"End of Tank Dump"

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"End of Tank Dump"

Postby PeeBee » Mon Jul 11, 2016 17:41

Here's a good one to scare the kids with. But how relevant is it to us? I guess not at all, or I would have come across it by now?

I'm messing about with fish tank CO2 apparatus (specifically regulators) as an alternative to the commonly used clunky great big welders' gas regulators. And the fish tank mob are very particular about whether they have single-stage or two-stage regulators - whereas we brewers don't seem to give a fig. Single-stage regulators have a habit of no longer regulating if the input pressure drops too far (i.e. the tank of CO2 has emptied of liquid CO2 and there is just gas left - so tank pressure starts dropping from the usual 8-900PSI). If the regulator isn't regulating the remaining gas (at potentially up to 800PSI?) it is "dumped" through the regulator ("end of tank dump"). If connected to a fish tank all the fish die. If connected to a keg of beer...?

Don't confuse single and two stage regulators with primary and secondary regulators (as I did), the subjects are very different.
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Re: "End of Tank Dump"

Postby PeeBee » Tue Jul 12, 2016 10:15

Let's raise the "scare" factor...

The commonly used cheap "welders" regulators are all SINGLE STAGE! And therefore many of us are at risk of this "End of Tank Dump". Some of us can take comfort that their kegs have "pressure relief valves" (mine haven't) but that would still leave a very high pressurised keg. And if like me you have downstream low-pressure ("secondary") regulators, what protects them?

I'm convinced (scare easily) so I'll be getting a 75-100PSI relief valve installed after my main ("primary") regulator.

Don't have nightmares.
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Re: "End of Tank Dump"

Postby mark1964 » Tue Jul 12, 2016 10:32

I use welding regs and gone through around 7 refills of gas. Can't say I've ever experienced my cylinder dumping loads of gas in a keg

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Re: "End of Tank Dump"

Postby Joe1002 » Tue Jul 12, 2016 11:01

mark1964 wrote:I use welding regs and gone through around 7 refills of gas. Can't say I've ever experienced my cylinder dumping loads of gas in a keg

If the reg fails you would.

A fine beer may be judged with only one sip, but it's better to be thoroughly sure.
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Re: "End of Tank Dump"

Postby PeeBee » Tue Jul 12, 2016 11:25

Joe1002 wrote:...
If the reg fails you would.

Thanks. But I'd better point out its not a "failure", its an unpredictable "feature" of single stage regulators.

mark1964 wrote:I use welding regs and gone through around 7 refills of gas. Can't say I've ever experienced my cylinder dumping loads of gas in a keg

Pop along to the "aquarium" Websites and search "EOTD". You'll find plenty of folk, like you, saying "it has never happened to them", and then you'll find the others still crying in their bubble counters...
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Re: "End of Tank Dump"

Postby supersteve » Tue Jul 12, 2016 11:32

If you don't have a PRV on your keg or regulator then you need to get that sorted.. most of us have them and personally wouldn't use kegs without a PRV at some stage.
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Re: "End of Tank Dump"

Postby PeeBee » Tue Jul 12, 2016 12:21

supersteve wrote:If you don't have a PRV on your keg or regulator then you need to get that sorted.. most of us have them and personally wouldn't use kegs without a PRV at some stage.

Good point.

Even before I learnt about "EOTD" I had a "corny" keg of high FG "old ale" that kicked off again and got up to 100PSI before I noticed. It's easy to get blasé when you typically use very low pressures (LPG regulators) and have kegs that withstand 100+PSI. But if I don't sort the (lack of)PRV situation soon, I will get my backside bitten.

As for PRVs on regulators: Are the ones sometimes fitted not for the high pressure side? Which isn't the issue, nor do I see its point, because in a "EOTD" the pressure on the high pressure side is falling, and with CO2 the high pressure side isn't going to be above 8-900PSI anyway (one of those "laws of physics"): Or have I been assuming the position of this PRV on regulators all wrong?
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Re: "End of Tank Dump"

Postby mark1964 » Tue Jul 12, 2016 12:33

Joe1002 wrote:
mark1964 wrote:I use welding regs and gone through around 7 refills of gas. Can't say I've ever experienced my cylinder dumping loads of gas in a keg

If the reg fails you would.


I have inline taps on all my gas lines so nothing would get through

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Re: "End of Tank Dump"

Postby PeeBee » Tue Jul 12, 2016 12:59

mark1964 wrote:...
I have inline taps on all my gas lines so nothing would get through


What about the keg you are using and have opened the gas line tap?

EOTD doesn't just happen on its own, in happens when you are using CO2 and input pressure drops below an unpredictable level.

But do keep trying to discredit the warnings. I am one who will have nightmares about it.
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Re: "End of Tank Dump"

Postby PeeBee » Tue Jul 12, 2016 15:47

Okay, I'm getting further information from the "aquarium" side: Seems the problem isn't as catastrophic as "Tank Dump" seems to suggest (several thousand dead fish beg to differ). I now get the impression that the regulator becomes unreliable as input pressure falls and increasing output pressure is the result; so if the regulator is set to 3bar it might start putting out 4bar (depending how well-made the regulator is; may be more, could be less). Such a change won't threaten upstream secondary regulators and would probably go un-noticed by many affected brewers (but you'd notice it if you're a fish!). So that explains the lack of excitement on the subject?

Still, been a useful exercise. Like appreciating that PRVs aren't vital just for situations you might be able to imagine, but are just as vital for situations you haven't imagined yet! Like: "where has that muck come from that's jamming the regulator open" ...

...boom!
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Re: "End of Tank Dump"

Postby PeeBee » Fri Jul 15, 2016 12:23

The easiest to understand explanation I could find of "single stage" and "two stage" regulators, and associated "end of tank dump", was on "Wikipedia": https://en.wikipedia.org/wiki/Pressure_regulator.

It explains why this "EOTD" is a feature of single stage regulators, not an occasional fault. I assume the reason some single-stage regulators cope with it better than others depends on how smoothly it operates (some do tend to be a bit sticky and clunky). But it also explains (I think) why "EOTD" doesn't need to be so cataclysmic for us brewers.

But users of Nitrogen for home-brew dispensing (for reasons that go outside "the sensible section" of my comprehension) do need to be more aware of it. I thought the much quoted "special" regulator for N2 would be because it has to be a two stage. Well they're not, cheap ones will still be single stage. And nitrogen being a pressured gas (CO2 liquefies) will reduce in cylinder pressure as it is used, and therefore increase in output pressure unless manually compensated. But I suppose users of nitrogen (or mixed gas) use such ludicrously high serving pressures they don't notice if pressure goes up.

As I use secondary regulators (such as LPG or propane regulators) I don't have to be concerned by my single-stage main regulator (combined the two regulators are the same as "two-stage"), but to be safe I've purchased parts to install a 75psi blow-off valve (PRV) in the pipes between primary (main) regulator and the secondary regulators.
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Re: "End of Tank Dump"

Postby krazypara3165 » Fri Jul 15, 2016 17:32

Im all too families with EOTD, but i dont think its relavent in the home brew scene. In an aquarium a few additional PSI will wine out an aquarium where in a keg it simply raises the pressure slightly. The co2 tank have to be pretty empty to get a dump and I doubt home brewers would even notice it happen.

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Re: "End of Tank Dump"

Postby PeeBee » Sat Jul 16, 2016 08:42

krazypara3165 wrote:Im all too famili[ar] with EOTD, but i dont think its relavent in the home brew scene. In an aquarium a few additional PSI will wine out an aquarium where in a keg it simply raises the pressure slightly. The co2 tank have to be pretty empty to get a dump and I doubt home brewers would even notice it happen.

Thanks. I was beginning to feel a bit of a lonely evangelist on this subject.

I was beginning to accept we (as brewers) don't need to be concerned about EOTD, but the route getting there has been very informative. Like: What are "dual stage" regulators? Why are these "welders'" (single stage) regulators so inaccurate? What are the risks of using high pressure cylinders and cheap regulators?

The adoption of a 75PSI PRV in my CO2 "bus" circuit wasn't because of EOTD, but concern about the faith I put into cheap "single stage" regulators.

As more of us inadvertently try to push these "single stage" regulators beyond their abilities, its worth understanding what those limits are. Many home-brewers are adopting "carbonation calculators" without realising their regulator makes a mockery of those calculations.
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