Inaccurate Low Pressure Gauges

[Bigscience]

For Christmas my wife ordered me a 4 way secondary regulator system. When I opened it on Christmas morning, it was a 4 way manifold. Trying not to offend her (since I asked Santa for the regulator setup), I asked where she got it, how she ordered it and a few other questions until I figured out that they sent her the wrong part (still charged for the right one though). After much hassle, the correct one arrived today so I started to set it up. Finally I can run 4 beers at the correct pressure!

Upon closer inspection, I noticed that one of the gauges is reading ~7psi with nothing hooked up to it. I backed the regulator all the way down, played with the shutoff valves and nothing. I figured it may need some pressure on it to make things read correctly so I hooked it up to my tank and set that regulator at 10 psi, set each of the 4-way regulators almost to the max and closed the shut off valves. With that I got 18, 17, 25, and 20 psi on the gauges. Now, for a while I've felt that my secondary gauge may be reading low since I seem to over carbonate and have to practically turn it off to pour no foam. I was hoping to solve this by having the new setup.

Here is a picture:






So my questions are:
Has anyone else actually checked the accuracy of their gauges?
Can you even calibrate these type of gauges?
Should I return this thing do the inaccuracies/imprecision across the gauges?
Should I just try to figure out what the offsets are for each gauge (when compared to a know good, calibrated gauge) and go from there?

[BDawg]

Remember that you have to set the set screw on each one individually to set the output pressure.
They are "expecting" high pressure coming in, so the 10psi might be throwing things off. Set the regulator on the tank to 30 or so and then set each individual regulator's set screw so that it's valve shows 10psi.

Then, take a keg and connect it to a regulator (set at 10). After the first one fills it up, change to another regulator. Pushing it onto the post should NOT add more pressure to the keg. Then, drain some pressure through the pressure relief valve, then refill using the current regulator. switch back to the FIRST one and you should not hear gas coming in.
Test each combination and you should be able to figure out if they are all ok or if something is really broken.

HTH-

[ajdelange]

I noticed that one of the gauges is reading ~7psi with nothing hooked up to it. I backed the regulator all the way down, played with the shutoff valves and nothing.

That's not so good. It should read 0 with nothing connected. Seven - 8 psi is a common serving pressure so you would want to have some confidence that the gauge reflects close to that amount of pressure when it indicates that amount of pressure. A frequent problem with these gauges is that they get a sharp knock (this especially happens when they are on a tank without a gauge cage and the tank gets knocked over. These things are very flimsy. The case distorts and the scale plate gets bent so that the needle touches it and tends to stay in position. So I'd check for that. You should be able to see it if this is the case. OTOH you have new gauges and there may be some "sticktion". Try cycling pressure, tapping on the lens etc. If you can't get it to read 0 with no pressure applied (and the outlet cock open) I would replace that gauge.

I figured it may need some pressure on it to make things read correctly so I hooked it up to my tank and set that regulator at 10 psi, set each of the 4-way regulators almost to the max and closed the shut off valves. With that I got 18, 17, 25, and 20 psi on the gauges.

That's not so great either. It implies that the manifold pressure was 20 ± 3.6 i.e. that the standard error for the gauges is 3.6 psig. That is not, as I say, great accuracy but it is probably reasonable. This conclusion depends on the regulators all going to full open when you tighten the adjustment screws down (reasonable assumption). If you take the cover off one of these gauges (remove the 2 screws on the back) you will see that this is not precision machinery we are dealing with here.

Now, for a while I've felt that my secondary gauge may be reading low since I seem to over carbonate and have to practically turn it off to pour no foam. I was hoping to solve this by having the new setup.

That's entirely possible especially on a tank which gets knocked about a home brewery. Check for the stuck needle condition.

Has anyone else actually checked the accuracy of their gauges?

I haven't - maybe I should.

Can you even calibrate these type of gauges?

By comparison with a higher quality instrument you could come up with a calibration curve but there is no adjustment/caliubration screw.

Should I return this thing do the inaccuracies/imprecision across the gauges?

I'd tell them that you have one that reads 7 psi when it is disconnected. They shouod replace that one.

Should I just try to figure out what the offsets are for each gauge (when compared to a know good, calibrated gauge) and go from there?

That's probably the best you are going to be able to do. But ± a couple psi isn't in intolerable error. You'll find that you tend to read the gauges relatively rather than absolutely. If a keg draws all foam, back off the pressure a couple of psi and bleed the tank every day for several days. If it draws lifeless increase the pressure a couple of psi and wait a week.

[Bigscience]

Remember that you have to set the set screw on each one individually to set the output pressure.
They are "expecting" high pressure coming in, so the 10psi might be throwing things off. Set the regulator on the tank to 30 or so and then set each individual regulator's set screw so that it's valve shows 10psi.

Then, take a keg and connect it to a regulator (set at 10). After the first one fills it up, change to another regulator. Pushing it onto the post should NOT add more pressure to the keg. Then, drain some pressure through the pressure relief valve, then refill using the current regulator. switch back to the FIRST one and you should not hear gas coming in.
Test each combination and you should be able to figure out if they are all ok or if something is really broken.

HTH-

I tried putting 30 psi on the setup and the readings were 30, 31, 37, 35. I like your suggestion but the issue is that I don't want to hook up all the lines if I'm just going to send it back. Also, what I'm thinking is that it's not so much a regulator issue but a gauge issue. Assuming the tank secondary gauge is accurate and puts out a pressure, when the manifold regulators are set to the highest setting, they should read the same at the feed, or at least the same as each other with a specific offset due to the inaccuracy of the feed gauge.

I have one nicer replacement gauge that I ma try to make a calibrator setup with and get it checked at work against a NIST traceable gauge so I can check out all my gauges.

Has anyone tried to adjust a gauge? I also checked and the needles are not catching on the dial plates.