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PI Suffix

05/02/2017 2:47 PM

Rupture Disc assembly with excess flow check valve and a tell-tail pressure gauge. The PI symbol on the P&ID has a W/E suffix over it and the Excess flow has an EC. Something Raytheon added to our P&ID's. Suggestions?

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#1

Re: PI suffix

05/02/2017 3:02 PM

That would be telltale rather than tell-tail. PI = pressure indicator, such as gauge. I've never seen the others.

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#2

Re: PI suffix

05/02/2017 3:10 PM

Call Raytheon and ask?

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#4
In reply to #2

Re: PI suffix

05/02/2017 3:22 PM

Yea, generally a good idea. However, this project was in '97. As I recall, Raytheon became Mustang Engineering, then later became Pegasus. While I was on the net looking for abbreviations, I queried this forum on a lark.

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#10
In reply to #4

Re: PI suffix

05/02/2017 4:12 PM

It is something of a surprise to learn that the P&ID has not been kept up-to-date through the 20-year operation of this process!

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#17
In reply to #10

Re: PI suffix

05/05/2017 2:04 PM

Seriously? I'd like to work where you've been. After 40 years, I can still go out in the field and find hidden treasures that's been sitting there overlooked. But as to this particular item, the piping and appurtenances are updated. I assume this particular abbreviation has been overlooked since it wasn't used or needed.

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#3

Re: PI suffix

05/02/2017 3:20 PM

Is there a legend with/on the P&ID? Best is to take Andrew's advice...

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#5
In reply to #3

Re: PI suffix

05/02/2017 3:27 PM

And yes, after looking through 4 packed file drawers, I finally found their symbol sheet that was never incorporated into our drawing files. It was our symbol sheet that made one addition to. Just not any of the other additions they added to the P&ID's.

I suspect I'll be having these outlaw abbreviations removed.

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#6
In reply to #5

Re: PI suffix

05/02/2017 3:31 PM

It appears that some companies do have some of their own 'customized/modified' symbols.

Good luck!

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#12
In reply to #5

Re: PI suffix

05/02/2017 4:19 PM

And replaced with what, pray tell us? How about writing out abbreviations that are so out of common parlance that no one a year from now could decipher them, unless it is the intention to cover up the intention of the invention.

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#18
In reply to #3

Re: PI suffix

05/05/2017 2:06 PM

yea. as previously stated, I found their legend in the project files. It was a copy of ours with one addition to it. Just not the additional abbreviations.

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#7

Re: PI suffix

05/02/2017 3:35 PM

I think the W/E abbreviates "working/exhaust" (pressure), and I suppose the flow check valve stands for "excess check." It probably is intended to limit the outflow after a rupture disc burst so that it does not shoot a stream too far.

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#8
In reply to #7

Re: PI suffix

05/02/2017 4:08 PM

<...It probably is intended to limit the outflow after a rupture disc burst so that it does not shoot a stream too far...> Nonsense. The flow through the disc is determined by the reaction going on in the pressure vessel. Once pressure of that reaction has exceeded the burst point of the disc, that pressure needs to be relieved so as to protect the vessel structure.

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#11
In reply to #8

Re: PI suffix

05/02/2017 4:17 PM

Then why put a outflow check valve on the thing at all? That to me sounds like you can't see nonsense when it is staring you in the face. I still say it is probably some sort of safety device to limit injury to nearby personnel, perhaps.

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#15
In reply to #11

Re: PI suffix

05/05/2017 1:56 PM

No such thing, a rupture disc outlet has to allow free-flow under any conditions that caused the disc to rupture. If there's piping to direct the flow it has to be designed for minimal back pressure. One thing that might be in the line could be a backflow preventer so that nothing would be sucked back into the process should the sudden release of pressure create a vacuum. Of course it would help if we knew the process fluids and conditions.

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#16
In reply to #15

Re: PI suffix

05/05/2017 2:01 PM

That is what it is, I realize now, it is truly there and needed to be there as a non-return valve on the RD. It must by definition be a substantially large one though.

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#9

Re: PI Suffix

05/02/2017 4:11 PM

Go to the Process Description document and read about it there. However if the process has changed since the Process Description document was written, then carry out a HazOp Study without delay and take immediate action on any problem areas that arise from the study.

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#13
In reply to #9

Re: PI Suffix

05/02/2017 4:20 PM

Or just take all the defective (improperly documented devices (and personnel)) out to the weapons testing area, and test away.

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#14

Re: PI Suffix

05/03/2017 8:00 AM

Sorry, I can't help. But I did for Raytheon during this time frame on JT coolers for IR seekers. These devices had high pressure gas reservoirs (several thousand psi) attached to them. If a hypodermic gas supply line is cut or ruptured, it can act like a scalpel and surgically remove a limb. Proceed with caution.

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