A Protection Tube is essentially very similar in purpose to a thermowell,
but it’s typically smaller, thinner, and specifically designed to house
thermocouples and RTD’s. It protects the sensor from mechanical damage,
corrosion, and high temperatures while allowing accurate temperature measurement.

Key Features

1. Purpose

  • Shields the thermocouple or RTD from harsh process conditions (abrasion, corrosion, high pressure, or high flow velocity).
  • Allows the sensor to be replaced without opening the process or stopping operations (if designed as removable).

2. Materials

  • Stainless steel (304, 310, 316, 321, 347, 446, etc.), Inconel and various alloys, or ceramic for very high temperatures.
  • Material choice depends on temperature, corrosion, and mechanical stress.

3. Design

  • Tube may be straight or tapered; sometimes stepped.
  • Often thin-walled to improve thermal response. Heavy schedule tubes are available upon request.
  • Closed-end or open-end depending on whether the thermocouple measures fluid or air.

4. Mounting Styles

  • Can be threaded, flanged, welded, or inserted into a standard thermowell.
  • Some are part of a hot junction assembly for immersion sensors.

Advantages

  • Protects thermocouple from physical and chemical damage.
  • Can improve sensor lifespan in harsh conditions.
  • Permits sensor replacement without opening the process in some designs.

Applications

  • Industrial furnaces, boilers, kilns
  • Chemical reactors and pipelines