What E means on a P&ID.
Most voltage measurements never make it onto a process P&ID. They live on the electrical single-line drawing set instead. The E tags you do find tend to be MCC bus voltages or generator outputs that the BPCS pulls in for operator indication. Treat E tags as imports from the electrical scope rather than instruments the I&C team designs.
Also stands for.
- Electrical, any electrical measurement
Common second letters.
| Tag | Meaning |
|---|---|
| ET | Transmitter, ET. Voltage transmitter |
| EI | Indicator, EI. Voltmeter |
| EAH | Alarm high, EAH. High voltage alarm |
Example tags.
| Tag | Meaning |
|---|---|
| ET-501 | Voltage transmitter, loop 501 |
| EI-505 | Voltage indicator, panel meter |
Typical placement.
On electrical systems that interface with the process control system. Motor control center signals, generator output monitoring, electrical room metering brought into the BPCS for indication. E-prefix tags are not common on process P&IDs but appear on integrated drawings that overlay process and electrical scope.
Common questions
What does the ISA 5.1 first letter E stand for?
In ISA 5.1, the first letter E stands for Voltage. It can also stand for Electrical, any electrical measurement.
How is letter E typically used on a P&ID?
On electrical systems that interface with the process control system. Motor control center signals, generator output monitoring, electrical room metering brought into the BPCS for indication. E-prefix tags are not common on process P&IDs but appear on integrated drawings that overlay process and electrical scope.
What second letters commonly follow E in ISA 5.1 tags?
Common combinations include ET (Transmitter, ET. Voltage transmitter), EI (Indicator, EI. Voltmeter), EAH (Alarm high, EAH. High voltage alarm).
What are example ISA 5.1 tags starting with E?
ET-501 (Voltage transmitter, loop 501); EI-505 (Voltage indicator, panel meter).
Run it on your drawings.
Upload a P&ID set and see every tag read in the convention the drawing already uses.