#Large ram pressure pump fluid series

The hydrostat or hydraulic ram pump is another example of reciprocating pump still in occasional use. Small single-throw bucket pumps are also still used, often wind powered, to provide water supplies for remote farmland. Modern versions of these machines are still being installed for village water supplies in remote regions of the world.

The village pump is a single-throw bucket pump, operated manually it illustrates one of the chief advantages of the bucket pump apart from its low cost: it is always ready for use and able to function even if erratically operated. This type of pump is known as a ‘lift and force’ pump.

#Large ram pressure pump fluid series

An alternative arrangement makes the descent of the bucket force water up the rising main through a series of valves. When the bucket rises, the valve closes and water is lifted. The bucket incorporates a valve which opens as the bucket descends below water level. Instead of a piston, a ‘bucket’ is given a vertical reciprocating motion in the rising main. The bucket pump is another form of the ram pump, arranged to operate vertically for drawing water from a well or borehole. With appropriate design of the pump and its driving system, both the pump speed and its stroke are varied to maintain any desired rate of chemical injection per unit volume of water. Their property of delivering a constant volume of liquid per stroke makes them well suited to the metering duty required. Small ram pumps, usually driven by variable speed electric motors, are however still in widespread use for the injection of the chemical solutions needed for dosing in water treatment. However, since very high head centrifugal pump designs are now available, the use of new ram pumps for high head duties in water supply has almost completely ended. Efficiencies of more than 90% can be obtained, falling off with piston and cylinder wear. Driven nowadays by an electric motor, the triple-throw ram pump may sometimes be used where exceptionally high heads must be produced, since no special design is necessary other than making the working parts strong enough to sustain the pressure. Their slow speed suited the reciprocating steam engines which usually drove them. Ram pumps were common for high head duties in water supply before the widespread introduction of centrifugal pumps. The type of pump with three cylinders is termed a ‘triple-throw ram pump’, the pistons being connected to the operating crank 120° apart. With all ram pumps the output fluctuates cyclically, but if three or more cylinders are used, a reasonably constant flow is maintained. Water is drawn in by one stroke of the piston and expelled by the next. The ram pump is the most common form of reciprocating pump it consists of a piston reciprocating within a cylinder provided with water inlet and outlet valves. Most pumps used for water supply nowadays use a rotating impeller, but the reciprocating pump still has its uses. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM, in Twort's Water Supply (Seventh Edition), 2017 19.6 Reciprocating Pumps