What is the difference between plunger pump and piston pump?

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BISON Santy

Hello, I am Santy, the funder of bisonclean.com. I have been in cleaning machinery field for more than 5 years now, and the purpose of this article is to share with you the knowledge related to pressure washer from a Chinese supplier's perspective.

Industrial pumps play a crucial role in various sectors, facilitating the movement of fluids in applications ranging from water treatment and oil refining to chemical processing and manufacturing.Among the many types of pumps, plunger and piston pumps stand out for their efficiency and reliability in high-pressure environments. While both types of pumps are positive displacement pumps, and many people often use the terms piston and plunger pumps interchangeably, they have distinct structural.

The purpose of this article is to provide a clear comparison of plunger pumps and piston pumps, highlighting their main differences and guiding you in making an informed decision for your industrial needs.

what is the difference between plunger pump and piston pump

how piston pumps work?

A piston pump operates by mechanical motion that moves a piston back and forth within a chamber, drawing fluid in through an intake valve during the intake stroke and pushing it out through an exhaust valve during the exhaust stroke, creating a vacuum and pressure. This continuous motion circulates the fluid through the pump in a smooth and controlled manner, giving piston pumps efficiencies as high as 85-90%.

It is often used in situations where high pressure and low fluid flow rates operate, such as hydraulic systems, chemical processing plants, and water or oil extraction industries.

Advantages of piston pumps

  • Positive displacement designs make flow proportional to speed, so they can predictably transfer fluids in batching and metering applications.
  • High pressures are generated with a relatively simple mechanism, and self-priming designs with high suction are available; consistent flow rates are provided, and designs that can accommodate viscous fluids are also available.
  • Driven directly by a motor or a V-belt protected by a guard, there is no need to go through a gearbox to increase transmission losses.

Limitations of piston pumps

  • Reciprocating motion causes vibration and noise, and additional damping or isolation may be required in sensitive environments.
  • Mounted units take up a lot of space, primarily when driven by a V-belt, because the unit is bulky and the motor is located next to the pump head, rather than inline as is common in other designs.
  • High-flow designs may require a separate booster pump to feed the unit and ensure that cavitation does not occur.

how plunger pumps work?

Similar to piston pumps, plunger pumps are also positive displacement pumps, but the high-pressure seal is fixed and a smooth cylindrical plunger slides back and forth in the cylinder sleeve. This configuration allows higher pressures to be handled than piston pumps. When the plunger retracts, it creates suction, drawing fluid into the cylinder through the inlet valve. When the plunger is pushed forward, it forces the fluid out through the outlet valve. This action provides a continuous, steady flow rate that is very efficient at high pressures.

Plunger pumps are often used in applications that require very high pressures, such as water jet cutting, the oil and gas industry, pipeline pressure testing, and various types of high-pressure washers.

Advantages of plunger pumps

  • Compared to piston pumps, plunger pumps are designed to handle higher pressures more efficiently and adapt to applications with greater power.
  • Its structure allows the use of harder materials and ceramic plungers, which are more resistant to wear and corrosion, extending service life and durability.
  • Plunger pumps can precisely control flow and pressure, allowing operators to adjust parameters according to specific needs and improve process control and productivity.
  • There are fewer moving parts in the high-pressure area, and their maintenance procedures are simpler.

Limitations of plunger pumps

  • Although rugged and durable, they are less efficient in certain types of viscous or slurry fluids than piston pumps.
  • Due to the complex design, special materials and precise manufacturing process of plunger pumps, their initial cost is generally higher than other pumps.
  • They may require more precise alignment and settings, which increases the complexity of initial installation.
  • Similar to piston pumps, plunger pumps also generate a lot of noise and vibration, which requires sound insulation and vibration isolation measures to solve this problem.
  • There may be some limitations on the suction capacity of plunger pumps, and proper priming and inlet conditions are required to maintain normal operation and prevent cavitation.

What is the difference between plunger pump and piston pump?

Design differences

Plunger pumps are complex in design and operate at high pressures, so operating and maintaining plunger pumps may require personnel with specialized training and technical expertise. From an engineering perspective, the main difference between piston pumps and plunger pumps is the location of the seals or O-rings. Also, plunger pumps use a plunger through a packing seal that remains stationary while moving through the seal, while piston pump seals move with the piston.

Performance and efficiency

Efficiency under different pressure conditions: Compared to piston pumps, plunger pump seals are not attached to the rod, which reduces friction and increases pressure output. They are designed to be more durable under high-pressure conditions and adapt to applications with stronger forces.

Handling a variety of fluid viscosities: Due to the strong seal between piston pumps and cylinders, they are generally better suited to handling fluids of different viscosities, including mud and more viscous liquids. Although plunger pumps are efficient when handling fluids under high pressure, they are less efficient in certain types of viscosities or liquids.

Flow capacity: Piston pumps are often preferred in applications where high flow rates and smooth, continuous fluid delivery are required. plunger pump, while efficient at high pressures, may experience slight variations in flow rate due to the nature of their packing seals.

High temperature and chemical resistance

The most important factor is the material composition of the reciprocating plunger or piston and the pump housing. To prevent scratches and seal breakage, it is usually desirable to make the parts with the highest wear capacity as hard as possible. The materials used in plunger pumps usually include ceramics or hardened metals for plungers and packing, which can resist wear and chemical corrosion. Nevertheless, the challenge of designing and manufacturing tubular cavity walls made of ceramic or other materials and making them smooth on the inside is far greater than making a perfectly smooth plunger exterior from the same material.

That is, it is much easier to make a plunger from a more complex material than to make a housing from the same material. Therefore, plunger pumps can be designed to be more robust than piston pumps.

Impact on applications

Although plunger pumps are powerful, they may require specialized seals and cylinder materials when faced with highly corrosive or hot fluids. The inherent design of a piston pump offers excellent resistance to these conditions, facilitating its use in chemical processing and high-temperature applications.

Maintenance and cost

Many piston pumps require an oil bath. Some versions also have a second oil pan or reservoir with a wick to lubricate the back of the piston seal. These reservoirs must be refilled and maintained if you want the pump to keep running. And piston pumps often have moving parts that wear, requiring more frequent maintenance or replacement.

Piston pumps, are simpler to maintain because their packing is replaceable and can be replaced without extensive disassembly or the use of specialized tools. Compared to piston pumps, piston pumps have fewer parts and a simpler design, which typically requires maintenance such as lubrication, seal replacement, and high-wear parts. In short, piston pumps are less likely to fail.

What else do fewer parts and a simpler design bring? Low cost. Piston pumps generally have lower upfront costs than piston pumps of similar performance. Over time, piston pumps have lower maintenance requirements and longer service intervals, making them more cost-effective.

Conclusion

In summary, while both plunger and piston pumps are essential tools in industrial fluid handling, they have differences in design, operation, and performance. Plunger pumps excel in high-pressure environments and have excellent durability and easy maintenance due to their replaceable packing seals. They are particularly suitable for applications that require precise flow control and stable pressure delivery. On the other hand, piston pumps have effective cylinder wall seals that provide consistent flow capacity to handle a variety of fluid viscosities.

After reading this article, I believe you can judge the specific situation of your application and choose the pump that best suits you. Here I also recommend a simple judgment method – contact the BISON Industrial plunger pump manufacturer, we invite you to explore our products and consult our experts. At BISON, we pride ourselves on offering a wide range of tailor-made pumps to meet your specific requirements. Whether you need a pump that handles high pressures and flows, adapts to a variety of fluid viscosities and temperatures, or meets your budget and maintenance schedule, BISON has the perfect solution for you.

Differences between plunger pumps and piston pumps FAQ

In some cases, especially in applications where pressure and flow requirements overlap. However, it is often best to select a pump type that meets the specific requirements of the application for optimal performance and longevity.

Plunger pumps:

Plunger pumps are often preferred for applications that require very high pressure, such as water blasting, pressure washing, and high-pressure hydraulic systems.where deep well pumping and pipeline testing are common, as well as in reverse osmosis systems for water purification and high-pressure cleaning systems in the food processing industry.

Piston pumps

Piston pumps are more commonly used in applications such as car washing, especially high-pressure washers, which provide high flow rates and smooth continuous fluid output.

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