9803/3280
Issue 1
8 - 9
8 - 9
Circuit Descriptions
Section E
Section E
Pilot - Operated Pressure Relief Valve
Operation
Component Key:
A
Service Pressure
B
Poppet
C
Piston
D
Spring
E
Poppet
F
Spring
G
Locknut
H
Cavity
J
Sleeve
K
Exhaust Cavity
L
Cavity
1
Valve at Rest
A.R.V's are positioned in the excavator valve block in order
to relieve excessive pressure in the services as described in
Excavator Valve - ARV Operation
.
When the service is in neutral and there are no excessive
forces acting on the equipment, service pressure at
A
will be
acting on the lower face of poppet
B
and will also be felt
inside the valve via hollow piston
C
.
The force of springs
D
and
F
, combined with the service
pressure acting on the upper faces of poppet
B
and piston
C
, keeps poppets
B
and
E
tightly seated.
The force of spring
F
is adjustable to suit the relevant service
by means of adjuster screw and locknut
G
.
2
Pilot Valve Opens
As service pressure reaches the pilot setting of the valve,
pilot poppet
E
lifts, allowing oil to escape into cavity
H
and
pass down the sides of sleeve
J
into the exhaust gallery
K
.
3
Main Poppet Opens
As service pressure continues to rise and oil escapes from
cavity
L
, the pressure differential between the upper and
lower surfaces of piston
C
causes this piston to rise and
seat on the point of pilot poppet
E
.
Oil continues to escape from cavity
L
but the incoming flow
to the cavity has been cut off. This produces a pressure
drop above poppet
B
, causing the poppet to lift and release
service pressure into exhaust gallery
K
.