While considering a comment I wanted to make in another forum, I had to stop and consider my basic understanding of hydraulics. Some basic information that I have regarding how hydraulics work, that once seemed clear enough to me, all of a sudden became more fuzzy. Basically, there is what I think I know, and then there is reality. And being aware that reality is rather more complicated then my simple understanding of how hydraulics work, I'd like to try and fill in, maybe just a bit, the gaps in that knowledge base.
I assume in the case of tractors in general, that system PSI is held constant by means of a pressure compensator, regardless of Flow rate or Engine RPM. If system pressure can be maintained at a set working value, I then assume that a maximum quantity of (Work = force x distance), can also be accomplished regardless of Flow rate or Engine RPM.
Example. If a FEL is rated to pick 1000 LBS maximum to full height, then so long as operating PSI is maintained, that FEL should be able to lift that Maximum load of 1000 LBS to full height regardless of Flow rate or Engine RPM. The difference being the time required to move that force through the maximum distance. (Lift Height).
Thus, the ability to do work remains constant where the (Power = Work/Time) is variable.
Power is therefore dependent on flow rate, and flow rate is dependent on the pumps capacity to produce flow, which is in turn is dependent upon the Engines RPM's.
It then follows that two different hydraulic configurations could produce the same amount of work, but not necessarily the same amount of hydraulic power. The importance of which comes into play where a given piece of equipment requires a set amount of Power in order to operate effectively.
This is my general understanding of how hydraulics work. Can someone confirm, deny or help fill in the gaps here. I realize not every hydraulic system is built exactly the same. So I tried to keep this a general as I could. The million foot view if you will.