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Heat generated in hydraulic systems can be responsible for reduced life of equipment. Current Industry trends look to load-sensing variable-displacement pumps and closed-center valves to combat the problem. A comparison is made between the load-sensing variable-displacement pump with closed-center control valves and the fixed-displacement pump (both wet and dry valve types) with open-center control valves, to determine the heat generation tradeoffs. The use of tanks, lines and cylinders as a heat radiator is considered. Heat generated by high-pressure leakage of driven members is addressed. The primary focus of this paper is on packer and body hydraulics of refuse trucks.

The end use of high-pressure, telescopic, hydraulic cylinders for hoists requires that they undergo integrity testing, an exacting and laborious process. By integrating the mechanical structure and hydraulic power of the test stand with personal computer control and data acquisition, cylinder test data can be directly archived for permanent storage. Automated testing in the cylinder production process has proven to result in greater test repeatability, secure data archival, and reduced test time. The features and benefits of an integrated test stand are discussed, with general information on testing, mechanical design, and computer logic included for insight.