I finally had a pressure test go sideways on a tank last month

We were testing a 500 gallon tank for a dairy plant in Wisconsin. Everything looked good on paper. Hooked up the air and got it to about 80 PSI when I heard a hiss I didn't like. Turns out a seam weld on the bottom head had a tiny pin hole that we missed during inspection. Had to drain it, grind it out, and re-weld the whole seam before we could test again. Any of you guys had a weld fail that looked solid but wasn't?

3 comments

3 Comments

rowanellis19d ago

Hold up though 80 PSI on a 500 gallon tank for a dairy plant that's a pretty low test pressure for that size. Usually you'd want to hit at least 100 to 125 PSI for a proper pressure test on a tank that big especially if it's gonna hold milk or cleaning chemicals. A pinhole at 80 PSI is definitely a sign that weld was weak but it could have blown out completely at higher pressure. Just saying maybe bump your test spec up next time so you catch those issues earlier rather than after a real failure.

terrybennett18d ago

Wait 80 PSI is considered low for a 500 gallon tank? Wow @rowanellis that's crazy to me.

knight.mason18d ago

Rowan's got a point. You don't want to find out that weld was only good to 80 PSI after the tank's been in service for six months and someone's elbow deep in caustic cleaning solution. I've seen tanks tested too low pass initial inspection, then blow a month later when the temperature drops and the metal contracts just enough to stress that weak spot. Bumping the test up to 100 or 110 might pop a few pinholes, but that's way cheaper than a chemical spill or a lost batch.