- 4 cracking pressures
SV and SL valves are hydraulic pilot operated check valves in poppet type design which may be
opened to permit reverse flow.
These valves are used for the isolation of operating circuits under pressure, to prevent a load from falling or creeping movements of hydraulically locked-in actuators.
Basically these valves consist of housing (1), poppet (2),compression spring (3), control spool (4) as well as a optional pre-opening ball poppet valve (5).
Type SV (without drain port)The valve enables free flow from A to B, in the
counter direction the poppet (2) is held on its seat by the system pressure, additionally to the spring
force. Through the pressure connection at control port X the control piston (4) is moved to the right.
This pushes the poppet (2) from the seat, then fluid flows from B to A.
Function and configuration
In order to ensure the proper opening of the valve via the control piston (4) a certain minimum control pressure is necessary.
Type SV...A...and SL...A... (with pre-opening)
This valve has a additional pre-opening see hereinafter left configuration. Through pressure
connection at control port X the control piston (4) is pushed to the right. The ball poppet(5.1) leaves
first then the poppet (2) leaves from the seat.
Now the valve may also have a flow from B to A.
Because of the pre-opening there is a dampened decompression of the fluid under pressure to
avoid possible pressure shocks.
Type SL... (with drain port )
The function of this valve is principally the same as the valve SV hereinafter right configuration.
The difference is the additional leakage port Y.
The annulus area of the control piston (4) is separated from port A. The pressure at port A only