I’m not quite sure about some of the symbols in the process flow diagram
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Part of the process flow diagram for the gas transmission station. What do the XV in XV34104 and XV34106, and the FV in FV34105 refer to? What do XA, XSLL, XSH, ZAH, and ZAL correspond to in relation to FV34105? I know there should be high and low alarms, but what kind of alarms can a valve have? It’s not temperature or pressure. Thank you.
There should be such tables indicated in the general plan.
xv is the on/off valve, xsov is its solenoid valve with interlock, fv is the flow control valve, xa is the comprehensive fault alarm, and xsll is the interlock low-low ZAL level low alarm.
See Floor 3; additionally, the valve is equipped with a position alarm, for example, an alarm is triggered when the valve opening is at 100%, indicated as ZAH
What does chain low low mean? What kind of faults can cause cascading low-low conditions?
Is zal the valve opening at 0?
It depends on the point list provided by the design institute
When to use chaining also depends on the design documents
It should be indicated on the drawing: xv is the switch valve, xsov is its solenoid valve with interlock, fv is the flow control valve, xa is the comprehensive fault alarm, and xsll is the interlock low-low ZAL level low alarm.
Agree; it’s best to ask whether the process allows for full opening or full closing
Shouldn’t one look at the title page of the drawing in question to find out what the symbols on it mean?