Pilot - Operated Pressure Relief Valve Operation - jcb 214e Service Manual

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Section E
8 - 9
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
9803/3280
Hydraulics
Circuit Descriptions
Purchased from www.WorkshopManuals.co.uk
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.
Section E
8 - 9
Issue 1