TM 5-3810-306-20
HYDRAULIC CONTROL VALVE RELIEF SETTING CHECKS AND ADJUSTMENT
TOOLS:
Pressure gauge (0 to 5000 psi)
General mechanic’s tool kit: automotive (5180-00-177-7033)
SUPPLIES:
None
EQUIPMENT CONDITIONS: None
GENERAL:
Relief valves are checked and adjusted
by causing a given circuit to reach its
prescribed pressure limit (stall). At this
point, the relief valve opens, returning oil
to the reservoir. Hydraulic motor circuits
may be stalled by preventing rotation of
the motor shaft prior to actuating the
control valve. Cylinder circuits may be
stalled by extending or retracting a
cylinder to its limit of travel.
By placing a pressure gauge in the
proper line or port, a pressure reading
will indicate the point at which the relief
valve opens. The needle on the meter
face will climb until it reaches the relief
valve setting. At that point, the needle
will
stop
climbing
and
fluctuate,
indicating the relief valve is open and
returning oil to the reservoir.
Correct
relief
valve
adjustment
is
mandatory if any hydraulic circuit is to
function properly. Settings must be
within
tolerances.
Therefore,
adjustment should be made using the
correct equipment, after the need for
adjustment has been established.
The hydraulic system utilizes four valve
banks. Each valve bank has one main
relief valve limiting maximum operating
pressure of the component(s) in that
circuit.
CAUTION
Do not hold relief valve open for more
than one minute at a time.
NOTE
Release control lever after taking
each
reading
and
while
making
adjustments.
NOTE
An accurate 0 to 5000 psi (0 to 34,475
kPa/345 bar) pressure gauge should
be used when adjusting relief valves.
1.
ADJUST RELIEF VALVE (1).
a. Loosen locknut (2).
b. Turn adjusting screw (3) in to increase pressure
or out to decrease pressure to obtain desired
relief pressure as indicated on pressure gauge.
CAUTION
Do not overtighten the adjusting
screw (3) or locknut (2).
c. Hold adjusting screw (3) and tighten locknut (2).
d. Recheck pressure setting.
16-54
