Shimadzu Gear Pump, Bent Gear Teeth
Posted by Doug Hanson - 06/09/09 at 11:09 pmShimadzu gear pump failure: on a Caterpillar dozer. Here are some pictures of a recent gear pump failure. It is a Shimadzu gear pump from a D5C cat. It is the implement pump. This particular Cat has a core drill mounted to the back of it which is supplied oil from the ripper control valve.
Hanson Hydraulics Ltd. Blog article:
Before dissmantling
The main implement control valve has a pilot operated main relief as well as a direct acting work port relief for the ripper down port. Oil from the ripper down port feeds the control valve that operates the functions of the core drill. This control valve also has a direct acting relief.
In an effort to increase available pressure at the core drill, the main relief valve and ripper relief setting was increased. The particular shop that was working on the machine must not have been aware of the relief at the drill. The relief at the drill was the pressure limiting factor, however the two reliefs on the implement control valve were left substantially increased. All was well until implement fuctions were activated and dead headed that did not have work port reliefs.
Gear teeth bent back from excessive pressure
This sudden increase in pressure bent the teeth of the gears back, producing excessive tip clearance. This resulted in a decrease in performance, as well as a decrease in maximum available pressure, as in a dead headed state, the entire volume of oil was bypassing across the gears tip clearance, overheating the oil and eventually blistering the paint on the pump.
Beyond economical repair
Situations like this can be avoided by 1) find out exactly why the pressure won’t increase past a certan level when increasing the main relief setting. The question must be asked, “where is the oil going?” and 2) always be sure to readjust the main relief pressure after making work port pressure adjustments.
The most common over pressure failures on gear pumps are split gear housings or extruded seals or extreme gear housing wear, but on this particular make of pump it seems the weak link is the amount of material at the base of the tooth. I have heard of similar Shmadzu gear pump failures on Komatsu dozers.
Written for Hanson Hydraulics Ltd. Blog
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Thank you for visiting the blog of Hanson Hydraulics Ltd. I hope you find this information on hydraulic repair, design and troubleshooting valuable. If you have any sugestions suggestions or requests, please email me doug@hansonhydraulics.com
February 21st, 2011 at 10:24 am UTC
This is really interesting. Have you seen that problem more than once? I’d be curious what it cost to fix.
On another note, do you have any details on whether an internal or external gear pump is best for a sanitary transfer of milk fluid?
I’m not finding much on the internet besides this gear pump basic description. I need of some more detail if you have any suggestions. Thanks.
February 21st, 2011 at 8:02 pm UTC
Ive seen it twice. This unit was beyond economical repair so a new one was purchased. Due to delivery requirements, a new pump was purchased from a Caterpillar dealer and net price was around $1200.00, pretty pricey for a gear pump.
Pumping milk? No idea what so ever. Does it have to be a positive displacement pump? Cant be a centrfugal pump? There must be something out there in the food industry.