Could you help me understand what these instruments indicate?
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Recently, I came across a PID control system for a cooling tower. The instruments related to the motor of the cooling tower were a bit confusing to me; see the screenshot below. I saw that in the legend, terms starting with V indicate vibration, but when a letter S is added to them, it refers to a switch. There is also an explanation regarding the Note 4: “4. TWO-SPEED MOTORS WITH HIGH & LOW SPEED SWITCHES. LOCAL STOP SWITCH SHALL BE LOCKING TYPE.” How exactly should we understand the local and interlocked functions of VS, VAH, and HS?
vs, vah – it can roughly be understood as a speed chain reaction, an alarm for high speed.
Learn about HG/T 20505-2014 \"Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\"
For a single motor, the HS-61104 is the motor local stop switch (with lockable position). HS-61014/61004 are soft switches on the control system that regulate the two speeds of the motor. VS-61002 is an instrument for measuring motor vibration. VAH-61002 is an alarm for high motor vibration in the control system (PLC or DCS).
I think the same way; it’s drawn that way in the project’s PID as well. Sometimes it’s necessary to take into account the company’s conventions and standards as well.