What Are Positive Displacement Pumps?
A positive-displacement pump is a pump that conveys liquids or gases by enclosing a defined volume in a chamber and displacing it from the inlet to the outlet through mechanical motion. Unlike centrifugal pumps, it is not a fluid-flow machine and conveys a constant volume that is virtually independent of pressure.
KAMAT is an expert for positive displacement pumps in the industrial sector. Our advanced positive displacement pumps are at the heart of efficient and reliable processes in numerous industrial sectors. With a combination of innovative technology, robust design and customized functionality, our pumps offer unmatched performance tailored specifically to the needs of demanding industrial applications.
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Functionality of Positive Displacement Pumps
The main function of a positive displacement pump is to contain a certain amount of the fluid to be pumped in a chamber and to move it from an inlet to an outlet by mechanical movement (e.g. turning or pushing). This process is achieved by various mechanisms, such as pistons, diaphragms, screws or gears. These mechanisms periodically increase the volume in the chamber (to draw in the medium) and then reduce it (to displace it). If the displacement is done by a plunger, the pumps are also called plunger pumps. Plunger pumps are oscillating positive displacement pumps.
- Suction phase: The displacer (e.g. a piston or plunger) in the pump retracts, enlarging the working chamber and allowing fluid to flow in through the suction valve. The discharge valve prevents the fluid from flowing back from the discharge line into the working chamber.
- Displacement phase: The displacer moves forward, reducing the volume of the working chamber and increasing the pressure inside. The pressure valve opens and the fluid can flow into the pressure line, while the suction valve prevents the fluid from flowing back into the suction line.
- The working chamber is then back in the suction phase.
Where are Positive-Displacement Pumps Used?
Due to their efficiency and precision, positive displacement pumps are indispensable in a variety of industries. Some of the most common applications include:
- Industrial cleaning
- Mining
- Shipyards (as part of industrial cleaning)
- Construction (concrete cleaning)
- Chemical industry
- Net cleaning in aquaculture (as part of industrial cleaning)
- Oil and gas industry
- Process technology (= chemistry)
Positive Displacement and Centrifugal Pumps: What Are the Differences?
Positive displacement pumps and centrifugal pumps, also known as centrifugal pumps, are two basic types of pumps that differ significantly in their mode of operation and areas of application. The following table provides an overview of the main differences between these two pump types:
| Feature | Positive Displacement Pump | Centrifugal Pump |
|---|---|---|
| Operating Principle | Mechanical displacement of a defined volume of liquid. Delivers a discontinuous flow. | Uses centrifugal force generated by a rotating impeller to accelerate and convey the liquid. A turbomachine that delivers a continuous flow. |
| Flow Rate | Nearly constant, independent of operating pressure: ideal for precise volume dosing. | Varies with system pressure. As pressure increases, the flow rate decreases. |
| Efficiency | Extremely high | Medium |
| Pressure Sensitivity | Low: the flow rate remains stable even when pressure changes. | Highly sensitive to pressure changes, which affects the flow rate. |
| Self-Priming | No | No |
| Applications | Suitable for highly viscous liquids and applications requiring precise dosing or high pressure, e.g. industrial high-pressure cleaning, mining, shipyards, construction, chemical industry, aquaculture, oil and gas, and process technology. | Ideal for applications with high flow rates and low pressure, e.g. water supply and cooling systems. |
| Critical Fluids | Suitable for a wide range of corrosive, toxic or explosive fluids, as components and seals can be manufactured from a wide variety of materials with various sealing systems, even as one-off custom parts. | Difficult to adapt to critical fluids, as they are usually built from cast parts that can only be modified at considerable expense. |
Positive Displacement Pumps – Variants
Positive displacement pumps are a class of pumps that pump liquids by periodically enlarging and reducing a working chamber. They are available as
- oscillating pumps (e.g. piston or diaphragm pumps)
- rotating pumps (e.g. gear or rotary lobe pumps)
- as well as pumps with a combination of a rotating and oscillating movement (e.g. radial piston pumps).
A very well-known type of oscillating positive displacement pump is the plunger pump. Plunger pumps use a plunger piston (plunger) that moves back and forth in a cylinder. With plunger pumps, the seal does not move with the plunger (as with pistons), but is attached to the pump housing. The back and forth movement of the plunger, which is often made of ceramic, draws liquid into the cylinder, which is then expelled by the movement of the plunger in the direction of an outlet valve. Plunger pumps are not used for gases, as plunger pumps generally have too large dead spaces.
Positive-Displacement Pumps: Versatile Solutions for Precise Fluid Transfer
Positive displacement pumps are known for their ability to move precise volumes of liquid in a variety of industries. These pumps are ideal for applications that require precise flow control.
Reciprocating Pumps
Reciprocating pumps are a key category of positive displacement pumps specifically designed for precise fluid transfer. These pumps use one or more pistons that move back and forth in cylinders. This movement creates a vacuum that draws in the liquid and pushes it out as it moves back. This mode of operation enables extremely precise control over the volume pumped. Reciprocating piston pumps are particularly effective when handling highly viscous liquids and can generate extremely high pressures. Their robust design ensures durability and reliability even under demanding operating conditions. Their adaptability makes them ideal for a wide range of industrial applications, including the chemical and food industries, where precise metering and handling of viscous products is required.
Diaphragm Pumps
Diaphragm pumps are characterized by a flexible diaphragm that moves up and down regularly, thus conveying the liquid through the pump. This pump technology is particularly advantageous when handling corrosive or abrasive media, as the liquid is completely isolated from the mechanical parts and there are no dynamic seals. This minimizes wear and increases the service life of the pump. Diaphragm pumps are therefore ideal for use in process engineering and other industries where clean and contamination-free processes are critical. Their ease of maintenance and ability to run dry without damage make them a popular choice in many industrial applications. However, diaphragm pumps are extremely expensive and are therefore increasingly being replaced by much cheaper plunger pumps.
Screw Pumps
Screw pumps use two precisely intermeshing screws to deliver media continuously and evenly. This type of pump is particularly known for its ability to produce a pulsation-free flow, making it ideal for applications where vibration and pulsation are undesirable, such as in food processing or the pharmaceutical industry. Their design allows them to efficiently move both low and high viscosity fluids, further increasing their versatility and popularity. Screw pumps are also known for their durability and low maintenance requirements, making them a cost-effective solution in many industrial processes.
Gear Pumps
Gear pumps are known for their robustness and reliability, making them suitable for a wide range of industrial applications. These pumps work with two or more gears that mesh together to transport liquids. The gear pump is particularly effective when handling different viscosities, from thin to very thick media. Their design enables a smooth, efficient flow with little turbulence, making them ideal for precise dosing and pumping tasks. Their ease of maintenance and high performance make gear pumps a preferred choice in the chemical, petrochemical and food industries.
Gerotor Pumps
Gerotor pumps utilize an internal gear design in which an internally toothed gear drives the internal externally toothed gear, which is positioned eccentrically. This design provides a smooth, even flow that is ideal for lubricant applications and hydraulic systems. Their compactness and efficiency in low to medium pressure ranges make them popular in the automotive industry and in machines that require precise fluid handling.
Peristaltic Pumps
Peristaltic pumps offer gentle and sterile handling of liquids, as the medium only comes into contact with a flexible tube that is compressed by rollers. These pumps are ideal for sensitive media such as in biotechnology and medical applications as they prevent contamination and are easy to clean. Their precision and reliability are particularly appreciated in food processing and pharmaceutical production.
Vane Pumps
Vane pumps work with a rotating disk in an oval housing, with several movable vanes in radial slots varying the volume of the working chamber. They are particularly suitable for medium pressures and are characterized by their ability to handle a wide range of liquids. Their adaptability makes them useful in many industries, including the automotive and aerospace industries.
Positive Displacement Pumps from Kamat: High Performance Meets Quality
At KAMAT, the specialist for high-pressure technology, we understand that every industry has its own challenges and requirements. That’s why we offer a wide range of positive displacement pumps suitable for a variety of applications – from the chemical and process industries to mining and construction. Discover how our positive displacement pumps can help boost your productivity and reduce operating costs while ensuring the highest safety standards.
Find out how we can revolutionize your industrial processes with tailor-made solutions and first-class service.
Benefits of Positive Displacement Pumps by KAMAT
KAMAT positive displacement pumps are synonymous with innovation and quality, specifically designed to meet the demanding needs of industry. Here are some of the key benefits that make KAMAT high-pressure pumps a preferred choice in various industries:
- High efficiency and precision: KAMAT positive displacement pumps are known for their high flow accuracy. They enable precise control of flow and pressure, which is crucial in processes that require accurate metering. The high efficiency leads to considerable energy savings
- Robustness and durability: The pumps are known for their robust design and ability to operate reliably even in harsh conditions. They can withstand corrosive, abrasive or highly viscous media, ensuring a longer service life and lower maintenance costs.
- Flexibility in applications: KAMAT has a wide range of positive displacement pumps suitable for a wide variety of requirements. From the chemical and food industries to mining and the oil and gas industry, KAMAT offers customized solutions for diverse industrial requirements.
- Customer-specific service and support: KAMAT is characterized by outstanding customer service. From advice and customization of pumps to after-sales service and technical support worldwide, KAMAT offers comprehensive support for its customers.
This combination of performance, reliability and customer focus makes KAMAT positive displacement pumps an ideal solution for industrial companies looking for high-quality and efficient pump systems.
Frequently Asked Questions About Positive Displacement Pumps
A positive displacement pump moves liquids or gases by trapping a defined volume in a chamber and mechanically transferring it from the inlet to the outlet. Unlike a centrifugal pump, it is not a dynamic flow machine.
During the suction phase, the displacement element increases the volume of the working chamber so that fluid can enter. During the displacement phase, the chamber volume is reduced and the fluid is forced out through the discharge valve.
Positive displacement pumps deliver a defined volume largely independently of pressure and typically operate with a pulsating flow. Centrifugal pumps use centrifugal force and provide continuous flow, but their delivery rate depends on pressure and system conditions.
Positive displacement pumps include reciprocating designs such as piston, diaphragm, and plunger pumps, rotary designs such as gear and screw pumps, and combined designs such as radial piston pumps.
A plunger pump is a reciprocating positive displacement pump with a stationary seal mounted in the housing and a plunger that moves back and forth, often made of ceramic. It is generally unsuitable for pumping gases because of its comparatively large clearance volumes.
Positive displacement pumps are used in industrial cleaning, mining, construction and concrete rehabilitation, chemical and process engineering, aquaculture, and the oil and gas industry.
No. According to the comparison table, neither positive displacement pumps nor centrifugal pumps are self-priming.
