R ECIPROCATING P UMPS Prof. Shrikant M. Harle Dept of Civil Engg PRMCEAM, Badnera

PRINCIPLE OF SINGLE ACTING PUMP

PRINCIPLE OF DOUBLE ACTING PUMP

R ECIPROCATING P OSITIVE D ISPLACEMENT P UMPS Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms), and restrict motion of the fluid to the one desired direction by valves. These positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.

T YPICAL RECIPROCATING PUMPS Plunger pumps - a reciprocating plunger pushes the fluid through one or two open valves, closed by suction on the way back. Diaphragm pumps - similar to plunger pumps, where the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids. Piston displacement pumps - usually simple devices for pumping small amounts of liquid or gel manually. An example is the common hand soap pump. Radial piston pump

'Reciprocating' and 'Rotary pumps' are called positive displacement pumps. Because the medium pumped together with any air which may have entered into the suction pipe gets positively displaced from the suction side to the delivery side at every revolution.

R ECIPROCATING PUMP

C OMPONENTS OF RECIPROCATING PUMPS :- Piston or plunger : – a piston or plunger that reciprocates in a closely fitted cylinder. Crank and Connecting rod : – crank and connecting rod mechanism operated by a power source. Power source gives rotary motion to crank. With the help of connecting rod we translate reciprocating motion to piston in the cylinder. Suction pipe : – one end of suction pipe remains dip in the liquid and other end attached to the inlet of the cylinder.

Delivery pipe: – one end of delivery pipe attached with delivery part and other end at discharge point. Suction and Delivery value : – suction and delivery values are provided at the suction end and delivery end respectively. These values are non-return values.

WORKING OF RECIPROCATING PUMP Operation of reciprocating motion is done by the power source (i.e. electric motor or i.c engine, etc). Power source gives rotary motion to crank; with the help of connecting rod we translate reciprocating motion to piston in the cylinder (i.e. intermediate link between connecting rod and piston). When crank moves from inner dead centre to outer dead centre vacuum will create in the cylinder. When piston moves outer dead centre to inner dead centre and piston force the water at outlet or delivery value.

S UBMERSIBLE P UMP Submersible Pump is a turbine pump coupled to a submersible electric motor. Turbine pumps consist of impellers placed below the water level and are driven by a vertical shaft rotated by an engine or motor placed at the ground level or under the water. A cable passing through the water supplies power to the motor. Both the pump and the motor are suspended and operate under the water, pumping water through the discharge column.

The pump eliminates the long shaft and bearings that are necessary for a vertical turbine pump. Submersible pumps are cheaper than the vertical turbine pumps. Suitable for deep settings and also for crooked wells which are not perfectly vertical. The installation of the pup is easy and the initial cost of installation low. The repair of the submersible pumps, when they go out of order is not easy and require technical skill.

Submersible pump requires little maintenance, after 6000 hours of operation or two years of service life, it may be necessary to with draw the pump from the bore hole and overhaul it. Selection of the submersible pump is mainly depending upon the bore well size, type, well discharge etc.

J ET P UMPS Consist of a combination of a centrifugal pump and a jet mechanism or ejector. Jet pump is used when the suction lift of the centrifugal pump exceeds the permissible limits. A portion of the water from the centrifugal pump is passed through the drop pipe to the nozzle of the jet assembly. This water is forced through the throat opening of the diffuser, creating a vacuum which causes water to be drawn from the well

The water mixed with the boost water is carried up through the diffuser where the high velocity energy is converted into useful pressure energy, forcing the water up through the delivery pipe to the centrifugal pump.

Jet Pumps are mounted above ground and lift the water out of the ground through a suction pipe. Jets are popular in areas with high water tables and warmer climates. There are two categories of jet pumps and pump selection varies depending on water level.pump selection Shallow well installations go down to a water depth of about 25 feet (7.62 m). Deep wells are down 150 feet (45.72 m) to water, where surface pumps are involved.

The jet pump is a centrifugal pump with one or more impeller and diffuser with the addition of a jet ejector. centrifugal pump A JET EJECTOR consists of a matched nozzle and venturi. The nozzle receives water at high pressure. As the water passes through the jet, water speed (velocity) is greatly increased, but the pressure drops. This action is the same as the squirting action you get with a garden hose as when you start to close the nozzle.

The greatly increased water speed plus the low pressure around the nozzle tip, is what causes suction to develop around the jet nozzle. water speed Water around a jet nozzle is drawn into the water stream and carried along with it. For a jet nozzle to be effective it must be combined with a venturi. The venturi changes the high-speed jet stream back to a high-pressure for delivery to the centrifugal pump. The jet and venturi are simple in appearance but they have to be well engineered and carefully matched to be efficient for various pumping conditions. The jet nozzle and venturi are also known as ejectors/ejector kits.

H OW A JET PROVIDES PUMPING ACTION ? Water is supplied to the Jet ejector under pressure. Water surrounding the jet stream is lifted and carried up the pipe as a result of the jet action. When a jet is used with a centrifugal pump a portion of the water delivered by the pump is returned to the jet ejector to operate it. The jet lifts water from the well to a level where the centrifugal pump can finish lifting It by suction.

H OW DOES HYDRAULIC RAM WORK The working principle of hydraulic ram is to use surge pressure which is produced after flow blocked and ten times higher than normal to lift water. hydraulic ram is composed by drive pipe, pump body, waste valve, delivery valve, pressure valve and air chamber Before working, waste valve stays open under the action of magnet spring while delivery valve keep closed under the action of magnet spring and its gravity.

It can work automatically when we control the waste valve to repeat the operation procedures of open and close. After that, water with different levels will flow out through water drive pipe and opened waste valve, and running water will drive the waste valve to close when the pressure inside the waste valve surpass that in magnet spring, and that is the water hammer. At the moment, water pressure rapidly increases and enforces the delivery valve to open, and some water flows into air chamber.

Pressure inside the waste valve drops promptly and the waste valve reopens under the action of magnet spring and negative pressure. While delivery valve closes again by the action of self gravity and the pressure in magnet spring and air chamber. By the action of water flow, movements foregoing repeat automatically. And water will flow out through the delivery pipe when the pressure in air chamber exceeds that in lifting pipes.