What Is Reciprocating Pump?
Reciprocating pumps are used where the distribution pressure of the fluid is quite large. In this article, we will discuss single-acting reciprocating pumps. As the name itself indicates, it has a single-piston as well as a single component of the suction valve, delivery valve, suction pipe, and delivery pipe.
A pump is a mechanical device or hydraulic machine that converts mechanical energy into hydraulic energy. The pump gives pressure energy to the fluid at its outlet. A revolving pump is a special type of pump in which the reciprocating motion of a piston is used to pump water into the required area.
Reciprocating pumps are mainly used where the distribution pressure of the fluid is very large. 200 BC The reciprocating pump was invented by the Greek inventor Ctesibius. Reciprocating pumps fall under the category of positive displacement machines.
A revolving pump is favorable where a small discharge and a high head are required. In revolving pumps, reciprocating motion is used to increase the pressure energy of the fluid. Hence it was renamed as Pump. A swirling pump is a special purpose pump. This pump is not commonly used as a centrifugal pump. It is used only in special cases, such as in-car washing centers where too much water pressure is required to wash cars.
By using a reciprocating pump, we can achieve very high liquid pressure in about 10 – 20 bars at the outlet, while in centrifugal pumps, we can only get 2 – 5 bar pressure. Reciprocating pumps are mainly used where you need a precise flow rate. In this pump, the flow rate is controlled by controlling the piston speed. For low flow rates, the piston will move slowly, and for high flow rates, the piston will move at high speed.
Using a revolving pump, we can obtain very accurate flow rates with an inaccuracy of plus-minus one (+ -1). Suppose we need a flow rate of 40 liters/min, then using reciprocating pumps, we can have very accurate flow rates that can vary from 39 liters/min to 41 liters/min. Since it can give an accurate flow rate, it is known as a dosing pump.
Parts of Reciprocating Pump:
A reciprocating pump consists of several parts & those are:
This cylinder consists of a piston. The cylinders stores water before delivery to the required area. It is also used to create a vacuum for the suction of fluid.
The piston is present inside the cylinder. This piston moves back and forth. These pistons are used to create a vacuum & exert thrust on the fluid.
#3. Piston Rod
A rod is attached to a piston and is known as a piston rod. This piston rod is further connected to the connecting rod.
#4. Connecting Rod
The connection rod is connected to the piston rod at one end and the crank at the other end.
The rotational motion of the crank provides reciprocating motion to the piston.
#6. Suction Valve
When the piston is repeatedly forward and backward, the suction valve in the front part of the piston is locked together and off with the piston. The suction valves are fitted in the suction pipes.
#7. Suction Pipe
This is the pipe that contains suction. The sump or reservoir water is sucked through this pump, and this pipe carries water to the cylinder.
#8. Delivery Valve
The delivery valve is fitted in the delivery pipe. It is a non-return valve. This valve opens when the fluid needs to be transported to the required area.
#9. Delivery Pipe
The delivery pipe is used to deliver water from the cylinder to the desired area where water needs to be delivered.
#10. Reservoir or Sump
The reservoir is present in the bottom and is used to store the fluid that has to be pumped using a reciprocating pump.
Definition of Reciprocating Pump:
It is the machine that converts mechanical energy into hydraulic energy. Reciprocating pumps are in use, where a certain amount of fluid (mostly sump) is to be transported from the lowest zone to the highest zone by application of pressure.
For Example:- When you go to servicing the bike’s water, you can see that the water that is being used is only collected from the sump, and by the application of pressure through the nozzle, spraying water on the vehicle is done.
Working of Reciprocating Pump:
The suction valve in the suction valve and delivery valve opens and closes simultaneously with the speed of the piston when the piston moves in a forward and backward direction. The distance from the surfaces of the fluid to the center of the piston where the piston rod is attached is called the suction head, and the distance from the center of the piston to the outlet of the delivery pipe is called the delivery head.
The connecting rods are connected to a crank. The cranks have a radius in which it rotates. The crank is connected to a motor. The crank also rotates as the motor rotates.
The crank rotates in a clockwise direction. When the crank rotates from P to Q in the top semi-circle, the piston moves backward, and when the crank moves to the lower semi-circle, i.e., from Q to P, the piston moves forward.
The piston moves according to the angle created by the crank, from point P ( θ=0 ) to Q ( θ=180 ). Initially, the piston is at point P ( θ=0 ), when the tip of the crank reaches the rightmost point Q ( θ=180 ), the piston also moves to the rightmost side, and a vacuum is formed in the cylinder.
Atmospheric pressures act on the surface of the fluid, and there is also atmospheric pressure on the suction pipe. The suction valve above the suction pipe can only open in the top direction.
Because the suction pipe has a vacuum in the cylinder and atmospheric pressure, the suction valve will open due to the pressure difference, and a partial vacuum is created in the suction pipe as the suction valve opens.
Since there is a partial vacuum in the suction pipe and the atmospheric pressure works on the surface of the fluid, the fluid moves from the high-pressure area to the low-pressure area and will enter the suction pipe, and thus, the entire cylinder is the fluid—stuff with. The suction valve closes when the cylinder is completely filled with water.
After that, the crank moves from the lowest position to the lowest position ( θ=180 to θ=270 ). As the crank move towards the bottom-most position, the piston moves forward, & pressure in the fluid present inside the cylinder increases and when the pressure in the cylinder exceeds the atmospheric pressure, the delivery valve is opened, and the fluid flows upward at high pressure and flows out to the required area from the outlet of the delivery pipe.
Mathematical Analysis of Reciprocating Pump:
Some symbol used below,
D= Diameter of cylinder
A = Cross section area of piston or cylinders = π/4 D²
r = Radius of crank.
N = Speed of crank (rpm).
L= Length of stroke = 2r
Amount of liquid Pumped in revolution = Volume Displaced by Piston in one revolution = A x L
Amount of liquid pumped in one sec = A x L x N/60 = ALN / 60
Weight of water lifted per second ( W/s ) =mg = ρQg
W/s = ρgALN / 60
Work was done per second by a pump ( WD/s )
= Weight of water lifted per second x Total height up to which water is lifted ( Suction Height + Delivery height)
= ρgALN / 60 x ( hs + hd )
Power of pump = WD/s (in 1000 kW).
Advantages of Reciprocating Pump:
- A reciprocating pump can deliver the required flow rate very precisely.
- It gives a continuous rate of discharge.
- It can deliver fluid at very high pressures.
- No priming is needed in the reciprocating pump.
- The efficiency of a reciprocating pump is 10% to 20% greater than the efficiency of a Centrifugal Pump.
Disadvantages of Reciprocating Pump:
- The pump is very costly (Capitals cost is high).
- Viscous liquids are difficult to pump using a reciprocating pump.
- The maintenance cost of the pump is very high as there is a large number of parts.
- The flow rate is less.
Applications of Reciprocating Pump:
- It is used in vehicle washing centers.
- It is used in small hand-operated pump such as cycles pump, football pumps, etc.
- It is used as an important part of the hydraulics jack.
- It is commonly used in gas industries.
- It is also used in oil refineries.
- Used in petroleum industries.
- It is also used in the pneumatic pressure system.