PRV on Bright trips at 10PSI

[Geoff@drinkzeds]

Hey all. I'm at a loss with carbing in my bright tank. Sometimes I can get my head pressure up to 11.5 but half the time the pressure relief valve seeps at 10-psi. I'm not changing my technique: After filling the bright and cooling the tank to 36 degrees, assuming I want a 2.6, I'll bring head space up to ~9.5 psi and gradually bring my carb stone up to ~20. (11psi+8 wet pressure + 1 for height of Bright tank). When the head space starts to hit 11, I'll take samples until I'm happy.

Sometimes this works perfectly. Half the time, though, the PRV seeps. It doesn't blow, but seeps. (I know this because I'll spray sanitizer on it and can see the bubbles.) I've also switched PRVs from unused tanks and the same thing happens. Any ideas? the only thing that varies (beside the beer) is sometimes I'll have more physical head space depending on how much I've brewed.

5BBL system, glycol cooled jacketed bright tank.

Thanks in advance.

[hokus]

If your PRV is adjustable tighten it so it will hold back more pressure. If it isn't you may need a new and/or heavier spring. A lot of the low end PRV's will have issues like this. You could also install a valve in front of the PRV to be able to 'cap' the tank in this situation, just keep an eye on the pressure for safety. (I.E. done at your own risk)

Also make sure you PSI gauge is accurate. 11 PSI might actually be higher.

[TGTimm]

Are you using calibrated pressure gauges? It's not at all unusual to see a 3+ psi difference between uncalibrated gauges, especially those that have been in use for a while.

I built a calibration set-up around a certified digital pressure gauge and a small, low-pressure regulator. The regulator allows me to check for linearity on the gauge--does it calibrate the same at 10 and 15psi? If not, I toss them. I'm currently using nothing but Zahm and Nagel gauges, as they are the only ones I've found that are capable of being calibrated.

Once you have a grasp on actual pressure, address the PRVs. You'll likely find that they are fine, but your gauges are not. If the PRVs are still blowing at too low a pressure, rebuild them. You should be able to get all the parts--including the spring--from your supplier.

I also test our PRVs and spunding valves on my tester.

[UnFermentable]

If your PRV is adjustable tighten it so it will hold back more pressure. If it isn't you may need a new and/or heavier spring. A lot of the low end PRV's will have issues like this. You could also install a valve in front of the PRV to be able to 'cap' the tank in this situation, just keep an eye on the pressure for safety. (I.E. done at your own risk)

Also make sure you PSI gauge is accurate. 11 PSI might actually be higher.

+1 on gauge accuracy

Are you disassembling your PRVs periodically? IF you have any junk in them, the can have a hard time seating properly, allowing gas to leak below the designed pressure.

I have had spring issues in a few myself....You CAN try to stretch the spring in order to adjust the blow off pressure, but you should test with a rigged pipe and good pressure regulator to see the new cracking point. Another option is to add stainless steel shims inside to raise the spring tension. Again, you should test the adjustment for cracking pressure.

Yet another option (and my preference) would be to use a burst disk instead of the PRV. Then you know it wont leak....but it could rupture if you are not careful. Put it above an open valve if you are smart, then you can close the valve when your new guy stops watching the gauge. It'll scare the you know what out of him, and he will always watch from then on. Keep a spare one or two just incase.

[Geoff@drinkzeds]

Appreciate the ideas!

Thanks to everyone for the ideas.

[briangaylor]

+1 on gauge accuracy

Are you disassembling your PRVs periodically? IF you have any junk in them, the can have a hard time seating properly, allowing gas to leak below the designed pressure.

I have had spring issues in a few myself....You CAN try to stretch the spring in order to adjust the blow off pressure, but you should test with a rigged pipe and good pressure regulator to see the new cracking point. Another option is to add stainless steel shims inside to raise the spring tension. Again, you should test the adjustment for cracking pressure.

Yet another option (and my preference) would be to use a burst disk instead of the PRV. Then you know it wont leak....but it could rupture if you are not careful. Put it above an open valve if you are smart, then you can close the valve when your new guy stops watching the gauge. It'll scare the you know what out of him, and he will always watch from then on. Keep a spare one or two just incase.

We now chuck the PRVs in a soaking cleaner every time we break down the tanks - we had a few that were tripping (luckily early and not late) and even a 10 minute soak in 160* pbw got it back to normal.