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HomeIntroductionThe Simple TestThe Most Basic BasicsLet's Talk HydraulicsBack-Engineer This!BattlefieldKaboomLibraryNews ArchiveBla-BlaimerContactsGuestbook |
     About a month ago a reader from the US sent me an email that made my jaw drop - in his letter John described an emergency repair performed on the main pump of his Koehring 6611 excavator, and now I am officially declaring that this overhaul is, by far, the baldest and most insane pump repair I've ever seen or heard of in my entire career!

   One of the pistons of the main double pump lost a slipper, and since an overhaul estimate was fourteen grand in parts alone, the quick, cheap and, I must say, most ingenious solution was - to open a thread in the damaged barrel bore and plug it with a threaded piece of rod!

   And it worked! Like a charm it did! Obviously the flow pulsation during high regimes was present, so after 30 hours of operation a bladder accumulator was installed in the P line, which took care of 90 percent of the noise and vibration. Last time I heard from the man the excavator had done eight more hours of service since the accumulator introduction. I don't know if the machine is still working, but I do hope the man contacts me if his unconventional creation fails!

   I was honest with John when I told him that, although I found the idea of solving a damaged bore problem by plugging it a brilliant avant-garde  invention I would never think of, the unit wouldn't last long, because when an axial piston pump wears down to the point where piston shoes start slipping off of the pistons - there isn't much you can do to make it last longer without replacing old parts with new ones. It's amazing that the pump didn't disintegrate when the slipper came off in the first place (apparently the machine was stopped just in time)!

   In any case - everybody should know that it is possible to make an axial piston pump work with one of the barrel bores plugged - and for this radical discovery alone the man deserves praise and standing ovation! Unfortunately there are no pictures of the plugged bore, so these few pics John took to identify the parts are the only images there are.

   To all regular IH readers - take this knowledge, and use it wisely... To John - I truly wish your pump last for at least ten thousand hours!!!
Koehring excavator
Hydraulic Pump
Shoeless piston
Rotary group
Accumulator connection
Bladder accumulator