Reciprocating pump cylinder

Reciprocating pumps operate by the direct action of a piston on the liquid contained in a cylinder. As the liquid is compressed by the piston, the higher pressure forces it through discharge valves to the pump outlet. As the piston retracts, the ne. t batch of low pressure liquid is drawn into the cylinder and the cycle is repeated. 

Reciprocating pumps are positive displacement piston units driven by a direct connected steam cylinder or by an external power source connected to the crankshaft of the pump piston. Being positive displacement, these pumps can develop very high pressures (10,000 psi and higher) for very low or high capacities (up to 1000 GPM). 

Engine drivers are well adapted for reciprocating compressor cylinders, direct connection to power generators, direct or through gear connection to fans, centrifugal compressors, pumps, etc. ... 

Since discrete quantities are trapped and transferred, the delivery pressure and flow varies, as shown in Figure 32.21, which also illustrates how increasing the number of cylinders in a reciprocating pump reduces fluctuations. In the case of lobe and gear pumps the fluctuations are minimized by speed of rotation and increasing tooth number, but where, for control or process reasons, the ripple in pressure is still excessive, means of damping pulsations has to be fitted. Often a damper to cope with this and pressure pulses due to valve closure is fitted, and two types are shown in Figure 32.22. 

Figure 32.21 Reciprocating pump variation of flow rate with numbers of cylinders...

A single-acting reciprocating pump has a cylinder diameter of 110 mm and a stroke of 230 mm. The suction line is fi m long and 50 mm in diameter and the level of the water in the suction tank is 3 m below the cylinder... 

A single-acting reciprocating pump has a cylinder diameter of 115 mm and a stroke of 230 mm. The suction line is 6 m long and 50 mm in diameter, and the level of the water in the suction tank is 3 m below the cylinder of the pump. What is the maximum speed at which the pump can run without an air vessel if separation is not to occur in the suction line The piston undergoes approximately simple harmonic motion. Atmospheric pressure is equivalent to a head of 10.4 m of water and separation occurs at a pressure corresponding to a head of 1,22 in of water. 

During deep pumping extraction of petroleum, emulsion formation occurs in the valves, in the pump cylinders and in the elevating pipes during the reciprocating movement of pump bars. 

In the first major class of pumps a definite volume of liquid is trapped in a chamber, which is alternately filled from the inlet and emptied at a higher pressure through the discharge. There are two subclasses of positive-displacement pumps. In reciprocating pumps the chamber is a stationary cylinder that contains a piston or plunger in rotary pumps the chamber moves from inlet to discharge and back to the inlet. 

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