Case Study Of Greenco Cable Cylinder Returned Under Warranty For Evaluation

What at first appeared to be a cable tensioning issue, turned out to be an alignment issue in the application!

Greenco issued a return authorization for a rodless cable cylinder which was under warranty, and was reportedly leaking air at the cable seal. Upon receipt of the cable cylinder, the first thing we noticed is that the nylon jacket on the cables was noticeably worn down one side. Our initial thoughts were that the customer might not have tensioned the cables properly after installation, and that the lack of tension might have caused the cables to rub against the pilot washers, wearing out one side of the coating on the cables. This would result in a leak at the cable seal because the cable seal would not be able to seal against the severely damaged cable coating. Upon disassembly we did find that the cable seals were very loose fitting over the severely worn cables. This all seemed consistent with the hypothesis that the customer might not have tensioned the cables properly after installation.

However, it was then that we noticed that one of the sheaves (pulleys) had been severely damaged on one side. The thrust washer had completely worn into the side of the sheave, creating a counter-bore where there normally was not one. That was when we realized that the issue could be due to the application itself. It could be that the cylinder is installed in such a way that the trolley is constantly pulled to one side, away from the center-line of the cylinder. This would explain why the cable & sheave are both wearing out prematurely on one side.

We went ahead and replaced the cables under warranty, as a customer consideration, even though we suspected that the application was the cause. We also replaced the worn sheave under warranty as customer consideration. We then returned the worn sheave to the customer with the repaired cable cylinder, so that they could see what had happened. The evaluation provided to the customer alerted them to our findings, and we recommended that the end user should ensure that the trolley is not being pulled to one side in the application. Just in case the cables were not tensioned properly, in addition to the suspected pulling issue, we also recommended that the end user should properly tension the cables after unit is securely mounted. We provided them with page 6 of the Greenco catalog for the cable tensioning specifications. The customer made the recommended changes to their cable cylinder application and they are now running smoothly!

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