Instrumentation Question:

Answer #1
In numerous applications, it is neither desirable nor practical to expose a temperature sensor directly to a material. Wells are therefore used to protect against damage corresion, arosion, aborsion and high pressure processes. A thermo well is also useful in protecting a sensor from physical damage during handling and normal operations.
Materials used in thermo wells: Stainless steel, Inconel, Monel, Alloy Steel, Hastelloy

Answer #2
Protect the sensor for damage and main thing during maintenance we can remove the sensor without stop the process.