View Full Version : p & i diagram

April 24th, 2004, 08:53 AM
hello everybody,

First of all thank you all for your ready support. Next, i have posted a topic regarding p&i diagram basics, i.e - how to read the symbols & accordingly use the symbols in process flow sheets & the international standards available, but i did not get the help yet.

Is there any thing wrong with my question or i have asked for help in a wrong place. Atleast you guys plz. let me know so that i will seek any where else.

Hoping for your co-operation.


April 24th, 2004, 09:01 AM
Ok so first of all What does "P & I" mean? Please spell it out. I've looked at a lot of diagrams in my time but I've never heard of this term before.

Maybe I live in a small world...

April 24th, 2004, 09:06 AM
Piping and Instrument. Usually P&ID for Piping and Instrument (Diagram)
or Drawing

April 24th, 2004, 09:13 AM
Ok Check this link: http://www.coade.com/cwpid.htm

Do a Google on PI&D and you'll find a lot of stuff.

Tom Jenkins
April 24th, 2004, 09:15 AM
First off, Mike, P&ID stands for Process and Instrumentation Diagram, and is the basis for system design in most process control applications. It has symbols for showing the process flow stream, process equipment, and electrical and pneumatic signals. It is also used to establish tag numbers for various control loops and devices and can show the fundamental logical relationships between the process and various control loops. There are standardized abbreviations for sensors and control devices. This type of diagram is seldom used in the discrete manufacturing industry.

Now, sevensages, your question is not one that can be answered easily on this forum. It requires too many graphics, the explanation would be lengthy, and to do it properly would require a lot of interaction. In the US the ISA (Instrument Society of America http://www.isadirectory.org/ ) has a standard, ANSI/ISA-S5.1, that explains the sysmbols, establishes the abbreviations, and gives examples. I suggest you purchase this, or its equivalent in ISO standards. I have no idea if the standards for P&I Diagrams in the rest of the world are anything like those in the US, and I've not seen any sample P&IDs from Europe.

April 24th, 2004, 09:39 AM
P & ID => Pipe & Instrumentation Diagram
Is representation plant and instruments, position, details...

PID => Piping Industry Designer.Is build fisic tubulation industry.

P&ID: See is Image1 (http://www.niigata-eng.co.jp/shinko/images/pid-1.gif) Image2 (http://www.prosys.ie/topreactorpid.htm) Image big (http://www.aurelsystems.com/images/detail.gif)

Piping and Plant Design Softwares (http://www.click4links.com/D11.asp?l=0019Software&l=1927Piping_and_Plant_Design_Softwares) , is not diagram sometine tubulation industry

Software for P&ID, Smart P&ID,AutoPLANT P&ID, and others tool search:
One (http://www.gdseng.com/software/pcadpid.htm)
two (http://www.coade.com/newsrls/nrcwpid2002.html)

I have paper explain about more 60 pages, in Spanish
Not work with P&ID, the stuff that myself is not extense.

P&ID: Aplication industry discrete process. (Oil, petroil,gas, farm,...more)
More informations, search forum Instrumentation... any have link add?

April 25th, 2004, 01:20 PM
thank you guys,

First of al the question i have asked is not going to be answered in this session. As i am aware that p&i basically stands for - process & instrumentation diagram & for power plant application its mostly known as piping & instrumentation diagram. Now I am specifically concerened about power plant applications.

Whatsoever the drawings are good to study over. Now I have came across CADWorx P&ID s/ware - so guys can I continue with this! Further how can I get to know the symbols normally used in the p&i diagrams. Plz. suggest.

Waiting for your replies.

p.s: I do first make a search on p&i diagram on google but it was not help full as you are. So plz. help me to have symbols & their meanings.


April 25th, 2004, 02:02 PM
Whatsoever the drawings are good to study over. Now I have came across CADWorx P&ID s/ware - so guys can I continue with this! Further how can I get to know the symbols normally used in the p&i diagrams. Plz. suggest.

The way to get to know the symbols used in P&ID drawings is to use them. As silly as this may sound, you have to work with anything to become really familiar with it. You said you were interested in the power production industry. The same symbols and practices used for power plants are used in every other industry as well. The following is a brief definition of what a P&ID drawing is.

P&IDs are the instrument and piping layout drawing much as an electrical schematic is in the electrical/electronic field. Symbols are used to indicate the types of equipment that will make up a process. For a fairly large process, such as power production plants, may take several pages to as many as a hundred or more. After all, the purpose is to define the types of things that make up the system and show the piping connections between them. Obviously this is done in a "not to scale" fashion. The P&IDs purpose is to show what is connected, the size, specifications but not where or how you install it. The instrument systems are indicated by a set of ISA symbols that describe what is needed at particular points on the process. Process equipment such as reactors, vats, tanks, heat exchangers and the like are shown with a set of ISA symbols scaled to fit the drawing being constructed. In addition to pipe sizes, the P&IDs contain information about valves, regulators or other apparatus needed to make the system function.

The other respondents here have tried to point you in the right direction so please, be willing to do some leg work here.

April 25th, 2004, 02:35 PM
P&ID Tutorial (http://www.plcs.net/downloads/index.php?)
As Mike recommended, you should do a Google search and spend some time looking over the returns. This .PDF file is one I found in just a few minutes and seems to have some good basic info. Also, the company that sells this software offers a 25day free trial. You might consider that.

May 1st, 2004, 05:24 AM
hi guys,

thank you for your sugestions. i am practicing on it. just a few details needed, where i am getting confused -

1) connecting lines definations between different instruments, i.e remote instrument to panel, local instruments to dcs or plc, between instruments etc.

2) is there any standard symbol library available from where i can have the symbolic representation of instruments, viz. - vessel, conveyor, valves etc.

3) i have came across with a simple p&i loop diagram as follows - there is a vessel which level has to be controlled, now the level element is sensing & afterwards transmitting the signal to a summing card, where the set point is being set externally, pid operation is going on & the final output is being fed to a i/p converter & finally the signal is controlling a motorised gate valve to maintain the level in the vessel.
now, how i can develop other applications in such loop diagram fashion (i dont have the symbol library). i know that i need to practice but is not there any standard process guideline available for developing such loop diagrams (closed or open loop)!!


May 1st, 2004, 07:10 AM
For the 15 years in process control I have always heard that P&ID is for piping and instrument diagram(drawing) because it give the size and mat'l of the pipe, however process adn instrument diagram also makes sense.
If you want to learn how to interpret P&ID's you must (as others have said), get a copy of the stndards. Many companies
have their own internal standards that should be available.

May 2nd, 2004, 03:36 AM
thank you for your advise.

now the fact is that i am in a phase of changing my job to a new company who deals a lot with power plant engineering, as i am concerned with plc only i think a bit knowledge in p&i diagrams will help me in future. now the problem is that i dont have any resources to study with, right now. thats why i am seeking help.

hope you will understand the situation & help me out.


May 3rd, 2004, 07:48 PM
7 sages,
First of all everyone that has responded in there own way and I think that is good but like Microsoft is basically incorrect to answer your question. P&ID is a piping and instrument diagram but also depicts control expectations.
For example you may see a stacked symbol of squares and circles with letters and numbers in them. one may be
a circle with the letters and numbers PIT-1234.
This is as the standard explaination of symbols states...
P = pressure
I = indicator
T = transmitter
- = separation
1234 a numerical designator to reference a drawing or system.
The industry uses these symbols to convey control information.
PIC-1234 indicates what?
Pressure indication control, in most processes a PID loop.
Or sometimes is just PIC-1234 in a circle in a box stacked on such things as,,,,
could be construded unless otherwise indicated.....
2 alarms for pressure 1234 (device)
PAL is pressure alarm low
PAH is pressure alarm high
in process control they like PAHH and PALL! guess what those mean?
Just a bitmore!