ENGINEMAN 1 & C(low speed) spring. Maximum speed control is ef-fected by the action of the high speed (small)flyweights acting against a heavy (high speed)spring. (See figure 3-16.)Mechanical governor faults usually manifestthemselves in speed variations; however, not allspeed variations indicate governor faults. Whenimproper speed variations appear do thefollowing:1. Check the load to be sure that speedchanges are not the result of load fluctuations.2. If the load is found to be steady, check theengine to be sure all cylinders are firing properly.3. Make sure there is no binding in the gover-nor mechanism or operating linkage betweengovernor and engine, and that no binding existsin the injector control rack shaft or its mountingbrackets. If you find no binding anywhere andthe governor still fails to control the engine prop-erly, you may assume the governor is worn orunfit for further service until the unit has beencompletely disassembled, inspected, and rebuiltor replaced.121.23Figure 3-16.—Mechanical governor control mechanism.Adjustment procedures for the replacement ofany governor are listed in the manufacturer’sinstruction manual and should be followed withparticular attention given to the precautions listed.OVERSPEED SAFETY DEVICESMechanical overspeed trips depend on the cen-trifugal forces developed by the engine and shouldbe maintained in good working condition. Afaulty overspeed device can endanger not only theengine but also personnel if the engine explodesor flies apart because of uncontrolled speed.The engine instruction manual contains infor-mation as to the speed at which the overspeed issupposed to function. Most overspeed trips areadjustable. Prior to making any change in the ad-justment of the overspeed trip, determine if theengine did not trip out for some reason other thanthe action of the element of the overspeed trip.It is highly advisable that you first check the ac-curacy of the tachometer and then test theoverspeed trip. All spring tension adjustments andlinkage adjustments to an overspeed trip arecritical. Instructions given for making these ad-justments are found in the manufacturer’s instruc-tions manual and must be followed.Hydraulic overspeed trips are extremely sen-sitive to dirt. Dirt or lacquer-like deposits maycause a trip to bind internally. The speed sensitiveelement must be kept clean and so should all partsof the linkage and mechanisms incorporated inthis speed sensitive element. When paintingaround the engine, the painter should be cau-tioned against allowing paint to fall on joints,springs, pins, and other critical points in thelinkage.All linkage binding should be eliminated. Ifparts are bent, badly worn, improperly installed,dirty, or if their motion is restricted by some otherpart of the engine, the trip will not functionproperly. On occasion the drive shaft of theoverspeed trip may be broken and prevent rota-tion of the flyweight and the overspeed trip.Insufficient oil in the hydraulic trip may beanother source of this problem. Oil should bemaintained at the level specified in the instruc-tion manual.The cause of any malfunction should be deter-mined and eliminated. This will involve cleaningthe trip and its linkage, removing the source of3-24
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