Valve Adjustments
Setting hydraulic pressure is an extremely complex and intricate operation and should be
performed only after satisfying the following conditions:
1. Warm the hydraulic oil to 130° F in normal conditons. NOTE: If the normal hydraulic
reservoir operating temperature is substantially above or below 130° F, use that value
instead.
2. Be sure the correct engine speed is used, as the relief valve setting will vary with the
flow rate.
3. Be certain to calibrate the pressure gauge used. Gauge calibration can be lost if the
gauge is subjected to rapidly pulsating pressure for a few seconds. The gauge must
have a proper snubber to read center of pump pressure ripple or erroneous readings
will result.
MAINTENANCE CHECKS
All relief valve maintenance checks are conducted on a SEMIANNUAL BASIS. Check the
relief valves and make the necessary adjustments by the following procedures.
The relief valves used on this hydraulic crane have screw-type adjustment. If it is
determined that a valve is out of adjustment, follow this general adjustment procedure.
Install a good quality 5000 psi gauge in the designated test port locations and proceed with
pressure check and adjustment as follows.
THIS MACHINE USES A PRESSURIZED HYDRAULIC RESERVOIR. THE
PRESSURE MUST BE RELEASED BEFORE ANY HYDRAULIC LINE OR
CONNECTION IS OPENED. Failure to do so will result in substantial loss of oil
and may cause personal injury. The pressure is relieved by turning the reservoir
cap counterclockwise to the first stop. DO NOT turn the cap beyond the first stop
until pressure has been released. This will cause the cap to be blown off the
reservoir with sufficient force to cause personal injury. DO NOT place any portion
of your body above the reservoir cap while relieving pressure or removing cap.
BOOM HOIST & MAIN RELIEFS
Check the boom relief settings as follows:
1.
Operate the boom over relief to warm the oil if necessary.
2.
Attach a calibrated pressure gauge to test port on the inlet pressure port at the valve
bank.
3. Lower the boom completely and continue to boom down with the engine running at
full governed rpm. The relief setting per chart below:
T300-1 BOOM HOIST SET TO:3500 psi
T500-1 BOOM HOIST SET TO:3500 psi
T780 BOOM HOIST SET TO: 4500 psi
BOOM RELIEF ADJUSTMENTS
T300-1_T500-1_T780
Service / Parts
478 P/N 12261-683
REVISED: January 2015
To Next Page
