Chapter 7—AUXILIARY MACHINERYof excessively worn parts, abnormal and con-tinuous vibration, excessively high operatingpressures, or faulty or careless assembly. Exter-nal leaks usually have little effect on the opera-tion of equipment other than a steady drainingof the oil supply; but even a small leak wastes oil,and the resulting unsightly appearance of amachine is indicative of poor maintenanceprocedures.External leaks may result from any of thefollowing causes: improperly tightened threadedfittings; crossed threads in fittings; improperlyfitted or damaged gaskets; distorted or scoredsealing rings, oil seals, or packing rings; scoredsurfaces of working parts; improperly flared tubeends; or flanged joints not seating squarely.Internal leaks usually result in unsatisfactoryoperation of the equipment. Large internal leaksare signified by loss of pressure and failure ofequipment. While large internal leaks can usuallybe located by installing pressure gages in variousparts of the equipment, the location of small leaksgenerally requires disassembly and visual inspec-tion of the parts. Internal leaks may result fromworn or scored valves, pistons, valve plates orbushings, or improperly fitted or damagedgaskets.The symptoms of trouble in a hydraulic systemare frequently unusual noises. Some noises arecharacteristic of normal operation and can bedisregarded, while others are evidence of serioustrouble. Even though the exact sound indicatinga specific trouble can be learned only throughpractical experience, the following descriptiveterms will give a general idea of the noises whichare trouble warnings.If POPPING and SPUTTERING noisesoccur, air is entering the pump intake line. Airentering the system at this point may be the resultof too small an intake pipe, an air leak in the suc-tion line, a low oil level in the supply tank, coldor heavy oil, or possibly the use of improper oil.If air becomes trapped in a hydraulic system,HAMMERING will occur in the equipment ortransmission lines. When this occurs, check forimproper venting. Sometimes, a POUNDING orRATTLING noise occurs as the result of a par-tial vacuum produced in the active fluid duringhigh speed operation or when a heavy load isapplied. This noise may be unavoidable under theconditions stated and can be ignored if it stopswhen speed or load is reduced. If the noise per-sists at low speeds or light loads, the system needsto be vented of air. Air in a hydraulic system canalso cause uneven motion of the hydraulic motors.When a GRINDING noise occurs, it canusually be traced to dry bearings, foreign matterin the oil, worn or scored parts, or overtightnessof some adjustment.The term HYDRAULIC CHATTER issometimes used to identify noises caused by avibrating spring-actuated valve, by long pipes im-properly secured, by air in lines, or by bindingof some part of the equipment.SQUEALS or SQUEAKS indicate that thepacking is too tight around some moving part orthat a high-frequency vibration is occurring in arelief valve.Electrical TroublesEven though troubles occurring in electricalequipment are the responsibility of the Electri-cian’s Mate, the Engineman can facilitatemaintenance of such equipment by making a fewsimple checks when electrical troubles occur.Failure to have a switch in the ON position willcause unnecessary delay in operating electricalequipment. If the switch is closed and the equip-ment still fails to operate, check for blown fusesand tripped circuit breakers. Troubles of this typeare usually the result of an overload on the equip-ment. If a circuit breaker continues to cut out,the trouble may be caused by damaged equip-ment, excessive binding in the electric motor,obstruction in the hydraulic transmission lines,or faulty operation of the circuit breaker. Checkfor visual indication of open or shorted leads,faulty switches, and loose connections. Do notmake repairs to the electrical equipment or systemand do not open enclosures of electrical equip-ment, but report the condition to the Electrician’sMate when evidence of electrical failure is found.Mechanical TroublesWhen an electrohydraulically driven auxiliarybecomes inoperative because of a mechanicalfailure, a check should be made for improper ad-justment or misalignment of parts; shearing of7-17
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