Hello guys, I wanted to adjust the relief valve on my Komatsu PC27R-8 and bring it up about 100psi. Looking in the shop manual, it references the "LS" valve, "PC" Valve and the Main Relief valve with adjustment procedures on all three. I get the concept of the main relief valve, but can someone explain what the other two valves do? From the shop manual: LS valve adjustment If the APLs value is not the one indicated, adjust the LS valve (1) as follows: 1 - Disconnect the tube (2). 2 - Loosen the lock nut (3) and turn the adjusting screw (4) To INCREASE pressure, turn in a CLOCKWISE direction. To DECREASE pressure, turn in a COUNTER CLOCKWISE direction. Each turn of the adjusting screw (4) varies the pressure by about 13 bar (13 kg/cm³). 3- Lock the nut (3). Nut: 31±3.5 Nm After the adjustment, check the setting of the LS valve (1) following the procedure used for the test. REGULATION OF THE PC VALVE (PC27R-8) If the engine speed decreases when an increase pressure or delivery is requested, or when the speed the working equipment is low, even though the en gine speed, the delivery pressure and the LS differen tial pressure are all normal, the PC valve (1) should be regulated as follows: 1 - Loosen the check-nut (2). 2- Turn the adjustment screw (3). If the working equipment speed is low, turn the screw (3) in a CLOCKWISE direction to INCREASE the torque absorption of the pump. If the engine rpm suffer an abnormal drop, turn the screw (3) in a COUNTER-CLOCKWISE direc tion to DECREASE the torque absorption. 3 - After adjustment, tighten the check-nut (2). Main Relief valve: 1. Adjustment of the main relief valve If the pressures measured for the working equipment and machine travel do not fall within normal values, adjust the main relief valve (1) as follows: 2 - Loosen the lock nut (2) and rotate the adjusting screw (3). To INCREASE pressure, turn in a CLOCK WISE direction. 3 - Lock the nut (2). To DECREASE pressure, turn in a COUN TER-CLOCKWISE direction. Each turn of the adjusting screw (3) varies the pressure by about 125 bar (128 kg/cm²). Nut: 59±10 Nm After adjustment, check the adjustment of the main relief valve with the same procedures as used for the measurements.
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