Posted on December 5th, 2016

This is a picture of a balanced relief valve poppet that has a 1/2mm pilot oil hole.

If you examine it carefully, you can see that the hole in the center has been blocked by a piece of debris or dirt in the hydraulic oil. This blockage caused the machine, a medium sized excavator, to stop instantly. Fortunately in this case the default failure was to low pressure. In a poorly designed system it’s not inconceivable that a blockage like this could have resulted in an increase of the relief pressure. This could have resulted in much greater damage to several major components.

In this particular case we managed to diagnose the problem fairly quickly and rectifying it was even quicker, (unlike the previous repairer, according to their invoice!) Pieces of debris like this have resulted in huge invoices for ongoing fault finding, especially with modern electronically controlled machines.

Keeping the oil and filters appropriately clean would have saved our customer at least two invoices, one of them for a great deal of unnecessary parts and labor.

www.hydraulicsolution.com

PS: The other lesson is to choose your repairer carefully.