working ppt of a Reciprocating Pump.pptx
- 2. Classification of reciprocating pump (1) According to the water being in contact with one side or both sides of the piston: (a)Single acting pump (b)Double acting pump (2) According to number of cylinder: (a) Single cylinder pump (b) Double cylinder pump (c)Triple cylinder pump.
- 3. Reciprocating pump The reciprocating pump is a positive displacement pump and consists of a cylinder, a piston a suction valve, a delivery valve, a suction pipe, a delivery pipe and crank and connecting rod mechanism operated by a power source e.g. steam engine, I.C. Engine or an electric motor. Positive Displacement Pumps, unlike a centrifugal pumps, will produce the same flow at a given speed (RPM) no matter the discharge pressure. A Positive Displacement Pump must not be operated against a closed valve on the discharge side of the pump because it will continue to produce flow until the pressure in the discharge line are increased until the line bursts or the pump is severely damaged
- 4. Working principle In reciprocating pumps the mechanical action causes the fluid to move using one or more oscillating pistons, plungers etc. During the suction stroke the piston moves left thus creating vacuum in the Cylinder. This vacuum causes the suction valve to open and water enters the Cylinder. During the delivery stroke the piston moves towards right. This increasing pressure in the cylinder causes the suction valve to close and delivery to open and water is forced in the delivery pipe.
- 5. Air vessel Air vessel is a closed chamber containing compressed air at the top and liquid at the bottom. Uses: 1. It provides uniform discharge from pump. 2. The chances of cavitation or separation are considerably reduced. 3. A considerable amount of work is saved as frictional resistance. 4. The pump can run at higher speed and provides higher discharge.
- 6. Use of air vessel
- 7. Discharge through a pump per second is given as Where A= the cross sectional area of the piston in L= the stroke of the piston in m N= the speed of crank in rpm 3 3 for single acting pump 60 2 Q= for double acting pump 60 ALN m Q s ALN m s 2 m
- 8. Work done by reciprocating pump per second is given as for a single-acting pump for a double-acting pump Power required driving the pump for a single-acting pump for a double-acting pump (Where ρg = weight density of liquid in N/m3) ( ) 60 s d gALN h h 2 ( ) 60 s d gALN h h ( ) 60 1000 s d gALN h h kW 2 ( ) 60 1000 s d gALN h h kW
- 9. Slip & Co-efficient of discharge Slip = Volume swept/stroke – actual discharged/stroke The value of slip is generally positive. However in practice sometimes delivery valve opens before suction stroke is completed, thus delivering a greater volume of water than actually swept by the piston. Hence the slip will be negative in such a case. Co-efficient of discharge actual discharge/stroke volume swept/stroke act d th Q C Q Percentage slip= th act th Q Q Q
- 10. Pressure head due to acceleration (ha) in the suction and delivery pipes is given as Where 2 cos for suction pipe s as s l A h r g a 2 cos for discharge pipe d ad d l A h r g a length of suction/discharge pipe a= cross section area of suction/discharge pipe l
- 11. Work done by the pump per second due to acceleration and friction in suction and delivery pipes 2 2 for single-acting 60 3 3 s d fs fd gALN h h h h 2 2 2 for double-acting 60 3 3 s d fs fd gALN h h h h
- 13. Indicator diagram with acceleration and friction head effect
- 14. Operating characteristic curve Head Discharge Input power Efficiency Discharge(ideal) Speed N=constant