What do the gauge symbols in the diagram mean?
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What do HZSC and HZSO mean inside the ellipse in the diagram, HZSH and HZSL inside the rectangle, and C and O outside the rectangle?
HZSC limit switch: off position; HZSO limit switch: on position. HZSH indicates the on status in DCS, while HZSL indicates the off status in DCS. C and O outside the rectangle represent off and on, respectively.
C should be an abbreviation for CLOSE, and O should be an abbreviation for OPEN
The reply on the second floor was very good. However, according to \"HG/T 20505-2014 Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\", Z is the second character in the functional alphabet and indicates a SIS instrument. It is best for limit switches to be labeled ZSO/ZSC.
In the figure, the letter Z is not in the second position; it is a modifier of the first letter. HZ together constitute the variable being measured or induced.
So what do the letters HZSH and HZSL mean?
In HZSL, H refers to the manual control valve, while ZSL denotes the signal indicating that the valve is fully closed； In contrast, ZSH represents the signal that the valve is fully open. HIC: Manual control module (often referred to as a controller at the panel). FT: Flow measurement transmitter. FIA: Flow display alarm, usually including a low-level or high-level alarm. FC: Valve fully closed in an emergency situation