SELF PRIMING CENTRIFUGAL PUMP:
The self-priming pumps are available in stationary and portable models. These pumps are primarily used where low discharge is needed at higher heads. Due to selfpriming features, pump can handle air and gases entrained in water. These pumps are primarily designed for handling of water. The pump does not
require any foot valve. The pump has high suction lift characteristics and can suck water from much lower depth. The construction of the pump is similar to other centrifugal pumps and has enclosed impellers and can have many stages. The pump can be coupled with electric motor or engine.
Uses: The pump is used for water supply in hilly areas, small villages and multistoried buildings, sprinkler irrigation, domestic water supply and general industrial use for pumping water.
A Jet Pump is a diffuser pump that is used to lift water from both shallow and deep wells. During working, the output of the diffuser is split, and half to three-fourths of the water is sent back down the well through the pressure pipe. At the end of the pressure pipe water is accelerated through a cone-shaped nozzle. The water goes through a venturi in the suction pipe. The venturi has two parts: the venturi throat, which is the pinched section of the suction tube; and above that is the venturi itself which is the part where the tube widens and connects to the suction pipe. The venturi speeds up the water causing a pressure drop which sucks in more water through the intake at the very base of the unit. The water goes up the suction pipe and through the impeller, most of it for recirculation around to the venturi.
Uses: The jet pump is used for lifting .of water from shallow and deep wells for irrigation and domestic applications.
It is one of the most common types of centrifugal pumps employed for irrigation. It consists of impeller or rotor and progressively widening spiral or volute casing. The pump is directly connected to the prime mover, which may be electric motor or engine. The direct coupling feature reduces transmission .losses. Upon rotation of the impeller, the water enters at the eye, which is thrown radially outward to the periphery. Such an action causes vacuum at the eye and thus more water enters the suction pipe to maintain the continuous flow. The impeller accelerates the water to a high velocity and the casing converts this velocity head into pressure head due to volute design. Volute pumps usually employ closed type of impeller for irrigation, which has curved vanes for smooth flow of liquid. There are other kinds of impellers like open, semi open and non-clogging impeller, but these are used for purposes other than irrigation.
Uses: Monoblock pumps are used for agricultural purposes. These are also suitable for domestic and industrial applications of pumping water.
Reciprocating pumps are normally used for drinking water supply in addition to irrigation. The main parts of the reciprocating pumps are the pump cylinder in which an airtight piston or plunger moves up and down with the help of pump rod, handle for operation of pump, valves, pipe and strainer. As the plunger rises, water is drawn through a non-return valve at the bottom of cylinder into the cylinder, and on the downward stroke the water is released to the upper side of plunger. On the next upward movement of plunger water is raised to pump head and discharged through the spout. By changing either the frequency of reciprocation or stroke length of the piston the discharge rate can be varied. The reciprocating pumps are available in various designs and models, which can be operated manually, with animal power and auxiliary power sources.
Uses: Reciprocating pumps are used to lift water from underground sources; therefore, if the water level is deep, the pump cylinder has to be lowered close to water surface to reduce the suction head. The number of cylinders can be increased according to power sources.
Submersible pumps are also turbine pumps where long vertical shaft connecting the motor and pump unit is replaced by a short shaft and the prime mover and pump become closely coupled and submerged in water. Submersible pumps are suitable for tube wells having a bore of 100 mm or more. Impeller of the pump may be closed, semi open or open. For irrigation usually closed types of impeller with bowl and
stabilizing vanes are used. Several impellers may be used in series, which depends on head and discharge. The discharge from one impeller is guided to the inlet of the second and so on and finally to the outlet. The complete assembly of the pumping unit is suspended from the discharge column. Submersible pumps consume less power for the same output and also require less space.
Uses: Ideal for lifting of water from tube wells for irrigation, domestic and industrial applications.
These pumps are used in tube wells or in open wells where the water level is below the practical limit of centrifugal pump. The vertical turbine pump consists of a driving motor with discharge connection and the bottom suction centrifugal pump to which one or more impellers are attached. The impeller(s) are of either the volute or mixed flow type. The PUn’lp unit remains submerged in water where as the prime mover (motor or engine) is kept above the ground level. The pump unit is connected to the motor with the help of long vertical shaft supported on bearings, which may be water or oil lubricated. Although the turbine pump also operates on centrifugal principle, it differs from volute type as stationary guide vanes guide upward the water thrown by the impeller to the periphery. The gradual enlarging vanes guide the water to the casing, thus converting kinetic energy into potential energy. Therefore, the turbine pump generates heads several times that of a volute pump. Turbine pumps are most effective for tube wells, and applications requiring high heads and discharge. A well-maintained pump provides trouble free service for several years.
Uses: It is used for lifting of water from tube wells, open wells for irrigation, domestic and industrial applications.