ABSTRACT

Turning now to the delivery branch, it is customary in the case of centrifugal pumps to control the flow by means of a sluice or gate type valve situated in close proximity to the pump. Normally the pump is started with this valve closed and then when the unit is running at normal speed it is opened the required amount, preferably to the full extent if energy is not to be wastefully expended. When the pumping main is of considerable length, a reflux valve is usually fitted on the pump side of the delivery valve. This is a flap type valve, arranged so as to open in the direction o f flow only. On the cessation of pumping, and immediately the water column reverses in direction, the reflux valve closes, thus protecting the pump and suction piping from any harmful pressure rise.