Industrial pumps and valves move liquids through a plant and control the flow. A pump pushes the liquid along a pipe. A valve opens, closes or narrows the pipe. Pumps and valves move the milk in a dairy, the crude oil in a refinery and the slurry of crushed rock and water in a mine.
Say a dairy plant pumps 10,000 litres of milk an hour from a storage tank to a chiller. A pump, driven by a motor, pushes the milk along a steel pipe. A valve at the chiller opens and closes, so that the milk reaches the chiller only when it is ready. If the milk is not cold enough on its way out, a second valve sends it back for chilling again.
The pump needs a different design for each liquid. A pump for milk must be easy to clean, since bacteria can grow in any corner. A pump for slurry must resist wear by the sharp particles that scrub its inside. A pump for crude oil must withstand heat and pressure.
Valves are of two kinds. An on-off valve is either fully open or fully shut, for example to send milk to one tank or another. A control valve opens by any amount, such as 30% or 70%, according to a signal from the controller. A control valve is how a plant holds a flow at its set point. A valve that does not shut fully lets the liquid leak through, so a plant tests its important valves at fixed intervals.
A pump consumes a large share of the electricity in many plants. A variable frequency drive slows it down when less flow is needed. The distributed control system opens and closes the valves to hold the flow, the pressure or the level at its set point.
Like all rotating machines, pumps wear out. Sensors for predictive maintenance measure their vibration, and asset performance management software decides when to repair them. The makers earn heavily from spare parts, as described under aftermarket services. Pumps also form a part of special-purpose machines, such as a milk processing line.