Mean time To fail in Pressure Gauges?

[LuisCuellar00]

Hello fellow colleagues.

Since a 4 years of growth, construction & startup of a new production lines in our fine chemical facility the engineering department will be focusing in improvement projects.

I detected increasingly failures in pressure gauges. After some investigation we found out we are replacing 200 manometers per year of a total of 1000. I'm going to start a plant installation review in a couple of days, based on best practices and the provider comments.

So I want to ask you about your thoughts, and experience in your plants.
What would you say it's a mean time between failures on manometers (I understand it totally depends in the application) is there any average? What number will be ok? Any recommendation that you can share with me? Any further reading or technical information that you could share?

Thank you very much.

95 % of our PG are from 0 to máximum of 7kg/cm2, 0.5% to 1% error, 4.5 in dial, plastic enclosure, SS burdon%conection.

 

[danw2]

Given the incredible range of service conditions gauges are subjected to, I'm not surprised that I've never seen an MTBF number. I suppose your maintenance service records are as good as anything for getting a number like that.

It could be as simple as having replaced the original quality gauge with an inferior gauge and the inferior product just doesn't hold up.

Some of the things people look at for increasing pressure gauge lifespan are
- doing a forensic on what (and presumably, why) a given gauge in a given location failed, so you have a baseline knowledge to work from in deciding on an alternative
- examining the actual gauge construction - Like my father said, "there's nothing someone can't make cheaper".
- remounting gauges with impulse tubing, capillary or extensions to address temperature failures
- adding snubbers to limit hydraulic shock
- liquid fill - lubricates the movement as well damps some vibration
- seals for corrosion issues
- using a more robust construction, like a helical tube
- training class for the wrench twisters to increase their awareness of the delicate nature of a pressure gauge.


Some vendors, like the German Wika, clearly target the high end user who values quality and understands life cycle cost vs purchase price. They even have a video on 'top 7 reasons gauges fail'.
[URL unfurl="true"]http://wika-fast.com/best-practices-animation/[/url]

 

[MikeHalloran]

From your description, I can't figure out what sort of gauge you are using, or how they are failing.

I have long ago come to prefer Dwyer Magnehelic gages to u-tube manometers where they make sense.

It's fairly common to install a damper on the gage stem where pressure changes fast, or to use a 'press to read' valve that keeps the gage isolated and vented except when taking a pressure reading. I can't tell from here if either makes sense in your applications.



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

So, with 200 gauges failed, what were the root causes? To not have the data and then to attempt speculate on a process improvement seems highly dubious, at best.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[itsmoked]

That sounds waaaaAAAAY too high of a failure rate. Seems misuse or misapplication may be involved. A most likely method of methodically destroying gauges is the simple impulse. Opening valves suddenly ahead of the gauges will easily kill many. The other more subtle method of wrecking them is pulsations that work the gauges back and forth furiously.

In both cases an appropriate restriction installed ahead of the gauge can often be all the protection needed.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LuisCuellar00]

Thank you for all your responses, there are some grat Ideas.

In your experience how much time could a manometer be in operation with out failing, if installed in a correct application.

Dawn2:
I read al wika information it will be put in good use. Thx.

 

[MikeHalloran]

Luis, please provide a photo of what you think a manometer is.


Mike Halloran
Pembroke Pines, FL, USA

 

[LuisCuellar00]

Mikehalloran

Somthing like this.

http://www.wika.us/23x_34_en_us.WIKA.

 

[MikeHalloran]

Okay, that's a Bourdon tube type pressure gage.

I use the word manometer for something else, generally a liquid filled u-tube, or a pressure gage with equivalent range, usually 0 to a meter or less of liquid column.

As mentioned, pressure gages are usually protected from surge/shock by isolation valves or dampers. If your facility doesn't use something like that, do start.

Do also examine any replaced gages you can acquire, to find out why they failed.



Mike Halloran
Pembroke Pines, FL, USA

 

[roydm]

"If it;s installed in a correct application", 100 years.

 

[roydm]

Seriously I would be disappointed if a gauge didn't last 5 years.

Roy

 

[wfsymon]

Hi Luis,

For High temperature use the Pig tail assembly.
For Over pressure & vibration , use the glycerin filled gauges .

If possible extend the impulse lines and transmit the location of the Gauges from the process area to avoid the process vibration,pulsation and easy accessibility.

Regards,
symon

 

[MikeHalloran]

Just a note about glycerin filled gages:

They typically come with a little sticker that instructs you to, after installation, remove or pierce the little rubber plug that keeps the glycerin from running out during shipment.

An amazing proportion of experienced mechanics, and a larger proportion of engineers, claim to have never noticed the label when their failure to vent the gage is mentioned.

That conversation usually follows their reportage of improbably low pressures, often invalidating several hours of work.



Mike Halloran
Pembroke Pines, FL, USA