Customized Stainless Steel Thermocouple Thermowell For Temperature Sensor

Stainless Steel Thermocouple Thermowell For Temperature Sensor

1. Brief Introduction

Thermowells are tubular fittings used to protect temperature sensors installed in industrial processes. A thermowell consists of a tube closed at one end and mounted in the process stream. A temperature sensor such as a thermometer, thermocouple or resistance temperature detector is inserted in the open end of the tube, which is usually in the open air outside the process piping or vessel and any thermal insulation. Thermodynamically, the process fluid transfers heat to the thermowell wall, which in turn transfers heat to the sensor. Since more mass is present with a sensor-well assembly than with a probe directly immersed into the process, the sensor's response to process temperature changes is slowed by the addition of the well. If the sensor fails, it can be easily replaced without draining the vessel or piping. Since the mass of the thermowell must be heated to the process temperature, and since the walls of the thermowell conduct heat out of the process, sensor accuracy and responsiveness is negatively impacted by the addition of a thermowell.

To be representative of the average temperature of fluid, the thermowell must extend a few per cent of the inside diameter of the process pipe or vessel (Normally 1/3 rd of the pipe inside diameter). A rule of thumb that is sufficient for most industrial applications (approximately 1% accuracy) is to ensure that the thermowell projects 5 times its own diameter into the process plus the length of its sensing element. So, for a grounded thermocouple spring-loaded into a thermowell with a 1-inch-diameter shank and a tip thickness of .25 inch, a typical immersion length would equal 5.5 inches (1 inch OD x 5 + .25 inch well tip thickness +.25 inch sensor wall thickness = 5.5 inches).

A thermowell is typically machined from solid bar stock and gun-drilled to ensure a long straight bore that closely approximates the diameter of the installed sensor (ex: a .260-inch bore matching a .250-inch sensor). A thermowell is typically mounted into the process stream by way of a threaded, welded, sanitary cap or flanged process connection. The temperature sensor such as a thermometer, thermocouple or resistance temperature detector is inserted in the open end of the thermowell and typically spring-loaded to ensure that the outside tip of the temperature sensor is in metal to metal contact with the inside tip of the thermowell.

2. Characteristics

• Optional Tantalum sheath, which can be permanently attached, for added protection
• Wake Frequency, Flow-Induced Stress, and Process Pressure calculations can be made to support the thermowell design.
• Full penetration weld standard
• Wake frequency calculations
• Integrated Extension for simple installation
• Wide variety of material options

3. Features

1. Design according to IEC standard
2. Resistance against high pressure
3. Be manufactured and installed during the same term with concerned equipments
4. Different pressure classes to meet different demands

4. Parameter.

5. Application

• They are also used on thermocouples with double protecting tubes
• Applicable under the conditions of high pressure and temperature, high flow-rate media
• Thermowells are mainly used on detachable thermocouples and RTDs or on the facilities of high pressure for later installation of thermocouples and RTDs