Questions about P&ID
Thread Content
I would like to ask everyone: In a P&ID, should pressure gauges be denoted as PG or PI? Thank you
As I understand it, PG generally refers to the on-site pressure gauge, while PI can refer to the local display of the transmitter. Looking forward to an authoritative explanation~
The oil system standards specify many abbreviations for PI; in practical applications, PG is also quite common
If PI refers to a transmitter, and no signal is sent to the DCS or PLC, it merely displays the pressure; it’s unclear why a transmitter is used in this case.
Have you never seen a PID chart like this?
PG is a local pressure gauge, while PI is a remote pressure gauge
What do you mean by that? I don’t know; I don’t understand what you mean. Try to explain it: A pressure gauge is installed on-site and displays the pressure directly; a pressure transmitter converts the pressure signal into a standard 4-20mA signal that is sent to the DCS system; pressure display refers to the showing of pressure on the DCS screen.
The designer should be clear about what needs to be displayed on-site and what needs to have its signal sent to the DCS, as determined by the process designer when designing the PID
Most design institutes use PG to denote it, but some manufacturers’ drawings or those for complete sets of equipment use PI instead.
This post was last edited by myface on 2018-11-13 at 11:23. It mainly deals with how to use the meaning of PI; it is displayed on-site as well. Therefore, in some diagrams, PI is used for measurements taken on-site, while PT is used for those taken from a distance. So the key point is: do you mean that the PI shown on the DCS screen indicates its source? If it is clear that only what is transmitted to the screen can be called PI, then there is no doubt.