P&ID Line Number

I am not sure there is any absolute answer to this question. In general, it is a decent idea to number wires or pipes consecutively, without gaps. This avoids questions such as "Where is pipe 003?" which is absent from your example, for instance.

However, suppose that you have several identical zones of piping or wiring, each of which requires 17 different wire/pipe numbers. Rather than numbering 1-17, 18-34, 35-51, etc., it might make more sense to use 1-17, 21-37, 41-57, etc., with a notation that x8, x9, and x0 are unused. That way, your pipe/wire numbers are consistent from zone to zone, and more easily understandable. And thus safer.

However, there is no damned limit whatsoever as to what some dumbass bureaucracy might require you to do, regardless of how stupid.

If your drawings account for any omitted numbers, you SHOULD be okay, but alas that does not necessarily mean that you ARE okay. In any case, it is a good idea to account explicitly for any skipped-over numbers in a sequence.

For another example, suppose that you eliminate one switch (and consequently one wire number). Maybe it is wire #13 out of 450 wires. Why should you renumber all the wires beyond #12?

What you have done is fine.

The basic concept described by the other responder is correct. Many times after numbering all the lines in a process plant P&ID a line or two will be deleted. We do not go back and renumber all the lines to fill in the gaps. However, we do not account for the missing numbers.

Giving line a certain number is just giving it a name so that we can easily trace it especially if it continues to the next P&ID. Therefore, naming it in sequence is a good practice even though it is not compulsory.

In addition to line size and service type, I have noticed that some oil companies include line class, type of material of construction, temperature rating and corrosion allowance as part of line numbering.

earlier searching line numbers in drg was tedious. Now in latest autocads you have word search facility. No doubt it is good to go in some sequence.

As has been said there are any number of ways of numbering lines on P & ID all with their drawbacks and unfortunately you just have to go with what is required by your client / jurisdiction.

You should be creating a linelist (or if you have intelligent P & IDs one can be created) along with the P & ID and the two should be used together in the checking as the one backs up the other.

I would normally number the main circuit first sequentially as this makes it easier. BUT often you need to add a line into a sequence - eg if there is a change in piping material which you didnt initially realise so your sequence of lines would go 001, 002, 003, 018, 004 etc. So you need to accept that there are lots of reasons why a neat sequence gets messed up.

I would always try and provide a common numbering for similar lines eg on my current project we have five 70000m3 Propane and 5 70000m3 Butane tanks. The piping arrangements for all 10 are the same so our line numbering which has 5 figures of is

021XX for a line on the first Propane Tank

022XX for the equivalent line on the second tank etc

031XX for the equivalent line on the first butane tank

This leaves a lot of gaps but makes the it easy to check all the lines because of the common numbering. (Our instrument colleagues have follwed the same pattern for numbering instruments).

The problem with this is that no one knows why there are gaps, but if you can't find a line on the P & ID or on the line list is safe to assume it doesn't exist.

As a general principle between two equal options I would go with whatever engineering prefer over what QC would like. Obviously QC is an important job but we need to make sure that the engineering is as straightforward as possible.

And I forgot to add as I work in contracting for the oil industry I would always expect to see at least a pipe code - when specifying pipe this is key information and when the piping group are laying out piping they need to know what hte materials are and the best place for this is on the P & ID. It also gives you a good check that you havent done anything silly eg specified 150# piping when your vessels are at 40bar (the limit for 150# is 19.6barg so 40 barg should be at least 300# depending on temperature).

Typically where I work the metallurgist will produce a Piping Materials sketch which shows the material and corrosion allowance t be usd in each service. The process group use this and the pipe spec from Piping Materials to select pipe classes for each line and put this on the P & ID and the line list. Finally the Piping / Piping Stress do layouts stress calcs etc using the data for the lines as selected by process and then telling us why we cant use a particular spec!!!!

These are 4/5 figure charcters which identify properties of the pipe eg the 5 figure codes we currently use

11031

First 1 - Flange Rating 1 for 150#, 3 for 300# etc

Second 1 - Pipe MAterial 1 carbon Steel, 2 Alloy, 3 Stainless then others for plastics, glavanised etc

Third - Cant remember

Fourth Digit Corrosion allowance in mm

Fifth a sequential number so that if there are similar but distinct pipe specs they can be separated

Also (not applicable here) I would expect to see a letter code for the insulation type including N if no insulation is required

In general it's a good idea to have some sort numbering system like you propose; however, there's no standard or regulation that FORCES you to do so, if that's the meaning of your question.

There are two things to keep in mind: once a pipe number is finalized, it can't be changed, otherwise it would be very hard to keep track of it in maintenance records, etc; and when changes are made to a process and its piping is changed (pipes added, removed, or resized), you can't renumber all of the pipes just to keep their numbers in order.

Good question, though; I'm running into other matters concerning standards and practices myself. In other situations, I'm asking (and getting asked) the same questions: why do we have to do it that way? and is there a standard that forces us to do it that way?

Cheers! DZ