I suppose that depends on what code you'll be designing your spec break to. We adhere to installing two forms of independant overpressure protection when doing a spec break which doesn't neccessarily involve a PSV.
Would this not be a safety issue as there is a possibilty of contaminating parts and piping rated for sweet service with H2S if not properly protected?
I assumed this would atleast be would in a some set of recommended practices like API.
It has been standard practice at our company to use two check valves on a sweet pipeline when tying into a sour pipeline in order to protect against back flow. I've been looking through all the codes I can get my hands on to find this as a requirement but can't find it written anywhere...
