Motor control diagram in P&ID legend

[knapee]

Dear Sir/Madam

Our client ask us to included the motor control diagram for the pump and compressor on our P&ID legend sheet.
This motor control diagram example sheet (attached in the post) show several panel-mounted ISA devices (circle with line through the balloons)
for their function.
(1) HOA(hand-off-auto) or on-off switch associated with the starter, shown as a HS(HS for a HOA switch,a HS for the remote Start/Stop signal),
(2) running status included run/stop/trip/ready also be shown on DCS system.
(3) Emergency stop from DCS commend also be operated in any mode of HOA.
(4) start/stop command in remote mode is a momentary signal line an type should be hard wire.
(5) for greater than 80kw (compressor and pump monitoring), the vibration sensor will be installed.

Also, In diagram shows that
case (1) motor power rating>80kw,
case (2) 380 kw>motor power rating > 80kw,
case(3) 800 > motor power rating > 380kw.

My question is
(1) There is no interlock in this diagram now, and it seems it should be some interlock from (DCS or ESD) should be including in.
Is the interlock simply be a hard wire line from DCS to motor?
(2) How do we determine the interlock should be included a permissive signal or stop signal both?

Thank you very much.

Regards

 

[controlsdude]

Estop Compressor?
Some questions to ask yourself?
Is it required to dump the air and not just stop the pump? If you dump the air thru an air dump will you cause some valve to go to a non fail safe condition?
Since this is petro maybe there are needs to have air pressure still pressurized? Not that familar with the petro industry. Maybe you need to ask more questions of the PID process engineer?

Estop is mostly driven by a safety commmitee at plants. So its best to have a meeting with these guys to drive what they want for estop functionality.

Remote start from DCS
Provide contacts to your auto start condition circuit.

 

[Nadalizadeh]

Dear Knapee
The interlock usually implemented using feedback signals with PLC programming.The interlocks are determined in process discriptions and P&ID s.

 

[lacajun]

I've never done a true E-stop from a DCS. Those were always a physical switch mounted on the housing with the DCS monitors or a panel board located nearby and hardwired to the motor control. The operator will have to actuate that switch to stop the motor. Some switches were pull to actuate and some were push to actuate. This was true in chemicals and refining.

Your process engineers or operations people will be able to tell you whether to wire that into your ESD or not. It depends on the process and what happens, if it does not shut down. Hopefully they've done SIL reviews on their processes.

Depending on where the project is your electrical engineer may have this information already, since he will need it for his elementary diagrams.


Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[eeprom]

It is a code violation to "wire" any emergency devices through software. I don't recall if this is a UL508A code or a NEC code. I think it's UL508A. In either case, I think it is too much a risk to put an estop in software.