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Piping Line Numbers on a P&ID

Piping Line Numbers on a P&ID

Piping Line Numbers on a P&ID

Can anyone tell me if the piping line number changes after a reduction in the pipe, or if the pipe branches off into several sub-branches?

Thanks in advance.

RE: Piping Line Numbers on a P&ID

First, there is no single right answer to this question.  Every company (Engineering and/or Owner Operator) has it's own practices.
However the most common practice followed by most Engineering companies would answer your question as follows:
 - A line number does not change at a reduction in the line size.
 - A line number may or may not change at a  branch.
 - A line number will normally change for a branch from a primary Utility header to a Sub-header in utility lines.  The line number will also normally change from the Sub-header to the branch to a utility user.
 - A process line that originates at a single nozzle on one piece of equipment (Vessel) and terminates at multiple nozzles on another piece of equipment (a multiple unit Fin-Fan) will not normally change line number at the branch to the multiple nozzles.
 - The line number for a pump suction line does not normally change line numbers when the line splits to the two pumps.
For additional information on Line Numbering and Line List check the pipingdesigners.com website and the article under "Training"

RE: Piping Line Numbers on a P&ID


I don't think any codes govern this.

My experience (30 years of it) is that each owner/operator/client has their own rules for line numbering.

Typically line numbers do not change after a reduction of pipe, but on my current project, the client is requesting this and it's the first time that I've seen it. Local regulations, NORSOK, has been mentioned as the reason but I haven't personally verified that.

Logical places to change Line Numbers are:
1.  Pipe Specification change
2.  Materail change
3.  Pressure Class change
4.  Change in Design Conditions (Pressure/Temperature)
5.  Branch piping, sub-branches, sub-headers etc. (Sometimes if the main header doesn't continue, one branch or sub-header will continue with the original line number and the other branches are each assigned their own numbers.)

Houston, Texas

RE: Piping Line Numbers on a P&ID

I am confused about the answer about "Changing line number after reducer". Generally line numbers carry line size. If there is no need to assign a new line number after a reducer, we can have a 2" line with line number of
Am I right?

RE: Piping Line Numbers on a P&ID

You have the elements of the Line number mixed up.

You have: BFW-3000-4"-AA!
It should be: BFW-3000-AA-4"

The "BFW-3000-AA" is the line identification or line number.  The 4" is just the size where the information was posted.  Thus you can have both BFW-3000-AA-4" and BFW-3000-AA-2" on the same line.

RE: Piping Line Numbers on a P&ID

pennpiper ...It all depends on the company standard for line numbers. I've seen the line size positioned in the front, middle, and the end (as you have indicated). BUT your basic premise is correct, the "number" of the line number is 3000(in this example) and the only time it changes is as NozzleTwister as indicated. SO adding my $0.02 to the face question, line size "normally" does NOT dictate a piping line number change. ...Good Luck!

RE: Piping Line Numbers on a P&ID

I concur, the line number is the unique sequence number and it can change per internal proceedures.    The only time I would change the line number is a change in spec break, ie materials, rateing, code 31.3 vs 31.8.

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