Speed Range - A key parameter for selecting a suitable hydraulic gear pump
Definition Of Speed Range And Its Importance In The Selection Of External Gear Pumps
Speed Range Definition:
Speed range refers to the interval between the lowest and highest speeds at which mechanical equipment (such as hydraulic pumps) can operate safely and effectively, usually expressed in revolutions per minute (RPM). It reflects the adaptability and performance stability of the equipment under different working conditions.
The Importance Of Speed Range In Selecting External Gear Pumps Includes:
Ensuring normal pump operation: Operating below the minimum speed may cause insufficient lubrication and vibration; exceeding the maximum speed can lead to mechanical damage and overheating.
Matching system requirements: Selecting a pump with an appropriate speed range ensures system efficiency and stability, as speed directly affects flow and pressure output.
Energy saving and longevity: A suitable speed range helps reduce energy consumption and mechanical wear, extending pump life. Optimal operating speeds can be determined by combining engine and pump power curves for energy-efficient control.
Adapting to varying conditions: Pumps with appropriate speed ranges can handle different loads and speeds, meeting performance needs across diverse operating conditions and preventing frequent failures.
How To Optimize The Performance Of External Hydraulic Gear Pumps
As the core parameter of the external gear pump, the speed range (300-6000rpm) directly determines the optimal working range of the pressure rating and displacement range. Taking the Bosch Rexroth G5 series as an example, its speed-pressure curve shows:
At the rated speed of 1800rpm, it can continuously output 250bar pressure
When the speed is increased to 3000rpm, the maximum pressure needs to be reduced to 180bar
When the speed is lower than 600rpm, the pressure output is unstable and the volumetric efficiency decreases by 40%
The golden rule of displacement matching:
Small displacement pump (1-10cc/rev) such as Eaton Vickers V10 series:
Optimal speed range: 1500-4000rpm
Still maintain 92% volumetric efficiency at 4000rpm
Large displacement pump (50-100cc/rev) such as Kawasaki K3VG series:
Recommended speed: 800-1800rpm
Noise increases by more than 15dB when exceeding 2000rpm
The external meshing hydraulic gear pump is a fixed displacement pump, and its displacement is linearly related to the speed. The higher the speed, the greater the amount of oil discharged per unit time, and the flow rate is significantly improved.
For example, a certain type of pump can reach the maximum displacement at 3500 rpm, while the displacement is correspondingly reduced at a lower speed.
When purchasing, it is necessary to combine the system flow requirements and select a pump type with a suitable speed range to avoid insufficient or excessive flow causing a decrease in system efficiency.
The pressure rating of the gear pump is mainly determined by the mechanical structure and sealing performance, but the speed has an indirect effect on the pressure bearing capacity.
When running at high speed, the internal friction and heat of the pump increase, which may limit the maximum continuous pressure of the pump and affect the service life and reliability.
Low speed is conducive to stable operation under high pressure conditions and reduces the risk of wear and overheating.
For example, the maximum speed of some industrial gear pumps at 250 bar pressure is 3000-4000 rpm, and exceeding this range may damage the pump body.
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External Gear Pump Speed Range: How It Impacts Your Hydraulic System? (Data-Backed Guide)
Did you know? The speed range (300-6000 rpm) of external gear pumps determines their pressure limits, efficiency, and service life:
Low speed (300-800 rpm): Ideal for heavy-duty systems (e.g., steel mills). Kawasaki K3VG maintains 15MPa at 600 rpm but requires viscosity compensation.
High speed (2500-4000 rpm): Best for machine tools. Eaton Vickers V10 achieves 92% efficiency at 4000 rpm, with pressure capped at 21MPa.
Wrong speed = Wasted energy + Costly downtime! Explore our data-driven guide with Bosch, Parker OEM specs to optimize your selection.
Speed Range: 300-800rpmMetallurgy Industry - rolling mill hydraulic
Delivers stable oil flow (10-16MPa) at low speed for roll gap adjustment, ensuring steel slab positioning accuracy.
Speed Range: 300-800rpmMining Machinery - Crusher hydraulic adjustment
Provides high-pressure oil (14MPa) at 500rpm to drive jaw plates, avoiding seal damage from high-speed impacts.
Speed Range: 800-1500rpmAgricultural Equipment - Combine harvester
Drives header adjustment and grain tank at 800-1200rpm (16-21MPa), tolerant to field vibrations.
Speed Range: 800-1500rpmMunicipal Vehicle - Refuse compactor unit
25cc/rev pump @900rpm generates 18MPa for consistent waste compaction.
Speed Range: 1500-2500rpmPlastics Machinery - Injection Molding Machines
Delivers 28-35MPa at 1800-2200rpm for precise mold closing (0.1mm repeatability) and stable screw propulsion. 15-20cc/rev models optimize speed-pressure balance.
Speed Range: 1500-2500rpmDie Casting Equipment - mold cooling
Tandem pump setup: main pump (25cc/rev @2500rpm) provides 30MPa injection pressure, auxiliary pump drives cooling circuit for 5m/s molten metal flow.
Speed Range: 2500-4000rpmAviation Ground Support - Aircraft Test Rigs
Delivers 15-21MPa at 3000-3500rpm with <3% flow pulsation, testing aerospace components for 10,000+ fatigue cycles.
Speed Range: 2500-4000rpmSemiconductor Manufacturing - Wafer Dicing Machine
1.5cc/rev micro pumps maintain 8MPa @3800rpm for ±1μm cutting accuracy.
Speed Range: 4000-6000rpmMachine Tools - spindle cooling
1cc/rev pumps @4500rpm generate 6MPa mist flow (0.5mL/min ±0.1mL accuracy).
Speed Range: 4000-6000rpmMarine Power - Turbocharger Cooling
Twin 1.5cc/rev pumps @5500rpm maintain 7MPa to control turbo temperature at 80℃±2℃.
How to Select Gear Pump Speed Range Based on Equipment Needs?
1. Define Equipment Requirements
Load Type:
High Pressure (>20MPa): Choose 800-2500rpm mid-speed (e.g., Bosch Rexroth G5: 92% efficiency @2000rpm)
High Flow (>50L/min): Use 1000-1800rpm large-displacement pumps (e.g., Parker PGP500, 50cc/rev)
Motion Profile:
Frequent Start/Stop: Limit speed ≤3000rpm (anti-cavitation per ISO 4409)
Continuous Duty: Allow 80% rated speed (e.g., Eaton Vickers V10: 4000rpm max, 3200rpm sustained)
2. Industry Benchmarking
Industry Speed (rpm) Pressure (MPa) Model Example
Construction 1200-2000 16-25 Kawasaki K3VG
Injection Molding 1800-2500 25-35 Bosch Rexroth G3-18
Aviation Ground 3000-4000 10-21 Moog MGG-2
Turbine Lube 4000-6000 ≤10 SKF LGP-3
3. Critical Checks
Minimum Speed: Must > Viscosity Threshold (e.g., ISO VG68 oil requires ≥600rpm)
Maximum Speed: Stay below Cavitation Limit (NPSHr curve per ANSI/HI 9.6.7)
Efficiency Peak: Target Best Efficiency Zone (e.g., Bosch G series >90% @1500-2200rpm)
4. Procurement Tips
Request OEM Data: Ask for Speed-Pressure-Efficiency 3D Maps (e.g., Parker PGF whitepapers)
TCO Analysis: High-speed pumps (>4000rpm) need pre-charged tanks (+15% cost)
FAQs
The speed range of an external gear pump is usually between 400 rpm and 3500 rpm, and some high-performance models can reach more than 5000 rpm. The minimum speed is limited by lubrication and pump structure, and the maximum speed is limited by mechanical strength and heat. The common speed limit of brands such as Bosch Rexroth is 3000-3500 rpm, and the pressure level is around 250 bar.
Gear pumps are fixed-displacement pumps, and the displacement of the pump is linearly related to the speed. The higher the speed, the greater the volume of liquid discharged per unit time, and the flow rate increases significantly. Reasonable selection of the speed range can ensure that the system flow meets the working conditions and avoid insufficient or excessive flow.
Although the pressure is mainly determined by the system load, high speeds increase the internal friction and temperature rise of the pump, causing the seals and mechanical components to bear greater loads, limiting the maximum continuous pressure. Low speed is conducive to stable operation under high pressure conditions and prolongs the life of the pump.
When purchasing, the system flow and pressure requirements should be combined, the minimum and maximum operating speeds of the pump should be referred to, the oil viscosity and the driving equipment capacity should be considered, and the manufacturer's selection table and performance curve should be used for accurate matching. For example, Bosch Rexroth recommends a speed range of 500-3500 rpm and a maximum pressure of 250 bar.
Too high a speed may cause the pump body to overheat, increase mechanical wear, seal failure, and shorten the life of the pump. Too low a speed may cause insufficient lubrication, vibration and noise, and affect the stability and efficiency of the pump.
The speed range of the pump must match the maximum speed and torque of the drive shaft to avoid overspeed or overload. Reasonable matching helps improve system efficiency, reduce failure rate, and extend equipment life.
The speed range of gear pumps of different models and brands varies greatly, and needs to be selected according to specific product parameters. Some metering gear pumps have lower speeds (tens to hundreds of rpm), while industrial pumps are mostly in the range of several thousand rpm. When purchasing, you should carefully check the manufacturer's technical manual and performance curve.
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