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S.E

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I think that it's safer to have two options for excess CO2 to vent than just the one. If others disagree that's their prerogative.
But if your theory is correct and hops will block up a PRV then you wouldn’t have two reliable options to vent CO2 would you?

It wouldn’t make a lot of difference if you are using the PRV instead of a spunding or as well as. If a PRV would as you say block with hops then by the same argument it is totally unsuitable as a safety device on a pressure fermenter isn’t it?
 

ThirstyFish

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Just because one blocks doesn't mean the other would...

You'd be unlucky to have 1 get blocked. For both to get blocked in the same ferment is incredibly unlikely.
 

S.E

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Just because one blocks doesn't mean the other would...

You'd be unlucky to have 1 get blocked. For both to get blocked in the same ferment is incredibly unlikely.
Ok, I get that you would be unlucky to get one blocked, but why would it be incredibly unlikely to get two blocked under the same circumstances and in the same ferment?

Do you think it follows that if a third PRV was fitted it would be absolutely impossible to block in the same ferment?
 

Grmblz

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This discussion has been had many times, the issue largely has to do with insufficient head space for the high krausen with highly hopped beers, all that "stuff" ends up in the lid trying to get out, and PRV's/posts offer little exit, if they are side by side you are pretty much guaranteed that if one blocks then so will the other, no luck involved just the way it is. as previously stated there's a reason for blow off tubes, and it's only really the advent of cheap, suspect quality PET pressure fermenters coupled with brewers unfamiliar with pressure fermentation that this whole thing has become an issue.
End of day just look at at a couple of pressure vessels, your Bunnings compressor, the kitchen pressure cooker, your hot water system, all these things have a fail safe, but only the compressor and hot water system have the equivalent of a PRV, why? because they are dealing with a clean source, air in one case and water in the other, introduce solids (pressure cooker full of vegetable soup) and a different approach is required, in a ferment with solids be a it hoppy beer or a fruit laden mead a PRV or post supplied spunding valve will have the potential to become blocked and compromise the integrity if the pressure vessel.

As to why anyone would want to pressure ferment from day one is a whole different discussion :rolleyes:
 

Keg King

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Agreed, although both PRV's and ball lock posts are readily blocked by hop debris, which is one reason I use a 13mm blow off tube till after high krausen.
I'm surprised no-one has thought to incorporate a burst disc type device similar to what a kitchen pressure cooker has. It wouldn't need to be sophisticated, just a shaped grommet with a large enough hole, say 15mm and a plastic plug in it that blows out at 30psi or whatever, easy enough to fit it into a lid, and idiot proof. You might still have a huge mess to clean up but at least it would prevent catastrophic failure of the vessel.
Burst discs is something I plan to revisit. Our lid designs are also made of a material which lets them deform so the O-ring can unseal and let pressure decline.
 

S.E

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This discussion has been had many times, the issue largely has to do with insufficient head space for the high krausen with highly hopped beers, all that "stuff" ends up in the lid trying to get out, and PRV's/posts offer little exit, if they are side by side you are pretty much guaranteed that if one blocks then so will the other, no luck involved just the way it is. as previously stated there's a reason for blow off tubes, and it's only really the advent of cheap, suspect quality PET pressure fermenters coupled with brewers unfamiliar with pressure fermentation that this whole thing has become an issue.
End of day just look at at a couple of pressure vessels, your Bunnings compressor, the kitchen pressure cooker, your hot water system, all these things have a fail safe, but only the compressor and hot water system have the equivalent of a PRV, why? because they are dealing with a clean source, air in one case and water in the other, introduce solids (pressure cooker full of vegetable soup) and a different approach is required, in a ferment with solids be a it hoppy beer or a fruit laden mead a PRV or post supplied spunding valve will have the potential to become blocked and compromise the integrity if the pressure vessel.

As to why anyone would want to pressure ferment from day one is a whole different discussion :rolleyes:
Yep that pretty much sums it up. So the main points are:

1. A PRV is fine to use instead of a spunding and is no more likely to block up.

2. If you overfill your fermenter and don’t leave enough headspace you are asking for trouble and it won’t make much difference how many PRVs or spundings you have, especially if you add hops, fruit, woodchips or whatever at the start.

3. If you really want to overfill your fermenter and pressure ferment from the start you really want to fit a burst disc or similar.
 

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