Estimate CO2 pressure?

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Matt in Birdham
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Estimate CO2 pressure?

Post by Matt in Birdham » Fri Dec 01, 2017 8:15 pm

Minor crisis - my better half has knocked over the CO2 cylinder and stuffed the regulator pressure dial. The regulator itself still appears to work fine (pressure increases when I turn the knob), but I have no idea what the pressure is (dial is totally stuffed, plastic cover and needle off and bent and not repairable). It wouldn't be an issue if I was at serving pressure, but I was giving a new keg a 40psi head start and have since turned the whole thing off to try and fix it. Since I probably won't be able to get hold of a new regulator/pressure dial until later next week, I was just wondering if there any kind of old lore about the place that might help me estimate approx 10-12psi? I do have a carbonation cap so I could fill and squeeze test a plastic bottle. I know roughly what 40psi feels like for a plastic bottle because I occasionally do a sparkling water..

Matt in Birdham
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Re: Estimate CO2 pressure?

Post by Matt in Birdham » Fri Dec 01, 2017 9:10 pm

Also - perhaps a simpler question :) I think my regulator is a "bog standard" from Malt Miller a couple of years ago (can't see them on the site now, could post a pic if required). If I was want to replace the gauge, does anyone know the thread size? Seems 1/8 and 1/4 bsp are the most likely candidates (this is what most fleabay gauges seem to be).

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PeeBee
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Re: Estimate CO2 pressure?

Post by PeeBee » Sat Dec 02, 2017 12:30 pm

Firstly (stern face) don't blame the other half for knocking the cylinder over. Your other half should be blaming you for not securing it. Securing gas cylinders isn't to prevent breakage of gauges but to prevent breaking off the regulator with the cylinder open. You are fortunate not to have experienced what that would have done.

Secondly. 1/4 BSP is about 1/2" across (male thread), 1/8 BSP about 1/3" across. My guess is they are probably 1/4 BSP. You can also get adapters so as to fit 1/8 BSP gauges to 1/4 BSP if needs be. You are right thinking the thread is likely one or the other.

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Kev888
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Re: Estimate CO2 pressure?

Post by Kev888 » Sat Dec 02, 2017 1:11 pm

Is there some way that you could briefly bodge the gas line to a tyre pressure gauge or similar? A certain caution would be needed, but it would only need to be leak-free for a moment, just long enough to let you set the pressure screw.

There are probably things you could do to measure the force the gas exerts on a known area, but I can't immediately think of a good yet simple one. A water column would need to be extremely tall (and water a risk to the regulator), and plungers like bike pumps would include a fair degree of friction to give a false reading.

As peebee says though, get the cylinder strapped up before you do anything else. It would also be worth checking that only the low pressure dial is broken - any signs of damage to other parts of the regulator or the cylinder valve/connector would lead me to avoid using it.
Kev

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Re: Estimate CO2 pressure?

Post by jaroporter » Sat Dec 02, 2017 1:22 pm

if it's the common parweld regulator that a few of the brewshops carry then it's a 1/4" BSPP thread.

as to the first problem, not sure. i've degassed and regassed mine enough times to know roughly what turn and sound hits to roughly 10psi, but i'd probably err on the low side and just keep a regular check on it. once it's at a decent fizz and not foaming maybe turn the gas off at the regulator to make sure that only the gas in the keg headspace can get absorbed, not a continual supply, which will make venting quick and simple if you do go past what you want

failing that i also know there's a tire pressure gauge kicking around the garage somewhere so i might be considering hacking that into something..
dazzled, doused in gin..

Matt in Birdham
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Re: Estimate CO2 pressure?

Post by Matt in Birdham » Sat Dec 02, 2017 7:26 pm

Thanks guys. Yeah, you're right - cylinder should be secured. Lucky its a short 15kg one, so didn't have too far to fall, but still. My only defense is that we have recently moved so things are still in "temporary accommodation"..
Regulator seems OK apart from the dial, which obviously took the brunt of it, so will pick up a new gauge and also end up with a better PSI range while I am at it. Got it set lowish but still doing something seems OK and no foam bombs yet.

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Re: Estimate CO2 pressure?

Post by Fil » Sat Dec 02, 2017 7:59 pm

be prepared with a long lever and bench vice when removing the old valve they use some strong threadlocking superglue on regs, took a 5ft steel tube lever to crack the seal on one i had to service..

pull the old valve to check the thread before buying it likely to be 3/8" bsp.

Or simply fit inline after the reg with a T or Y a 'stand alone' dial generally a 3/8" jg to male 1/4"bsp thread adaptor and a f/f 1/4" bsp barrel nipple with a few wraps of ptfe is all you need to attach a 1/4" bsp threaded gauge to some gas/beer line, which can come in useful as a tester for off gas kegs too ;)
ist update for months n months..
Fermnting: not a lot..
Conditioning: nowt
Maturing: Challenger smash, and a kit lager
Drinking: dry one minikeg left in the store
Coming Soon Lots planned for the near future nowt for the immediate :(

Matt in Birdham
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Re: Estimate CO2 pressure?

Post by Matt in Birdham » Wed Dec 06, 2017 4:46 pm

jaroporter wrote:
Sat Dec 02, 2017 1:22 pm
if it's the common parweld regulator that a few of the brewshops carry then it's a 1/4" BSPP thread.
OK, so the regulator I have is this one. They do indeed state a 1/4 inch "parallel threaded" gauge, but this gauge that I have just received seems to have a larger thread on it. Have I been sent the wrong one or am I suffering from thread confusion? The thread I have is about 1/2 inch across. Caveat - I haven't actually removed the old gauge yet and am just going on what the top of the existing thread gauge looks like. It does look quite a lot thinner though.

Edit: My bad. I was thrown a little by a narrower "stem" between the square bit and the thread on my existing gauge, and in fact my new one seems to fit OK. No sound of leaking yet - I used tape, which I know is sometimes frowned on but others seem to use it no problem. Fil - yes it was tough to get the old one off! Didn't quite need the scaffold pole but a good bit of "percussive maintenance" did the trick.

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Re: Estimate CO2 pressure?

Post by Fil » Thu Dec 07, 2017 12:21 am

Ha, been there .. it was a pressure gauge that led me to make an embarrassing phone call, I ordered an ebay 1/4" bsp pressure gauge and when it arrived the fixing was 12mm in diameter??? the very polite and patient young woman who answered the phone when i rang the UK seller to complain about the mix up explained that BSP pipe sizes didnt reflect diameter measurements DOH!!
ist update for months n months..
Fermnting: not a lot..
Conditioning: nowt
Maturing: Challenger smash, and a kit lager
Drinking: dry one minikeg left in the store
Coming Soon Lots planned for the near future nowt for the immediate :(

DaveGillespie
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Re: Estimate CO2 pressure?

Post by DaveGillespie » Thu Dec 07, 2017 9:15 am

Or simply fit inline after the reg with a T or Y a 'stand alone' dial generally a 3/8" jg to male 1/4"bsp thread adaptor and a f/f 1/4" bsp barrel nipple with a few wraps of ptfe is all you need to attach a 1/4" bsp threaded gauge to some gas/beer line, which can come in useful as a tester for off gas kegs too ;)
This. I have one busted gauge on my 3-way regulator and this now sports a John Guest T-piece just off the regulator with a replacement gauge connected to it. Does the job and no problem faffing about breaking/resealing the regulator itself.

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PeeBee
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Re: Estimate CO2 pressure?

Post by PeeBee » Thu Dec 07, 2017 12:31 pm

Matt in Birdham wrote:
Wed Dec 06, 2017 4:46 pm
...
OK, so the regulator I have is this one. They do indeed state a 1/4 inch "parallel threaded" gauge, but this gauge that I have just received seems to have a larger thread on it. Have I been sent the wrong one or am I suffering from thread confusion? The thread I have is about 1/2 inch across. Caveat - I haven't actually removed the old gauge yet and am just going on what the top of the existing thread gauge looks like. It does look quite a lot thinner though.

Edit: My bad. I was thrown a little by a narrower "stem" between the square bit and the thread on my existing gauge, and in fact my new one seems to fit OK. No sound of leaking yet - I used tape, which I know is sometimes frowned on but others seem to use it no problem. Fil - yes it was tough to get the old one off! Didn't quite need the scaffold pole but a good bit of "percussive maintenance" did the trick.
Sorry, I should have said in my earlier post that '1/4 BSP is about 1/2" across (male thread)' was NOT a typo; BSP thread sizes can be a bit baffling if not accustomed to them.

As it seems you only needed to replace one gauge I should also have asked which gauge needs replacing. The high pressure gauge doesn't tell you much useful info and if it was broken and didn't leak you'd get along just fine without it reading anything. The low pressure gauge is useful though (though my cylinder regulator doesn't have one as its output is fixed - but I use "downstream" secondary regulators which do have gauges).

Matt in Birdham
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Re: Estimate CO2 pressure?

Post by Matt in Birdham » Thu Dec 07, 2017 5:23 pm

Yeah - I was aware that the 1/4 inch thread was 1/2 inch or so across, but what threw me was that the existing gauge had a thinner section between thread and the square nut. This thinner section was the only bit visible (thread was entirely within regulator), so I was a little thrown by that - simply holding my new gauge next to the existing one and the existing one looked thinner. I was trying to decide whether to take the old one out, and risk being without a regulator at all if the new one didn't fit, but happily it all worked out in the end :)
Even more confusing is that the 1/8 inch thread is 9 ish mm across, so quite a bit more than half the width of the 1/4 inch..

Fil
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Re: Estimate CO2 pressure?

Post by Fil » Fri Dec 08, 2017 2:47 am

https://www.google.co.uk/url?sa=t&rct=j ... to41SJiQMG

contains a very useful table of tread measurements in metric ;) armed with a cheap set of ebay calipers you can id any bsp thread..

another titbit you should pick up as a brewer if not already on your back burner is that upto about 1 and 1/2" size bsp and ntp threads are a good match even in rock hard SS..
ist update for months n months..
Fermnting: not a lot..
Conditioning: nowt
Maturing: Challenger smash, and a kit lager
Drinking: dry one minikeg left in the store
Coming Soon Lots planned for the near future nowt for the immediate :(

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