Dry Hydraulic Valve?

The only place I have heard of this application is on Garbage Trucks to extend pump life and reduce fuel cost.

It is as you explain and works very well I am told.

Gresen (Now part of Parker) discussed the Dry Valve at their Training Class I attended in 1976. You might try the Parker web site and look at the Gresen Division.

The farm equipment maker Massey Ferguson used this principle in the hydraulic pumps on their equipment starting in about 1955. A conventional piston pump with inlet and outlet poppet-valves was immersed in the closed oil reservoir. The inlet valves were opened only when hydraulic pressure was needed. Tremendous energy savings were achieved with high output when needed.

'Engineers' warned you can't block off the suction to a positive displacement pump and predicted rapid failure of the pumps. The pumps often worked 20 years or more without any maintenance.

Carefull! If you let a piston pump cavitate it is dead meat. If you don't want to pump against a relief valve you could always use a pilot activated check valve to avoid this.

Your absolutely right but..... this application is only for a fixed displacement GEAR pump!

Skelly wrote:

"Carefull! If you let a piston pump cavitate it is dead meat. If you don't want to pump against a relief valve you could always use a pilot activated check valve to avoid this."

All Dry Valve installations I am familiar with are on pumps that supply Open Center circuits that allow flow to Tank if the Actuators are not being operated. That means there is low back pressure at full pump flow and practically no back pressure when the pump inlet is restricted to lubrcation flow (1.5-3 GPM).

No Back Pressure, No Bubbles Crashing, No Pump Damage occurs due to the almost complete reduction of the pumps rated flow with a Dry Valve setup.

I have never tried one on any design Piston Pump since a circuit with a Load Sensing feature would be equal to or better than blocking inlet flow. Load Sensing on a Prssure Compensated Variable Volume pump eliminates the need for added energy input while the circuit is idle.