Hey everyone I have a Oil Pressure Gauge I received from Mr. Bill Cody for my new GAST pump when I put it in. It would appear its getting a bit low on oil in the face of the gauge. I was wondering if I can add a certain type of oil to this gauge with the small hole on the top of the gauge? When I first got the gauge it was about 3/4 or so full. It had a small air bubble at the top which Bill said was fine it needs to be that way. But my small air bubble is almost half of the gauge now... So if I can put oil in it through that small hole my next question would be of course what type of oil?

Thanks,
RC

Usually Glycerin, but some use Silicone oil.

Some of the gauges I have purchased in the past came with a bottle, and you filled it after installation.

Call the manufacturer or distributor, if you know who they are.

JKB, what is the purpose of the oil in the gauge and how do you know when you filled it 'enough'?

The oil acts as a damper to limit needle oscillation. It performs a function similar to the shock absorbers sometimes used on vehicles....without them, your car or truck wants to continue bouncing when you drive over a bump or pothole. Some types of air compressors, especially piston types, do not provide a continuous supply of air, rather they exhaust (pressure) on one stroke, and intake (vacuum or negative pressure), on the other stroke. This makes pulses in the air supply, and the gauge will register these pulses with rapid needle movement.

A liquid filled gauge slows down the action of the needle, so it remains at a more constant reading. greatly increasing gauge life, as well as making it a whole lot easier to read.

Liquid filled gauges usually have a space or bubble at the top, to allow for expansion and contraction of the liquid. I've never had to fill one, but most I've seen have around 1/8 to 1/4" space.

Makes the gauge more robust.

I'll let WIKA explain it to you: (copied from their website)

Liquid-filled gauges are generally preferred over dry gauges for two reasons: performance and ROI. Liquid-filled gauges are filled with a liquid, usually glycerin or silicone oil and are designed to perform optimally in less-than-ideal conditions. While WIKA’s liquid-filled gauges are engineered to function in difficult environments, they’re also more economical from a long-term perspective: High heat, pulsation, or vibration lead to instrument breakdown, but WIKA’s liquid-filled gauges stand up to these harsh conditions.

Liquid Filled vs. Traditional Gauges

The primary reason for gauge failure is vibration. In traditional dry gauges, delicate links, pivots, and pinions are prone to damage from vibration, leading to inconsistent performance. In a liquid-filled gauge, the fluid fill effectively dampens system pulsation, making the gauge pointer easier to read.

Likewise, humidity and moisture pose problems for dry gauges. Condensation can make a gauge difficult to read or, in some cases, can cause failure due to icing. Liquid-filled gauges, though, are sealed to prevent internal condensation, and by keeping moisture out of the system, gauge movement is protected during icing conditions.

The choice of fill fluid is based on the application, but glycerin is typically used for room-temperature applications and silicone oil is commonly used for extreme temperature applications, especially when icing is a problem. An oil with insulating properties is ideal if the system has exposed electrical contacts.

Why Liquid Filled?

Liquid-filled pressure gauges offer a number of advantages over traditional, dry case pressure gauges:

Liquid-filled gauges have longer lives than traditional (non-hermetically-sealed) gauges because of their viscous fluid filling. Over time, this design advantage results in costs savings due to lowered instrumentation costs as well as lessened unscheduled downtime.
Internal liquids protect against severe temperature fluctuations and vibrations—major factors in the breakdown of regular gauges. Because they dampen temperature spikes and vibrations, WIKA’s liquid-filled gauges are easier to read, allowing for greater accuracy and process control.
In traditional gauges, condensation build-up results in visibility issues. This can be a crucial (and costly) flaw in high-humidity environments—an unreadable gauge is a worthless gauge. A solution to the impact of high humidity situations, WIKA’s liquid-filled gauges are designed to prevent moisture from entering not only the body casing but also the inside of the case lens.
Because they are sealed and constructed to meet rugged specifications, liquid-filled gauges are commonly used in highly corrosive chemical processes or in manufacturing or refining processes, and where products must be transported, stored, or handled in extreme temperature conditions.


Learned something new here. Use a silicone fluid for gauges that will encounter low freezing temperatures.

As far as how much oil, I know there needs to be a bit of air in there. The ones we got with the bottle had a predetermined measure with each gauge so just pour it in.

I also have a couple of expensive gauges that have a burp valve on top of the casing. That's to equalize the internal case pressure with atmosphere for a more accurate reading.

RC - Any indication of why the fluid level is becoming low?

Spark types faster, but basically the same thing.

Also, it's a good practice NOT to mount your gauge on a compressor, but you can if you like.

Iv'e seen this happen before one or twice. About the only way the gauge will loose glycerin is if you cut the nipple off the rubber plug on top of the gauge. Then the gauge usually has to be mounted at an angle for the liquid to slowly drip out. Make sure the gauge is mounted vertical. I usually suggest a pin hole be pushed through the rubber plug instead of cutting off the tip/nipple on top of the gauge as suggested by the manufacturer. The manufacturer is McDaniel Controls if you want to contact customer service to know what fluid is in the gauge (model J6B). The info page says glycerin is in the gauge.
http://www.mcdanielcontrols.com/
http://www.mcdanielcontrols.com/pdf_files/BRO_GRAY1015.PDF

Never heard of that brand before, but they seem to make some nice stuff. I looked up the equivalent of a couple I have here, and list is quite a bit less. ($184.00) They are all made to the same standards with testing and conformity.

In industrial/process controls, we seldom use pressure gauges anymore. Maybe on a regulator, or in a few remote spots for a quick visual when walking by, but mostly ignored.

Need to know detailed info about the system, so use transducers instead. Some are better than others as well as the cards you hook them up to.

Anyway, if it's leaking, I would find out why? That don't sound right.

As stated liquid filled gauges dampen the pulsation. Pulsation can quickly wear out the gear mechanism in the gauge either destroying it or making it inaccurate. More important in hydraulics than air applications (since liquids do not compress, the pulsations from a hydraulic pump are more severe than with a compressible gas).

One thing that will quickly ruin any gauge is letting some moisture get up into the gauge then letting it freeze. The frozen water in the flattened tube that actuates the dial will deform and best case make the gauge fail completely or worst case just cause it to be inaccurate.

A simple check for anyone paranoid about accuracy is to plumb in a Schrader valve (tire valve stem) in line along with the pressure gauge in your air application. They are available with 1/4 male pipe thread one end and the tire type valve on the other. Then any time you want to check the gauge accuracy simply use a low pressure tire gauge (like used for ATV tires) on the Schrader valve.

The leak may be minor, but the fluid level should never drop. If no oily, dusty residue is visible on the outside of the gauge or plug, chances are the diaphragm separating the gauge from the system has failed and it is leaking into your system, and giving a false reading...I'd replace it or try getting it warranted.

I thought most liquid filled gauges used mineral oil, few gauges are compatible for use on/with compressed oxygen due to spontaneous combustion hazards.....? No explosion/combustion hazard with silicone or glycerin, right? (unless mixing glycerin with potassium permanganate)

It seems we have thoroughly hashed out the inner design behind liquid filled gauges. Everyone is saying the same thing.

YEP!!

In some high pressure hydraulic applications I have seen even liquid filled gauges more pretty durn fast..... I think that I would have seen a bent needle in the gauge if it wasn't liquid filled!

Seen a number of messed up needles in plant air applications with a standard gauge when they buy cheap stuff, but never on a quality gauge. Never saw a hydraulic system without liquid filled tho, but have seen some out of considerable whack with a cheap rig.

You get what you pay for.

You also get what your limited knowledge is