Straight Talk About Bent Hydraulic Cylinder Rods

BentRodIn Chapter 13 of Insider Secrets to Hydraulics, I explain how to check the straightness of a hydraulic cylinder rod and calculate allowable run-out. This is an essential task when repairing any hydraulic cylinder, because if a bent rod gets put back in, the life of the rod seal(s) is compromised and the cost of the repair largely wasted.

I also explain that bent rods can, in many cases, be successfully straightened and re-used. Provided they can be straightened to within the allowable tolerance. One of our members who works for a cylinder repair company, sent me his counter … continue reading »

You Can’t Fix Stupid. But You Can Avoid Hydraulic Failures Due To Memory Lapse!

Hydraulic Maint HandbookHydraulics 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 »

One Important Fact About Hydraulic Spool Valves

Hydraulic Solenoid Valve (Bosch Rexroth)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 »