Diagnosing gas leaks

[Narapoia]

Just sense checking myself here more than anything. I've had my keg system go through a couple gas bottles in quick succession. I did carbonate and serve circa 11 19 litre cornys across the two bottles but my understanding is that isn't enough to go through two of them (2.8kg bottle).

I've done overnight tests and the high pressure gauge:

1. Maintains pressure when pressurized & gas turned off and disconnected from the manifold with a QD on the end - regulator seems to be fine, not bleeding pressure.
2. Maintains pressure when in same situation attached to the manifold with all the gas taps turned off - so seems manifold is fine
3. Maintains pressure when in same situation attached to the manifold with all the gas taps turned on and QDs disconnected from the gas posts - so seems the lines up to the kegs are fine
3. Once beer is carbed and gas lines connected - same test results in a drop of 55 bar to 45 bar overnight. Re-opening the bottle the high pressure gauge pops back up to 55.

Spray tests with Starsan show no bubbling around the posts or lid seals. Keg lids are seated under pressure and I generally haven't been using keg lube on the lid o ring.

My running assumption has been that I have a slow leak around the gas o-rings. Yesterday replaced all of them and applied fresh keg lube but still see the high pressure gauge drop. I'm going to see if I can isolate it to a specific keg/line in the coming days. I'm guessing that while I am carbonating I am also losing gas to the slow leak, running the bottles dry faster. Easy to manage once the beer is carbonated by turning off the bottle between serving - but while carbonating not much that can be done other than having to periodically hit the kegs with pressure and remove the disconnects, but that will make it take much longer.

Am I doing anything wrong or any suggestions?

 

[TwoCrows]

I am not entirely sure that the Oring could seal that sort of pressure, clearly as you stated it can around 45PSI. If it was bar it would be 600 PSi.

If you pressure the lines at 55 and it drops the gauge to 45 then the C02 is going into solution if connected to the beer keg.

The disconnect post on the keg, these are machined to a size and tolerance. The problem that I have seen is that they are dimensions most likely taken from samples of samples and the sizes do vary.
The disconnect on your gas line is the same as well.

The Oring on the post plays an important role in sealing, and some lube is helpful. The slide over fit is important so that the gas disco does not rock side to side or twist and disrupt the seal of the Oring.
Things have a life span and do wear out.
I have very recently gone through this issue and again I just changed the Orings and C02 disconnect on the gas line.
All is well in the world again.
I still turn off at the bottle after carbonating the keg when I am not serving to have some control of the system.

 

[Narapoia]

I am not entirely sure that the Oring could seal that sort of pressure, clearly as you stated it can around 45PSI. If it was bar it would be 600 PSi.

If you pressure the lines at 55 and it drops the gauge to 45 then the C02 is going into solution if connected to the beer keg.

The disconnect post on the keg, these are machined to a size and tolerance. The problem that I have seen is that they are dimensions most likely taken from samples of samples and the sizes do vary.
The disconnect on your gas line is the same as well.

The Oring on the post plays an important role in sealing, and some lube is helpful. The slide over fit is important so that the gas disco does not rock side to side or twist and disrupt the seal of the Oring.
Things have a life span and do wear out.
I have very recently gone through this issue and again I just changed the Orings and C02 disconnect on the gas line.
All is well in the world again.
I still turn off at the bottle after carbonating the keg when I am not serving to have some control of the system.

Ah sorry should have been clearer - the low pressure side to the kegs is set to 14 psi.

The high pressure side is the pressure straight off the brand new gas bottle - around 55 bar. My understanding is that when you close off the bottle, if there is a leak, the residual CO2 on the high pressure side will keep the low pressure side regulated to the set pressure - 14 psi until the high pressure side equalises at around 1-2 bar. It's not much gas in the reg itself, so when looking for leaks you read off the high pressure gauge as it drops first on a closed bottle.

I'm in the process of testing each of the lines individually now to see if all my kegs are leaking or just one of them, then I'll try lubing up the lid o Ring and maybe changing the disconnects, see if that makes a difference. Might need to order some more gas QDs.

 

[DJ_L3ThAL]

Ah sorry should have been clearer - the low pressure side to the kegs is set to 14 psi.

The high pressure side is the pressure straight off the brand new gas bottle - around 55 bar. My understanding is that when you close off the bottle, if there is a leak, the residual CO2 on the high pressure side will keep the low pressure side regulated to the set pressure - 14 psi until the high pressure side equalises at around 1-2 bar. It's not much gas in the reg itself, so when looking for leaks you read off the high pressure gauge as it drops first on a closed bottle.

I'm in the process of testing each of the lines individually now to see if all my kegs are leaking or just one of them, then I'll try lubing up the lid o Ring and maybe changing the disconnects, see if that makes a difference. Might need to order some more gas QDs.

That is correct.

To hasten testing for leaks, I recommend an isolation valve immediately out of your regulator so you can isolate downstream of the regulator, then you would see immediate pressure drop if there is a leak (ie. within an hour, seconds if it is a big leak). The smaller the volume of the tested system, the larger effect on pressure any leaks have. Never have kegs etc connected as they just add to the volume (unless it is the keg itself you are trying to leak test of course).

 

[golfandbrew]

Wait, am I reading this right? you carb'd and served 5.5 x 19L kegs per 2.8 kg bottle? If you're also closed transfering to your kegs that seems pretty good. Someone tell me I'm crazy.

 

[DJ_L3ThAL]

Wait, am I reading this right? you carb'd and served 5.5 x 19L kegs per 2.8 kg bottle? If you're also closed transfering to your kegs that seems pretty good. Someone tell me I'm crazy.

2.6kg cylinder has ~1.4 standard cubic metres (1400 Litres).

Carbonating at 4.5 g/L and closed transferring at a low pressure (you’ll use more gas volume overall if running at a higher pressure…

Carbonating 5.5 kegs = ~500 L of gas
Closed transferring 5.5 kegs = ~200 L of gas.

So no, not efficient he’s used roughly double. I’ve been quite conservative in the above calcs rounding up etc too.

My 2.6kg on my kegerator (dispensing 4 taps only and pushing 5L mini kegs of cleaner through when I clean taps) lasts around 2 years as a rough guide.

 

[Narapoia]

2.6kg cylinder has ~1.4 standard cubic metres (1400 Litres).

Carbonating at 4.5 g/L and closed transferring at a low pressure (you’ll use more gas volume overall if running at a higher pressure…

Carbonating 5.5 kegs = ~500 L of gas
Closed transferring 5.5 kegs = ~200 L of gas.

So no, not efficient he’s used roughly double. I’ve been quite conservative in the above calcs rounding up etc too.

My 2.6kg on my kegerator (dispensing 4 taps only and pushing 5L mini kegs of cleaner through when I clean taps) lasts around 2 years as a rough guide.

Thanks - yes roughly aligns with my expectations based on reading. I prepped a lot of beer for a party otherwise wouldn't usually do that much volume so quickly.

I've been isolating the lines, looks like some were/are leaking around the gas post, so I am going to change the disconnects as replacing & lubricating the o-rings has not worked. One of the lines seems to be leaking at the disconnect when not even attached to the keg, Yay. Both of these problematic ones are metal QDs - has anyone has more trouble with these forming seals or leaking?

 

[DJ_L3ThAL]

Thanks - yes roughly aligns with my expectations based on reading. I prepped a lot of beer for a party otherwise wouldn't usually do that much volume so quickly.

I've been isolating the lines, looks like some were/are leaking around the gas post, so I am going to change the disconnects as replacing & lubricating the o-rings has not worked. One of the lines seems to be leaking at the disconnect when not even attached to the keg, Yay. Both of these problematic ones are metal QDs - has anyone has more trouble with these forming seals or leaking?

Which metal ones? I've used the cast SS type for many years and found them to be the best. I recently forked out for one of the "machined" SS type and plan to use that and see, but at first glance it doesn't seem to be any better to be honest. I know with the cast SS ones you should nip them up with a shifter after disassembly to ensure it won't loosen with time (the body assembly).

 

[Narapoia]

Looks like a cast SS QD. So far I am having issues with the 2 stainless QDs I inherited, replaced one with a new plastic one, might take the ss one apart and clean/inspect. The body assembly felt fairly loose (Hand tightening) but even after fixing that still seemed to leak when not connected to a keg.