The Reliability and Efficiency of Hydraulic Pumps
Even the best-performing hydraulic pumps from top hydraulic gear pump suppliers need to be replaced eventually. Because work and environmental conditions are different on every work site, it can be difficult to place an exact timeframe on how long a pump will last. In order to stay on top of the condition and remaining lifespan of hydraulic pumps, and hydraulic systems overall, it’s important to consider two things: 1) remaining seal life 2) how fast a pump’s efficiency is deteriorating.
Efficiency is the easier of these two criteria to keep track of. If a pump’s performance has been steadily deteriorating or has suddenly declined, then it is probably reaching the end of its lifespan and will need to be replaced to sustain a reliable hydraulic system. The easiest way to judge the deterioration in a pump’s performance is to monitor and compare cycle times (i.e., the speed at which the machine operates).
However, sometimes it is necessary to take exact measurements of a pump’s performance efficiency, which can be quantified by three different categories: volumetric efficiency, mechanical/hydraulic efficiency, and overall efficiency:
• Volumetric flow: Determined by dividing the actual flow delivered by a pump at a given pressure by its theoretical flow. Actual flow is measured using a flow meter. To calculate theoretical flow, multiply the pump’s displacement per revolution by its driven speed. The result will give you the volumetric efficiency at a particular pressure so it will be necessary to take these readings over a range of pressures as the pump may be very efficient at low pressure but very inefficient at higher pressures.
• Mechanical/hydraulic efficiency: Determined by dividing theoretical torque required to drive the pump by the actual torque required to drive the pump. Theoretical torque is measured in Newton meters. Measuring actual drive torque requires a dynamometer.
• Overall efficiency: Determined by multiplying volumetric efficiency and mechanical/hydraulic efficiency.
Volumetric efficiency helps assess the pump’s condition in the field. If there is wear or damage increasing internal leakage, this measurement can help identify whether pump maintenance is required. In addition to mechanical performance, overall efficiency helps determine if hydraulic pump replacement is necessary. To help calculate the drive power the pump requires at a given flow and pressure, you need to know its overall efficiency. If the drive power required increases or decreases, the pump is probably operating less efficiently.
Maximizing Hydraulic System Reliability
A hydraulic pump system must be properly maintained to ensure it remains reliable, but there are other factors that impact reliability. These include temperature; a hydraulic pump is most stable in cooler temperatures. Overheated hydraulic oil will lose its lubricity and become oxidized, causing increased wear on metal parts and potentially hydraulic pump overheating. The ambient temperature of the operating environment needs to be considered as well and regulated using equipment such as forced-air coolers or a liquid-to-liquid cooler.
Any hydraulic pump installation requires a clean environment. Particle contamination is a common cause of equipment failure; high-pressure flow can impact particles in a way they ordinarily wouldn’t react. Therefore, specialized filtration systems are required, such as kidney-loop filtration systems that circulate oil through a filter to maintain a particulate-free flow. Water contamination is another threat; water intrusion and even the slightest amount of moisture and humidity can affect hydraulic fluid and components. Desiccant breathers, absorbent filters, and vacuum dehydrators may be used in a plant to control moisture levels.
For more information on maintaining hydraulic pumps and motors, or to order hydraulic pumps, and other hydraulic component supplies, contact White House Products Ltd. today at +44 (0) 1475-742500.
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