What H means on a P&ID.
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.
Also stands for.
- Manual operator action
Common second letters.
| Tag | Meaning |
|---|---|
| HS | Switch, HS. Hand switch, manual operator pushbutton or selector |
| HV | Valve, HV. Hand-operated valve, often the manual block valve in a control loop |
| HIC | Indicating controller, HIC. Manual loader, hand station where the operator sets the controller output directly |
Example tags.
| Tag | Meaning |
|---|---|
| HS-101 | Hand switch on loop 101, operator pushbutton or two-position selector |
| HV-205 | Hand-operated valve, often a manual block valve |
| HIC-330 | 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.
Common questions
What does the ISA 5.1 first letter H stand for?
In ISA 5.1, the first letter H stands for Hand. It can also stand for Manual operator action.
How is letter H typically used on a P&ID?
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.
What second letters commonly follow H in ISA 5.1 tags?
Common combinations include HS (Switch, HS. Hand switch, manual operator pushbutton or selector), HV (Valve, HV. Hand-operated valve, often the manual block valve in a control loop), HIC (Indicating controller, HIC. Manual loader, hand station where the operator sets the controller output directly).
What are example ISA 5.1 tags starting with H?
HS-101 (Hand switch on loop 101, operator pushbutton or two-position selector); HV-205 (Hand-operated valve, often a manual block valve); HIC-330 (Hand indicating controller, manual loader where the operator drives the output by hand).
Run it on your drawings.
Upload a P&ID set and see every tag read in the convention the drawing already uses.