Hydraulics Pro Club member Rich Catalo sent me this tragic story:
“We deal with a very large dock and dredge company. They have many pieces of hydraulic equipment from different manufacturers. The last call I received was due to a tech who removed a hydraulic cylinder that was in need of a reseal. The tech did OK removing the cylinder but failed to cap off the hydraulic hoses with proper plugs.
He stuffed shop towels in the hose ends instead. The cylinder was reinstalled and the hydraulic hoses reconnected. But the tech forgot about the shop towels and ran the … continue reading »
In response to my previous post about troubleshooting hydraulic cylinder drift, a couple of our members thought the influence of valve-spool configuration on cylinder drift warranted discussion. Charlie Field from Perry Slingsby Systems in the UK sent me this message:
“By far the most common reason for cylinder drift is the DCV controlling it. Closed to actuator spools almost always leak pressure to both service ports. If you effectively plug the actuator lines with gauges you will see something like 30% to 50% of the “P” line pressure in the actuator lines.”
This CAN be a problem with closed-center … continue reading »
A popular misconception about hydraulic cylinders is that if the piston seal is leaking, the cylinder will drift down. Fact is, if the piston seal is completely removed from a double-acting hydraulic cylinder, the cylinder is completely filled with oil and its ports are plugged, the cylinder will hold its load indefinitely – unless the rod-seal leaks.
What happens under these conditions – due to the unequal volume either side of the piston, is fluid pressure equalizes and the cylinder becomes hydraulically locked. Once this occurs, the only way the cylinder can move is if fluid escapes from the cylinder … continue reading »