What R means on a P&ID.
When conventional level measurement gives up, violently agitated slurry, heavy fouling, extreme service radiometric level, RT, RE earns its keep. The radioactive source emits a calibrated beam through the vessel. A detector across the wall reads attenuation. Mining ore composition gauges use the same physics. R tags carry no inherent SIS meaning. The SIL allocation comes from the SRS, not the prefix.
Also stands for.
- Resistance, rare
Common second letters.
| Tag | Meaning |
|---|---|
| RT | Transmitter, RT. Radiation transmitter |
| RE | Sensor, primary element, RE. Radiation detector, the receiving side of a radiometric pair |
| RAH | Alarm high, RAH. High radiation alarm |
| RSH | Switch high, RSH |
Example tags.
| Tag | Meaning |
|---|---|
| RT-901 | Radiation transmitter, often on a level measurement using radiometric source-detector pair |
| RE-901 | Radiation detector, the element reading attenuation across the vessel |
| RAH-905 | Radiation alarm high |
Typical placement.
On radiometric level transmitters, where conventional level measurement is impossible due to coating, agitation, or extreme service, on personnel safety monitors near radioactive sources, on nuclear gauging in mineral processing.
Common questions
What does the ISA 5.1 first letter R stand for?
In ISA 5.1, the first letter R stands for Radiation. It can also stand for Resistance, rare.
How is letter R typically used on a P&ID?
On radiometric level transmitters, where conventional level measurement is impossible due to coating, agitation, or extreme service, on personnel safety monitors near radioactive sources, on nuclear gauging in mineral processing.
What second letters commonly follow R in ISA 5.1 tags?
Common combinations include RT (Transmitter, RT. Radiation transmitter), RE (Sensor, primary element, RE. Radiation detector, the receiving side of a radiometric pair), RAH (Alarm high, RAH. High radiation alarm), RSH (Switch high, RSH).
What are example ISA 5.1 tags starting with R?
RT-901 (Radiation transmitter, often on a level measurement using radiometric source-detector pair); RE-901 (Radiation detector, the element reading attenuation across the vessel); RAH-905 (Radiation alarm high).
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