Having gone through quite a few sites and reading through several threads, can someone confirm whether or not I am understanding this correctly?
In an OC system the system pressure stays relatively low when a function is engaged due to the fact that there is relatively no internal resistance within the circuit as the there is "free" flow between P and T or P and PB. The flow rate is relatively fixed but the resistance applied by the inertia of the load against the ram is what causes the measurable pressure increase within the system. Once the work is done, as in returning the spool to neutral, the pressure drops back down to some fairly small level.
That is putting it in my own words after reading the following excerpt from a thread on a talk.newagtalk.com forum:
"...1- the pump is usually a gear-type pump with a constant or "fixed" displacement,
2-the gear pump puts out a constant volume (fixed displacement) of oil for every revolution,
3-the pumped oil goes through a system of "open" valves that do not internally restrict or divert the flow of oil until the valve is activated, so the hydraulic system stays at a relatively low pressure until a valve is activated.
5- The pressure rise in the system is caused solely by the resistance of the hydraulic work to be done (i.e., the weight of the disk harrow against the hydraulic cylinder raising it)
6- when the work is done, the open center valve is returned to neutral, and the oil flow through the valve is unrestricted once again. The pump's flow doesn't change from neutral to full pressure; just the pressure in the system changes..."
