Vane Pump vs Gear Pump

Want to choose a reliable power component for your device but are unsure which one, a vane pump or a gear pump, is truly suitable for you? This article will compare and analyze the differences systematically between vane pumps and gear pumps. From working principle to practical application, we provide you with clear selection references.

Vane Pump vs Gear Pump: Working Principle

How does a Vane Pump Work?

A vane pump is a type of positive displacement pump. It is mainly composed of rotor, blades, stator, and oil distribution plate. When the hydraulic motor drives the rotor to rotate at high speed, the blades are pressed tightly against the inner wall of the stator under the action of centrifugal force.

The inner surface of the stator is not a regular circle. It has a contour with a regular variation. This structure allows adjacent blades to enclose a sealed chamber together with the rotor, stator, and oil distribution plate. The volume of the chamber will change according to the rotational pattern of the rotor.

When the sealed chamber rotates along with the rotor to the expansion section of the stator contour, the volume of the chamber increases gradually. A negative pressure environment will be formed inside the chamber.

At this moment, the oil in the fuel tank is drawn into the chamber smoothly through the suction port under the action of atmospheric pressure.

As the rotor continues to rotate, the sealed chamber filled with oil will enter the contraction section of the stator contour. At this time, the chamber space continues to shrink, and the pressure of the internal oil increases continuously after being squeezed.

When the pressure reaches the system’s requirement, the high-pressure oil is discharged through the oil outlet. This provides power for the hydraulic system.

Depending on the structure, vane pumps can be classified into single acting and double acting types.

• The stator and rotor of a single acting vane pump are arranged eccentrically. After each rotation of the rotor, the sealed chamber only completes one oil suction and pressure cycle. You can change the displacement by adjusting the eccentricity.
• The stator and rotor of the double acting vane pump are concentric, and their contours are distributed symmetrically.  The sealed chamber will complete two oil suction and discharge actions within one rotation of the rotor. The radial force of the double acting vane pump is more balanced and the operational stability is stronger.

How does a Gear Pump Work?

The gear pump is also a type of positive displacement pump. It mainly consists of a pair of meshing gears, a pump body, and an end cap.

The motor drives the driving gear to rotate, and the driving gear then drives the driven gear to rotate synchronously. The tooth tips of the gears are tightly attached to the pump body and end cover. The tooth groove and these components together form multiple independent sealed spaces.

When the gear teeth are disengaged, the sealing space between the teeth expands and negative pressure is formed inside. Under the action of atmospheric pressure, the oil in the tank will be sucked in smoothly and fill the entire tooth groove.

As the gears continue to rotate, the grooves carrying the oil will move to the area where the oil is being pressurized. At this point, the gear teeth begin to mesh. The interlocking teeth will continuously squeeze the space inside the tooth groove and reduce the volume of the sealed space gradually.

Under the action of pressure, the oil pressure increases and flows out eventually through the oil outlet. The tooth surfaces at the meshing points of the gears can strictly separate the oil intake area and the oil pressure area. This prevents the backflow of the oil effectively.

According to the different meshing methods of gears, gear pumps are mainly divided into two types: internal meshing and external meshing.

• The internal meshing gear pump is composed of a large and a small gear. The small gear is installed inside the large gear. It is the driving wheel that drives the large gear to rotate in the same direction.

The internal gear pump is also equipped with a crescent shaped partition in the pump body to separate the oil suction area from the oil discharge area.

• The external meshing gear pump is composed of two gears of the same specification. These two gears are installed in parallel. When the motor drives the driving gear to rotate, the driven gear rotates synchronously in the opposite direction.

Vane Pump vs Gear Pump: Flow Characteristics and Pulsation

Vane Pump

The flow output of the vane pump is stable with low pulsation. This characteristic is due to its unique structure and working method. The sealed chambers have a smooth transition in volume changes.

From the expansion phase of oil absorption to the contraction phase of oil pressure, there are no significant abrupt changes throughout the entire process. Therefore, the output flow rate of the vane pump can be maintained continuously and stably without significant fluctuations.

Gear Pump

The flow output of the gear pump shows periodic pulsation. This is determined by the transmission characteristics of gear meshing.

The gear pump achieves oil suction and discharge through the meshing rotation of a pair of gears. When the gear teeth disengage and enter the oil suction area, the volume of the tooth groove will increase. When the gear teeth enter the oil-pressing area and start to mesh, the volume of the gear groove decreases suddenly.

This volume change will cause periodic peak and valley fluctuations in the oil output flow rate. Although the pulsation amplitude of internal meshing gear pumps is usually lower than that of external meshing types, their basic pulsation cannot be eliminated.

Vane Pump vs Gear Pump: Working Pressure

Vane Pump

The vane pump is suitable for medium pressure conditions. The blades are tightly attached to the inner wall of the stator under the action of centrifugal force. Combined with the precise sealing of the oil distribution plate, it can reduce the leakage of high-pressure oil effectively.

Many standard models of vane pumps have a rated pressure between approximately 150 and 200 bar. By enhancing the wear resistance of the blade material and optimizing the contour of the stator curve, the vane pump can also be applicable to high pressure working conditions.

Gear Pump

The gear pump operates mainly within the range of low to medium pressure. It achieves sealing through the gap between the gears and the pump body as well as the end cover. The pressure bearing capacity of this gap seal is limited. Some models of gear pumps can also withstand high pressure during design.

The gear pump has a strong ability to impact pressure. Under the sudden overload conditions, the simple structure of the gear pump can still maintain high reliability.

Vane Pump vs Gear Pump: Noise

Vane Pump

The operation noise of the vane pump is very low. During the operation of the vane pump, the liquid is drawn in and discharged continuously through the sealed chamber. This makes the liquid flow smoother and more continuous, thereby reducing noise caused by fluid impact and pulsation.

Under normal operating conditions, the operating noise of a vane pump can usually be controlled at around 65dB. Some vane pumps that have been optimized for noise reduction can even be as low as around 60dB.

Even under high and medium pressure, the noise increase of the vane pump is relatively gentle. There will be no significant sudden noise changes. At the same time, it can avoid interference with the operational accuracy of peripheral devices caused by high-frequency noise.

Gear Pump

The noise of gear pumps is relatively high. The gear pump transmits power through the rigid meshing of a pair of gears. The meshing and disengagement process between gear teeth will generate periodic mechanical impacts.

This impact will cause the gears to vibrate on their own and also cause the pump body to resonate. Then the gear pump will produce obvious mechanical noise.

In addition, the tooth slot volume of the gear pump changes in a stepwise manner. During the process of oil suction and discharge, the flow rate and pressure of the oil will fluctuate instantaneously, which is also prone to cause fluid noise.

Normally, the operating noise of a gear pump is around 75dB. The low-pressure type gear pump generates relatively low noise, but it is generally around 70 dB.

However, you can alleviate the noise by installing a simple soundproof cover. You can also use it outdoors or in scenarios where noise requirements are not strict.

Vane Pump vs Gear Pump: Efficiency

The Efficiency of the Vane Pump

The vane pump has a high energy utilization efficiency. The blades are tightly attached to the inner wall of the stator, which can reduce the internal leakage of high-pressure oil effectively.

Under normal medium and high pressure conditions, the volumetric efficiency of the vane pump is approximately 85% to 95%. The sliding friction resistance between the blades and the rotor slots is relatively small, and the mechanical efficiency usually remains at 85% – 90%. The overall efficiency of the vane pump can reach 80% to 88%.

The high efficiency features of vane pumps can reduce motor energy consumption and operational costs for you.

The Efficiency of the Gear Pump

The structure of gear pumps is simple, and the transmission loss between gears and bearings is relatively small. Under low pressure and medium low speed conditions, the mechanical efficiency of gear pumps can reach 80% to 85%.

However, the gap seal of the gear pump is prone to leakage, which leads to a decrease in volumetric efficiency. Under low pressure conditions, the volumetric efficiency of the gear pump is about 80% to 85%, and the overall efficiency can reach 70% to 85%.

Under medium and high pressure conditions, both the volumetric efficiency and overall efficiency of the gear pump will decrease.

Vane Pump vs Gear Pump: Applicable Medium

Vane Pump

The core components of the vane pump are matched precisely and have strict requirements for parameters such as the purity and viscosity of the medium. Vane pumps are capable of handling very thin fluids as well as liquids of medium thickness and viscosity.

The clearance between the components of the vane pump is extremely small. If the oil contains solid impurities such as metal debris and dust, it is very easy to scratch the inner wall of the stator and wear the tip of the blade.

Therefore, you need to use a medium with high cleanliness and regularly replace the filter element.

Gear Pump

The gear pump has a stronger compatibility with media and a wider range of applications. It can transport media with a very wide viscosity range. The gear pumps are particularly suitable for transporting fluids with high viscosity or those with a certain thickness.

The clearance of the gear pump is relatively large. Even if the oil contains a small amount of fine impurities, it is not easy to experience sticking or severe wear.

You can use gear pumps in harsh working conditions where the cleanliness of media is difficult to guarantee, such as agricultural machinery and mining equipment.

Vane Pump vs Gear Pump: Maintenance

The Maintenance of the Vane Pump

The structure of the vane pump is complex. Its core components have high coordination accuracy and require stricter maintenance.

In daily life, you need to keep the cleanliness of the medium and monitor the changes in pressure and noise during operation.

During regular maintenance, you need to disassemble and inspect the wear status of the blades, the condition of the sealing surface of the oil distribution plate, and replace aging seals in a timely manner.

During the assembly process, you should pay attention to the balance of force on the components. The maintenance of vane pumps requires high professional skills from operators.

The Maintenance of the Gear Pump

The structure of the gear pump is simple and it has a small number of components. In daily life, you only need to clean the oil suction filter regularly and observe the vibration and noise changes of the pump body.

The disassembly process of the gear pump is simple during troubleshooting. The assembly process of gear pumps does not require complex precision calibration. You only need to make sure that the gear and shaft are tightly matched, and the coaxiality of the coupling meets the standard.

The gear pump requires low professional skills from maintenance personnel. You can complete basic maintenance with simple training.

Vane Pump vs Gear Pump: Applicable Scenarios

The Application of the Vane Pump

Vane pumps are mainly used in fields that require high operational stability and noise.

For instance, in the industrial manufacturing field, vane pumps are commonly used in the hydraulic systems of equipment such as CNC machines, precision machining centers, and injection molding machines.

The stable and low pulsation flow characteristics of the impeller pump can prevent the impact of pressure shock on equipment operation. At the same time, its low noise feature is also suitable for the precise production environment of the workshop.

You can also use vane pumps in scenarios that require high cleanliness and hygiene standards for the medium, such as food and beverage production, pharmaceutical industry. The vane pump can be applied to low viscosity media with qualified cleanliness standards, and its precise structure is unlikely to cause contamination or damage to the materials.

The Application of the Gear Pump

Gear pumps are more suitable for harsh working conditions, heavy load requirements, or cost sensitive applications.

The hydraulic systems of construction machinery such as excavators, loaders and agricultural tractors widely adopt gear pumps. These devices are used for long periods of time in dusty and impure environments such as outdoors, mines, and fields.

In this environment, gear pumps are less prone to jamming faults and can adapt to frequent start stop and load fluctuations.

In industrial medium transportation, gear pumps are good at transporting high viscosity media, such as crude oil, lubricants, and resins in the petrochemical industry.

In addition, gear pumps can also be used in low-pressure and low precision scenarios such as small presses, lifting platforms, and ordinary industrial lubrication systems.

Vane Pump vs Gear Pump: Advantages and Disadvantages

Vane Pump

Advantages of the Vane Pump

Stable Operation: The flow output pulsation of the vane pump is extremely small, and the radial force is balanced. It can provide smooth power for the hydraulic system.

Low Noise: The vane pump does not have rigid meshing or sudden volume changes during operation. The expansion and contraction of the blades in the rotor slot is gentle. This makes the operation noise of the vane pump low.

High Efficiency: Under medium pressure conditions, the volumetric efficiency and overall efficiency of the vane pump can be maintained at a high level. Its precise sealing structure can reduce leakage and help lower the energy consumption of the motor.

Variable Displacement: Some models of vane pumps can adjust their displacement by changing the relative position of the stator and rotor. You don’t need to install additional auxiliary devices to accurately match the power requirements of different load scenarios.

Disadvantages of the Vane Pump

Weak Anti-Pollution Ability: The core components of the vane pump have high coordination accuracy and small gaps, and they have strict requirements for the cleanliness of the working medium. Tiny impurities in the medium can easily cause the blades to get stuck or lead to component wear.

Complex Structure: Compared to gear pumps, vane pumps have a more complex structure and higher procurement costs. Its later maintenance requires professional technicians to operate. And the replacement cost of precision components for vane pumps is relatively high. The overall maintenance cost is higher than that of gear pumps.

Gear Pump

Advantages of the Gear Pump

Simple Structure and Low Cost: The gear pump has a small number of components and the transmission path is direct. The cost of gear pumps is lower than that of vane pumps, and it is a cost effective type of hydraulic pump.

Strong Adaptability: The gear pump has a large clearance and loose requirements for oil cleanliness. It can be applied to fluids of various viscosities and those containing a small amount of impurities. The gear pump can operate stably in harsh environments such as dust and vibration.

Easy Maintenance: The disassembly process of the gear pump is very simple during maintenance. The replacement of easily worn parts such as gears, bearings and seals is also very simple.

Flexible Installation: The compact structure of the gear pump occupies a small space and offers flexible installation options. You can use it in equipment with limited installation space, such as construction machinery and agricultural machinery.

Disadvantages of the Gear Pump

Significant Flow Pulsation and Loud Noise: The gear pump transmits power through the rigid meshing of gears. This will generate flow fluctuations and noise inevitably.

High Pressure Efficiency Decline: The sealing performance of gear pumps will decrease under high pressure conditions. The high pressure oil is prone to leakage through gaps, which will lead to a decrease in volumetric efficiency.

Limited Adjustment of Displacement: Most gear pumps are of the constant-displacement type, with a fixed and unchanging displacement. It cannot adjust the output flow dynamically according to load changes. If you want to adapt to different load scenarios, you may need to install a flow control device.

To handle continuous high pressure, manufacturers of hydraulic power units often integrate custom sintered gear pump components to optimize internal flow control while ensuring long-term durability.

Vane Pump vs Gear Pump: How to Choose

When choosing a hydraulic pump, you need to consider the following aspects:

• System working pressure
• Operating noise and flow stability
• The working medium used
• Initial budget and long-term operation and maintenance budget.
• Do you need to adjust the output flow rate?

If you need a system that runs smoothly and quietly, the working pressure of the system should be stable within the medium pressure range. And you have enough budget. Then you can prioritize choosing a vane pump.

If your budget is limited and you need easy maintenance. The working environment of the equipment is harsh, and the medium may contain trace impurities or high viscosity. The system operates within the medium and low pressure, or it needs to be able to withstand high impact pressure. And you can accept flow pulsation and noise. The gear pump is your best choice.

You can make a quick comparison based on the table below.

FAQs

What are the Differences in Seal Selection Requirements between Vane Pumps and Gear Pumps?

The vane pump is suitable for clean, medium to low viscosity oil. Conventional seals made of nitrile rubber (NBR) or polyurethane can meet the sealing requirements for most working conditions.

Gear pumps can be adapted to high viscosity, low impurity or corrosive media. The seals need to have greater wear resistance and corrosion resistance. You can choose FKM or PTFE materials.

What Factors Limit the Displacement Adjustment Range of Variable Vane Pumps?

The displacement adjustment range of variable vane pumps is mainly affected by the maximum eccentricity of the stator and rotor, blade length, and oil viscosity.

The eccentricity determines the upper limit of the displacement. Exceeding this threshold will accelerate the wear of the blades. The length of the blade limits the volume of the sealed chamber. Low viscosity can cause leakage, you need to narrow down the adjustment range.

What Causes the Sharp Whistling Sound when the Vane Pump is Operating?

When the vane pump produces a sharp whistling sound, it is due to cavitation inside the pump chamber.

When the suction side pressure is lower than the saturation vapor pressure of the current temperature of the oil, the oil will vaporize and form bubbles. After entering the high-pressure area, the bubbles quickly burst, producing high-frequency hydraulic shock and harsh noise.

The specific causes include excessive resistance in the oil suction pipeline, a clogged filter element, a low oil level in the tank, or inappropriate oil viscosity. These issues will disrupt the pressure balance on the suction side and lead to cavitation noise ultimately.

What Special Treatment should be done for Shutdown Maintenance of Gear Pumps after Long-Term Transportation of High Viscosity Media?

Before the power cuts off completely, you need to drain all the remaining medium from the pump. Then, inject low viscosity cleaning oil to flush the inside.

Alternatively, you can have the pump circulate a low viscosity cleaning solution for a short period of time before it stops running.

After disassembly, you need to inspect the seals and other components and replace them in time.

What is the Impact of the Gear Module on the Output Pressure and Flow Rate of Gear Pumps?

When the gear module increases, the gear strength becomes higher. It can withstand a greater output pressure and the displacement will also increase accordingly.

Gears with a small modulus are suitable for low-pressure scenarios. If the modulus is large, it is suitable for medium and high pressure working conditions.

Final Thoughts

By this point, we believe you have gained a clear understanding of the characteristics of vane pumps and gear pumps. A suitable hydraulic pump can make your system run more reliably.

If you have any further questions, please feel free to contact us. We can also provide you with professional customized services.