| Code | Description |
| HQ | Cooling tower (natural draft) |
| HX | Spiral heat exchanger |
| HY | Cryogenic heat exchanger |
| HZ | Miscellaneous heat transfer equipment |
| EG | Electric generators (AC or DC) |
| MW | Aero Generator |
| FS | FLOW SWITCH |
| FSH | FLOW SWITCH HIGH |
| FSHH | FLOW SWITCH HIGH HIGH |
| FSHL | FLOW RATE SWITCH HIGH LOW |
| FSL | FLOW RATE SWITCH LOW |
| FT | FLOW TRANSMITTER |
| LDT | LEVEL DIFFERENTIAL TRANSMITTER |
| LG | LEVEL GLASS GAUGE |
| LSH | LEVEL SWITCH HIGH |
| LSHH | LEVEL SWITCH HIGH HIGH |
| LSHL | LEVEL SWITCH HIGH LOW |
| LSL | LEVEL SWITCH LOW |
| LSLL | LEVEL SWITCH LOW LOW |
| LT | LEVEL TRANSMITTER |