Do you show flanges on a plant P & ID? 18

[LittleInch]

Ok, we're having a debate internally here about what is "normally" done on a P & ID.

Do you
A) Show deliberately a little vertical line next to each flanged valve to indicate it's a flanged valve or
B) Assume all the valves in a plant are flanged valves.

If B how do you show when it is deliberately a welded end valve you want (e.g. last valve going into a long gas pipeline)

I've seen both ways and A really annoys me as you get little lines all over the place and then you can't see it or it gets lost in all the other data.
We're talking fairly basic P & IDs here, not the all singing all dancing "intelligent" P & IDs.

Spool pieces, blind flanges on e.g. drain valves are shown but "normal valves"?

Answers on a postcard please....

Thanks, LI

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Also: If you get a response it's polite to respond to it.

 

[Gator]

No. Use a note to detail anything out of spec or unusual.

Piping Design Central

 

[bimr]

Agree with Gator.

A Piping and Instrumentation Diagram - P&ID, is a schematic illustration of functional relationship of piping, instrumentation and system equipment components.

A Piping and Instrumentation Diagram is not a fabrication drawing.

 

[EmmanuelTop]

The most common approach I have seen so far is to indicate flanges and their size on all vessels and all valves. For flanged connections between two piping segments this was rarely indicated on P&IDs, but also not uncommon.

Welded valves have their own symbol in the P&ID legend and they are distinctive on the drawings.

With Process and Safety background, I am a big fan of capturing this kind of information on P&IDs. When defining various unsafe scenarios, seeing the number of flanges (as potential leak paths) and at the same time being able to determine isolatable inventories at the P&ID level only, is a tremendous thing. Having this information on P&IDs also helps in defining isolation philosophy for turnarounds (where to insert a spade or a blind flange), doing troubleshooting of the plant operations, defining piping specification breaks, HP/LP interfaces etc. I think the reasons for providing this information on P&IDs are numerous.

As for the clarity of drawings - a proper P&ID should not be congested and if rules of good practice are followed (e.g. one vessel per sheet etc.) showing flanged connection on the drawings should not really affect their clarity.

Dejan IVANOVIC
Process Engineer, MSChE

 

[EmmanuelTop]

Other interesting readings/views:

http://fumblog.um.ac.ir/gallery/280/e-pr-230a.pdf

http://mcsetender.kockw.com/Commerc...ds/Engg Drawing Practice Code/EG-DO-C-001.pdf

http://www.red-bag.com/engineering-guides/255-rb-eg-ue410-preparation-of-pfd-and-efd-p-id.html

Dejan IVANOVIC
Process Engineer, MSChE

 

[MortenA]

We dont show spool breaks but we show other flanges (vessels, valves, pumps etc.)

 

[BigInch]

It's a bit ironic that today you are asking about showing flanges after I had a similar discussion about trying to get you all to show major valves just last year.

My opinion is that if something is important, show it, however it usually is not necessary to show flanges, especially since a PID should have adopted different symbols for flanged and weld-end valves, if indeed it would be important to show the difference.

On plant drawings made by major engineering companies, the likes of Flour, Brown & Root and Stone & Webster, etc., back in the day, proper piping plans and profiles were made. On those flanges were shown. Two lines were made for pipe only when D>12", with pipes smaller than that represented by one centerline line. All valves were shown as above as well, except with valve lengths and flange widths to scale.

Don't see why the argument. Nobody's drawing them in pen & ink on vellum. Either way, it's JUST A CUT & PASTE!

If all valves are flanged, then no, a simple general note, "All valves flanged, except as noted otherwise." should do the trick.

 

[racookpe1978]

It DOES HELP on P&ID's to know what joints can be broken for temporary fittings, flush or hydro connections, Backwards flow attachments, blind flanges, or blank connections.

The "dot" and "line" connections in Big Inch's sketches above are the usual practice, and they should be encouraged.

 

[pennpiper]

Do not show Flanges on P&ID's unless there is a compelling reason.
Show Flanges at Vessel Nozzles only where there is an installed Spec Blind.
Show Flanges for inline Flanged Valves only where there is a Spec Blind.

Do not show Weld Dots on any P&ID.

The manner of connection (Flange, Threaded, Socket-weld, etc) of a valve in a line is covered by the Piping Material Line Class Specification and the line size.

Sometimes its possible to do all the right things and still get bad results

 

[MJCronin]

pennpiper is the respected senior authority on this subject ...... Bravo !

Ummm ... No one has mentioned the PIP P&ID Industry standards ????!!

MJCronin
Sr. Process Engineer

 

[BigInch]

I agree that weld dots are not normally shown on PIDs, but if they are important for some reason, they certainly could be.

 

[uaepiping]

Normally we do not bother about this if process has shown flanges or not, as anyhow for detailing we need to go to the relevant material classes. And as BIMR put it above, P&IDs are not fabrication drawings only schematics though I have seen clients asking for (to consultant process engineer):
1) Your P&IDs must show lines from east to west so we can recognize from the P&ID itself. (I don't know how it was solved finally!!!!!).
2) Your lines should be showing the road crossing (going down and then coming out)....

 

[LittleInch]

Gentlemen and I think sadly it really is all gentlemen unless anyone tells me otherwise, thank you for your valued input. As I expected there are two views on this and to summarise and respond to a couple of points,

Dejan, thanks for the links and the symbols sheets etc

People seem split about 50:50 on this.
One problem I now have is that the legend sheet I'm working to as we're designing an add-on to an existing plant, does not appear to have any symbol or way of identifying if a valve is welded or indeed one weld end, one flanged. I've searched the sheet and looked at some P & IDs where this should be and can't see anything there or any symbol or note or type of valve to indicate a weld end valve. Maybe they don't have any, but it seems surprising. The piping spec is non descriptive about flanges or welds and doesn't seem to have any options on this, but maybe that ends up buried in the valve schedule.

It think the thing to do is to generate a symbol for a weld end valve - does anyone have an example? - and then assume all are normally flanged.

Flanges on vessels, flanges where you specifically need to show them (removable spools, spectacle blinds etc) are in there and seem a good idea.

The symbols BI has loaded to me are more isometric piping drawings to me and I've never seen a weld dot on a P & ID.

BI- the valves you refer to were valves on a PFD, but that's another post/story.

Thanks again for the valued input
LI

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Also: If you get a response it's polite to respond to it.

 

[cjabhijit]

Dear All,

The trend is changing because of intelligent P&IDs where MTO of all the pick-able (except Pipe & Elbow) items is now started coming from Intelligent P&IDs.
You will see these changes in approach of P&IDs are now becoming spec intelligent to account for Flanges as well.

Working on such project currently where this is being observed. Great utitlity if you look at MTO aspect of this change.



Thanks & Regards,
Abhijit

 

[BigInch]

I was just going to mention the same thing. Great post Abhijit.
One hardly ever sees plans and elevation drawings anymore. That's where the MTOs used to come from, but no longer.

 

[ehbadger]

The piping spec is non descriptive about flanges or welds and doesn't seem to have any options on this, but maybe that ends up buried in the valve schedule.
LI

The PIDs I've dealt with generally do not show flanges. Only at vessel connections. However many times a valve or random component does get drawn with flanges. It is quite inconsistent depending on the age of the PID and who drew it... always a challenge keeping things consistent across the plant(s).

Per your sentence I quoted above; Our pipe specs are very detailed on what valves/piping components are allowed to be flanged/welded/threaded. The PID indicates the pipe spec on each process line. From that I generally assume it follows said spec. Usually any anomalies are called out with a Note.

 

[Killstadogg]

Drawings are just a means to convey information.

If the people actually using the P&ID aren't going to need to differentiate a flanged valve from a welded flange for their purposes then don't bother showing them.

If there is a good reason to show them then show 'em.

I lean toward the former. But when it comes down to it, all that matters is that the information needed is conveyed.

 

[LittleInch]

I agree, but equally established conventions are also useful.

The issue partly arose because someone who was used to seeing flanges identified on each valve, got a P & ID which worked the other way and then assumed, without seriously thinking about it, that all the valves were welded.

I still haven't got any feedback on how people show welded valves if the convention is to not show flanges. - Anyone?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Gator]

The primary purpose of the P&ID is effective communication between process and piping design. I've seen various other groups in meetings/design reviews asking for non-process things to be included but doing so only adds to the workload and adds more contributors to the workflow.

As mentioned upthread, valve particulars such as end connection type are detailed in the valve specs.

Sometimes smaller companies/suppliers can get very detailed on their P&IDs since this may suit them better but they're typically not issuing dozens, maybe hundreds of drawings for one project and likely have only a few people using the P&IDs, so communication is simpler.

Of course, with CAD, it's tempting to say, "Hey, why don't we just include X, since everything's digital and easy to add or revise?".

What was the reason to propose showing flanges in the first place - for maintenance? Purchasing/MTO? Safety?

Piping Design Central

 

[LittleInch]

Gator,

The initial issue was the ease of the piping designer, but as others have noted above, p & ids get used for lots of other reasons as the plants goes into operation and modifications.

TBH, we're probably in the smaller company mode and as pipeline engineers our plant processes are relatively simple. At most we issue tens of p & ids, not hundreds.

Thanks for the input.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.