What tests and inspections are stipulated for thermowells?
In accordance with DIN 43772 Point 4.6, all tests and certifications should be agreed between the manufacturer and operator.
What tests are usual or possible for thermowells?
Common non-destructive tests are the pressure test and, for welded thermowells, the liquid penetrant test. In addition, to test the centrality of the bore, ultrasound or X-ray testing is possible.
To test the sealing, helium leak testing is an option. The surface finish or surface hardness may also be tested. A material test would be Positive Material Identification (PMI test).
source - wika