Positive displacement pumps are a type of pump that work by trapping a fixed amount of fluid in a chamber and then compressing it to force it out of the pump. The fluid is trapped in the pump by a set of rotating gears, a piston, a diaphragm, or some other mechanical device, and is then forced out of the pump as the chamber is compressed. They are commonly used in various applications due to their ability to handle high-viscosity fluids, deliver a constant flow rate, and maintain a high level of pressure.
Types and Applications
There are several types of positive displacement pumps, each with its own set of applications:
- Piston Pumps: Piston pumps use a piston to move the fluid through the pump. They are commonly used in high-pressure applications such as water jet cutting, pressure testing, and hydrostatic transmission.
- Diaphragm Pumps: Diaphragm pumps use a flexible diaphragm to move the fluid through the pump. They are commonly used in applications where the fluid being pumped is abrasive or contains solids, as well as in the food and beverage industry for pumping liquids with high viscosities.
- Gear Pumps: Gear pumps use meshing gears to trap and move the fluid through the pump. They are commonly used in oil transfer, hydraulic systems, and fuel delivery applications.
- Vane Pumps: Vane pumps use rotating vanes to trap and move the fluid through the pump. They are commonly used in applications such as oil burners, power steering, and hydraulic systems.
- Lobe Pumps: Lobe pumps use two rotating lobes to trap and move the fluid through the pump. They are commonly used in applications such as food processing, waste treatment, and viscous liquid transfer.
- Screw Pumps: Screw pumps use two intermeshing screws to trap and move the fluid through the pump. They are commonly used in applications such as oil transfer, chemical processing, and viscous liquid transfer.
Advantages and disadvantages of positive displacement pumps
| Advantages | Disadvantages |
|---|---|
| Constant flow rate: Positive displacement pumps are able to maintain a constant flow rate regardless of changes in the system’s pressure or flow conditions. This makes them well-suited for applications where a constant flow rate is required, such as in metering, dosing, and dispensing systems | Higher initial cost: Positive displacement pumps are typically more expensive than other types of pumps, such as centrifugal pumps. |
| High pressure capability: Positive displacement pumps are able to generate high pressures, making them ideal for applications that require high pressure delivery, such as in the oil and gas industry or in water treatment systems. | Complex design: Positive displacement pumps are often more complex in design than other types of pumps, making them more difficult to repair and maintain |
| Handling of viscous fluids: Positive displacement pumps are able to handle viscous fluids, such as thick liquids or suspensions, with ease. This makes them well-suited for applications where the fluid being pumped has a high viscosity, such as in food and beverage processing. | Limited maximum flow rate: Positive displacement pumps have a limited maximum flow rate, meaning that they may not be suitable for high flow rate applications. |
| Efficient at low flow rates: Positive displacement pumps are efficient at low flow rates, making them ideal for applications where low flow rates are required, such as in laboratory and research applications. | Poor efficiency at high flow rates: Positive displacement pumps are often less efficient at high flow rates, making them less suitable for applications where high flow rates are required. |
In summary, Positive displacement pumps are a type of pump that are well-suited for applications where a constant flow rate, high pressure delivery, or handling of viscous fluids is required. However, they can be more expensive and complex in design than other types of pumps, and may not be suitable for high flow rate applications.
Useful software
Pumping power calculator – Calculates the pump power of fluids
