1. What is a Reciprocating Pump?
A reciprocating pump is a type of positive displacement pump in which fluid is moved by the to-and-fro (reciprocating) motion of a piston or plunger inside a cylinder.
It is mainly used where high pressure and low discharge are required.
In simple words:
Mechanical Energy → Reciprocating Motion → Hydraulic Energy
2. Principle of Operation
A reciprocating pump works on the principle of positive displacement:
- A piston moves back and forth inside a cylinder
- During backward motion, it creates a vacuum, drawing fluid into the cylinder
- During forward motion, it pushes fluid out at high pressure
3. Working of Reciprocating Pump
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Step-by-step Working (Single Acting Pump):
- Suction Stroke:
- Piston moves away from cylinder head
- Vacuum is created
- Suction valve opens
- Fluid enters the cylinder
- Delivery Stroke:
- Piston moves towards cylinder head
- Pressure increases
- Suction valve closes
- Delivery valve opens
- Fluid is pushed out
4. Main Components of Reciprocating Pump
(a) Cylinder
- Main body where fluid is enclosed
(b) Piston / Plunger
- Moves back and forth
- Responsible for suction and delivery
(c) Crank and Connecting Rod
- Converts rotary motion into reciprocating motion
(d) Suction Valve
- Allows fluid to enter
- Prevents backflow
(e) Delivery Valve
- Allows fluid to exit
- Maintains one-way flow
(f) Suction Pipe
- Draws fluid from source
(g) Delivery Pipe
- Delivers fluid to required height
(h) Air Vessel (optional)
- Smoothens flow
- Reduces pulsations
5. Types of Reciprocating Pumps
(1) Based on Working
- Single Acting Pump
- Fluid is pumped on one side of piston
- Double Acting Pump
- Fluid is pumped on both sides
- Higher discharge
(2) Based on Construction
- Piston Pump
- Plunger Pump
- Diaphragm Pump
6. Important Terminology
- Stroke Length (L): Distance moved by piston
- Discharge (Q): Volume of fluid delivered
- Slip: Difference between theoretical and actual discharge
- Coefficient of Discharge: Ratio of actual to theoretical discharge
7. Advantages of Reciprocating Pump
- High pressure output
- High efficiency
- Suitable for viscous fluids
- Accurate discharge
8. Disadvantages
- Pulsating flow
- Complex design
- High maintenance
- Not suitable for large discharge
- Heavy and bulky
9. Applications
- Boiler feed water supply
- Hydraulic presses
- Oil and gas industries
- Chemical dosing
- Irrigation (low flow, high head)
10. Comparison with Centrifugal Pump
| Feature | Reciprocating Pump | Centrifugal Pump |
|---|---|---|
| Type | Positive displacement | Dynamic |
| Flow | Pulsating | Continuous |
| Pressure | High | Low to medium |
| Discharge | Low | High |
| Efficiency | High | Moderate |