In order to safeguard temperature sensors such as thermistors, thermocouples, and bimetal thermometers from damage caused by high pressure, high material velocity, and corrosion, thermowells are often used in industrial settings. They extend the life of a sensor, enabling it to be replaced without depleting the system, and decreasing contamination risk.
High-pressure thermowells are often fabricated from bar stock, which ensures their structural integrity. Tubing with one end welded may be used to construct smaller thermowells for use in low-pressure settings.
What is a Thermowell, and how does it work?
Thermowells are cylindrical fittings that protect industrial processes’ installed temperature sensors. There are two types of thermowells: closed-end and open-ended. The open end of the tube, which is often outside the process vessel or pipe and any thermal insulation, is implanted with a temperature sensor, such as a thermocouple, thermometer, or resistance temperature detector.
The process fluid heats the thermowell wall, which then transmits the heat to the temperature sensors using thermodynamic principles. The additional bulk of the sensor-well combination reduces the sensor’s responsiveness to changes in process temperature compared to a probe directly submerged in the process.
The sensor may be simply changed if it stops working correctly without requiring any alterations to the vessel or pipework. The inclusion of a thermowell reduces sensor responsiveness and accuracy, since the mass of the thermowell has to be heated to the process temperature before the sensor can respond.
List of Thermowells Types
RTDs, Temperature Recorders, Thermometers, Thermocouples, and Temperature Controllers may all be used with Thermowells, which are compatible.
Thermowells may be constructed in a number of different ways. The broadest range of possibilities A 1/2, 3/4, or 1 NPT threaded connection may be used. Connections may also be made using the socket weld, the raised face flange, or the weld-in method. To alleviate internal pressure, bimetal thermowells are available with a 1/2 NPSM instrument connection.
Various Thermowell Types
It is possible to identify thermowells by their process connection of stem design. The following are some of the most common thermowells types used in diverse sectors.
1. Threaded thermowell
A threaded thermowell is a thermowell that is screwed directly into a thermowell threadolet or into a tapped pipe wall, as the name indicates
2. Thermowells with Flanges
There are two flange collars on a flanged thermowell: one on the mating flange and one on the collar itself. A pipe nozzle is attached to this mating flange.
3. Weld in thermowells
There are thermowells that are welded into the pipe or the process vessel itself, called weld-in thermowells. An option for socket welding thermowells is available, which allows you to directly weld them into the socket of the weldolet. Instead of being welded into the pipe, these tools may be inserted into it.
It is the distance from the thermowell’s tip to the root of its threads that is used to determine the depth of a thermowell’s insertion into a process piping system or vessel. That sensitive component of a temperature instrument stem or bulb’s stem or bulb must be at least as long as the U-length of the temperature sensor.
5. Shank Thermowells
Straight, stepped, and tapered hex shanks are all options for Shank Thermowells. Thermowells with tapered shanks are ideal for heavy-duty use. Standard duty applications often use stepped shank thermowells. Designed for instruments with short stems or large stem diameters, straight shank thermowells are ideal for use with straight shank thermowells.
6. Extension thermowells
Whenever a vessel or pipe system is covered with insulation, lagging extension thermowells are used. T-length is the distance between thermowell’s instrument connection and process connection, which is known as the extension length.
What’s the Purpose of a Thermometer?
Thermowells serve as a shield between the process medium and the temperature sensor. In refineries, chemical, and petrochemical facilities, thermowells may be found in industrial process systems. As an added benefit, thermowells simplify maintenance and save operating costs for these sensitive devices.
- A Barrier to Keep You Safe
The main purpose of a thermowell is to protect a thermometer from the elements, which it does by enclosing the instrument. The thermowell can withstand corrosive or abrasive process media and turbulent or high-pressure conditions, as long as the thermometer is protected within. When the thermometer is installed in a thermowell, extreme heat or cold won’t damage the sensor.
- An Improved Usability
Thermowells make it simple to replace or remove a sensor since they provide easy access. While a thermometer is being serviced, they are still attached to the piping system. As a consequence, the system continues to function, preventing any downtime and ensuring that media content is not lost.
- Reduced Costs of Doing Business