Field pressure and temperature gauges 1

[kimawi]

Hi All,

Just wanting to get people's opinion about whether the field mounted pressure and temperature gauges have lost their significance in the plant since a transmitter reading is always available in the CCR and the operator can get the reading on the radio.
I am always having this argument with colleagues because there is a trend to cut back on field instruments to save on cost.

Regards.

 

[DRWeig]

To me, it's a pain when they aren't there. The radio is a poor substitute. Plus, I prefer an independent local reading since occasionally the trouble I'm investigating involves the sensing loop in question.

Then again, I'm an old fogey whose cell phone has no e-mail, no text-messaging, and no internet capabilities at all. It's a phone. Perhaps the younger generation will take the no-local-gauge issue in stride.

Good on ya,

Goober Dave

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[danw2]

The old Fart (me) agrees with the Old Fogey.

 

[GHartmann]

I am with the grey hair group (me).

What I see today is quite a few DCS readings sent to the DCS "just because". Deleting these would save the "real money", but that is not the industry trend.

There is something to said about forcing the field operator to look, listen, and even smell out in the operating area for unusual events.

The old field devices made them do this.

 

[zdas04]

Field gauges always have questionable calibration. When someone calls me about an odd difference between two field gauges I always find myself questioning the gauge. For example, too many operators have never heard of "paralax" and don't (or can't) position themselves in front of the gauge face and the readings can be quite far off.

My last few years with field responsibilities I pulled all the field pressure gauges and installed Parker fittings in their place. Then I bought all the operators test gauges (with the mirror behind the needle) and taught them how to read the gauge. That was a funny meeting. A room full of very experienced operators who were pretty sure that this stupid Engineer was wasting their time. I stood in the front of the room and held up a $50 bill and said "I'll give this bill to anyone who can tell me what the mirror on the face of this gauge is". 25 guys and I kept my $50 and they listened to what I had to say. The gauges had 2 ft hoses on them (so the operator could avoid some of the awkward body positions that permanent gauges require) with male Parker fittings. The guys could take a dozen readings with gauges we all trusted (and trusted that they were properly read) in about 5 minutes. After that change we spent a lot more time evaluating problems than we spent questioning data.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[kimawi]

Thanks all.
David, is that Parker fitting and operator test gauge you described similar to what's called "Pete's plug"? I've seen this hand held guage that ends with a "needle" probe that can be inserted in any test point (Pete's plug) to measure the pressure.

 

[pmover]

zdas04,
I agree with you; however; digital pressure gauges are easier to read than test gauges. Yes, the digital gauges are calibrated yearly. I find reading the test gauges acceptable, but when accomplishing yearly tests on safety shutdown devices, the digital gauge is a much better option. my eyes are not what they used to be . . .

kimawai, PIs & TIs ought to be placed in services/systems that are not monitored by transmitters, rtd's, etc and are not critical to operations. save on costs? on a plant wide basis, probably so. but what does the client state?

Lastly, there have been several occasions in which the TI or PI displayed values are not accurate & not within acceptable calibration error margins. If a parameter is not where is should be, do not trust the TI or PI currently in use. Like zdas04 wrote, use the test gauge to verify the operating parameters and the fittings are an easy/safe means of obtaining the values.

good luck!
-pmover

 

[lacajun]

It's a good idea to have local gauges, just in case. The plants I've worked in require operators to make rounds and take readings. That in part, gets them out of the control room to look at the unit, which is good. Some aren't too prone to wandering around an operating unit in good weather let alone bad weather.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[zdas04]

When my test gauge broke a few years ago I replaced it with a digital gauge. I like it a lot.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Latexman]

Before I troubleshoot a problem I check and replace the pertinent gauges. I prefer the needle type because it's easier to see the dynamics going on at a glance.

Good luck,
Latexman

 

[thalathb]

It always nice to have such bach-up to your DCS readings...Never rely on one source..

 

[macmet]

I like the local gauges too. If I'm standing beside the unit and I want to get a reading I can just take a look. I don't look at them for accuracy, I look at them to get a sense of what the temp/pressure is at that time.

So, for the price of the temp/pressure gauges, it is worth it IMO. It is one of the things I look for in a P&ID and I always ask to have them added where I think they will be useful.

Besides, it is a lot easier to ignore the gauge if you don't like them than it is to add one later on.

 

[rmw]

Count me in on the "old Fart" and "old Fogey" crowd.

That said, I never met a gauge I trusted. I am a gauge tapper and much like Macmet, I am more interested in the "feel of things" than the accuracy of the readings in most cases. When I am lookng for accuracy, then I'll tap the gauge or do the other necessary things (replace with a calibrated guage, mount a test guage, etc.)

I don't necessarily trust transmitters either unless they are fresh calibrated.

Zasd's method of swapping a guage around (which I have done to remove guage error from the mix) is OK if there is no danger of mixing components within the process - sometimes not advisable.

rmw

 

[lacajun]

If they don't want to buy the gauges, ensure they put the fittings on for them in case they find they have value.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[zdas04]

I work in gas fields, mixing fluids is not an issue on the kind of stuff I deal with. I can see a LOT of places where that wouldn't be true, thanks for bringing it up.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[786392]

I am on the old (grey hairs) group of guys; having said that [ul]
[li][/li]
[/ul]Essentially go for/practice some minimal verification for zero errors and [ul]
[li][/li]
[/ul]the tapping connection's credibility to provide representative reading of material contained inside the system being "gauged"or "sensed"

Additionally same errors would need to be looked-up and taken care off for any/all digital gauges.
As regards the 'radio' or "wireless system" I have slight reservation on these being susceptible to being most probably [ul]
[li][/li]
[/ul]affected by nearby "radio waves emission interference" and/or [ul]
[li][/li]
[/ul]"some hacking or intentional interference attempts"?????
Other forum Giants may correct my confused understanding;Thanks in advance

Best Regards
Qalander(Chem)