What is Plunger Pump?
A plunger pump represents a specific category of positive displacement pumps, notable for its stationary high-pressure seal and a smooth, cylindrical plunger that moves through this seal.
This design sets plunger pumps apart from traditional piston pumps, as the fixed seal and moving plunger enable operation under significantly higher pressures. Because of this robust construction, plunger pumps are frequently chosen for handling municipal and industrial wastewater.
In contrast, piston pumps rely on a reciprocating plunger mechanism to move fluid, drawing and expelling it through a set of valves with each stroke. These devices might be more familiar in everyday settings—for instance, a bicycle pump, spray bottle, or even a simple squirt gun all operate on the same basic principle.
On the commercial side, plunger pumps have found a wide range of applications. They are integral components in electrically powered equipment used for cleaning, disinfection, pest control, and agriculture, among other purposes. Equipment such as pressure washers, atomizers, and sprayers frequently utilize these pumps due to their reliability and ability to generate high pressures.
Historically, the development of the plunger pump is traced back to Samuel Morland, who secured a patent for the design in 1675.
How does Plunger Pump Work?
Piston pumps and plunger pumps both fall under the category of reciprocating pumps, relying on the movement of a piston or plunger within a cylindrical chamber to transfer fluid. The motion of the piston or plunger is driven by actuators, which may be powered by steam, compressed air, hydraulic systems, or electricity, depending on the application.
In rotary piston and plunger pumps, a crank mechanism generates the reciprocating motion required for operation. As the piston or plunger moves back and forth along a linear axis, pressure builds within the cylinder. This pressure is what drives either gas or liquid through the pump, while valves at both the inlet and outlet are actuated in response to the pressure fluctuations, ensuring directional flow.
The operating range for piston pumps is quite broad, with typical working pressures spanning from 70 up to 2,070 bar (1,000 to 30,000 psi). Piston pumps are generally preferred for lower-pressure scenarios. The amount of fluid the pump discharges with each stroke is determined by the cross-sectional area of the piston or plunger, combined with the stroke length.
When assessing the performance of piston and plunger pumps, several factors come into play: the piston or plunger area, the stroke length, the total number of pistons or plungers involved, and the drive speed. The power needed for the drive is directly related to both the required pressure and the desired capacity of the pump.
Sealing plays a crucial role in these pumps, as it separates the actuation fluid from the medium being transferred. Typically, a gland or packing is used to create a seal between the chamber and the moving piston or plunger. The stuffing box—composed of elements such as bushings, packing or sealing rings—ensures that this interface remains leak-free.
Material selection for the components of plunger pumps is guided by the demands of wear resistance and compatibility with the specific medium being pumped. Common choices include bronze, brass, various grades of steel, stainless steel, iron, and nickel alloys. For instance, in oilfield or general service settings, it is not uncommon to find pumps with iron cylinders and plungers.
The parts of the pump that directly contact the fluid—such as the piston, and the suction and discharge valves—are carefully matched to the properties of the liquid. In cases where continuous-duty performance is required, especially in water or oil applications, all-ceramic plungers may be employed. However, their suitability drops off sharply with highly acidic media.
Differences Between Piston and Plunger Pumps:
| Piston Pump | Plunger Pump |
| A high-pressure seal reciprocates with the piston in the cylinder | The high-pressure seal is stationary. Plunger slides through seal allowing the pump to be used at higher pressures. |
| Inlet Design Pressure of 8.5psi to 40psi | Inlet design pressure of 60-70psi |
| Best suited to short duty cycles unless larger pump running slowly | OK for continuous operation when running slowly |
| Inlet valves mechanically actuated | Requires flooded suction or higher inlet pressure supplied by a booster pump |
| Output pressure 100-1200psi | Output pressure 100 to 10,000psi |
Applications of Plunger Pumps
The plunger pumps have the capability to deliver high pressure. These pumps have the capability to pump heavy substances and high viscous fluids. Due to these features, plunger pumps use for the following applications:
- These pumps use for chemical Injection.
- These pumps also use for odor control and misting
- A plunger pump uses for drill cutting injection
- Use for water cutting
- Use in oil and gas production
- The plunger pumps also use for gas dehydration
- They use for surface preparation
- Plunger pumps also use for urea production
- They use for cleaning applications
- These pumps use for coal liquefaction
- These are used for pressure testing
Advantages of Plunger pump
- It has self-priming capability (self-priming pump) and high efficiency.
- Very high developed/discharge pressure is possible
- Linear capacity control if you are using variable speed
- Leak can be mitigated without shutting down the pump if your company permit you to tighten the packing while the pump is running
- These have the capability to generate more pressure than piston pumps.
- Flow rate and pressure changes have a very low
- Impact on the performance of the plunger pump.
- These have the capability to pump abrasives and slurries.
- These have the capability to move high viscosity and heavy substances.
Disadvantages of Plunger pump
- Very low flow when compared to centrifugal or axial pump
- Irregular flow cause pulsation
- Prone to cavitation because of acceleration head, especially if the suction pipe is long
- Inherently higher vibration because of reciprocating motion, although the rotational speed is generally lower than dynamic pumps
- These pumps have high operation costs.
- This pump needs high maintenance costs.
- Plunger pumps can’t deliver pulsating free flow.
- These pumps can handle only low flow rate fluids.
- These are bulky and heavy.
FAQs
What is a plunger pump used for?
Commercially, plunger pumps are commonly used in soft wash, portable sanitation, disinfection, pest control, agriculture, and other high-pressure applications. They can be configured into electrically powered equipment such as pressure washers, misters, and sprayers.
What are the disadvantages of a plunger pump?
The advantages of piston and plunger pumps are their self-priming capability (self-priming pump) and high efficiency; disadvantages include their pulsating delivery and, especially in the case of large units, their space requirements, their large mass and their high investment costs per unit of pump output.
What is the difference between a plunger pump and a piston pump?
Unlike a piston that fits tightly inside the cylinder, a plunger fits loosely. The plunger creates negative and positive water pressure inside the cylinder as it moves up and down.
What is the advantage of the plunger pump over the piston pump?
Plunger pumps have a relatively simple design, fewer parts, and require much less maintenance than piston pumps.
What is the purpose of a plunger?
In plumbing, the term plunger commonly refers to handheld tools used to clear blockages in drains and pipes. Plumbing plungers consist of a rubber suction cup attached to a stick (shaft) usually made of wood or plastic.
What is the maximum pressure for a plunger pump?
The maximum pressure for a plunger pump is the highest pressure that the pump can generate without compromising its performance or damaging the components. The maximum pressure for the machine typically ranges from 1000 to 5000 psi (pounds per square inch), depending on the design and construction of the pump.