Displacement Range of Internal Gear Pump
Definition of Displacement Range & Its Importance in Internal Gear Pump Selection
Definition of Displacement Range:
The displacement range refers to the volume of fluid an internal gear pump displaces per revolution, typically measured in cubic centimeters per revolution (cm³/rev). It directly determines the pump’s flow capacity and is a critical performance parameter. Internal gear pumps deliver a fixed volume per rotation, making flow rate proportional to rotational speed and ensuring accurate and stable fluid delivery.
Importance in Internal Gear Pump Selection:
Flow Rate – Flow (L/min or GPM) = Displacement × Speed (RPM). A higher displacement pump delivers more fluid at the same speed.
System Compatibility – Must match the hydraulic system’s flow and pressure requirements (e.g., low-displacement pumps for precision applications; high-displacement for industrial machinery).
Efficiency & Heat Generation – Oversized pumps may cause excessive heat due to bypassing; undersized pumps lead to insufficient flow.
Pressure Capability – Displacement affects the pump’s pressure limits (e.g., gerotor-type internal gear pumps typically handle lower pressures than crescent-type designs).
Internal Gear Pump Performance
Small displacement pumps can usually withstand higher pressures. For example, in the Parker PGP series internal gear pumps, small pumps with a displacement of 3 to 6 cm³/rev have a maximum continuous working pressure of 275 bar (about 27.5 MPa), while the maximum pressure of larger displacement pumps (such as 12 cm³/rev) drops to about 220 bar. This is because small displacement pumps have smaller structural dimensions, and their mechanical strength and sealing performance are easier to optimize, and they can withstand higher pressures.
Large displacement pumps have relatively low pressure levels. Due to the increase in gear size and pump body, the increase in sealing clearance and mechanical stress, leakage and wear are aggravated, limiting their maximum working pressure.
The industry generally divides hydraulic pump pressure into low pressure (≤2.5 MPa), medium pressure (2.5-8 MPa), medium-high pressure (8-16 MPa), high pressure (16-32 MPa) and ultra-high pressure (>32 MPa) levels. The pressure level of internal gear pumps is usually concentrated in the medium-high pressure to high pressure range. The smaller the displacement, the greater the possibility of reaching the high pressure level.
The displacement is inversely proportional to the speed. In order to meet the same flow demand, small displacement pumps can operate at higher speeds. For example, the maximum speed of the 3 cm³/rev pump in the Parker PGP series can reach 4000 rpm, while the maximum speed of the 12 cm³/rev pump is limited to about 2400 rpm.
The speed of large displacement pumps is limited by mechanical load and oil suction performance. High speed will increase the risk of wear and cavitation. In particular, large displacement pumps are more prone to insufficient oil suction, resulting in performance degradation and shortened life.
Generally, the recommended maximum speed of internal gear pumps is in the range of 1500 to 3000 rpm, and the specific value varies with the displacement and design.
Select displacement according to system pressure: If the system pressure is high (≥30 MPa), a small displacement pump is preferred to ensure mechanical strength and sealing performance to avoid leakage and increased wear.
Match displacement according to flow and speed: When the flow demand is large, a large displacement pump can be selected to run at a lower speed to reduce wear; when the flow demand is small and fast response is required, a small displacement pump is selected and the speed is increased.
Consider working conditions and medium characteristics: For high-viscosity media, it is recommended to use a pump with moderate displacement and low speed to ensure oil absorption performance and stability.
Refer to authoritative product parameters: For example, the hydraulic IGP series provides detailed displacement, pressure, speed and efficiency data. When selecting, the manufacturer’s technical manual should be strictly followed to ensure that the pump operates under rated conditions.
Recommended Internal Gear Pumps
Single Gear Pump For KOMATSU PC75UU-2 Excavator
Double Gear Pump For CATERPILLAR E305.5 E306 E308 Excavator
Triple Gear Pump For KOMATSU 3-5 Ton Excavator
Internal Gear Pump Displacement Range Guide: How to Select the Right Gear Pump For Your Machine?
Selecting the right displacement range of an internal gear pump is a critical factor in hydraulic system design and procurement. Displacement directly affects pump flow rate and pressure capacity, impacting overall efficiency and system stability. For example, the industry-leading Hydraulic IGP series offers displacements from 3.6 ml/rev to 251.7 ml/rev, suitable for applications ranging from precision machinery to construction equipment, agricultural machinery, and industrial automation. Accurate displacement matching optimizes energy consumption, reduces operational costs, and enhances system reliability while minimizing maintenance.
Need a gear pump that fits your exact displacement and pressure requirements?
Displacement Range: 3.2–10 cm³/revMedical Equipment - Dental Chair Hydraulic
Powers smooth chair movement (10–20 bar) without vibration.
Displacement Range: 3.2–10 cm³/revEnergy & Environmental - Solar Wafer Cutting
Supplies slurry at 5 cm³/rev for <1μm cutting tolerance.
Displacement Range: 10–40 cm³/revIndustrial Automation - Robotic Arm Hydraulic
Powers joint rotation with 15 cm³/rev pump (<50ms response).
Displacement Range: 10–40 cm³/revAgricultural Machinery - Combine Harvester
Provides 220 bar steering pressure for rough terrain.
Displacement Range: 40 – 100 cm³/revMining Equipment - Roadheader Cutter Head
Twin 55 cm³/rev pumps deliver 320 bar for 160kW cutter motor.
Displacement Range: 40 – 100 cm³/revPort Equipment - Gantry Crane Slewing
Enables 0.1°/s slewing of 200-ton loads.
Displacement Range: 100 – 250 cm³/revSteel & Metallurgy - Continuous Casting Machine
Twin 150 cm³/rev pumps deliver 2000 L/min at 150 bar for mold oscillation, critical for slab surface quality.
Displacement Range: 100 – 250 cm³/revHeavy Transport - Rocket Transporter Leveling
Achieves ±0.05° leveling for 1000-ton transporters in 3 mins.
How To Choose The Appropriate Displacement Range According To The Equipment Requirements?
Identify system flow requirements
The flow required by the equipment directly determines the displacement of the pump. The displacement (cm³/rev) multiplied by the pump speed (rpm) is the theoretical flow.
When designing, the minimum design flow, average flow and peak flow must be considered to ensure that the pump can meet the requirements under all working conditions.
For example, an industrial automation equipment needs to supply oil at a stable rate of 30 L/min. If the maximum speed of the pump is 1500 rpm, the displacement is about 20 cm³/rev (calculation formula: displacement = flow / speed).
Determine the system pressure rating
The displacement selection must meet the pump’s rated pressure higher than the system’s maximum working pressure to avoid over pressure damage.
Small displacement pumps usually support higher pressures (up to 30 MPa or more) and are suitable for high-pressure precision equipment; large displacement pumps have relatively low pressure levels and are suitable for high-flow and low-pressure conditions.
For example, the hydraulic IGP series 8 ml/rev pump has a rated pressure of up to 315 bar, while the large displacement 160 ml/rev pump has a pressure of about 210 bar.
Consider the speed range of the pump
The displacement and speed are inversely proportional. The flow demand can be met by adjusting the speed or displacement.
High speed is suitable for small displacement pumps to obtain the required flow, but too high speed may cause wear and cavitation.
The maximum allowable speed provided by the manufacturer should be referred to during design to ensure the life and stability of the pump.
Taking into account the characteristics of hydraulic medium and working conditions
The viscosity, temperature and medium characteristics of hydraulic oil affect the efficiency and life of the pump. It is necessary to select a pump model and displacement suitable for the medium.
For high-viscosity liquids, it is recommended to use a pump with moderate displacement and low speed to ensure oil absorption performance and stable operation.
Refer to authoritative product parameters and design manuals
Preliminary screening of pump type and displacement is carried out in combination with the manufacturer’s pump type curve, performance parameters and industry design specifications.
For example, brands such as Parker, Bucher, and Duplomatic all provide detailed displacement, pressure, and speed matching tables.
FAQs
Internal gear pumps generally have displacement ranges from about 3 cm³/rev up to 250 cm³/rev. For example, Bosch Rexroth’s PGH series covers 20.1 to 250.5 cm³/rev, suitable for applications from precision machinery to large industrial equipment.
Selection depends on system flow and pressure requirements. Displacement multiplied by speed equals flow. Small displacement pumps suit high-pressure, high-speed applications; large displacement pumps fit high-flow, low-speed conditions. Refer to manufacturer datasheets (e.g., Parker, Duplomatic) to ensure rated pressure and speed meet system demands.
Smaller displacement pumps generally support higher pressures (up to 30 MPa or more) due to compact structure and better sealing, while larger displacement pumps have relatively lower pressure ratings mainly limited by mechanical strength and leakage.
Displacement is inversely related to speed. Small displacement pumps can operate at high speeds (up to 3000 rpm) to meet flow requirements, while large displacement pumps are limited to lower speeds to reduce wear and cavitation risk.
Small displacement (3–10 cm³/rev) suits precision machinery and instrumentation for stable pressure and flow; medium displacement (10–40 cm³/rev) is common in industrial automation and agricultural machinery; large displacement (40–250 cm³/rev) fits construction machinery and large industrial equipment.
Displacement can be calculated by q=2πrKZBm2q=2πrKZBm2, where Z is number of teeth, B is tooth width, m is module, and K is displacement compensation factor. For practical selection, refer to standard model parameters from manufacturers.
When purchasing, the displacement range should be reasonably matched based on the system flow, pressure and speed requirements, combined with the parameters of authoritative brand products, to avoid excessive or too small displacement causing increased energy consumption or insufficient performance, thereby improving system efficiency and reducing maintenance costs.
Enpower Your Machine Business Now!
Welcome to consult installation, maintenance and care, after-sales, price and other issues, we will reply you as soon as possible.
Support customization and distributor.