Introduction
A reciprocating pump is a positive displacement pump.
The positive displacement pump the liquid is transferred positively by to and from motion of a member known as piston (or) plunger of the pump.
Classification of reciprocating pump.
1) According to the number of cylindrical provided.
Single cylinder pump.
Double cylinder pump.
Triple cylinder pump.
Duplex double acting pump.
2) According to the water being in contact
Single acting pump
Double acting pump
Single acting Reciprocating pump
When the liquid pressure is acting on only one face of the piston then the pump is known as a single acting reciprocating pump. The pump has one suction pipe and delivery pipe on only one side of the cylinder .
Construction
A reciprocating pump consists of the following parts.
- Cylinder
- Piston (or) plunger
- Crank
- Crank shaft
- Connecting rod
- Suction & delivery pipe with non-return valves.
The piston reciprocates inside the cylinder. The reciprocating motion of the piston is obtained by connecting the piston rod to a crank by means of a connecting rod. An Electric motor rotates the crank. One end of the suction pipe is immersed into the sump and another end is fitted to the bottom of the cylinder with a suction valve. The delivery pipe is connected to the top of the cylinder with a delivery valve. Both suction and delivery valves are one way valves.
Working principle
Suction stroke
During this stroke, the crank rotates from A to B in clockwise direction. The piston is moved from left to right by means of connecting rod. This creates a vacuum inside the cylinder. Due to the low pressure, the suction valve opens and the liquid from the sump enters into the cylinder through suction pipe and suction valve. Delivery valve remains closed during suction stroke.
Delivery stroke
During this stroke, the crank rotates from B to A in clockwise direction.
This piston is moved from right to left. Due to the high pressure, the delivery valve opens and the liquid is delivered to the required height through the delivery valve and delivery pipe.Suction valve remains closed during delivery stroke. The same cycle is repeated as the crank rotates.
Double acting Reciprocating Pump
This pump is said to be double acting, when the liquid pressure acts on both sides, of the piston (or) plunger. Two suction and delivery pipes with non-return valves are provided on each end of the cylinder as shown in fig. Since both the end of cylinder is closed, the piston is connected to a crank through a cross-head. When the crank starts rotating, the piston or plunger reciprocates inside the cylinder. When the plunger or piston moves from left to right, the following two activities are taking place .
- The partial vacuum is created inside the cylinder on the left side of the piston or plunger.
- Therefore, the atmosphere pressure acting on the liquid surface forces the liquid into the cylinder through suction pipe, by opening the suction valve ‘b’ .
The liquid already available on the right side of the piston or plunger is compressed which increases the pressure of liquid. Due to the increment of pressure, the suction valve ‘d’ closes and delivery valve ‘c’ opens. Then, the liquid is delivered to the delivery pipe through the valve ‘c’. Therefore, when the piston moves from left to right, suction is taking place on the left side of the piston, while in right side, the delivery is taking place. Similarly, when the piston moves from right to left, the actual cycle is repeated and the liquid is delivered to the delivery pipe through ‘a’.
Thus in a double acting reciprocating pump, when there is suction on left side, there will be delivery on the right side. Hence the discharge of a double acting pump is double times the single acting pump
Plunger pump
It is similar to piston pump except that the plunger is used instead of piston. A plunger is a hollow cylinder and contains no rings. All the other elements are similar to piston pump. Since the length of the plunger is greater than its diameter, they produce high pressure and generally used for rough work.
Author Bio: The author of this article is writting articles for Mech Notes
