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Re: Need lesson in tractorology hydraulics terms
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Posted by Greg D. on February 14, 2001 at 18:33:54 from (209.240.221.72):
In Reply to: Need lesson in tractorology hydraulics terms posted by Rick from Paso on February 13, 2001 at 18:58:14:
Fudd, the term open center and closed center valves go a lot further than a heat build up as you say. True, an open center valve does just as you say. With a positive displacement pump as say a gear or vane, oil is passed directly through the valve body when a function is not selected by shifting a spool. However in a closed center system, it does not allow oil to flow through the valve body thereby requiring a pump of a different type, such as a load sensed piston pump. This will allow the pump to remain on minimm flow until the circuit is selected and thereby sending usually a pilot circuit pressure to the compensator thereby bringing the pump on stroke. Excavator type systems that are now being used on larger wheel loaders. True there are some exceptions to the gear pumps all being positive displacement, open center systems, but I can only think of one machine that uses it. Hope that clears up open center -vs-closed center valves
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