different-types-of-hydraulic-pumps-and-their-uses

Introduction

Hydraulic pumps convert mechanical energy into hydraulic energy by moving fluid under pressure. They form the heart of hydraulic systems in industries ranging from construction and agriculture to aerospace and manufacturing. Understanding pump types, their internal mechanisms and performance characteristics is essential for selecting the right unit and optimizing system efficiency.

Hydraulic Pump Fundamentals

Operating Principles

Hydraulic pumps create a vacuum at the inlet that draws fluid into the pump chamber. Mechanical elements then displace this fluid through an outlet under pressure. The incompressibility of hydraulic fluid ensures nearly all input mechanical power is converted into fluid flow and pressure.

Positive vs Non-Positive Displacement

  • Positive-displacement pumps maintain a near-constant volume per cycle. Types include gear, vane, piston, screw and gerotor pumps.

  • Non-positive-displacement pumps, such as centrifugal types, rely on imparting kinetic energy via impellers. Their flow varies with pressure and they are limited to lower-pressure, high-flow applications.

Classification of Hydraulic Pumps

Hydraulic pumps are grouped by their internal design and displacement characteristics:

  1. External Gear Pumps

  2. Internal Gear Pumps

  3. Vane Pumps (Fixed and Variable Displacement)

  4. Axial Piston Pumps (Swashplate and Bent-Axis)

  5. Radial Piston Pumps

  6. Screw Pumps

  7. Gerotor (Orbital) Pumps

  8. Centrifugal Pumps

  9. Diaphragm Pumps

  10. Peristaltic Pumps

1. External Gear Pumps

External gear pumps use two identical, intermeshing gears inside a housing. Fluid is carried in the spaces between gear teeth from inlet to outlet.

  • Displacement type: Fixed

  • Maximum pressure: 160–200 bar

  • Advantages: Simple construction, low cost, robust against contamination

  • Disadvantages: Pulsating flow, volumetric losses at high pressure

  • Typical uses: Industrial lubrication circuits, low- to medium-pressure hydraulics

2. Internal Gear Pumps

Internal gear pumps feature a smaller “idler” gear driving around the inside of a larger gear. A crescent-shaped partition separates suction and discharge zones.

  • Displacement type: Fixed

  • Maximum pressure: 200–250 bar

  • Advantages: Smoother flow, quieter operation, better suction lift

  • Disadvantages: Higher cost, limited maximum speed

  • Typical uses: Fuel delivery, plastic injection machines, mobile equipment

3. Vane Pumps

Vane pumps employ a rotor with sliding vanes that trap and move fluid as the rotor turns within an eccentric cavity.

  • Displacement types: Fixed and variable

  • Maximum pressure: 150–160 bar

  • Advantages: Relatively smooth flow, adjustable displacement (variable types)

  • Disadvantages: Sensitive to contamination, vane wear over time

  • Typical uses: Power steering, medium-pressure mobile hydraulics, machine tools

4. Axial Piston Pumps

Axial piston pumps contain multiple pistons arranged parallel to the drive shaft. A swashplate sets the piston stroke to control displacement.

  • Displacement types: Fixed and variable

  • Maximum pressure: 350–500 bar

  • Advantages: High pressure capability, excellent efficiency, precise control in variable displacement models

  • Disadvantages: Complex design, high manufacturing precision required

  • Typical uses: Excavators, injection molding presses, hydrostatic transmissions

5. Radial Piston Pumps

Radial piston pumps have pistons arranged around a drive shaft, moving in and out radially to displace fluid.

  • Displacement type: Fixed

  • Maximum pressure: 400–550 bar

  • Advantages: Very high pressure, exceptional durability, low noise

  • Disadvantages: Large footprint, highest cost among positive-displacement types

  • Typical uses: Test stands, high-pressure industrial presses, marine steering

6. Screw Pumps

Screw pumps use two or more intermeshed screws on parallel shafts to transport fluid axially through the housing.

  • Displacement type: Fixed

  • Maximum pressure: 80–120 bar

  • Advantages: Nearly pulsation-free flow, high volumetric efficiency, tolerant of viscous fluids

  • Disadvantages: Limited maximum pressure, sensitive to shaft alignment

  • Typical uses: Central lubrication systems, hydraulic elevators, oil transfer

7. Gerotor (Orbital) Pumps

Gerotor pumps consist of an inner rotor and an outer rotor with one extra tooth. Fluid is trapped and carried in expanding and contracting cavities.

  • Displacement type: Fixed

  • Maximum pressure: 150–200 bar

  • Advantages: Compact size, low noise, minimal pulsation

  • Disadvantages: Moderate efficiency, not ideal for heavily contaminated fluids

  • Typical uses: Automotive power steering, compact hydraulic power units

8. Centrifugal Pumps

Centrifugal pumps use a rotating impeller to add kinetic energy to fluid, which is converted to pressure in a volute or diffuser.

  • Displacement type: Non-positive

  • Maximum pressure: ≤ 20 bar

  • Advantages: High flow rates, simple design, low cost

  • Disadvantages: Flow drops sharply with pressure increase, cavitation risk

  • Typical uses: Water supply, cooling circuits, low-pressure fluid transfer

9. Diaphragm Pumps

Diaphragm pumps use a flexible membrane driven by mechanical or hydraulic actuators to move fluid.

  • Displacement type: Fixed

  • Maximum pressure: ≤ 80 bar

  • Advantages: Handles corrosive and abrasive fluids, leak-free operation

  • Disadvantages: Limited flow rates, pulsating output

  • Typical uses: Chemical dosing, wastewater treatment, acidic fluid transfer

10. Peristaltic Pumps

Peristaltic pumps squeeze a flexible tube with rotating rollers to propel fluid inside the tube.

  • Displacement type: Fixed

  • Maximum pressure: ≤ 15 bar

  • Advantages: Complete fluid isolation from pump, self-priming, gentle shear

  • Disadvantages: Low pressure capability, tube wear requires periodic replacement

  • Typical uses: Metering of slurries, sterile fluid transfer, medical infusion

Comparative Overview

Pump Type Displacement Pressure (bar) Flow (L/min) Efficiency (%) Key Applications
External Gear Fixed 160–200 5–500 80–85 Lubrication, low-pressure systems
Internal Gear Fixed 200–250 5–400 85–88 Fuel systems, plastics machinery
Vane Fixed/Variable 150–160 20–300 85–90 Mobile hydraulics, power steering
Axial Piston Fixed/Variable 350–500 5–1000 90–95 Heavy machinery, injection molding
Radial Piston Fixed 400–550 5–200 92–96 Test benches, high-pressure presses
Screw Fixed 80–120 50–2000 88–92 Lube systems, oil transfer
Gerotor (Orbital) Fixed 150–200 1–200 85–88 Compact hydraulics, steering units
Centrifugal Non-positive ≤ 20 100–20000 60–75 Water, coolant, low-pressure needs
Diaphragm Fixed ≤ 80 1–100 60–70 Chemicals, sludge, paint spraying
Peristaltic Fixed ≤ 15 0.1–50 50–60 Metering, sterile fluid handling
 
 

Selection Criteria

  • Required pressure and flow rates for actuators and motors

  • Fluid cleanliness and filtration level (ISO 4406 standard)

  • Fluid viscosity, temperature range and chemical compatibility

  • Duty cycle, speed and duty profile (continuous vs intermittent)

  • Installation space, noise constraints and cost of ownership

Materials and Construction

  • Pump housings typically use cast iron, steel or aluminum alloys

  • Rotors, gears and pistons are hardened steel or stainless steel for wear resistance

  • Seals and diaphragms use NBR, Viton, PTFE or EPDM based on fluid compatibility

  • Peristaltic tubing employs silicone, neoprene or thermoplastic elastomers

Maintenance and Troubleshooting

  • Monitor fluid cleanliness and change filters (5–10 µm rating) regularly

  • Perform vibration and temperature analysis to detect bearing or cavitation issues

  • Inspect seals, diaphragms and tubing for wear or leaks

  • Record performance data (flow, pressure) for predictive maintenance

Future Trends

  • Electrically driven pumps with integrated variable frequency drives for energy savings

  • IoT-enabled condition monitoring and cloud analytics for predictive upkeep

  • Development of bio-based hydraulic fluids and low-viscosity lubricants

  • Advanced composite materials for lighter, corrosion-resistant pump components

Conclusion

Selecting the optimal hydraulic pump involves balancing pressure, flow, efficiency and compatibility with fluid and environmental conditions. Gear and vane pumps excel in simplicity and moderate pressure, while piston and radial designs meet high-pressure, high-precision demands. Screw, gerotor, diaphragm and peristaltic pumps address niche requirements like low-pulsation, chemical handling or sterile transfer. A well-matched pump extends system life, enhances safety and maximizes operational efficiency.

Visit QTE Technologies to choose from a wide range of hydraulic pumps from trusted brands around the world, at competitive prices and with the best quality. We, a global MRO provider, serve customers in over 180 countries. Established in 2010, we offer over 1 million products for every industry and engineering discipline. Additionally, you can reach us anytime via 24×7 chat support, phone, WhatsApp or email. Discover what our valued customers have to say about our services on our dedicated review page.

Post Author By QTE Technologies Editorial Staff (with a solid background in both technical and creative writing - accumulated 15+ years of experience).