Pressure gauge accuracy

[brownsfn2]

Late last year I got a deal on some binks pressure pots. They cam with regulators and pressure gauges. I assumed that all the gauges were accurate since they were quality binks gauges. I had been using one of the pots at 80 PSI for a while and since that one was being used I used another pot last night. Well it seemed to fill quicker than the first pot and I could tell by looking at my casting that it did not have enough pressure applied to it. So I think the gauge is not accurate.

Does anyone know if there is a way I can test a pressure gauge for accuracy?

I think I am just going to replace them all. Can anyone recommend a good quality gauge? I see some oil filled ones on Amazon and they say they are really accurate. Anyone have an opinion on those?

Thanks for any help!

 

[KBs Pensnmore]

If you were to make a manifold from T pieces you could put the gauges on and check your readings, make sure you fit a pressure relief valve on it.
If possible you could fit a tire valve stem and check variances with a tire gauge.
Oil filled gauges just take out the shock of the needle abruptly moving, so I'm told. Don't know if that is correct though.:biggrin:

 

[yaroslaw]

Water or oil filled gauges are less likely to cause big problems in the case of gauge explosion, so it's mainly safety measures.

 

[MesquiteMan]

Don't mean to be argumentative but Liquid filled gauges are not filled with liquid for safety reason, Yaroslaw. Pressure gauges and vacuum gauges are usually bourdon tube gauges. Inside the case of the gauge is a curled tube that is connected to the fitting that screws in. The tube is also connected to a set of gears that are connected to the indicator on the dial. When pressure or vacuum is applied, the tube expands or contracts and causes movement. The tube is very small and even if it did rupture, it would be minimal. The case of the gauge never has any pressure on it.

Liquid filled gauges are normally installed in environments that experience vibration. The liquid dampens the vibration and makes it easier to read. It also helps keep the moving parts lubricated some to resist sticking gauges.

Liquid filled gauges are usually more expensive and, as such, typically have a better accuracy rating. Common accuracy ratings are stated at +/- 2, +/- 1.5, or +/- 3/2/3.

A gauge that is +/- 2 is accurate within +/- 2% over the entire range of the gauge. A gauge with +/- 3/2/3 is accurate +/- 3% in the first third of the gauge, +/- 2% in the middle third of the gauge, and +/- 3% on the last half of the gauge.

This disadvantage of the liquid filled gauge is that to be as accurate as possible, it needs to be vented. They will come with a rubber plug in the top of the gauge to keep the liquid from leaking during shipping. Once installed, the rubber plug needs to be perforated. Otherwise, the gauge will be reading the difference in pressure for the atmospheric pressure on the day the plug was installed. Once you cut the plug, if you tip your lid over, the liquid will leak out. Other than making a small mess, it is not a big deal since you can re-fill them. The liquid in most liquid filled gauges is simple glycerine.

Sorry for the long reply and probably telling you more than you care to know. I do know a thing about gauges, though!

 

[MesquiteMan]

Oh, and to answer your question directly, if the gauge has been kept in a relatively clean environment and not treated harshly, they usually stay accurate. In other words, they don't typically wear out.

One way to get an idea is to set the regulator on your compressor to some pressure, say 50 psi. Connect your hose and open the valve and let the air in. Let is go until you can no longer hear the air going in and read the pressure. It should be close to what you have your compressor regulator set to.

 

[brownsfn2]

Thanks for the information Curtis. I did not think about doing that with the compressor. That makes sense. I think I will test out my gauges first now before I order new ones.

BTW - Do you have the 3 gallon Binks pots? Do you take them above 80psi?

 

[BSea]

This one is probably over kill, but it is accurate within +-1% at mid range.
McMaster-Carr

Another thing about pressure gauges is that you want 1 that is for twice the standard pressure you want to use. So if you want to normally use 80PSI, get a gauge that's close to 160 psi at it's max.

EDIT: I forgot that McMaster Carr has a really high end web site. The links don't actually work like normal links. The 1 I gave will get you close, but it doesn't show the page I was on. About 1/2 way down the page You'll see liquid filled gauges. That's what I was looking at.

They also have a good section that basically tells about gauges. Look for a link that says "About Pressure Gauges"

 

[brownsfn2]

Thanks for the link Bob!