When a relief cartridge is adjusted using the test
relief and flow control assembly. Loosen the
casting, only its cracking pressure (initial opening
lock nut on the assembly and turn the adjusting
pressure) is adjusted because a very low volume of
screw clockwise to increase pressure, counter-
oil is forced through the relief poppet. When the
c l o c k w i s e to reduce the pressure. One turn of
same cartridge is installed in the pilot valve it is
t h e adjusting screw will change the pressure
subjected to much higher flow from the pump. If
approximately 600 psi (42,184 kg./cm. 2) on the
t h e relief pressure setting of this cartridge was
475.
checked in the machine the pressure reading on
7. Dump the bucket fully, hold over relief and read
the gauge could vary as much as 800 psi (56,25
t h e gauge. If the pressure is incorrect adjust
k g . / c m . 2 ) . Because of this, a cartridge must be
the bucket dump relief cartridge.
checked and adjusted in a test casting.
8. Power down on the boom, hold it over relief and
read the gauge. If the relief pressure is incor-
PRESSURE SETTINGS
rect, adjust the boom down relief cartridge.
175
CIRCUIT
NOTE: The bucket dump and boom down relief
2200 psi 50 psi
Main relief
cartridges should be checked only after the main
(157 3.5)
(in machine)
relief has been checked and adjusted.
2600 psi 50 psi
Boom up
CAUTION: Do not work under the bucket or
(182 3.5)
(in test block)
boom mechanism while the boom is in the raised
2600 psi 50 psi
Bucket up
position.
(162 3.5)
(in test block)
IMPORTANT: Do not adjust overload reliefs in
1750 psi 50 psi
Boom down
the machine. Use a test casting and follow the in-
(122 3.5)
(in test block)
structions given below.
1750 psi 50 psi
Bucket down
(122 3.5)
(in test block)
PROCEDURE FOR SETTING
O V E R L O A D RELIEF CARTRIDGES:
OPERATING TIMES
Install the overload relief in the test casting as
Check the time necessary to perform each hy-
shown in the diagram. Use a port-o-power or simi-
draulic operation of the machine. If the operation
lar device that will develop the necessary hydraulic
times do not agree with the following list, see the
pressure.
pages listing problems, causes, and remedies. The
checks are to be made with an empty bucket, the
Adjust the relief cartridge until the gauge indi-
engine at high idle, and hydraulic fluid at operating
cates the correct cracking pressure.
temperature.
TIME (Seconds)
OPERATION
175
6.5
Boom Raise
(From ground level to max. height)
4.1
Float Down
(From max. height to ground)
2.5
Bucket Rollback
(Full dump to full back)
1.9
Bucket Dump
(Boom raised way -
full roll back to
full dump (against stops)
[ 23 ]
