Gear pumps are the most widely used positive displacement pumps in various industries. Due to their simple design, reliability, and ability to pump viscous fluids, they are widely used in sectors such as food processing, pharmaceuticals, oil and gas, and petrochemicals. Despite their numerous advantages, pressure fluctuations pose a significant challenge to their operation. This article describes the design of gear pumps, the causes of pressure fluctuations, and suitable control methods.
What is a gear pump?
A gear pump is a positive displacement pump that uses two (or more) gears to move fluid from an inlet to an outlet. Based on their design, these pumps can be divided into two main categories:
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External gear pump: consists of two equally sized gears that mesh together.
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Internal gear pump: It consists of an internal gear and a smaller internal gear that work together.
Special feature:
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It can transport viscous substances such as oil, tar, and syrup.
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The design is simple and requires little maintenance.
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Under stable conditions, the outlet volume flow is uniform.
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Suitable for medium pressure environments.
Pressure fluctuations in gear pumps
One problem that occasionally occurs with gear pumps is pressure fluctuations at the outlet . These fluctuations can damage downstream system components (such as valves, piping, and equipment connected to the pump) and even impair the performance of the entire system.
Signs of blood pressure fluctuations:
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The needle of the tonometer showed clear changes.
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The water pump and pipes are making strange noises.
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Vibrations of the piping system.
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Fluctuations in the outlet flow and irregular fluid pulses.
Causes of pressure fluctuations in gear pumps
Pressure fluctuations can be caused by a variety of factors, including:
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Flow pulsations:
In positive displacement pumps, the flow rate at the outlet is not perfectly uniform; each rotation of the impeller generates pulsations. This phenomenon leads to pressure fluctuations. -
Gear and bearing wear:
Over time, gears wear down due to constant friction with viscous or corrosive fluids. This wear leads to increased backlash, reduced sealing effect, and ultimately to pressure fluctuations. -
Cavitation or air ingress: When air or gas is introduced into a liquid, this can lead to sudden pressure fluctuations as bubbles
are compressed and released during the cycle. -
Pipe blockage:
Blocked filters or particles in the flow can impede the normal flow of liquid and lead to sudden drops in pressure. -
Incorrect pump selection:
Using a gear pump with a flow rate that is lower or higher than the actual system requirement can lead to unstable operation and pressure fluctuations. -
Errors in pump installation and alignment:
Incorrect alignment of the shaft and connection can cause vibrations and pressure fluctuations at the outlet.
Solutions for reducing and eliminating pressure fluctuations in gear pumps
To improve performance and prevent system damage, you should consider the following measures:
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Use of a pulsation dampener:
By installing a damper at the pump outlet, the pulsations that occur can be absorbed, resulting in a more uniform flow. -
Selecting the right water pump:
Accurate calculation of the required flow rate and pressure, as well as selecting a water pump with the appropriate capacity, are crucial to avoid pressure fluctuations. -
Regular maintenance:
Timely replacement of the lubricating oil, inspection of gears and bearings, and periodic inspection of the filters can extend the service life of the pump and reduce vibrations. -
Preventing air from entering the system:
Properly closing the connections, preventing leaks, and ensuring the correct operation of the pump can prevent air from entering the fluid. -
Pump speed control:
The pump speed can be adjusted using a frequency converter (FC) to avoid sudden fluctuations. -
By optimizing the pipeline design –
for example by reducing sharp corners, eliminating flow obstructions and using suitable valves – the outlet pressure can become more stable.
The effects of pressure fluctuations on industrial plants
Pressure fluctuations in the system not only affect the performance of the pump, but also that of the devices connected to it.
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Constant vibrations shorten the service life of pipes and fittings.
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The constant pressure control valve is defective.
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— Deterioration of the quality of the production process , especially in sensitive industries such as the pharmaceutical and food industries.
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Incorrect operation of the water pump leads to increased energy consumption .
The price of ignoring pressure fluctuations
Ignoring pressure fluctuations in a gear pump can have the following consequences:
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The production line suddenly came to a standstill.
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Maintenance costs have increased .
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The company’s overall efficiency has decreased.
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This leads to damage to the final product.
In conclusion
Gear pumps are among the most widely used positive displacement pumps in various industries. Despite their numerous advantages, such as high durability and the ability to pump viscous fluids, these pumps are also susceptible to pressure fluctuations . These fluctuations are caused by flow pulsations, gear wear, air leaks, blocked pipelines, and unsuitable pump selection.
To resolve this problem, various measures can be taken, including installing shock absorbers, selecting a suitable pump, performing regular maintenance, preventing air ingress, monitoring pump speed, and optimizing pipework. Considering these aspects not only extends the pump’s service life but also improves the overall system efficiency.