SECTION 35 - HYDRAULIC SYSTEM 55
Pilot-operated pressure relief valve with anti-cavita-
tion feature subjected to overload and fully relieving
high-pressure oil
1. Sleeve
2. Poppet valve
3. Pilot valve
4. Pilot valve body
5. Piston
6. Control valve (cylinder) exhaust gallery
7. Cylinder supply gallery
Direct-acting pressure relief valve operation
High-pressure oil in the system is sensed in the cyl-
inder supply gallery and acts on the surface of the
pressure relief valve poppet.
When pressure in the system exceeds the pressure
relief valve setting, the oil pressure lifts the poppet,
allowing excess pressure in the overloaded cylinder
to escape to the drain gallery.
A. Direct acting circuit relief valve
Valve not subjected to overload conditions
B. Direct acting circuit relief valve
Valve subjected to overload conditions
1. Relief valve seat
2. Relief valve poppet
3. Valve pressure adjusting screw
4. Spring
5. Control valve exhaust gallery
6. Cylinder supply oil
Anti-cavitation cylinder resupply oil
Exhaust oil
1 2 3
7 6 5 4
F29543
1 2 3
A
6 5 2
F29544
Exhaust oil
High-pressure system oil
1 2 3
B
6 5 2
F29545
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