How to Select the Best Thermowell for Your Temperature Sensor

In industrial applications, the right temperature measurement depends on the protective barrier it resides in, as well as the accuracy of the sensor itself. Thermowells are useful barriers that protect thermometers from the process environment and all of it has to offer; high pressure, flow and corrosive media. It is critical to select the proper thermowell to ensure accurate temperature measurement, optimal process, and safe operations.

What is a Thermowell?

Typically a thermowell is a cylindrical, metallic fixture which houses a temperature sensor (thermometer, resistance temperature detector (RTD), or thermocouple). A thermowell is also installed directly into a process stream which allows a temperature measurement which avoids the direct process medium contact. The thermowell design provides an easy way to maintain (or change) sensors during the operation of process stimulation that not only improves the system reliability but also reduces downtime.

Significance of Choosing the Right Thermowell

The choice of thermowell directly impacts the accuracy and longevity of the temperature measurement system. An improper design will result in inaccurate measurement, damage to the sensor, or possibly a process safety issue.If you select wisely you will promote its compatibility with the operating environment, select proper industry standards, and allow for as much longevity as possible.

Selecting the Right Thermowell

1. Process Conditions

The temperature, pressure, and flow of the process help determine its thermowell design. Tapered or stepped thermowell designs may be preferred in high-pressure or high-velocity systems because they facilitate reduced stress and vibration.

2. Material

The most common materials for thermowells are stainless steel, carbon steels, and alloys. The thermowells must be appropriate to the process medium and provide appropriate resistance to corrosion, erosion, or chemical attack.

3. Mounting Type

Typical mounting types are threaded, flanged or welded. The design should account for the type of installation and future maintenance, as well as, the sealing level required for the process. 

4. Standards

For critical applications in all aspects of the industries including petrochemical, power generation, and pharmaceutical manufacture, thermowells must be designed in accordance with ASME PTC 19.3 TW standards for their safety and reliability.

Conclusion

Selecting the correct thermowell means considering the process requirements, materials used with the sensors, installation complexities, and industry requirements. A properly designed thermowell, can improve accuracy of measurement, can prolong the service life of the sensor, and can maintain continuous operation. For thermowell products offering high-quality, engineered solutions, Tempsens provides products for modern industry.