As a result of high flow rate, extreme pipe pressure or corrosion that weakens the thermowell, a thermowell can split. For most process applications, tapered shank cantilever style thermowells are used to solve the above, as they provide greater strength and vibration resistance than straight-shaft designs.

Install shield:

If the temperature of the gas or air is quite likely to differ from that of the container wall, the temperature of the wall will influence the sensing elements.

Therefore, the unit will be protected against false sensing by placing a shield between the temperature sensing element and the wall.

Sensor installation:

  • To maximize the responses and speed of the sensing factor in a thermowell, the sensor ends should be assumed to be at the bottom of the thermowell.

  • The heat transfer can be improved by using aluminum powder, mercury, or gasoline. Neither the bulb nor the well will react with the liquid.

  • The average cycle temperature should be kept below the boiling point of the material, and the minimum temperature above the freezing point