Measuring temperature is a crucial part of any industrial process system operation. Unfortunately, thermometers are not designed to withstand especially harsh environments. All thermometers are susceptible to damage from flow, corrosion, abrasion, temperature, pressure, and turbulence, whether they are mechanical (i.e. bimetal or gas actuated thermometers) or electrical (i.e. thermocouples or resistance temperature detectors). A thermometer that is damaged could cause safety issues, contribute to leaking media, or halt production to even the largest of manufacturing plants.

Three Ways a Thermowell Can Help

So how can you protect a thermometer? A thermowell serves as a protective barrier between a thermometer and the process media. Thermowells are often found in industrial process systems within refineries and petrochemical and chemical plants. In addition to protecting thermometers, thermowells provide easier serviceability and reduce operating costs.

Protective Barrier:

A thermowell’s main job is to protect a thermometer from external conditions, which it does by housing the thermometer, as shown in Figure 1. With the thermometer safe inside, the thermowell can handle an assortment of corrosive or abrasive process media and withstand turbulent or high pressure conditions. The thermowell prevents the thermometer’s sensing element from being exposed to extreme hot or cold temperatures.

Increased Serviceability:

If you need to remove or replace a thermometer, thermowells simplify the process by providing easy access. They stay installed in the piping system while a thermometer is being serviced. As a result, operations continue, which means there is no unnecessary downtime, and the process media continues to flow without worry of escaping the system.

Reduced Operational Costs:

Thermometers last longer and do not need to be serviced as often when thermowells are used to protect them. In effect, thermowells help decrease the total cost of thermometers by minimizing the time spent maintaining and servicing the instruments. The fact that you won’t need to replace thermometers as often or maintain a large inventory of them will also save you money in the end.

How to Choose the Right Thermowell

There are several specifications to consider when selecting a thermowell, including:

connection size and type

style

bore diameter

stem length

insertion length

wall thickness

type of weld or mount

media composition and condition

Positive Material Identification (PMI) or Mill Test Reports (MTR)

Non-destructive Testing (NDT), including Liquid Penetrant Inspection (LPI), ultrasonic (UT), hardness testing, radiography (RT), and pressure testing