Eaton Electrical PVE19 - Manual (Page 8)

8
Figure 3. Flat Cut-Off Compensator
Compensator Spring
Drain Pump Load
Cross Hole (Open to
Spring Area)
Compensator Spool
Yoke Stroking Piston
Rotating Group
Yoke Spring
Inlet
Outlet
D. Compensator
(Load Sensing Type - “CV”)
Application
A frequent application of pressure compensator pumps is to
supply sevo valves or mechanically operated metering
valves, whose function is to control flow to a hydraulic
actuator (cylinder or motor).
In such circuits it is often desirable that flow be proportional
only to an external valve spool position. This requires a
constant pressure drop across the external valve. (NOTE:
Flow through a valve varies with pressure drop as well as
with valve spool position.)
Pumps incorporating the load sensing feature have a
constant flow characteristic: Flow is constant regardless of
the load pressure.
CAUTION
A relief valve must be used to prevent outlet pres-
sure from exceeding pump ratings if the load is
excessive.
Minimum Pump Pressure
The minimum outlet pressure developed by the pump (no
load) is a function of the compensator spring force versus
the yoke spring force, whichever is greater. (Please note that
external valve spool position (orifice size), has nothing to do
with the minimum outlet pressure of the pump). The orifice
size controls pump rate of flow only. The minimum outlet
pressure will be constant for all settings of the valve spool
orifice and is considered the pressure drop across the orifice
(
n P).