Thermowell Construction

Eight Steps for Selecting and Ordering a Thermowell

Isatis Farayand Abzar Company is a manufacturer of various types ofthermowells. This device is used to protect the temperature sensor against harsh and severe process conditions and to allow the sensor to be removed from its place without the need to stop the process. Although at first glance the thermowell may seem like a simple device, its proper selection requires determining multiple parameters.

Parameters, each of which must be selected according to its characteristics, in order to achieve the goals of minimal adverse impact on measurement accuracy, minimal need for repair and maintenance, and consequently the reduction and elimination of risks arising from damage to the thermowell..

1 ) AND TYPE PROCESS CONNECTION SIZE The thermowell can be connected to the pipeline using one of three methods: flanged, threaded, or welded. However, the connection of the temperature sensor to the thermowell is always threaded, and is selected according to the installation conditions.

2 ) U LENGTH To select the appropriate length, first determine the minimum required length for the thermowell. This length is usually recommended by the temperature sensor manufacturer.

If the temperature sensor manufacturer does not provide a recommendation, API RP 550 standard states regarding the selection of thermowell lengthAPI RP 550that the thermowell should be chosen so that its tip is located in the middle third of the pipe, and the thermowell length should not be less than 2 inches.

3 ) T LENGTH :The distance between the connection to the system and the connection to the instrumentation device, which is standard at 3 inches (except for thermowells with lengthlength=2 ½” U، T Length=2”)

4 ) SHANK CONFIGURATION Thermowells are manufactured in three types: straight, stepped, and tapered. They are selected based on the fact that each fixed thermowell has a different response time and different stress resistance.

5 ) stress analysis

Based on the standard ASME PTC 19.3 TW:2010

6 ) BORE The internal channel of the thermowell, or the so-called thermowell bore, is the place where the stem of the temperature sensor element is inserted.

7 ) MATERIAL The material of the thermowell is determined according to the characteristics of the process fluid. These characteristics include the fluid temperature, the oxidizing properties of the fluid, the presence of sulfur in the fluid, the resistance of the selected material against the pressure exerted by the fluid, resistance to abrasion, and some other factors. This company is capable of manufacturing in stainless steel 316 and 304.

8 ) INSTRUMENT INSERTION LENGTH The length from the beginning to the end of the thermowell, which is specified to match the length of the thermometer sensor.

Thermowell Construction