Positive Displacement Pumps: What They Are, Their Advantages, and Applications

Positive displacement pumps are devices used to transfer liquids from one point to another, harnessing the principle of displacing a defined volume of fluid for each operating cycle. Generally, pumps are capable of transferring a fluid from low-pressure areas to high-pressure zones, from lower to higher locations, and from nearby to distant places.

Whatever the type of pumps, therefore, We always talk about moving fluids from point A to point B. Unlike dynamic pumps (like centrifugal pumps), which increase fluid pressure through acceleration and subsequent deceleration, positive displacement pumps transfer fluid by changing the volume in a pumping chamber.

This type of pump is useful in many industrial applications due to its ability to ensure a constant and controlled flow of liquids. Key areas of use include the chemical and pharmaceutical industries, automotive, oil and fuel sectors, as well as water and industrial fluid treatment.

We at CDR Pompe We want to talk to you about these pumps, their unique features, and their advantages in chemical, agricultural, and other fields.

Positive displacement pumps vs. dynamic pumps: what's the difference?

Dynamic pumps and positive displacement pumps are the two main types of pumps used for fluid transfer. What differentiates them is their operating principle and applications.

The dynamic pumps they work through the kinetic energy supplied to the fluid, which is then transformed into pressure. This type of pump is perfect when large quantities of fluid need to be moved with moderate pressure variations. The volumetric, on the other hand, act by moving a fixed amount of fluid for each working cycle (for example, each turn of a piston or each movement of a diaphragm). These pumps are ideal for applications requiring high pressures and constant flows. In addition to the ability to maintain a constant fluid volume, dynamic pumps work independently of pressure. This is very useful when a constant amount of fluid needs to be guaranteed even if the flow resistance changes.

Neither pump is better than the other. The choice depends entirely on the type of application required.

How does a positive displacement pump work

The operation of positive displacement pumps is based on An intake and discharge cycle. During suction, the fluid enters the chamber through an opening, while during the delivery phase, the chamber reduces in volume, pushing the fluid towards the outlet. Each operating cycle corresponds to a complete rotation of the pump shaft (360°), and the pumped volume is constant and independent of the fluid pressure.

Positive displacement pumps they are often used to handle viscous, corrosive, or solids-laden fluids. This makes them an excellent and reliable solution for many applications, including the food and beverage industry.

Just like the CDR magnetic drive pumps, there are also some variations of volumetric ones. Rotary positive displacement pumps and the Positive displacement reciprocating pumps Both are designed to move a precise volume of fluid continuously. They are differentiated by their operating principle and mechanical configuration.

Rotary and reciprocating positive displacement pumps

Rotary positive displacement pump

Both pumps, therefore, perform the same job but in different ways. Rotary positive displacement pumps utilize the rotational movement of an element (for example, gears, screws, or vanes) to trap the fluid and transfer it from one area to another. During the movement, the liquid is continuously pushed through the pump. The flow rate delivered is independent of the total head and it is instead directly proportional to the rotation speed.

Inside the rotary presses, you can find some operational distinctions:

• Gear pumpthey exploit the action of two gears that, rotating in opposite directions, move the fluid.
• Lobe pumpIn this pump, two rotating lobes create expulsion and suction chambers for the fluid.
• Screw pumps (or twin-screw pumps)The action of rotating screws is used to continuously move the fluid.

positive displacement pump

The reciprocating pump they work through a rectilinear movement of a component (like a piston or diaphragm) that changes the volume of the cavity in which the fluid is trapped. This alternating (or oscillating) movement allows a fixed amount of fluid to be moved with each cycle. This category of pumps is ideal for moving fluid in a constant and controlled manner. Based on the type of element that generates the movement, the alternatives are also divided into subcategories:

• Piston pumpThey use a piston that moves inside a cylinder, which compresses and displaces the fluid. These pumps are very useful for very high pressures and relatively low flow rates.
• Diaphragm pumps: They use a flexible diaphragm that moves back and forth to displace the fluid. This type of pump is often used in applications that require separation between the pumped fluid and the mechanical drive, such as in the food and chemical industries.

Advantages and disadvantages of using a volumetric pump

The Volumetric pumps they offer numerous advantages, making them ideal for applications where a constant and precise flow is essential. First and foremost, they ensure accurate flow regulation, regardless of pressure variations, allowing for precise control of the volume of fluid transported.

In addition, they are particularly suitable for viscous fluids, because their operating principle does not depend on fluid velocity. These pumps also offer high operating efficiency, especially in low and medium flow rate applications. Another strong point is their High pressure generation capability, which makes them indispensable in sectors where high pressure values are required.

Their operating principle also makes them very resistant to wear. This translates to lower maintenance costs and longer lifespan, thus considerable economic savings. Finally, they are also capable of handling very sensitive fluids, which could otherwise be negatively affected by more aggressive and direct pumping actions.

The disadvantages: Energy efficiency and mechanical complexity

In view of the actual and numerous advantages offered by positive displacement pumps, we cannot fail to mention some disadvantages in their use and maintenance. Firstly, their fundamental mechanical complexity makes them more difficult to maintain compared to
centrifugal pumps, especially when using mechanisms such as pistons or gears.

Secondly, they can sometimes be less efficient than other types of pumps, especially when dealing with high speeds or large volumes.

We at CDR Pompe We work with passion, also in 2025, to offer you the best possible fluid management solutions. Industrial, chemists and pharmaceuticals. Our ability to adequately respond to customer requests and our enormous range of pumps have allowed us to become leaders in the process pump industry.

Fill out the form on our website and contact us: together we can find the best solution for your business.

Frequently Asked Questions

What is a volumetric pump and how does the principle of fluid displacement work?

A volumetric pump transfers a liquid by moving a defined volume of fluid in each operating cycle. During suction, the fluid enters the pumping chamber; during discharge, the chamber shrinks in volume and pushes the liquid towards the outlet. The pumped volume remains constant and independent of the fluid pressure.

What is the difference between volumetric pumps and dynamic pumps such as centrifuges?

Dynamic pumps, such as centrifuges, provide kinetic energy to the fluid and convert it into pressure: they are suitable for large quantities of fluid with moderate variations in pressure. Volumetric pumps move a fixed amount of fluid per cycle and are ideal for high pressures and constant flows. None is absolutely superior: it depends on the application.

What are the types of rotary and alternative volumetric pumps?

Rotary volumetric pumps use a rotating element to trap the fluid and include gear, lobe and screw (or double-screw) pumps. Alternative designs utilize a rectilinear motion and include piston pumps, suitable for very high pressures with relatively low flow rates, and diaphragm or diaphragm pumps.

What are the advantages of volumetric pumps for viscous, corrosive, or sensitive fluids?

Volumetric pumps ensure accurate control of flow flow rate even when the pressure varies, and they work well with viscous, corrosive or solid fluids because the operating principle does not depend on the speed of the fluid. They generate high pressures, resist wear, reduce maintenance costs, and also treat sensitive fluids without aggressive pumping action.

What are the disadvantages of a volumetric pump compared to a centrifugal pump?

The main disadvantages are mechanical complexity and efficiency. With mechanisms such as pistons or gears, a volumetric pump is more difficult to maintain than a centrifugal pump. Furthermore, it may be less efficient than other types of high-speed or large-volume pumps, where dynamic pumps are more suitable.

In which industrial sectors are volumetric pumps and diaphragm pumps used?

Volumetric pumps are used in the chemical and pharmaceutical industries, in the automotive sector, in the oil and fuel industry, in the treatment of water and industrial fluids, and in the food and beverage industry. Membrane pumps are chosen when it is necessary to separate the pumped fluid from the mechanical drive, as in the food and beverage sectors chemical.