Machinery Lubrication

Machinery Lubrication September-October 2019

Machinery Lubrication magazine published by Noria Corporation

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26 | September - October 2019 | www . Va r i a ble - d i s pl a c e m e nt pu mps a re u sed i n hydraulic systems where the f low requirements var y. This usually means the system has several actuators and, depending on the current cycle of the machine, the number of actu- ators moving at a given time will fl uctuate. e most common type of variable-displacement pump is the pressure-compensating pump. Pressure-compensating Pumps Pressure-compensating pumps are designed to deliver only the amount of f low required by the system to maximize effi ciency and avoid heat generation. e compen- sator is adjusted to a pressure somewhat higher than that required to move the system's heaviest load. A pressure-compensating pump will deliver its maximum f low until the system pressure reaches the compensator setting. Once the compensator setting is reached, the pump will be de-stroked to deliver only the amount of fl ow that will maintain the compensator setting in the line. Whenever more fl ow is demanded by the system (such as would occur when an additional actuator begins to move), the pump will increase its stroke to meet the new fl ow demand. Whenever the system fl ow needs to decrease (such as when one or more actua- tors are stopped), the pump stroke is reduced. When the system is stopped completely, the pump stroke is reduced almost to zero. It will stroke only a very small amount or whatever is required to maintain the compensator setting in the line, overcoming any system bypassing or leaks. While a pressure-compen- sating pump is effi cient, the standby pressure remains high. Adjusting Pressure- compensating Pumps Adjusting a pressure-compen- sating pump is quite simple. With all fl ow blocked and the system idle, the compensator valve is adjusted to the When and How to Adjust a Load-sensing Hydraulic Pump HYDRAULICS Jack Weeks | GPM Hydraulic Consulting "The most common reason to adjust a load- sensing valve is because someone unfamiliar with the pump has mistakenly attempted to set the maximum system pressure by adjusting the load- sensing valve instead of the compensator." The compensator and load-sensing valves on a pressure-compensating pump can look almost identical. Load-sensing Valve Compensator

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