Gradall LOED 534A, Service Manual

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MAINTENANCE PROCEDURES - RELIEF VALVES
DISASSEMBLY
The cartridge type service port reliefs used in the Husco valves are of the pilot poppet type with external
adjustment. Any malfunctioning is usually the result of foreign matter lodging between the piston, relief
valve poppet, and check valve.
To s e r v i c e , c l e a n t h e s u r r o u n d i n g a r e a a n d r e m o v e t h e c o m p l e t e r e l i e f v a l v e c a r t r i d g e .
The design, of the pilot poppet and pilot poppet seat provides positive seating and seldom requires any main-
tenance. Therefore, the pilot section, check valve poppet and other internal parts, can be removed from the
cartridge without disturbing the valve setting. Disassemble these parts and examine for foreign matter.
INSPECTION AND REPAIR
Examine the seat in the main valve housing, if grooves or ridges are present, the valve must be returned to
Husco for re-machining.
All seats and seating surfaces should be smooth and free of nicks, scratches or grooves. Examine O-rings and
back-up washers for any damage. Replace damageed or faulty parts. All moving parts should slide, freely
w i t h o n l y s e a l f r i c t i o n p r e s e n t .
If operating difficulties indicate that the pilot poppet is leaking or sticking, remove internal parts of the
p i l o t s e c t i o n a n d f o l l o w s a m e p r o c e d u r e a s a b o v e .
ASSEMBLY
After inspecting andl cleaning, immerse all parts in hydraulic oil and re-assemble. Since pressure setting was
n o t d i s t u r b e d , u n i t c a n b e t e s t e d f o r p r o p e r f u n c t i o n i n g u n d e r a c t u a l w o r k i n g c o n d i t i o n s .
There are several variations to service port relief. However, all are similar in nature regarding service
a n d r e p a i r ( s e e M a i n t e n a n c e P r o c e d u r e R e l i e f Va l v e s , P a g e 7 ) .
TROUBLE SHOOTING - SERVICE PORT RELIEF CARTRIDGE
. Service Port Relief Cartridge
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FIGURE 31
FIGURE 32