Regarding the identifiers in PID
Thread Content
In PID diagrams, what do LO, LC, NO, and NC mean?
These require looking at the design’s homepage image (legend explanation); there may be slight differences between each item. LO — LOCKED OPEN: Locked in the open state. LC — LOCKED CLOSED: Locked in the closed state. NO — NORMALLY OPEN: Normally in the open state. NC — NORMALLY CLOSED: Normally in the closed state. Last edited by lsswyb01 on 2009-4-6 18:52.]
After a while, I can’t remember clearly; it seems that NO stands for Normal Open, NC stands for Normal Close, LO stands for open-loop control system, and LC stands for closed-loop control system. I can’t see your PID legend, so I’m not sure; after all, this is just an abbreviation.
I was still wondering today what LO and LC mean; I’ve learned it now, thank you
Secondly, OP, you mentioned that LO means locked on; some friends on Haichuan say it means always on. Is it the same as what you mean by locked on? What exactly does locked on mean? Please advise, friend from the second floor.
LO stands for locked open; it is in the open position during normal operation. Unless the device is shut down for maintenance and manually closed, it generally will not be automatically locked shut； LC locked off – same function. NO means normally open; it is also known as an emergency shut-off valve, equipped with interlocking that activates shutdown in the event of an accident ； NC normally closed valve, operates in the same way.
Locked open and normally open have similarities, such as remaining in the open state under normal conditions; however, locked open requires more stringent standards. For example, valves used at the inlet of safety valves need to be of the locked open type, and they are usually equipped with locks or seals.