Pressure Relief Valve

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Bender_

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Hey all,

After some advice please. 🙂

Upgraded my SS brew bucket to a domed lid today to do pressurerised transfers. Put the lid on a new batch and pitched the yeast starter early arvo then checked it later - no airlock activity (complete equilibrium on an S shaped kind) but Tilt is showing a drop in gravity and the smell is obvious. (I know airlock activity is not the be all and end all)

Anyway I noticed that when I took the lid off briefly to check the seal the airlock shows a build up in pressure but slowly reduces, and the only possible place I could notice any chance of CO2 escaping is the pressure relief valve.

So had a fiddle with it and added some washers to tighten it up, and yep that definitely the place where it's escaping. This was done more to ensure the seals on the new lid were connecting okay to the fermenter.

What I don't understand it what's the point in having an airlock if the lid already has the built in PRV? I get that it's needed for safety/structural integrity reasons for doing the closed transfer, but then again the kit has a PRV built in anyway.

A bit confused really, as all the photos online of the same lids don't have a built in PRV, so I'm guessing I got a Chronical specific one perhaps.

Anyway thanks for reading and sharing your thoughts if possible.
 

mynameisrodney

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The airlock will let air out at a negligible pressure. PRV will let it out much higher, higher than you want at the start of fermentation. Some PRVs are low enough for the tail end.

Prv is also a tiny hole. If you use this as your main blow off, it will get gunked up more readily than an airlock, and definitely more easily than a blow off tube.

3rdly redundancy. You want the prv there in case your other airlock or blow off gets blocked. Chances of 2 things getting blocked is low. If you only have a single point of failure there's more likely you'll have a bad time.
 

mynameisrodney

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Sorry, also should add that if you are adding washers to your prv then you don't really know when it will release any more. When this brew is done I'd disassemble and get it working properly.
 

Bender_

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Sorry, also should add that if you are adding washers to your prv then you don't really know when it will release any more. When this brew is done I'd disassemble and get it working properly.
Do you think the PRV is not working properly if it's already allowing this low end of pressure out instead of the airlock?
 

mynameisrodney

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Do you think the PRV is not working properly if it's already allowing this low end of pressure out instead of the airlock?
If that is where the air was escaping, then yeah it isn't working properly. Most airlocks have a fluid column of what, 3cm? So the pressure needed to cause a bubble is ~3cmH2O which is 0.04psi. Having a quick look at the SS brew tech website it looks like that prv is rated to 2 - 2.5psi, so at least 50x higher.

There is however also a chance that the air was escaping the lid seal, as you say you took off the lid off as well. Maybe re-seating that has caused it to seal.

EDIT: If you get a leak again, start spraying any questionable areas with starsan and look for bubbles before you take anything apart.
 

Bender_

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If that is where the air was escaping, then yeah it isn't working properly. Most airlocks have a fluid column of what, 3cm? So the pressure needed to cause a bubble is ~3cmH2O which is 0.04psi. Having a quick look at the SS brew tech website it looks like that prv is rated to 2 - 2.5psi, so at least 50x higher.

There is however also a chance that the air was escaping the lid seal, as you say you took off the lid off as well. Maybe re-seating that has caused it to seal.

EDIT: If you get a leak again, start spraying any questionable areas with starsan and look for bubbles before you take anything apart.
Will keep and eye on it and do some spraying if need be!

Thanks very much for your help mate, much appreciated.
 

Grmblz

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That's interesting, according to their web site the chronical lid (1.5") has no PRV, whereas the chronical "Brewmaster" edition has a 3" tri clamp and PRV.
I'd be inclined to seal the PRV completely, and see if the airlock then works normally, no real danger here (apart from a bit of mess to clean up possibly) you're not going to block a 1.5" port it'll just blow the bung out, but given the vessels are only rated at 1psi I doubt it would even do that before pressure started to leak from the seal.
As you've already noted the PRV on the standard lid seems a bit pointless, even a bit gimmicky.
 

Bender_

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Indeed, all the photos I saw of it when researching the lid before buying it had no PRV, I just assumed they updated their line to have them all come stock with the PRV now.

Funnily enough I took the washers off, reassembled the PRV and gave it a few before doing the starsan test and it appears to be working now. Might have needed a bit of fiddling to get it flush to work properly.

In the end I guess it's not a big issue anyway? If I'm going to do the pressurerised transfers I want to know it's definitely airtight is all, which I can adjust with the washers if need be.
 

MashBasher

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Indeed, all the photos I saw of it when researching the lid before buying it had no PRV, I just assumed they updated their line to have them all come stock with the PRV now.

In the end I guess it's not a big issue anyway? If I'm going to do the pressurerised transfers I want to know it's definitely airtight is all, which I can adjust with the washers if need be.
I don't have a brew bucket, but I do have a chronical. I've attached a pic of my lid and badly McGyvered pressure gauge/gas connector for pressure transfers. You can see the little PRV in the lid. My chronical is from 2015 and came with this domed lid.

Sounds like your lid is the same?

With mine, I don't need much pressure to do a transfer. I use 1 PSI and get a little help from gravity (i.e., receiving keg lower than fermenter). I have done, no joke, I reckon at least a hundred transfers this way.

Any more pressure than that and my PRV opens. If you went nuts with pressure, the spring clips on the fermenter would pop - they are designed that way as a safety "feature" according to SS Brewtech. Cheap-as, I reckon.

So just a suggestion - don't overthink the PRV and don't overdo it. There is much pleasure in nursing a pint of the good stuff while watching liquid move under (low) pressure.
Kaoa+ddPRhygxOgtLoD3pw.jpg
 

Bender_

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I don't have a brew bucket, but I do have a chronical. I've attached a pic of my lid and badly McGyvered pressure gauge/gas connector for pressure transfers. You can see the little PRV in the lid. My chronical is from 2015 and came with this domed lid.

Sounds like your lid is the same?

With mine, I don't need much pressure to do a transfer. I use 1 PSI and get a little help from gravity (i.e., receiving keg lower than fermenter). I have done, no joke, I reckon at least a hundred transfers this way.

Any more pressure than that and my PRV opens. If you went nuts with pressure, the spring clips on the fermenter would pop - they are designed that way as a safety "feature" according to SS Brewtech. Cheap-as, I reckon.

So just a suggestion - don't overthink the PRV and don't overdo it. There is much pleasure in nursing a pint of the good stuff while watching liquid move under (low) pressure.
View attachment 120626
Yep that's the one. Was more surprised as all the pics online didn't have that feature, and it was slowly letting lower end pressure out of the fermenter. Thanks for the photo and detail!
 
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