ASME B16.5 Bolting Surface Treatment

[Ollie42]

Delivery Of Plate Heat Exchanger
Customer requiring 200 my to be applied on the stud bolts (also the thread) of ASME B16.5 Class 150 nozzle connection, before assembly.
Painted nuts are re-taped or re-threaded to remove the paint and provide clearance inside for the coated bolt.


In the context of applying 200 my epoxypaint with lower hardness on top of bolting , is this really allowed
according to ASME, where steel flanges and fittings have to be selected for a design pressure and elevated
temperature, their size is dictated by individual code tables (e.g. ANSI
B16.5).

 

[gr2vessels]

You are not suppose to tamper with bolts and nuts with guaranteed properties by the manufacturer. That includes the coating provided by the manufacturer. If you need to provide another coating, you contact the manufacturer to supply the required coating on bolts and nuts. They have their own operating tolerances for the manufacture of threads, based on their own coating process.
If you modify the threads on nuts and bolts, you lose the warranty and the coating becomes your liability.
The manufacturer provided coating is based on maintaining the bolting assembly mechanical / tensile properties, certified by the manufacturer.
However, you can apply any coating on the external bolting surfaces, except the threads.
Cheers,
gr2vessels