What is a thermowell and what are its characteristics?
When temperature measurement and control instruments are used, they are not installed directly in the industrial process. The sensors are installed in Thermowells for temperature sensors, which isolates them from the stresses of the process.
Flow, high pressures and corrosive chemical effects can damage our probes, which is why they are protected with metal tubes or in process piping.
In today's post we are going to explain what a thermowell is, what its characteristics are and, briefly, what criteria to use to choose the model that best suits our needs.
WHAT IS A THERMOWELL?
As we have already introduced, a thermowell is a tool that serves to protect temperature sensors (such as thermocouples or PT100 sensors) against corrosion, high pressure, and material velocity.
Depending on the environmental conditions to which the temperature sensor will be subjected, the thermowell has different characteristics. This ensures the durability of the various types of sensors, allowing for their replacement without draining the system and reducing the likelihood of contamination.
In conclusion, thermowells protect the sensor from the harmful effects of the processing environment, preventing measurement errors. This allows all data to be documented using recording devices (such as a PT100 temperature sensor).
Characteristics of a thermowell
The types of thermowells They are classified according to the design of the thermocouple or sensor. They can be straight, stepped or tapered, depending on the diameter and size of the stem.
A straight thermowell It has the same diameter throughout its length and protects against corrosion and erosion.
The stepped thermowellsinstead, it goes from ¾ diameter at the top to ½ the diameter near the tip. This increases resistance, against smoother speeds, and response to temperature, for sensing devices.
He conical thermowell, on the other hand, has a diameter that gradually decreases along its length. With this design, resistance and response times to temperature changes increase.
Therefore, the use of straight or conical thermowells is recommended, using the latter in conditions with greater mechanical load, that is, when they are subjected to high speeds, vibrations or pressure.
In addition to the body design, a thermowell can be threaded, the most common in the industry; or have flanged connections, which allow the measurement instrument to be isolated.
The threaded thermowells They thread into the supply pipe or tank, so they can be easily installed and removed when needed.
The flanged thermowells,However, it is welded, which prevents its removal once it is installed in the process, unless it is introduced into a seamless forging.
Selection criteria for a thermowell
In order for the thermowell to fulfill its function of extracting calibration data from the industrial process more quickly and easily, we must take into account the requirements of the installation and select the appropriate one.
To do this, the characteristics of the temperature meter are related to those of our thermowell:
CONNECTION TYPES
The connection type refers to the nature of the thermowell: is it threaded or welded?
When selecting our model, we must take into account the industry in which we are going to be operating. For example, in the pharmaceutical and food industries, the weldable wires cannot be brought into contact with the product, so it will be relevant to perform a weld.
DIAMETER SIZE
There are Thermowells for temperature sensors designed to measure the dimensions of the digital thermometer that will be used to control the industrial process. However, there are also models with a standard diameter, which allows greater flexibility.
These adapt, thanks to their standard diameter, to the most used devices, with the following measurements:
- 0.26 inches in diameter.
- 0.385 inches in diameter.
TYPE OF MATERIAL
The next thing we will assess is the material it is made of, as this will contribute to the longevity of your product, making it resistant to chemicals, temperatures, and flow rate.
Chemical corrosion can be increased at low concentrations and high temperatures. In addition, we must add the possible erosion that the particles suspended in the liquid would produce.
Therefore, we highlight the following materials as the most used to produce thermowells:
carbon steels
Titanium
Molybdenum/Chromium Steels
Stainless steel
Nickel based super alloys (Incoloy®, Inconel®, Monel®, Hastelloy®, Haynes® Alloy)
Carbon steel has little resistance to corrosive substances and low temperature and pressure applications are limited. Stainless steel, on the other hand, is more resistant to heat and corrosion, which makes it even more interesting.
The rest of the alloys are more expensive than stainless steel, although they are much more resistant.
Find the thermowell you need for your project
Now that we know what Thermowells for temperature sensors are and what we must take into account to choose the one that best suits our needs, we must find the most suitable point of sale.
In SRC We are specialists in temperature measurement equipment. With almost 40 years of experience in the control, regulation and measurement of industrial parameters, we can offer our experience to improve your company.
get in contact with us to resolve any possible doubts that may arise, we will be happy to advise you and satisfy your needs.
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