Positive displacement pumps Manufacturers online

Positive displacement pumps are a special type of pump that pumps liquids by displacing a certain volume.

Their mode of operation is based on the fact that a certain volume of liquid is enclosed by a movable pump element and transported further by the movement of the element. There are various types of positive displacement pumps, each of which works differently, such as piston pumps, gear pumps, diaphragm pumps or screw pumps. What they all have in common, however, is that they can pump liquids precisely and independently of pressure.

Below you will find the basic principle and mode of operation and the different types of positive displacement pumps, their areas of application and their advantages and disadvantages:

Basic principle and mode of operation:

The pump element (e.g. a piston, a screw or a gear wheel) encloses a fixed volume of liquid. When the pump element moves, this volume is transported from the suction side to the pressure side of the pump. The displacement of the liquid volume creates a vacuum, which draws in new liquid on the suction side. On the discharge side, the liquid is then pushed further by the movement of the pump element. The liquid is transported in a fixed volume that remains largely unchanged during the pumping process. This enables a uniform and constant flow rate per revolution or stroke.

Types of positive displacement pumps:

• Piston pumps use a piston that moves in a cylinder to draw in and displace liquid. During a piston movement, the medium is sucked in through a valve and, during the subsequent movement, compressed and pressed out through an outlet valve.
  Application: Piston pumps for applications where high pressures are required, e.g. in hydraulics or for dosing liquids.
• Gear pumps work with two meshing gears that trap liquid in the spaces between the gears and transport it from the suction side to the discharge side.
  Application: They are often used in industry to pump viscous media such as oils, lubricants and chemicals, especially in applications that require smooth, pulsation-free pumping.
• Diaphragm pumps use a flexible diaphragm that is moved by pressure (pneumatic or mechanical). The movement of the diaphragm draws the medium in through a valve and then pushes it out through another valve.
  Application: Diaphragm pumps are ideal for the transfer of aggressive, abrasive or viscous liquids and are often used in the chemical, pharmaceutical and food industries as well as in water and wastewater management.
• Peristaltic pumps work by compressing a flexible hose through rotating rollers or sliding shoes. This movement pushes the medium forward within the hose, whereby the hose springs back elastically after each roller and draws in new medium.
  Application: They are often used in the chemical, pharmaceutical and food industries as well as for dosing processes and the transfer of liquids with solid particles, as the medium only comes into contact with the hose. Peristaltic pumps are ideal for transporting sensitive, viscous, abrasive or chemically aggressive media.
• Screw pumps work with rotating screws that convey liquid along the screw threads from the suction to the discharge side.
  Application: They are well suited for viscous, sensitive or solids-laden media and are used in the oil, food and waste water industries, where smooth and gentle transportation is required, as well as for low-noise conveying.
• Progressing cavity pumps convey liquid by the rotary motion of an eccentric rotor in a static stator, creating chambers that transport the medium evenly.
  Application: They are suitable for viscous, solid-containing or sensitive media and are used in the food, waste water and chemical industries where gentle, pulsation-free transportation is required.

Areas of application:

Positive displacement pumps are widely used in various industries and sectors:

1. Chemical and pharmaceutical industries:
For pumping and dosing aggressive chemicals or medicines.

2. Food industry:
In hygienically sensitive processes where precise quantities need to be dosed, such as for beverages or pastes.

3. Hydraulic systems:
Piston and gear pumps are used in hydraulic applications that require high pressures.

4. Oil and gas industry:
Screw pumps in particular are advantageous in the pumping of viscous media such as crude oil.

Advantages of positive displacement pumps:

• The flow rate is largely independent of the pressure, which makes them suitable for precise dosing.
• Positive displacement pumps offer a consistent flow rate without large fluctuations.
• They can transport a wide range of liquids, including viscous and abrasive substances.

Disadvantages of positive displacement pumps:

• Compared to centrifugal pumps, they often have a lower flow rate.
• Especially when using pistons or diaphragms, positive displacement pumps are mechanically more complex and require more maintenance.
• In liquids with solid particles, some positive displacement pumps can wear out more quickly.

Positive displacement pumps are robust, precise and versatile pumps that can pump liquids independently of pressure and in precisely definable quantities. This makes them a preferred choice for applications where high pressures or exact dosages are required. Due to the variety of designs, they can be used in many industrial sectors, from the chemical and food industries to oil and gas extraction.

Here you will find an overview of the most important criteria to look out for when purchasing positive displacement pumps:

Purchasing a positive displacement pump requires consideration of numerous technical and application-specific factors. A thorough evaluation of these criteria will help you make the right choice for an efficient, durable and cost-effective pump.

• The viscosity of the pumped liquid has a direct influence on the pump selection. Screw and progressive cavity pumps are well suited for highly viscous media such as oils or slurries. Abrasive media (with solid particles) can lead to increased wear, which is why wear-resistant materials (e.g. hardened steel, ceramics) are recommended. For corrosive media, pumps made of chemical-resistant materials such as stainless steel or special plastics should be used.
• Progressing cavity pumps or peristaltic pumps are particularly suitable for media containing solids, as they transport the medium gently and prevent blockages.
• The required flow rate (e.g. liters per minute or cubic meters per hour) determines the pump size. Pumps such as progressive cavity and screw pumps can handle larger volume flows, while piston pumps are well suited for smaller, precise volumes.
• Positive displacement pumps are known for their ability to generate high pressures. Piston pumps are particularly suitable for high pressure applications (hydraulics, compressed air applications). For medium pressures, gear, diaphragm or screw pumps are often sufficient.
• The pump materials must be able to withstand the operating temperatures of the medium. Heat-resistant materials and seals are required for high temperatures (e.g. when pumping oils). The seals and the lubricant (if required) should also be designed for the temperature requirements.
• The type of drive is selected depending on the availability of energy sources and the application. Electric drives are often ideal for precise and controllable delivery, pneumatic drives are often used with diaphragm pumps and hydraulic drives offer high performance with small dimensions.
• In applications that require precise dosing or variable flow rates, the pump should be controllable. With frequency converters, electric drives can be adjusted to the required speed to adapt the flow rate to different process requirements.
• Positive displacement pumps that convey solids or are exposed to high loads require regular maintenance. A pump with easily accessible wear parts facilitates maintenance and minimizes downtime.
• Pumps whose spare parts are available quickly and cost-effectively are more economical in the long term and reduce potential downtime.
• The size of the pump should fit into the available space. Some pump types require more space as they transport larger flow rates or need to be specially insulated.
• Make sure that the inlet and outlet connections of the pump match the existing piping and connections. The pump should also have sufficient space to its surroundings to enable safe operation and maintenance.
• In potentially explosive areas or in the vicinity of flammable substances, special protective measures (ATEX certification) must be observed. Electrical and pneumatic components must comply with local safety regulations. It must be ensured that they are not a source of ignition.
• If the pump is used in the food or pharmaceutical industry, certifications such as FDA or EHEDG approvals are often required. These ensure that the pump is hygienic and easy to clean.
• Depending on the industry and requirements, other certificates such as CE, ISO or UL may also be necessary.
• The energy efficiency of the pump has a long-term impact on operating costs. Choose a pump that matches the required flow rate to avoid unnecessary energy consumption.
• The pump should be designed for the operating cycles (e.g. continuous or intermittent operation). oversized or overloaded pumps increase energy consumption and reduce service life.
• In addition to the purchase costs, the long-term operating costs (e.g. maintenance, energy consumption, spare parts) should also be taken into account.
• A comparison of the various models and brands will help you find the best pump for your budget without compromising on functionality and durability.

When purchasing a positive displacement pump, it is important to carry out a holistic evaluation that takes into account the specific requirements of the application as well as the long-term operating costs and maintenance characteristics. The right choice of positive displacement pump will save costs in the long term, ensure stable and efficient pumping and minimize downtime.

Positive displacement pumps can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Positive displacement pumps from all over the world can be found on Exportpages.