H - Hand
Reference for the ISA 5.1 first letter H. HV and HS look similar at first glance but they belong to different document types. HV is a mechanical hand-operated valve. No wires, no PLC channel, lives on the instrument index but never on the I/O list. HS is a wired pushbutton or selector that consumes a DI channel. Mixing them up at bid time is the entry-level mistake that makes the cabinet count come in 5 percent low.
Read one of your own drawings.
Drop a P&ID, instrument index, or schedule. Tagsight reads it to the tag and opens a workspace you keep when you sign in.
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Also stands for.
- Manual operator action
Common second letters.
Switch, HS. Hand switch, manual operator pushbutton or selector
Valve, HV. Hand-operated valve, often the manual block valve in a control loop
Indicating controller, HIC. Manual loader, hand station where the operator sets the controller output directly
Example tags.
Hand switch on loop 101, operator pushbutton or two-position selector
Hand-operated valve, often a manual block valve
Hand indicating controller, manual loader where the operator drives the output by hand
Typical placement.
On HMI-side controls, operator pushbutton panels and on field-side manual valves. HV tags are mechanical-only and do not consume PLC channels. HS tags are typically DI inputs to the BPCS.