Hydraulic Filter Elements: Paper or Glass?

filtersHydraulic filter elements divide into two main categories: surface and depth. Surface filters typically have a wire mesh construction like, for example, a suction strainer. Depth filters are constructed from a matrix of fibres. Cellulose (paper), plastic, glass and metal can all be used to construct a depth filter.

Man-made glass fibers are smaller and more uniform than naturally occurring cellulose fibers. When glass fibers are woven into a layer, the result is a more consistent pore structure which captures and retains dirt better (high filtration efficiency). Plus glass’s smaller fiber diameter means there’s more of them in a given … continue reading »

The WORST Contaminate Of Hydraulic Oil: Heat

Mvc-399fA new client consulted me about the hydraulic oil turning black, smells bad and is depositing varnish in the Hitachi EX5600 excavators he is responsible for. These are BIG diggers. Twin Cummins QSK50s with 4 main pumps (250 GPM) on each engine. Bucket capacity is 40 tons. And a 240 ton dump truck is loaded in 6 passes, in around 3 minutes. Well that’s the machine’s performance target anyway, which the operators hit 90% of the time.

When I inquired about the hydraulic system’s operating oil temperature I was told normal operating temperature is 200ºF (93ºC) and the high temperature … continue reading »

What’s the Function of ‘Hoses to Nowhere’?

500HPU3One of our members wrote me with this question:

“On Cat diggers and some other makes they have two hoses off the pumps that are plugged. I call them hoses to nowhere. Some mechanics have told me they are there to reduce spike pressures. And others have said they are to make the pumps run quieter. Can you please tell me which one it is, or are they there for other reasons?”

I can’t confess to knowing the historical reasons for their presence on hydraulic excavators, but these ‘hoses to nowhere’ are in effect, an accumulator. Which means to some … continue reading »