Machinery Lubrication

Machinery Lubrication March April 2016

Machinery Lubrication magazine published by Noria Corporation

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ML It is important that the pressure of the shuttle relief valve be set below the charge pump relief valve. If set higher, the excess charge pump fluid will dump through the charge pump relief valve at all times, bypassing the cooler. This can cause the system to overheat. The hot oil shuttle valve and relief valve generally are bolted onto the hydraulic motor. They may also be mounted in a separate block along with the crossport relief valves. Inline Filters The fluid in a hydrostatic loop constantly recirculates, except for the oil flow through the shuttle relief valve. The best filter arrangement is to filter the fluid in both directions on each side of the loop. If filtering is not done in both directions, when the pump fails, the contamination from the pump can go directly into the motor or vice versa. The filters shown in Figure 1 will filter oil as it flows into the motor. If the element becomes contaminated, oil will flow through the spring-loaded bypass check valve. Oil that flows out of the motor will flow through the non-spring-loaded check valve. The filters should have visual or elec- trical indicators to reveal when the elements are contaminated. Charge Pump Suction Filter This filter cleans the oil from the tank to the suction port of the charge pump. It usually is non-bypassing and has a 10-micron rating. The filter should be changed and cleaned on a regular schedule. If it becomes contaminated, the charge and main pump may cavitate. Hopefully, by learning about the different components of hydrostatic drives, you now have a better understanding of these important systems and how they should function. About the Author Alan Dellinger has been a member of GPM Hydraulic Consulting's team of instructors and consultants since 2000. He has 16 years of previous hands-on mechanical, pneumatic and hydraulic troubleshooting experience with International Paper. Alan has trained more than 2,000 electricians, engineers and mechanics throughout Nor th America and the United Kingdom on how to troubleshoot their hydraulic systems. Contact Alan at gpm@ 45% of lubrication professionals use hydrostatic drives or transmissions at their plant, according to a recent survey at

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