A contractor was awarded a contract to build a hydraulic system that needed 60 gpm flow at up to 1000 psi, then a controlled flow from 20 down to 3 gpm in 12 sec, then up again to 2200 psi. It then had to return at full speed with a maximum required return pressure of 600 psi. They were told to build the entire system with a total maximum height of 24 in. The width and length of the complete system needed to be as small as possible. The cylinder was not specified or ordered from the contractor.

The circuit was designed and built per the accompanying schematic. The system was tested and inspected by the Dept. of Defense and shipped overseas.

About two months after shipment, the contractor received a call about a problem during start-up. They could not exceed 300 psi from the pump, and the return line filter element kept coming loose and leaking. They also told the contractor that they were able to set the load-sensing adjustment to a maximum of 500 psi and could cycle the cylinder somewhat. They wanted to know what could be causing the two problems.

Any idea what they should do next?

Robert J. Sheaf Jr., is founder and president of CFC Industrial Training, a Div. of CFC Solar, which provides technical training, consulting, and field services to any industry using fluid power technology. Visit www.cfc-solar.com for more information.