TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
ELECTRO-HYDRAULIC SYSTEM - CONTINUED
c.
When oil pressure in circuit is less than relief valve setting, force of spring on poppet keeps poppet in contact with
seat. No oil is allowed to flow to hydraulic tank.
d.
If there is any outside force on work tool, oil pressure at inlet and in spring chamber will increase. If oil pressure in
spring chamber exceeds relief valve setting, oil pressure overcomes force of pilot spring, causing pilot poppet to
move off seat and main poppet to move off poppet seat. Oil then flows through outlet to hydraulic tank.
e.
These line relief valves are engineered to have reverse free flow. If there is a loss of cylinder oil pressure, makeup
oil can flow back through valve outlet and out of valve inlet to prevent cylinder drift.
427-C1836
f.
Adjustment of line relief valve is made by loosening locking nut. To raise pressure adjustment, turn adjustment
screw clockwise. Turn adjustment screw counterclockwise to lower pressure adjustment.
427-C1837
0003 00-176
