Resi - Road
- Residual Current Device
- Resistance electric heaters
- Resistance Temperature Device
- Resistive temperature transducers or thermocouples
- Retroreflective warning sign
- Reverse Osmosis
- Reverse-complexing triode thyristor (RBTT) with a zero crossover starting circuit
- Revision
- RGI train
- rich / lean amine exchanger
- rich / semi-lean amine exchanger
- rich amine flash drum
