Number of thermocouples during PWHT according to ASME section I and B31.1

[JohnWE]

Hello engineers,
I am starting work on boiler pipelines according to ASME section I and B31.1. We will weld pipes with P no. 4, 5A and 15E with quite large diameters (up to 813 mm) and thicknesses (up to 57 mm). In his specification, the client specified the number of monitoring thermocouples (from 1 to 4 depending on the diameter), and there should be exactly as many control thermocouples as heating elements. Considering the large dimensions of the pipes, it results that up to 20 thermocouples should be used. We would have to use 2 annealing machines for 1 weld. Section I and B31.1 also require a large number of thermocouples. What do you think about this? From your experience, what is the approach to the number of thermocouples on projects according to ASME?

 

[r6155]

Control of uniform distribution of temperature in the wall.
ASME I is clear, try to understand.
Also contact the company that performs the PWHT.

Regards

 

[JohnWE]

@r6155
Thank you for your reply. All standards are clear and simple when you have experience working with them. If you have such, please confirm whether I have interpreted them correctly.

1. In s.I(2021) in Appendix VIII, the exact location and number of thermocouples are given in the drawings. However, point VIII-6.3.4 describes these drawings as "examples". Is this arrangement therefore not required, but only recommended?

2. The entire Appendix VIII applies to materials with P number 15E. Where are the requirements for the others?