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vvteja
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Join Date: Dec 2009
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Fluids in Pressure Gauges

12/27/2009 4:40 AM

hi all.......... do anyone know what type of fluids are used in pressure gauges?

i mean the lubricant used in the cavity between the gauge and the diaphragm

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Tornado
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#1

Re: pressure gauges

12/27/2009 4:50 AM

Glycerin is a traditional choice, but there might be some silicones or the like that would also work.

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vvteja
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#2
In reply to #1

Re: pressure gauges

12/27/2009 4:55 AM

ok..... but i think you have misunderstood the question.

I want more specifically the lubricating oils used in the pressure gauges

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Tornado
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#3
In reply to #2

Re: pressure gauges

12/27/2009 5:20 AM

Most (but not all) pressure gauges consist of a Bourdon tube with the fluid whose pressure is to be measured inside. The linkage connecting the tube to the indicating dial resides outside the tube but within the enclosure. This is where any lubricant will be. It helps if the lubricant is transparent, like glycerin, so that you can see the dial. If you want to tell me how gauges are built, at least take one apart first. Good grief!

If the gauge is air-filled rather than liquid-filled, any of a number of light lubricating oils might do: 3-in-1, SuperLube, WD-40,....

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lyn
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#4

Re: pressure gauges

12/27/2009 8:56 AM

If your gauge is for O2 service, you won't find any lubricants.

Here's what it looks like inside.

How Pressure Gauges Work
Most of our gauges are constructed with bourdon tubes to measure pressure and vacuum. The bourdon tube, which is a hollow metallic tube sealed at one end, flexes when pressure is applied. It flexes because it naturally wants to straighten out, but cannot because it is linked to a geared movement. As it tries to flex, this linear movement is changed to a rotational one by means of small gears. They in-turn cause the pointer to indicate the measured pressure. Gauges like this are designed for clean, non-clogging liquids and gases.

The pictures above, right, are of a less accurate, Grade B gauge (3-2-3%). Gauges rated for higher accuracy will have higher quality parts (perhaps machined instead of stamped, heavier coils or adjustable links).

To the left you can see the two most popular types of pressure gauges - dry and filled.

The two most common causes for gauge failure are pipe vibration and water condensation (which can lead to freezing in colder environments).

The delicate links, pivots and pinions of a regular gauge are sensitive to both condensation and vibration. Filled gauges last longer because they have fewer moving parts and the housing is filled with a viscous glycol or silicon fluid. The fill in a gauge helps dampen pointer vibration and eliminates corrosion resulting from condensed water when installed in areas that have humid air.
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orangel.pin@hotmail.com
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#5

Re: pressure gauges

12/27/2009 8:43 PM

In the company where I used to work we used Glicerine as a medium to avoid the needle moving when the pressure change fast.

Ansory if this not answer your question.

best regards
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