marking the MECHANICAL MINIMUM distance between fittings in P&ID

[ImRB]

Hello All,

i have a general query pertaining to marking the MECHANICAL MINIMUM distance between the fittings in the Piping & Instrumentation Diagrams (P&IDs).

Screenshot of one such marking is enclosed herewith.

my query is that as a process engineer, how should i come to know that MECHANICAL MINIMUM is to be marked between what types of fittings?

are there any guidelines available for the same? if so, can anyone share or tell the link to download?

if not, can anyone by virtue of experience suggest few tips on the same?

with thanks & regards,

ImRB

 

[MJCronin]

In my opinion, this is not a good idea ....

There is a lot of leeway in the development and structure of P&IDs, there are no hard and fast rules.

But when you begin to place recommendations and restrictions on component orientation or placement ONTO THE P&IDS, you are going down a path that has no end.

Ensuring that the correct physical location and orientation of piping and components is the job of the piping designer and Mechanical Engineer. It should be part of a formal review of piping drawings

What about Marking the P&IDs for the following ?

- Piping slope ?
- Valve Operator Orientation ?
- Pipe Insulation thicknesses on piping and equipment ?
- Sizing and locations of vents and drains ?

etc...etc...etc...

Obviously, if the client wants all these extreme details on their documents, so be it (and I have worked with many batshit/inexperienced clients)

But be aware, that by putting certain configuration requirements on your P&IDs, you are going down a road that you may regret..

My opinion only

MJCronin
Sr. Process Engineer

 

[gerhardl]

If you look at the basics, for instance programs for construction of P&ID's, the purpose of the diagrams are defined and limited.
As MJCronin suggest, stop there! See for instance

https://www.lucidchart.com/pages/tutorial/p-and-id

Of course you need a large amount of extra information to construct the optimum piping system. This amount of information is much more easily handled, distributed, changed and adapted if it can be handled separately, in stead of being drawn onto a diagram, which then has to be revised for each single change of any extra information.

Why complicate things with splitting up the same type of information or note it down on several documents?

Conclusion: Use a P&ID diagram with position or tag numbers and necessary (standard) components and information only.

All extra information for pipes and components separately and described/bound bound to tag numbers. The information is then available for each component for construction, purchasing, mounting, operational, maintenance and safety purposes at one easy found and easy to update place for each component.

 

[LittleInch]

Generally minimum is initially defined by the process engineer based on process requirements to minimise inventory in a particular section of pipe.

Sometimes it is added by another engineer or as a result of HAZOP or similar review.

BTw I've never seen a valve angled quite like XCV 4305 before now...

MJC - I've often seen slopes indicated, occasionally a note about a particular instrument to say "To be visible from .... - generally some manual valve, Insulation is usually shown, but thickness is in the pipe spec and vents and drains are often sized and located within a certain length, buit not usually dimensioned.

You need to guide other engineers and designers where you need to, but don't over do it.

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

 

[ImRB]

Dear All,

thanks for your valuable feedback.

@ LittleInch (Petroleum): to answer your curiosity: "BTw I've never seen a valve angled quite like XCV 4305 before now..."

would like to tell you that it is a FLUSH BOTTOM VALVE which is a kind of globe valve.

with thanks & regards,

ImRB

 

[mk3223]

IMO, for the general piping layout the fitting make-up is to be the minimum distance. Of course, the layout needs to be reviewed and accepted by you who specify this design requirement on P&ID.

 

[georgeverghese]

In this case, the statement "mechanical minimum" probably means "place this valve close to the downstream vessel", which is a sensible request from a plant operations perspective.

 

[don1980]

As a process engineer you only need to provide the pipe designer with distance/spacing instructions when there's a process reason for such instructions. Otherwise, and in the vast majority of cases, this isn't necessary and it's left to the pipe designer. There's no reason or value for the process engineer to specify such details except in those special cases where there's a process design reason to place such a constraint. For example, if a process engineer needs to create a liquid seal leg with a segment of pipe, then it's obviously critical that he/she mark the P&ID showing the specific lengths of that seal leg piping. Or, say for example you're injecting an additive into a process line; there may be a need to define the distance between a control valve and the injection tee. You communicate that to the pipe designer by showing the dimensional requirements on the P&ID, or by putting it in a P&ID note. But in the vast majority of cases we leave it to pipe designer to lay out the piping and piping components in a way that makes the best sense (provides the necessary accessibility and minimizes the installed cost).