Retrofitting digital hydraulics – An analytical study

Reason for the slow adaptation of new greener technologies is often the need for large modifications in products or systems. Different kind of regenerative pump-motor transformers might give an optimal solution for the energy efficiency of upcoming hydraulic systems, but the authors’ viewpoint is that it will take decades before the technology is going to be widely adopted. On the other hand especially the industrial hydraulic systems have long lifetimes and the large scale of the system often makes it unprofitable to fully rebuild the system for improved energy efficiency.

In order to improve the existing industrial and mobile hydraulic systems in a shorter time range, retrofittable digital hydraulic valve concepts are presented to replace the old proportional and servo valves. In this paper, the advantages of the three different digital valve system configurations are analysed. Configurations include utilization of a pressurized return line and a common regenerative pressure line attached to valve block through logic valves. The steady-state energy-efficiency of a multi actuator system is compared to a traditional proportional LS-system. As the improvements are highly dependent on the system work cycle and power distribution during the cycle, worst-case and optimal improvements are presented as well as additional calculations based on a work cycle presented in literature. Also the possibility to improve productivity and technical challenges in retrofitting are discussed.