High Volume Hydraulic Pumps
Hydraulic pumps are frequently the hardest working component in their system. When these pumps have to move large volumes of fluid, their design becomes especially important. It can have a significant impact on their performance and efficiency.
Kinds of Hydraulic Pumps
Four kinds of hydraulic pumps make up the pantheon:
Radial Piston Pumps
In addition to being the only pumps able to operate at up to 700 bars, radial piston pumps are also quiet. They’re essential to a large number of hydraulic operations.
Axial Piston Pumps
Axial piston pumps come in two designs: swashplate or bent axis. They accomplish change in fluid direction quickly and without a jolt. Input speeds can be fixed or fluctuating. They’re easy to operate and deliver a fast turnaround.
The most common pump design, gear pumps don’t have a lot of moving parts, so servicing them is easier. They’re also economical and handle contamination other pumps won’t. Gear pumps find their place in open center hydraulic systems, where the fluid flow is continuous.
Providing constant flow, so they’re much less noisy than many other pumps, vane pumps can function at high speed. Most of the time, they can’t operate at pressures above 175 bars, but some can withstand pressures above 300 bars. They play an important role in construction machinery.
Which Hydraulic Pump Has the Highest Volumetric Efficiency?
A measure of the flow a pump has available to do its work, volumetric efficiency is the amount of output the pump actually produces as a percentage of its theoretical production. The higher the percentage the more efficient the pump.
Among the factors affecting volumetric efficiency are leakage and fluid compressibility (ability for volume to be reduced under pressure). These issues can cause the pump to lose efficiency and waste energy as that energy converts to heat.
Of the four major kinds of hydraulic pumps, the radial piston pump offers the highest volumetric efficiency.
Signs of a Sick Hydraulic Pump
When air invades the hydraulic fluid, it causes aeration and cavitation. Aeration results in a loud banging as the air moves through the system and compresses and decompresses. It also can cause the fluid to foam.
The consequences of aeration include lubrication loss, overheating and burning seals. Cavitation occurs when vapor cavities implode under pressure, causing erosion of the metal and fluid contamination.
Preventing damage from aeration and cavitation requires:
• Keeping intake lines in good shape
• Making sure fittings and clamps are tight
• Maintaining a proper fluid level
• Checking for leaky pump shaft seal
Seal damage and fluid degradation can occur if the fluid temperature rises above 180˚F, depending on the fluid’s viscosity grade. It could be considerably lower.
Potential causes of overheating include:
• Low reservoir fluid level
• Reservoir airflow obstructions
• Blocked heat exchanger core
• Internal component leaks
• Aeration and cavitation
Warding off potential damage from overheated fluid calls for:
• Maintaining a correct fluid level
• Keeping reservoir area clear of obstruction
• Checking and replacing cooling circuit components
• Inspecting components that generate heat
• Checking potential aeration and cavitation causes
A hydraulic pump’s slow operation probably results from internal or external leakage. Internal leakage is more difficult to find than external leakage because the cause isn’t visible.
The pressure drop from leakage results in increased heat. As the heat rises, viscosity lowers, creating increased leakage and heat load and pushing the fluid temperature up. And the cycle repeats.
Ways to find and prevent abnormal slowness include:
• Checking for external leakage from hoses, etc.
• Using an infrared thermometer to locate leaking internal components
• Using a hydraulic flow-tester to discover leaking internal components
• Monitoring cycle times and fluid temperature
Finding the Right High Volume Hydraulic Pump
Choosing the best hydraulic pump for a particular application can be a challenge. The advice of an expert can be invaluable. It can mean the difference between lost time and money and a smooth operation.