Hit 60,000 psi on a hydro test and my numbers didnt match the chart

We were pressure testing a 14 inch header at the refinery outside Baton Rouge and I noticed the dial said 2,800 psi but the temperature corrected chart on my clipboard said we should have been at 2,745. I pulled out the old handbook and crunched the math again, turns out the coefficient they used in that chart was for schedule 40 pipe, not schedule 80. Took me 20 minutes to verify and redo all six weld locations. How many of you actually double check those correction factors before signing off, or do you trust the preprinted charts every time?

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tylerlane27d ago

That 20 minutes probably saved you a headache later, but I gotta ask, how much difference did it really make in the field? We're talking 55 psi on a 14 inch line, that's within most gauge error ranges anyway. I've seen guys get all wrapped up in chart math and miss the fact that the actual test setup has way bigger variables, like the pump leaking or the temp changing through the day. Don't get me wrong, it's good you caught it, but I wouldn't lose sleep over a preprinted chart being off by 2 percent. If the inspector signs off on it and the numbers are close, most of the time that's what matters.