TM 5-3810-306-20HYDRAULIC CONTROL VALVE RELIEF SETTING CHECKS AND ADJUSTMENTTOOLS:Pressure gauge (0 to 5000 psi)General mechanic’s tool kit: automotive (5180-00-177-7033)SUPPLIES:NoneEQUIPMENT CONDITIONS: NoneGENERAL:Relief valves are checked and adjustedby causing a given circuit to reach itsprescribed pressure limit (stall). At thispoint, the relief valve opens, returning oilto the reservoir. Hydraulic motor circuitsmay be stalled by preventing rotation ofthe motor shaft prior to actuating thecontrol valve. Cylinder circuits may bestalled by extending or retracting acylinder to its limit of travel.By placing a pressure gauge in theproper line or port, a pressure readingwill indicate the point at which the reliefvalve opens. The needle on the meterface will climb until it reaches the reliefvalve setting. At that point, the needlewill stop climbing and fluctuate,indicating the relief valve is open andreturning oil to the reservoir.Correct relief valve adjustment ismandatory if any hydraulic circuit is tofunction properly. Settings must bewithin tolerances. Therefore,adjustment should be made using thecorrect equipment, after the need foradjustment has been established.The hydraulic system utilizes four valvebanks. Each valve bank has one mainrelief valve limiting maximum operatingpressure of the component(s) in thatcircuit.CAUTIONDo not hold relief valve open for morethan one minute at a time.NOTERelease control lever after takingeach reading and while makingadjustments.NOTEAn accurate 0 to 5000 psi (0 to 34,475kPa/345 bar) pressure gauge shouldbe used when adjusting relief valves.1.ADJUST RELIEF VALVE (1).a. Loosen locknut (2).b. Turn adjusting screw (3) in to increase pressureor out to decrease pressure to obtain desiredrelief pressure as indicated on pressure gauge.CAUTIONDo not overtighten the adjustingscrew (3) or locknut (2).c. Hold adjusting screw (3) and tighten locknut (2).d. Recheck pressure setting.16-54
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