HAWE Hydraulics has released its proportional directional spool valve type PSL in the new nominal size 7. The PSL7 has been designed for applications such as mobile heavy load carrying machines, pile drilling machines, ship and railway cranes, etc. Global certifications for use in explosion hazardous zones allow this valve to be used in oil and natural gas exploration installations, mining and other similar environments.
Like all types in this series, the proportional directional spool valve serves to control the direction of movement of hydraulic consumers and also provides load-independent, stepless control of their speed. It can be fed either via variable displacement pumps or constant pump systems. A special feature of the size 7 design is that a flow of 264 gpm (1,000 lpm) can be fed in via only one inlet section, thereby allowing parallel operation of several functions at full speed. A volume flow of up to max. 105 gpm (400 lpm) is available per function regardless of the load. Valve spools with stepped maximum flow ratings offer a good match to the actual requirement of the consumer without sacrifying the resolution over the stroke. Thanks to the independent selection of the maximum flow rating on the A and B side, identical speeds can be achieved, for example, for moving a differential cylinder in both directions.
Key goals in developing this new construction size also included reduced back pressure to increase energy efficiency. This objective was achieved by flow-optimized design of the ducts. Two return connections have also been provided in the inlet section. The lowest possible control Δp is selected at the flow controller of each valve section same as with the three existing smaller “siblings” of the proportional directional spool valve. In practice, this reduction of the pressure losses results in a noticeably lower fuel consumption and reduced heat build-up of the system, especially advantageous at machines continuously running. This reduces operating costs and saves resources.
The proportional directional spool valve in nominal size 7 is manifold mounting. This enables the individual spool valve sections to be changed easily without the necessity to disconnect the consumer lines. The directional valve can be shifted electrically-proportionally, hydraulically, manually or via a combination of these methods.
Several valve sections can be combined to form a valve bank by means of a base plate combination. A choice of SAE flange or tapped port design is available. A major advantage is that all connections for pump, return and consumers are performed at the rear. Consequently the valve bank only needs a small installation space when the pipes are connected up. Because of the compact design the valve weighs comparatively little (55 lb per section).
Inlet sections for constant pumps or variable displacement pump systems complete the valve bank.