WHat does this P&ID symbol mean?

[BasakAbhishek]

Hello,

Please refer to the attached extract from an old P&ID diagram. I am unable to understand what does the symbol with "L" marked in it (at the top of PIC 517) mean?

Thanks!
Abhishek

 

[jari001]

Do you think you can find another set of drawings around the same age that has the legend sheet? If you can describe what that pressure control loop is meant to do and what type of process this is, maybe someone that has worked with something similar can give their thoughts.

My guess is that the PIC has an interlock at some defined low pressure, so therefore an "L" is shown. But again, complete guess.

 

[chicopee]

you should show more than the symbols. Show a good portion of the drawing with the title block and notations, the we may have a better idea to the meaning of the symbols.

 

[hacksaw]

That is local a pneumatic controller and valve, with an instrument air suppliy for the controller to directly modulate the valve.

Common symbols in the older plants.

 

[pennpiper]

The "L" is for "LOW" and is related to the "PCV" (Low Pressure Control Valve) and the "PIC" (Low Pressure Indicating Controller).

Sometimes its possible to do all the right things and still get bad results

 

[BasakAbhishek]

So does it mean that it is a symbol for "LOW" alarm/trip?

 

[MortenA]

@OP i think the conclusion is that it can mean a lot of things and that you will need to look at a legend or some other P&ID where its also used (and not used).

My best guess would be as hacksaw, self actuating valve but i would guess that the L symbol could mean that the SP is adjustable - maybe remotely adjustable? Maybe its a hacksaw says that its a plant air supply, if you have a high presure and a low pressure plant air system then the L would support this (meaning air from the low pressure system).

 

[BasakAbhishek]

Thanks for all the responses. I am attaching a few more examples from the other drawings of the same plant. Hope it makes things a bit clearer.

 

[LittleInch]

I always though it just indicates a supply of instrument air.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BasakAbhishek]

I finally got it!!. After a lot of digging through old documentation of the plant I finally got it: It means "leads to data logger"..thanks for all the help!

 

[pennpiper]

BasakAbhishek,
I am happy that you found the actual definition for the actual symbol for that specific Project.
I assume you found the actual P&ID Legend Sheet for that specific Project.
Having that symbol and using it for that specific purpose does not mean that some other Project, by a different Process Engineer, might use that symbol and the letter "L" for some other purpose.

Make sure that all your projects have a "P&ID Legend Sheet" with all Symbols identified.


Sometimes its possible to do all the right things and still get bad results

 

[MortenA]

So its a very good example that a symbol can have many meanings and that they will all make sense even though they can be very different!