A company that fabricates oil-field pipes starts with flat steel, rolls it into a round tubular shape, and simultaneously welds the inside and outside surfaces of the joined ends. Tooling removes excess weld material, creating a round pipe that actually looks like seamless pipe. A cutoff station then cuts the pipe coming off the production line to 21-ft lengths. When 12 cut pieces of pipe are collected in a saddle, a hydraulic cylinder quickly extends and dumps all 12 pieces onto a conveyor that takes them to a banding station.

The schematic shows the dump cylinder, control valves, and hydraulic power unit, which is about 50-ft away from the cylinder. The cycle time for the cylinder is quick, and once the gas pressure in the accumulator reaches 2,000 psi, the directional valve shifts to dump the batch of pipes. Again referring to the schematic, flow-control valves are mounted close to the cylinder, and the directional valve is mounted on the power unit.

The dump cylinder started failing after 1 to 1½ months of running two shifts, five days a week. The repair shop reported contamination and dirty, overheated oil as the problem. However, temperatures at the power unit do not exceed 135°F and the oil samples show an acceptable ISO cleanliness code for the components.

Any idea what was causing the problem and how to fix it?


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.