This paper discusses the benefits in efficiency realized by using distributed hydraulic control valves in load holding applications. Most load holding machines such as Telescopic material handlers and truck mounted cranes have a hydraulic system where the control valves are mounted remotely to the actuators. Because of this the vehicle must mount load holding devices with high parasitic losses, such as counterbalance valves, directly on the cylinders. These high parasitic losses increase the heat load and reduce the overall efficiency of the system. To improve efficiency in this type of vehicle, electrically controlled distributed valves with independent meter in and meter out capabilities can be mounted directly to the cylinder. Since the control valve is mounted directly to the cylinder, the control valve itself becomes the load holding device so the counterbalance valves are no longer needed. In support of the efficiency improvements and heat load reduction opportunities that exist on load holding applications, there will be a review of the existing hydraulic system in load holding applications, as well as a discussion of the design and capabilities of a system using electronically controlled distributed valves. The energy improvements will be supported with data and energy calculations taken from a typical lift cycle on a Telescopic Material Handler.
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