Coated bolting has been widely used on flanged joints of pressure vessels and piping whenever there is a potential for atmospheric corrosion. The applied bolt coating has to be dimensionally accommodated, typically by over tapping the nut or less frequently, under sizing the bolt threads. A recently published technical paper by MacMoy, Ian , alleged that this practice is not in compliance with relevant industry standards and potentially compromises the sealing integrity of the flange joint. MacMoy’s paper recommended that any coating that requires over tapping in order to apply a coating’s optimal thickness should be avoided.
In this paper, the authors investigated relevant industry practices, and performed proof testing of some sample bolt sizes. The outcome of this investigation and the details and results of the proof-testing are shared in this paper.