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Several years ago when I owned a large hydraulic repair shop, we received defective power steering cylinders off of a popular Clark forklift truck to be repaired. The Clark dealer would give us 8 to 12 cylinders at a time. Some leaked externally around the rod seal area, some had large dents in the outer tube, and some were scarred internally. This required replacing the inner tube, piston, or both.
We mounted the cylinders in a lathe and cut through the weld to remove the blind end cap so we could remove the rod and piston assembly. After repairing or replacing parts, we reassembled, welded, and tested the assemblies, usually in batches of 8 to 12 units. I always insisted that nothing was allowed to leave our shop without testing, documentation, and stamping our job number on the repaired item.
We subsequently received some few complaints and warranty returns for leaking rod seals. However, when we tested the cylinders to see where they leaked, we could not get them to leak at any pressure. We would give the customer a rebuilt exchange at no charge and put the questionable cylinders in with the next batch to be repaired.
The dealer called one day and insisted we go to one of his customers who purchased one of our “leaking” cylinders and installed it on his truck. When I arrived, the customer showed me a puddle of oil on the floor and wanted us to fix the problem. I cleaned up the oil mess and wiped the cylinder down, and asked their fork truck operator to drive around doing his job of moving stock for about a ½ hour and come back to where I was waiting. I then inspected the truck and could not find any oil leaking anywhere—but there sure was a puddle on the floor when I arrived.
The cylinder seemed to leak overnight, but not when the lift truck was being used. What do you think was the source of the mystery leak?
Find the Solution
Think you know the answer to this month’s problem? Submit your solution by e-mailing Mindy Timmer. All correct solutions submitted by July 5, 2016 will be entered into a random drawing for a $50 gift card. The winner will be notified, and his or her name will be printed in a future issue. Only one gift card will be awarded to any participant within a calendar year.
Congratulations to Keith Hills, of Fisher-Hills Machinery, Sweetwater, Tex., who won our May puzzler by having his name picked from those who correctly answered that problem. A $50 gift card is in the mail to him.
Solution to Last Month’s Challenge: Hoses Pull Away From Fittings
When a hydraulic hose pulls out of its fittings, there normally are only a few causes. If the hose is installed in a straight line without any slack, pressure cycles that cause the hose to contract reduce its effective length, thereby creating a tensile force that tends to pull the hose away from the end fittings. The other primary cause would be hose fabrication error. In this case, the technicians were trained in hose fabrication and installation, so neither of these causes seemed apparent at first.
However, we found that no one knew about measuring the crimp diameter of the fitting to verify the quality of the hose assembly. We found that the crimping dies were worn by more than 0.020 in. As a result, the connections were under crimped, causing the failures.
Looking for parts? Go to SourceESB.
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