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[deltaChe]

I have some question about the on-off valve (please see attachment)

N1.What is the Limit switches (in this case) used for?( Ex. permissive or trip initiators for interlock)

N2. Why does this limit switch on the on-off valve not provide any alarm in the control room?

(At least I can’t see any in the attachment drawing)

N3. Our (process engineers) are ask for deciding these pneumatic hand switch (*HS A/B in the attached drawing) remote open/close from DCS is necessary or not.

However, I understand it has to be depending on the process people’s apprehension for the process.

Anyone could kindly help me out, and give me suggestion that how to find any implication about this HS requiring or not from the process interlock description or any other document.



Thank you very much.

Attached Files

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[djack77494]

N1.What is the Limit switches (in this case) used for?( Ex. permissive or trip initiators for interlock)

Without the Logic Diagram or Interlock Description we cannot know what the limit switches do. They feed into the interlock logic in some unknown manner.

N2. Why does this limit switch on the on-off valve not provide any alarm in the control room?

Why do you ask? Do you want an alarm(s)? The limit switches DO illuminate lights telling you of the valve's status, AND they feed into the interlock logic which may or may not activate an alarm.

N3. Our (process engineers) are ask for deciding these pneumatic hand switch (*HS A/B in the attached drawing) remote open/close from DCS is necessary or not.

However, I understand it has to be depending on the process people's apprehension for the process.

Anyone could kindly help me out, and give me suggestion that how to find any implication about this HS requiring or not from the process interlock description or any other document.

The two hand switches are NOT pneumatic hand switches. They are located in the control room and send a logical signal to the Logic Block. According to the programming of the Logic Block, an electrical signal is then send to the solenoid valve which will apply or release the air pressure on the valve actuator. Without knowing the valve's function, I have no idea of the implications of this.