Cylinder drift is a common problem that can occur with hydraulic systems of all types.
This is something that FPE Seals Cylinder Parts Manager Tim Bone knows only too well and is often offering our customer advice on how to troubleshoot the problem. Here he explains more on how you can get to the root cause of your creeping cylinder.
What is causing a hydraulic cylinder to creep faster than expected?
Often the cylinder on a hydraulic application can creep. The popular assumption for this, is that the problem is due to oil passing over a worn piston seal.
However, Tim explains, “Often customers tell me that even when they have resealed the cylinder several times, it still weeps down.
“In many cases, the more likely cause is that the oil is passing across the spoil, rather than the problem being with the seals.
“A simple way to test this, is to lower the load onto the ground so that the cylinder is not under tension, isolate the power source i.e. the hydraulic unit and relax the pressure in the system.
“You can then remove the hose, from the cylinder port that the direction of the rod is moving in (i.e. if the rod is extending, then remove the hose from the annular side, if the rod is retracting then remove it from the bore side). Place a high-pressure ball valve in the line, attaching the hose to the opposite side of the ball valve.
“Make sure that all connecting joints are tight and leak-proof and clean up any spillages.
“Move the lever of the ball valve to open position. Restart the hydraulic power source and operate the valve block (levers), placing load onto the cylinder concerned.
“If the cylinder shows signs of dropping again, move the lever of the ball valve to the closed position.
“If the cylinder stops creeping, this proves that the fault is in the main valve block, as generally the only seals in a valve block are the ones at each end of the spool, to stop oil from leaking externally.
“Hydraulic spools in valve blocks are a machined precision fit, over time the spools can wear across the surfaces causing oil to pass between the internal galleries. Fitting a standard pilot operated check valve or over centre valve can stop this from happening.
“If the cylinder continues to creep, then the problem is with the internal seals of the cylinder. Once identified these seals can be easily replaced.”
Replacement seals for most applications can be picked up off the shelf. FPE Seals stock and supply a full range of seals, including piston seals for all engineered applications.
If you require any further advice regarding seals and their application, the team of experts at FPE Seals can help you source what you need.