Pressure relief valve on CO2 regulator

[mjensen52402]

I just hooked up my new tank of gas and gas started coming out of the pressure relief valve on the regulator. The regulator worked fine last week. Do I take my tank and regulator to Hawkeye Fire and ask them to check the pressure on my tank?
If my tank is just over filled I can just let the extra CO2 drain off. I don't want to try that and dump an entire tank of CO2.
Does Hawkeye Fire fix regulators?

[jjpeanasky]

I think I've seen that most regulators have the PRV set to 45psi, but that's on the regulated side. If your tank was truly over pressure, the PRV on the tank would blow off.

Sounds like it's a regulator problem.

- Josh Peanasky

[andrewmaixner]

Isn't it essentially impossible for a tank to be over-pressure, at room temperature?
Isn't the pressure constant given constant temperature, as long as there is liquid CO2 in it and some headspace, because physics? So if it sloshes, it has to be the regulator?

[karl]

The high-side PRV is on the tank valve itself. As our colleague says, the PRV on the regulator is on the regulated (low) side.

If it is leaking I'd agree that the PRV or regulator is at fault. If you have a low-side pressure gauge you can verify that the pressure is correct. If the pressure is ok, then the PRV is the culprit. Often these can easily be unscrewed and replaced.

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[mjensen52402]

HF once over filled my tank and it blew the pressure release valve on the tank. A faulty scale was to blame.
PV = nRT It makes sense an over filled tank would cause the PRV to blow.
The pressure relief on the regulator is just a spring. On one of the Interwebs I found the tolerance for the valves is 20%. If PRV on tank has a higher rating than PRV on regulator it could eventually work itself out.
Next step is to switch tanks and see if it still leaks.



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[mjensen52402]

It might just need to be screwed in further.

[tony b]

I figured there was a "loose screw" involved somewhere -

[andrewmaixner]

HF once over filled my tank and it blew the pressure release valve on the tank. A faulty scale was to blame.

Did it blow at the filling station, or was it something that happened after they gave it back to you?
(I'd guess that incomprehensibility of the fluid CO2 would make it blow the moment they overfilled?)

[mjensen52402]

It blew about 30 minutes after I got home. As the cylinder warmed back up it eventually hit the magic P. Dumped the entire tank in about 10 seconds.

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[andrewmaixner]

It blew about 30 minutes after I got home. As the cylinder warmed back up it eventually hit the magic P. Dumped the entire tank in about 10 seconds.

That sounds dangerous (asphyxiant, or while driving, etc)
How can a person make sure that hasn't happened to them -- shake it and make sure there is some headspace after a new fill?

[tony b]

Similar thing happened to John Buck, except it did happen in his truck on the way home. Fortunately, he'd stopped to do another errand and wasn't in the vehicle when it popped!

[karl]

Yeah, when John's popped it totally fogged the car. It was a good thing he was stopped and outside the vehicle. I always (even in winter) drive with the windows open when I'm carrying CO2.

As far as being a dangerous asphyxant, yes, but to a limit. Let's try to figure out that limit. Most of us have gas bottles that are at most 10-lb capacity. Even assuming that Mark's bottle was over-filled to 15 lbs:

15 lbs * (454 g / lb) * (1 mol / 44 g) * (22.71 litre / mol) * (0.0353 ft^3 / litre) = 124 ft^3.

Mark, the science teacher, is my chemistry and math correct? (Assuming S.T.P.)

That's enough to fill a 10-ft by 10-ft room to the bottom 15 inches full of CO2 if a slow leak (deadly to the cat or dog or passed-out brewer). But if there is even modest air movement typical to a home, it will diffuse and mix reducing the oxygen in the same 10x10 by 8-ft room from 22% oxygen to 18.6% oxygen. Dizzying certainly, but not yet deadly.

Now if I had a 20-lb bottle over-filled to 30 lbs... I'm going to make it a point to make sure my brewery has enough air exchange to diffuse the CO2 out event further.

Andrew, you are correct to point out that we should consider safety contingencies to handle catastrophic equipment failures.

[andrewmaixner]

Sounds about right. I was remembering the approximate rule of 1000 for liquid to gas volume -- but I guess the volume inside the cylinder isn't that much to start.