Motor Operated Valve

[npopic]

Does anyone have any suggestions on how to show MOV controls on the P&ID diagram using ISA standards. For instance an MOV that is opened and closed with discrete signals from a PLC and has limit switches for position indication also connected to the PLC inputs.

 

[JLSeagull]

Show the valve. If it is only operated by operator selection, consider tagging HV. Otherwise if by shutdown logic, consider UV or XV. The open and closed position switches for feedback to the operator are often labeled ZSO for open and ZSC for closed. Actual ISA characters may require ZSH and ZSL with a table indicating which is open or closed. The ZSO/ZSC is VERY common but not really proper ISA. Do not show the actual overtorque limit switches required for the motor controls. If you have a local/remote selector and open/closed pushbuttons at the valve tag them HS with the functions identified next to the bubble.

 

[Frutosbond]

You can also tag it as MV or MOV, showing the valve, of course, and add the ZSC ZSO just below the symbol of the valve.

If it's operated by PLC or DCS or operator, depends the symbol you use "around" the tagname

(sorry for my English, I've never been good in prepositions)

Cheers

 

[Ashereng]

The "head" of the operator is often shown as "M" inside a square.

The limit switches ZSC/ZSO is acceptable under ISA. I have never seen ZSH/ZSL (high and low for a linear valve I suspect) in my industry.

If the valve is used for on/off, it usually takes a XV or UV tag name. If the valve is used for regulatory control application, then they would take the normal PV, FV, TV type of designation. I have also seen HV for operator control only valves.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[ADMIRALKEN]

ZSC/ZSO does not meet ISA standards, ZSC would by ISA standards be a position switch control. ZSH/ZSL is the ISA standard, with the H & L, being HIGH and LOW

 

[JLSeagull]

Sometimes the ISA 5.1 P&ID symbology fails to reflect standard industry practices. ISA 5.1 was issued when TDC-2000 was the standard DCS. Using ZSH and ZSL requires a table to define whether H is open and L closed etc. ZSO and ZSC are far superior. If the P&ID legend reflects this terminology then who cares what ISA reflects.

I checked API RP 14C to see if it has the ZSO and ZSC. API regards the S for safety instead of switch. A check valve is tagged FSV - flow safety valve. Regardless, "ZS" was not found in a word search of API RP 14C or other codes and standards.

 

[Ashereng]

ADMIRALKEN,

I guess we disagree. That's okay.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[controlnovice]

I'm with Ashereng: The MOV operator is shown as a square with an 'M' inside it.

At several companies where I've worked, it's been ZSO and ZSC for the position switches.

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