Jargon Buster - R

The span of differential pressures or flow rates within which the sensing element of a given switch can be set to actuate an electrical switch.
Raw water
This is the input to the water treatment plant and program which then serves the steam system. Raw water is normally supplied from a well or borehole, or from a towns water supply connection. The raw water is then treated using a water treatment plant and program.
A type of pipe fitting used to reduce down the pipe size. The can be concentric or eccentric.
Relative humidity
The ratio of the quantity of water vapour in the air to the quantity of water vapour required for saturation at the same temperature.
Relief valve
A relief valve automatically discharges liquid as to prevent a predetermined safe pressure being exceeded. The term is commonly used for pressure relieving valves in which the lift is proportional to the increase in pressure above a set pressure.
Repetitive accuracy
The ability of a pressure or flow switch to operate repetitively at its set point under consistent conditions.
Reverse osmosis
A process which is used to treat ‘raw’ water. It is more commonly used to treat feedwater which is used in a steam boiler, where local water is ‘hard’. The raw water is forced through a semi-permeable membrane. This results in high quality boiler feedwater coming out of the reverse osmosis plant, while the impurities are rejected to waste.
Rotating cylinder
A steam heated cylinder used to heat paper or fabric.