Regulators: Whys and Wherefores

I've been making a nuisance of myself on "another" forum and thought I should share some conclusions about regulators. As I know I'm not the only forum itinerant around here, sorry if you've already read much of it.

I'd been looking into the classy and lightweight aquarium CO2 equipment as a suitable alternative to the clunky heavyweight "welders" equipment many of us use. And the aquarium bunch are very particular about using "dual stage" regulators over "single stage" ones because "single stage" ones have a habit of killing all their fish. I'd come across this before and gave it little thought, after all I already use primary and low pressure secondary regulators (like LPG regulators): Primary, Secondary, ... Single, Dual, ... going to be the same thing? No, completely different.

A look at the regulators we (as brewers) use concluded they are all (cheap) single stage regulators. Now single stage regulators have a feature such that when pressure in the cylinder drops then output pressure INCREASES! Not by much perhaps, 20-30%? I think how much depends on other characteristics, but if input pressure drops enough some regulators can completely fail. This is known as an "End of Tank Dump", and it kills fish!

We are fortunate in using CO2 which forms a liquid so pressure is fairly constant over the life of a cylinder (8-900PSI), it only starts to drop when the liquid is all gone (time for a new fill... quick). And I don't think there are serious implications for us using "single stage" regulators (certainly not heard of any). There is an easy to understand explanation on Wikipedia: https://en.wikipedia.org/wiki/Pressure_regulator.

It's worth getting an understanding to answer all sorts of niggles, like: Why are these "welders" regulators all over the place when trying to set close pressures? Why are regulators that claim to be more accurate that bit more expensive and keep describing themselves as "dual stage"? What are the hazards of dirt in a single stage regulator? (Answer to latter might well be: Boom!).

I'm immune to "end of tank dump" because I use secondary regulators, but the knowledge convinced me to get a 75PSI relief valve for the intermediate section (gas lines between main - primary - regulator and the low pressure secondary regulators). Dual-stage regulators have such PRVs as part of them.

We're happy having these "bombs" about the house, its worth understanding them a bit more.

Piccie of the "aquarium" style regulators I'm blabbing on about. CO2Art have slightly changed their design to output 5bar rather than 3 or 4. Trouble is 5 bar triggers my 75psi safety valve hence the gauges are over the place (awaiting new one). I carefully replaced the "needle valve" assembly that comes with it with the second gauge, manifold and PRV (a purely optional adaptation). Note the far more flexible 6mm gas pipe instead of usual 3/8" stuff.

This setup feeds the low-pressure secondary regulators on the Corny kegs.

Looks smart, even got a solenoid valve on the regulator to switch the gas on remotely. So expensive? Nope, about the same price as the rough and ready welders' regulators.

An updated picture with the pressure gauges reading what they are supposed to (courtesy of a new 115psi safety valve). There's also the "portable" version in shot using an older version of the regulator by CO2Art (only 3-3.5 bar output) and no solenoid switch on this one.

Another little feature of regulators that doesn't get much mention, though you might have suspected it:

This really only applies to "secondary" regulators that you attach to the main "primary" regulator (connected to the CO2 cylinder) to have more than one supply pressure and a hell of a lot more accuracy too. I think the main cylinder attached regulators are all the "non-relieving" type, but I can't say for sure.

Regulators come in two types: the "relieving regulator" and the "non-relieving regulator". A relieving regulator not only controls the pressure it delivers, but also relieves (vents) excess pressure that might build up in the target (for us that means from excessive priming kegs/casks, changes in conditions like temperature, and so forth). An example of a non-relieving regulator is an LPG regulator where you wouldn't want some means of venting explosive gas to the atmosphere!

The attached picture shows two regulators I use as "secondaries". The diminutive "Airbrush" regulator (Context Pneumatic Supplies via Ebay) available in 0-15PSI, 0-30PSI, and other sizes, (ignore "0-", such regulators only reliably regulate down to 7-8PSI) and the much chunkier regulator (Solenoid Valves of Bristol) available as 0.5to10BAR (7-150PSI). The big one looks more expensive, but its not! About 15 quid, and more accurate too, but really needs permanent siting and a gauge with a smaller range. Both could be adapted for panel mounting (remote gauge). Both are "relieving" regulators, but use different ways about this.

The "relieving" mechanism for the diminutive "Airbush" regulator is fairly crude and doesn't operate unless there is several PSI of over-pressure. The chunky regulator has a very accurate venting mechanism, but at a cost as it continually "breaths" minute amounts of gas from the high pressure side. Both will completely vent the low-pressure side (the keg!) if the supply drops to 0PSI.

So the "Airbrush" regulator might need a check-valve in the high pressure hose to stop it accidentally venting all the pressure in the keg. This wont help the chunky regulator as it is always using tiny amounts of pressure from that side so it needs a valve in the low-pressure line to isolate the keg (a check-valve wont do because that would disable the "relieving" feature). You might also turn off the supply pressure for the "chunky" regulator because although it needs only very small amounts from the high-pressure side, over several weeks that is going to be significant. I have a solenoid switch on the primary regulator that automatically turns it off; this is extended to a solenoid switch on the "chunky" regulator's low pressure side to automatically close that line too.

So I hope this explanation explains some of the weird actions you might see from regulators. If it saves just a handful of folk from the serious confusion it caused me its been worth my time writing this up! Just remember, these are secondary regulators and shouldn't be supplied with more than about 10BAR (DON'T attach them directly to a gas cylinder!).

peebee said:

... Both are "relieving" regulators, but use different ways about this...

Click to expand...

Hum, not so sure now. The diminutive "airbrush" regulator may or may not be "relieving" as it appears I fixed variable pressure relief valves to them set to go off before the regulator was subject to pressure that might damage the gauge. That would explain the "crude" relieving mechanism. Oops

Solenoid Valves of Bristol now have a Web site dedicated to Shako regulators and other stuff. In particular some very diminutive regulators at a very diminutive price (http://www.shako-online-sales.com/frl/regulators/miniature-regulator-nr200-01-nr200-02). Don't know yet if they are "relieving" or "non-relieving" (I'll work with either) as I'm waiting for them to turn up.

Just a note of caution, you don't really want relieving regulators on beer. Because when it relieves the gas escapes, taking all that lovely aroma with it. The main benefit of keg over cask (aside from resistance to infection) is the way it preserves the aroma.

I have one of these. Main regulator on the right sets the first gauge pressure, the two after that control the subsequent gauges. Each outlet has a quarter turn and non-return valve which prevents gas flowing from one keg to the next (so your bitter won't take on the aroma of the IPA on the next line over time).

You're not entirely wrong with your analysis of the benefits of relieving control valves, but in their main application is in things where there's something else influencing pressure, like pumping into a vessel whilst it's connected, for example large petrol tanks are kept under a nitrogen blanket to stop the vapour catching fire, when emptying the nitrogen flows in, when filling it goes out (usually to an incinerator where the fumes are burnt).

Spoon said:

Just a note of caution, ...

Click to expand...

Thanks Spoon.

I did post this as a caution; for people quite unaware that these things exist (including me until just recently) and in the wider scheme of things the "relieving" regulator is actually more common (which is how I accidentally learnt about them).

But if you know you've got one, rather than a disaster, they have a number a benefits:

* You can "tune" a keg's pressure up and down (within reason, not really suitable for big changes of pressure - nothing is!).
* They prevent problems because of casks over-pressuring because conditions change (e.g. gets warmer).

But they do things differently and can leave casks vented of all pressure. Simple to put right, but you do need to be aware it can happen first.

I'm aware of the "two stage" assemblies like you have, but I like the versatility of having independent secondary regulators (like managing very low pressure regulators - <2PSI - in the same setup).