It is my first time encountering this particular situation, so an expert's advice on this would be greatly appreciated. Is my interpretation correct? Should an in-service piping system per B31.8 be hydrotested at 268 bar? Wouldn't it be more reasonable to repeat the hydrotest at the original pressure of 54.6 bar? Its a little confusing to me. When I look in API 570, it states that hydrotest should be performed in accordance with ASME B31.3, which is 1.5 x design pressure, which turns out to be a lot less than 268 bar. When I did a calculation on what that pressure is, I get a pressure of about 268 bar. However, when I look in B31.8, it states that an in-service piping system must be tested at a pressure that will cause a hoop stress of at least 90% of specified minimum yield strength. The company that will perform the test wants to test at the original hydrotest pressure of 54.6 bar. My questions are as follows: For determining structural integrity of the pipeline, it is being proposed to perform a hydrotest on the piping system. Part of the line runs outside of industry boundary, which would put it in the ASME B31.8 scope, and the other part runs inside industry boundary, which would put it in the ASME B31.3 scope. The line was hydrostatically tested before commissioning at a pressure of 54.6 bar. operating conditions are 39 bar/45C, design conditions are 48.6 bar/65C. The line has been in service for about 3 years. Some history: As already mentioned, the pipe is a 3" Sch 40 API 5L Gr B seamless pipe transporting methane gas. I have a question concerning the pressure test requirements, particularly with the required test pressure, for a 3" Sch 40 gas pipe.
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