Talk:Process and instrumentation diagram

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Merge proposal[edit]

Given that the pages of Process and instrumentation diagram and Piping and instrumentation diagram both contain the same example image, it seems that the distinctions between these two diagrams is trivial or small enough that both diagrams could be covered by a single page on this topic. Any opinions? Jdpipe (talk) 00:46, 28 November 2007 (UTC)

I agree. However the digram shown is definitely NOT a P&ID. --130.15.92.49 (talk) 16:26, 18 January 2008 (UTC)


I've worked in industrial piping design for over thirty years. "P&ID" has progressed from an abbreviation to a name in and of itself. Today, if you asked around my office what P&ID stands for, many people would have to think for a minute. You'd probably get both definitions, but all people would mean the same thing. But I think "Piping and Instrumentation Diagram" would win by a large margin. The purpose of a "P&ID" is not primarily to show the process, (although it does that) but to show the piping components required in their correct relative order, connecting to the correct nozzles of the correct equipment. It is a highly detailed document with highly evolved symbology. If you want primarily to show the process, you make what we call a "Process Flow Diagram". (Incidently, the diagram shown is more like a PFD than a P&ID)

Therefore, I vote that we make a page called "P&ID", with "Piping & Instrumentation Diagram" as the preferred name, but show that "Process & Instrumentation Diagram" is an alternate name.```` —Preceding unsigned comment added by 142.59.78.33 (talk) 03:53, 14 February 2008 (UTC)


In my company, P&ID means Process & Instrumentation Diagram (by HHW2008). —Preceding unsigned comment added by Hhw2008 (talkcontribs) 14:46, 20 February 2008 (UTC)


I agree that the diagram is actually of a PFD. It's even found on the PFD page. A P&ID is much more detailed and shows all instruments instead of just control valves. It makes sense to merge the two pages. I had always heard of P&ID in reference to "Process", but just recently saw it written out as "Piping & Instrument Diagram"; that's what led me to wikipedia. 199.64.0.252 (talk) 20:30, 20 March 2008 (UTC)

In my experience (40 years as a piping designer) P&ID is more commonly understood to be Process and Instrumentation Diagram. Process Flow Diagrams, while containing most of the same graphics, add information regarding flow conditions/states. P&IDs are intended to sort out Instrumentation and Controls. I suggest a merge using "Process" rather than "Piping", as I believe that more people will use that as a search. —Preceding unsigned comment added by 204.50.168.206 (talk) 14:31, 29 May 2008 (UTC)

I've being working with diagrams like those for 5 years now, and I agree on the merging, as the diferences presented for the Process and the Piping are more of the routine work of each company than for the Diagram itself. - 201.91.26.237 (talk) 20:43, 22 July 2008 (UTC)


The Correct term is "Process & Instrumentation Diagram" - "Piping" is simply and straightforwardly incorrect. —Preceding unsigned comment added by 81.151.17.6 (talk) 11:09, 21 August 2008 (UTC)

I disagree with you. As a licensed Professional Engineer working as a Process Engineer at a very large company in Houston, I deal with these everyday. The correct and most commonly used definition for P&ID is "Piping and Instrumentation Diagram." 144.177.70.5 (talk) 20:24, 5 September 2008 (UTC)

Sadly the industry cannot agree on a single definition for P&ID. I vote for the P&ID as being it's historical context of a P&ID as a Piping and Instrumentation Diagram. However, this appears to be what Ken Arnold in "Design of Oil-Handling Systems and Facilities" would call a "Mechanical Flow Sheet" that is derived from the process flowsheets. In API 14J the industry confused the issue by developing a term for a "Simplified P&ID)Process and Instrumentation Drawing". It appears to be describing what we in the industry would call an process safety flow diagram. It does not have all the piping specifications that the historical P&ID would have and should not be confused with the former. Now that API 14J has been adopted as regulations by the US government, it tends to make everyone assume they need to be developing Piping & Instrumentation Diagrams for regulatory purposes. Really what is needed is PFDs, API 14C Safety Flow Diagrams and only from the well SSCV through the 1st Separator, Safe Charts and Cause and Effect diagrams. Detailed Piping &Instrumentation Diagrams are needed to distinguish high pressure to low pressure interfaces for HAZOP analysis before the design is finalized. This requries the more detailed (P&ID) piping and instrumentation diagram so that piping specfications and pressure ratings are clarified. Makes it hard to distinguish what the term P&ID actually means. Also depends on which discipline is being asked to progress the documements, a process engineer, a mechanical engineer or a facility engineer (a generalist from either of the aforementioned two disciplines)

API RP 14J (Section 6.2.1) definition should be listed for the Process & Instrumentation Drawing noting it is a simplified form of P&ID. "The simplified P&ID should show equipment and intersecting lines including relief, vent, and drain systems. It should include all control valves, check valves, relief valves and safety shutdown sensors. Set points of relief valves, maximum allowable pressure ratings of equipment and pressure ratings of piping systems should alos be shown. It is not necessary to show utility systems, details of instrument hookup, line numbers, valve types, individual instrument tag numbers or other such information."

A piping and instrumentation diagram should include utility systems, details of instrument hookup, line numbers, valve types, individual instrument tag numbers or other such information.

It should be noted that 14J also notes that process design information such as process flow rates, fluid properties, pressure and temperature used to size the different subsystems or individual pieces of equipment should be included either in a separate process flow diagrams (PFD), included as notes on the simplified P&ID, or in a separate narrative (or process description). Because of widely varying flow conditions to which offshore oil & gas production facilities could be subjected, it may not be necessary to have a detailed material balance. (I would still recommend having a consistent balance for several key constraint cases but these may not all need to be captured in the designer's drawings.) "The intent of the design flow information is to document the information required to adequately size relief valves and other critical components for the most critical service from a safety standpoint." 206.57.125.83 (talk) 15:52, 18 September 2008 (UTC)

Marc S. Young, PE, Manager of Process Engineering, OGS, Houston

So how about merging the two, and saying "There is a difference in opinion on whether P&ID stands for 'Process and...' or 'Piping and...' In the one interpretation... The other school of thought..."? Because there is clearly no internationally agreed description, and I, for one, would like to read both versions when I search for "P&ID"! --Leviel (talk) 06:52, 25 September 2008 (UTC)

I just want to say that an ISO norm exists about process description (ISO 10628) and gives the minimal content of each kind of diagram. They defined 3 types of diagrams: Block diagram, Process flow diagram and Pipe & instrument diagram. Biglama (talk) 14:13, 25 November 2008 (UTC)

As a chemical engineer, and has a reasonable experience in API manufacturing, in the case that the manufacturing plant / unit is a multi purpose; where several process can be produced using different equipments, the term "Process & Instrumentation Diagram" definitely will not be valid, so it is much more accurate to relate the abbreviation P&ID to "Piping & Instrumentation Diagram". P&ID drawings will cover the manufacturing unit and the supporting utilities & systems. Other separate diagrams that describe each single process or multiple processes, will be nominated as "Process Flow Diagram(s)", the P&IDs can be utilized as a base for that purpose or they can be just "Block Diagrams". —Preceding unsigned comment added by 212.62.97.20 (talk) 07:27, 5 January 2009 (UTC)

I am a Registered Professional Engineer with 20 yrs experience in various process industries. I think that what needs to be recognized here is that in many companies, the use of PFDs (Process Flow Diagrams) seems to have decreased over the years in favor of just using P&IDs. It used to be that the normal order for a new process would be to develop the Process on the Process Flow Diagrams and then develop the P&ID from that. The PFD is more abstract and less detailed than a P&ID. As many companies no longer create PFDs (sadly) and go straight to the P&ID, they then end up using the P&ID as both the representation of the process and the process implementation details. It is my belief that this is one key reason for the confusion. However, having said that, I believe that the earlier historical meaning of P&ID is "Piping and Instrumenation Diagram" given its historical relationship to "Process Flow Diagrams", and that "Process and Instrumentation Diagram" is a more recent derivation. Therefore, I vote for the merge with the primary meaning being "Piping and Instrumentation Diagram". —Preceding unsigned comment added by SteveTheTechie (talkcontribs) 08:48, 21 January 2009 (UTC)

I vote against merger. After 28 years as an engineer on three continents, I have observed bad habits become normal habits. This is one. A P&ID is a piping and instrumentation diagram. It is a multi-discipline drawing that can be used by instrument engineers (count of instruments) piping engineers (development of isometrics), maintenance supervisors (determine how to isolate something safely), and in extreme situations, lawyers. A process and instrument diagram is not a multi-discipline drawing ... it is purely a process engineering (or chemical engineering) document, with no relevance to the other disciplines. Keep them separate. Ljscro (talk) 04:11, 14 May 2009 (UTC)John Westover, Owner, John Westover Pty Ltd, Melbourne Australia

Google results 5110 hits for "Process and instrumentation diagram" and 9070 hits for "Piping and instrumentation diagram" (talk) 08:43, 21 May 2009

My apologies for coming to the party so late.

In my experience, Process Flow Diagrams (PFD) are used in proposals and conceptual development of a process; the Piping and Instrumentation Diagram (P&ID) is used to detail what is needed to make a process work. A PFD has minimal information such as major process vessels, pumps, and critical control valves, normal operating temperatures and pressures and what may be flowing in each process line. A P&ID has the details of the process, such as pipe sizes, reducers, flange types, vessel and pump specs, MOC, ALL valves, ALL instruments, how the instruments connect to a PLC, DCS, and control valves, etc. It also tells the piping designers the order of the instruments and equipment in a process line, and allows the piping designer to accurately develop isometric pipe drawings..

These are two very distinct documents that address two different issues: the PFD gives the details for the material and energy balances, the P&ID reduces the process to practice. The P&ID is the blueprint for how the plant is built, and during construction, it is common practice to "walk down" a P&ID to ensure all the items required by the engineers have been installed in the proper location. Finally, the P&ID is necessary for performing HAZOP and other safety reviews.

Therefore, I vote to keep PFD and P&ID distinctly separate. Keith Dackson, PhD, PE (talk) 13:30, 8 October 2009 (UTC)

Here's a vote to merge the two pages, though the diagram needs to be substituted, as it is a PFD, not a P&ID. —Preceding unsigned comment added by 194.164.237.96 (talk) 15:05, 3 November 2009 (UTC)

Time to close the discussion: Process and instrumentation diagram is merged into Process flow diagram, whereas Piping and instrumentation diagram remains as is. -- P 1 9 9 • TALK 16:30, 14 January 2010 (UTC)