Secondary regulators

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Secondary regulators

Postby PeeBee » Sun Sep 11, 2016 08:36

Secondary regulators (for those that don't know, they are low-pressure regulators installed downstream from the "primary" regulator attached to the CO2 cylinder) are great for supplying different pressures to different kegs from the same supply line (the primary regulator on the CO2 cylinder is set to output 2-4 bar and left like that). The "secondary" regulators are way more accurate than commonly used "primary" regulators and may operate at otherwise impossibly low pressure settings: An example of the latter being "LPG" regulators that can deliver 0.5-2psi, and "breathers" that deliver zero psi.

But they can also have "gotchas", features that would be useful in there intended application but which can cause problems when used in a beer dispensing environment. So this thread is to discuss some of the "features" I've come across and perhaps add some I don't know about yet.

There are two types of regulator; a "relieving" type and a "non-relieving" type. Most are "relieving" although you wouldn't necessarily know it because no-one seems to make an issue of it. "Relieving" regulators not only keep the supply pressure at the set value, but will also vent pressure on the side its supplying if it exceeds the set value. The mechanisms used to do this vary in method and accuracy and if you have an "accurate" example you'd better know it before you are forced to find out! First impressions are its a good idea as it will solve problems with "wild" kegs; those becoming inadvertently over-pressured because of unplanned secondary fermentations. But some methods will use gas from the high pressure side (wasting gas) and all (?) will completely vent the low-pressure side (i.e. the keg) if the high pressure side is disconnected or otherwise drops to zero pressure. Here's two "secondary" regulators I'm using, both are the "relieving" type:

20160908_120213_WEB.jpg
20160908_120213_WEB.jpg (114.4 KiB) Viewed 549 times


The little one is an "airbrush" regulator operating at about 7.5-15 PSI (Context Pneumatic Supplies via Ebay, available in different ranges). It has a fairly coarse "relieving" mechanism, needing several PSI of over-pressure before it operates. (EDIT: Oops, I overlooked the adjustable relief valves I fitted to these - now that would make for a coarse, and not really effective, "relieving" mechanism). The big one operates at 7.5-150 PSI (Solenoid Valves of Bristol) and is more accurate, but probably needs permanent siting because its quite heavy (like the airbrush one it can have a remote gauge and be panel mounted). Its relieving mechanism is quite accurate, but it continually pinches pressure from the supply line so in time will waste a considerable amount of CO2.

The little one probably needs a check valve in its supply (high-pressure) line to avoid inadvertently venting the keg it's attached to. A check valve is no good for the big regulator because it uses pressure from the supply, but probably needs a valve to shut off the supply - doing this will vent the keg of all pressure, so it will need a valve on the low-pressure side too (not a check valve because that will negate the "relieving" mechanism).

I automatically turn off the CO2 supply after a few minutes using the "primary" regulator that is fitted with a solenoid valve. Fitting a parallel wired solenoid valve into the output of the big secondary regulators sorts the potential problems with them (I hope).

All this explanation is to illustrate; if you use secondary regulators be very sure of what they are up to and whether they are relieving or not, or some unexpected disaster might affect your beer or your gas supply.

Last edited by PeeBee on Fri Sep 16, 2016 08:44, edited 2 times in total.
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Re: Secondary regulators

Postby Kev888 » Sun Sep 11, 2016 13:47

Generally the relieving aspect of valves used for beer dispensing are there more to cap the effects of things getting overenthusiastic than as an intended method of fine pressure control. So yes, they tend to allow a healthy margin for error over the set pressure in order to avoid wasting gas and dangerously flooding cellars with CO2. In my experience this margin allows the beer to become far too carbonated if something causes that to happen (say excessive priming or premature kegging) so the standard types are not a very good way to purposely control the desired limit of carbonation or pressure.

If one wanted pressure relief close to the set pressure then greater accuracy is needed. BUT not just of the regulator, also of the beer/keg temperature. Even if there were some way of venting just excess keg pressure (and not line pressure), changing temperature would cause a keg to draw in co2 when cool and vent it when warm - breathing away the CO2. That could be reduced by leaving the gas feed turned off between dispensing sessions, but the keg would not then be re-pressurised as it cooled after hotter spells - probably not a huge problem although maybe not desirable. Turning off the gas alone is a good way to prevent cooling beer becoming over-carbonated, and one doesn't lose carbonation during warmer spells if there is no (finely set) relief valve.

The effects of venting would also need to be considered. A corny full of carbonated beer suddenly seeing de-pressurisation will tend to foam, and especially if the de-pressurisation was via the gas line you can get beer up the gas line and in the regulator. So some gentle release may be needed. One-way/check-valves (as incorporated in sankey style keg couplers) would prevent this but would also potentially defeat the relieving regulator too, if they seal well enough. And any relieving regulator or valve should be in addition to the usual higher pressure safety valves that should be included around the primary regulator. Some primary flow regulators don't have these as they are intended to adjust flow-rate rather than see a build up of pressure; its a bad idea to use primaries without safety valves for pressurising things - if the primary regulator develops a pass-through leak (which one of mind did) the gas lines and keg can otherwise try to reach the same pressure as the cylinder.

So IMO a relief valve or relieving regular may be partially useful with problem kegs, but would need to be unusually accurate to be useful as an intended means of pressure/carbonation regulation and that would involve some challenges. In general it would seem better to get the kegging right to begin with and then rely on stable pressure and temperature to maintain things as wished.

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Re: Secondary regulators

Postby PeeBee » Sun Sep 11, 2016 15:30

Ah... Kev's pointed out something I should have made clear in the first post:

The "relieving" feature of regulators might be good for preventing a keg over-pressurising, but don't use the feature to correct a keg that's already over-pressurised or beer washed regulator and cloudy beer will likely result. For dealing with over-pressurised kegs see another thread of mine <http://forum.craftbrewing.org.uk/viewtopic.php?f=53&t=10477> (actually designed as a method for us HBers to replace the traditional "venting" process for "cask-conditioned" beer, but acts as an "emergency" fixing tool too).

Kev also reminds anyone to have a safety valve in the "supply" line (the pipes between primary and secondary regulators). I have a 115PSI safety valve in mine (the primary delivers a fixed 5 BAR), a 75PSI valve should be right for most. Actually that can be considered as an additional safety feature of using secondary regulators as most ("single stage") regulators in use by HBers won't have them.

Another point picked up is to be careful choosing a regulator as some adjust "flow-rate" not static pressure (not really regulators at all as I see it).
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DON'T LOOK! ...

Postby PeeBee » Thu Feb 02, 2017 19:38

... unless you're an incurable geek.

Well if you've got this far, too late.

These "relieving" regulators have been wasting a lot of my time since I last posted on this thread. I thought I'd post an update for readers to decide "wow, I've got to have one" or "crikey, those things are a pain in the nuts". If you fall into the latter camp, you'd better know these things exist and how to avoid them.

They were so kooky I had to draw out how I could use them and set them up so I didn't have to deal with them again. The first thing was to learn how to draw them, and that meant learning pneumatic symbols which are pretty kooky in their own right. (I then use this new skill to commit the gross sin of mixing pneumatic and electrical symbols; but I can figure what it means!).

I needed to isolate the offending regulators between solenoid valves so that when the gas is turned off (also on a solenoid valve) the regulator doesn't vent all the gas in the upstream "bus" lines and having done that vent all the gas in the downstream keg. The pressure gauge can then be moved downstream of the solenoid valves so it continues to indicate the pressure in the keg. Turning off the power (and therefore the gas) also closes the beer lines (they also have solenoid valves, but 24V not 230V).

Dispensing.jpg
Dispensing.jpg (121.4 KiB) Viewed 403 times


The pressure switch isn't needed, but while doing the rest... The switch is about £4 from China and will indicate if the gas cylinder isn't attached or is practically empty (unfortunately indicating whether the gas cylinder is nearly empty is very complicated).

The inset illustrates the simplicity of NOT having "relieving" regulators, but you wont have the "benefits" of them either.

Hope someone gets some benefit from this. I'd hate to think all this effort has gone to nowt. I'll now fit all this stuff in a box so it's done and dusted - the gauges are to be "panel mounted" on the box as are the regulators (so only the knobs show).
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