Piston pump or gear pump—which one should you choose?

The choice between a piston pump and a gear pump should be based on the specific requirements of the application. Piston pumps, despite their higher cost and greater complexity, offer higher pressures, better efficiency, and the ability to regulate flow rate, making them ideal for applications that require precision and high performance. Gear pumps, on the other hand, thanks to their simple design, reliability, and lower cost, are well-suited for applications with moderate pressure and flow requirements.

An analysis of the technical specifications, advantages, and disadvantages of both types of pumps presented in this article should help you make the best decision for your specific hydraulic system. Keep in mind that selecting the right hydraulic pump is critical to the efficiency, reliability, and cost-effectiveness of the entire system.

In power hydraulics, as in any field of engineering, there are no one-size-fits-all solutions—every decision should be based on a careful analysis of the specific application’s requirements and constraints.

Technical specifications of piston pumps

Design and operating parameters

Piston pumps feature a complex design consisting of pistons, cylinders, valves, and drive mechanisms. They can be manufactured as single-acting or double-acting pumps. They are characterized by the following parameters:

• High operating pressure – piston pumps can generate very high pressures, making them ideal for applications requiring high force
• Consistent performance regardless of the pressure and viscosity of the fluid being transported
• High energy efficiency—piston pumps achieve an efficiency of 80–95%
• Capability to operate at variable flow rates—many piston pump designs offer flow rate adjustment

Advantages of piston pumps

1. The pump's performance does not change with variations in the pressure and viscosity of the fluid being pumped
2. The ability to transport virtually any medium, regardless of its physical or chemical properties
3. The ability to achieve high outlet pressure while maintaining a stable flow rate
4. High energy efficiency in the range of 80–95%
5. Precise flow and pressure control

Disadvantages of piston pumps

1. A complex design requiring precise workmanship
2. High purchase and maintenance costs
3. Lower rotational speed compared to other types of pumps
4. The pulsating nature of the flow often requires the use of pulsation dampers
5. Sensitivity to contaminants in the working medium
6. More difficult maintenance due to the complexity of the design

Technical Specifications of Gear Pumps

Design and operating parameters

Gear pumps feature a simple design consisting of a housing and a pair of gears. There are two main types of gear pumps: external-tooth and internal-tooth. Their main specifications are:

• Medium operating pressures—gear pumps typically operate within a pressure range of 175 to 275 bar, depending on their size and design
• Flow rate proportional to rotational speed—the flow rate is directly related to the rotational speed of the drive shaft
• Rotational speeds—depending on the pump size, from 3,000 to 10,000 rpm
• Geometric displacement – from a few to several dozen cm³/rev

Advantages of gear pumps

1. A simple design with a minimal number of moving parts, which reduces the risk of failure
2. Reliability and ease of maintenance
3. Relatively low purchase and operating costs
4. Capability to handle high-viscosity fluids, such as oils, paints, or resins
5. Good performance in medium-pressure applications
6. Low noise levels when properly installed

Disadvantages of gear pumps

1. Lower efficiency at higher pressures compared to piston pumps
2. Limited capacity adjustment—gear pumps typically have a fixed capacity
3. Lower energy efficiency—typically 93–98% at low pressures, decreasing at higher pressures
4. Limited flow control precision
5. Lower resistance to contamination compared to some other types of pumps

Comparison of Performance and Efficiency

Flow parameters

Piston pumps offer a stable flow rate that is independent of pressure, which is a significant advantage in applications requiring precise dosing. Gear pumps, on the other hand, provide a flow rate proportional to rotational speed, making it easier to adjust the flow by changing the speed.

The specific flow rate of a pump is related to its design. For an external gear pump, it can be approximately calculated using the formula:
qp = π m z b h
where:

• m - module
• z - number of teeth on the gear
• b - gear width
• h - tooth height

Energy efficiency

Piston pumps achieve the highest energy efficiency among hydraulic pumps, reaching 80–95%. Gear pumps have slightly lower efficiency, which decreases further at higher pressures. During operation, a gear pump experiences a small loss of fluid, as it is used to lubricate the bearings and both sides of the gears. For this reason, a gear pump constantly loses 2–7% of its efficiency.

Operating pressure range

Piston pumps can operate at significantly higher pressures than gear pumps. While gear pumps typically operate in the range of 175–275 bar, piston pumps can generate pressures exceeding these values, making them ideal for high-pressure applications.

Applications of piston and gear pumps

Piston pumps - main areas of application

Piston pumps are used in industries that require high pressure and precise fluid flow:

1. Hydraulic industry - hydraulic systems requiring high pressures
2. Automotive industry - braking systems, power steering systems
3. Energy industry - turbine lubrication systems
4. CNC machine tools - precise control of tool movements
5. Aviation industry - control systems
6. Medical and food applications - precise liquid dispensing
7. Drilling rigs and hydrostatic systems in the offshore industry

Gear pumps - main areas of application

Gear pumps are used in less demanding applications where low to medium pressure and a constant flow rate are sufficient:

1. Lubrication systems for machines and equipment
2. Oil pumps in internal combustion engines
3. Agricultural and construction machinery
4. Food industry - transport of low-viscosity liquids
5. Cooling systems
6. Transportation of high-viscosity fluids, such as oils, paints, and resins
7. Medium-power mobile hydraulic systems