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raees
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Join Date: Aug 2010
Posts: 15

Glycerin Filling Not Allowed on Vacuum?

05/20/2014 3:04 AM

Hi,

i just wanted to know, for a Pressure gauge why we can't use glycerine filling (or any other liquid) on Vacuum application? while area has vibration as well so normally vendors don't recommend the filling on vacuum application. Please suggest
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jesw55
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#1

Re: Glycerin filling not allowed on vacuum?

05/20/2014 3:22 AM

Hi Raees,

I would think it is because if the gauge mechanism failed the glycerine would be sucked in and contaminate the system.

Have a good day.

John

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IdeaSmith
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#2

Re: Glycerin filling not allowed on vacuum?

05/20/2014 3:25 AM

Who says you can't? They are available to buy!

Where is your vaccum? Outside the manometer?

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raees
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#3
In reply to #2

Re: Glycerin filling not allowed on vacuum?

05/20/2014 3:51 AM

Dear Sir,

actually the end user is sugar plant and they need following ranges for pressure gauges with liquid filled although there isn't high pressure at all'

1) -30 ~ 0 inHg

2) -760 ~ 0 mmHg

Please suggest any vendor i am using Ashcroft pressure gauge who don't allow filled gauge at vacuum application.
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PWSlack
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#4
In reply to #3

Re: Glycerin filling not allowed on vacuum?

05/20/2014 4:37 AM

The end user will have standards that Engineering will follow. Follow those standards.

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IdeaSmith
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#5
In reply to #3

Re: Glycerin filling not allowed on vacuum?

05/20/2014 4:43 AM

A quick internet research will get you lots of hits on vendors

try search for "glycerine filled vacuum gauge".

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PWSlack
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#6
In reply to #5

Re: Glycerin filling not allowed on vacuum?

05/20/2014 4:49 AM

True. The description of the original poster's problem is one of consent. The applicable standards contain that consent, and the author and approver of the standards will have the reason for the standards being as they are. So, notwithstanding that glycerin-filled gauges are widely available, the answer to the original poster's query lies with the author of the applicable standards; any CR4 user's response is therefore a WAG based on commonsense elsewhere and if that does not correlate with the end user's standards, the original poster is in for re-work, additional costs and delays until the plant conforms to the user standard.

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PWSlack
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#7

Re: Glycerin filling not allowed on vacuum?

05/20/2014 6:46 AM

Asking the vendors why they do not recommend would be a good route to an answer.

Do bear in mind that vacuum doesn't vibrate very much...

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Relativity PL
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#9
In reply to #7

Re: Glycerin filling not allowed on vacuum?

05/20/2014 10:46 PM

"Do bear in mind that vacuum doesn't vibrate very much..."

We are re-using a vacuum tank from a chemical processing industry, fitted with sight-windows, as a vacuum accumulator. I can confirm from personally looking through the little windows, that I have never, NEVER seen the vacuum vibrate even a little.
The windows are helpful, however, in seeing how much vacuum we have in storage at any time.
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Bud
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#8

Re: Glycerin Filling Not Allowed on Vacuum?

05/20/2014 11:57 AM

The rule of thumb is that mechanical gauges under ±15psig or ±1 barg, [either positive or negative (vacuum) pressure] are not liquid filled (by vendors, users do whatever they want) because the liquid filling can affect the response of the measuring element thereby affecting the accuracy of the reading.

Typical bourdon tube vacuum gauges in the 30"Hg to 0 (atmosphere) range are routinely liquid filled by vendors.

Whether a plant allows liquid fill in any given application is up to the plant.
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old salt
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#10

Re: Glycerin Filling Not Allowed on Vacuum?

05/20/2014 10:56 PM

As some others have said, glycerin is not used to fill vacuum gauges to avoid contaminates from coming through a cracked or broken bourdon tube.

If you want to reduce/stop the vibrations of the gauge in the vacuum system install a "snubber" between the gauge and the vacuum system. This is a small device that fits in the pipe fittings of the gauge and the vacuum system. It is a small orifice that reduces the pulsations by reducing the speed or the air/vacuum passing in and out of the gauge/bourdon tube. This is a proven alternative to the glycerin filled gauges. Only problem with it is that if you have a very dirty vacuum system it may occasionally plug the orifice.

McMaster-- Adjustable Pulsation-Damping Snubbers, or Pulsation-Damping Snubbers various model such as typical 3820K26 http://www.mcmaster.com/#pressure-gauge-snubbers/=s1zt39

There is also another system that uses a glycerin filled gauge but instead of the snubber it has a flexible metal diaphragm on the pipe connection. This is mated up to an identical fitting without the diaphragm. As the pressure/vacuum in the system changes the diaphragm moves to equalize the pressures on both sides. This system has the advantages of not having dirty vacuum systems affecting the gauge and incorporating the vibration damping of the glycerin.

Good Luck, Old Salt

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Bud (1); IdeaSmith (2); jesw55 (1); old salt (1); PWSlack (3); raees (1); Relativity PL (1)

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