Chapter  7—AUXILIARY  MACHINERY of  excessively  worn  parts,  abnormal  and  con- tinuous  vibration,  excessively  high  operating pressures, or faulty or careless assembly. Exter- nal leaks usually have little effect on the opera- tion of equipment other than a steady draining of the oil supply; but even a small leak wastes oil, and  the  resulting  unsightly  appearance  of  a machine  is  indicative  of  poor  maintenance procedures. External  leaks  may  result  from  any  of  the following  causes:  improperly  tightened  threaded fittings; crossed threads in fittings; improperly fitted  or  damaged  gaskets;  distorted  or  scored sealing rings, oil seals, or packing rings; scored surfaces of working parts; improperly flared tube ends; or flanged joints not seating squarely. Internal  leaks  usually  result  in  unsatisfactory operation  of  the  equipment.  Large  internal  leaks are signified by loss of pressure and failure of equipment. While large internal leaks can usually be located by installing pressure gages in various parts of the equipment, the location of small leaks generally requires disassembly and visual inspec- tion of the parts. Internal leaks may result from worn or scored valves, pistons, valve plates or bushings,  or  improperly  fitted  or  damaged gaskets. The symptoms of trouble in a hydraulic system are frequently unusual noises. Some noises are characteristic  of  normal  operation  and  can  be disregarded, while others are evidence of serious trouble.  Even  though  the  exact  sound  indicating a specific trouble can be learned only through practical  experience,  the  following  descriptive terms will give a general idea of the noises which are trouble warnings. If   POPPING   and   SPUTTERING   noises occur, air is entering the pump intake line. Air entering the system at this point may be the result of too small an intake pipe, an air leak in the suc- tion line, a low oil level in the supply tank, cold or heavy oil, or possibly the use of improper oil. If air becomes trapped in a hydraulic system, HAMMERING will occur in the equipment or transmission lines. When this occurs, check for improper  venting.  Sometimes,  a  POUNDING  or RATTLING noise occurs as the result of a par- tial vacuum produced in the active fluid during high speed operation or when a heavy load is applied. This noise may be unavoidable under the conditions stated and can be ignored if it stops when speed or load is reduced. If the noise per- sists at low speeds or light loads, the system needs to be vented of air. Air in a hydraulic system can also cause uneven motion of the hydraulic motors. When  a  GRINDING  noise  occurs,  it  can usually  be  traced  to  dry  bearings,  foreign  matter in  the  oil,  worn  or  scored  parts,  or  overtightness of some adjustment. The   term   HYDRAULIC   CHATTER   is sometimes used to identify noises caused by a vibrating spring-actuated valve, by long pipes im- properly secured, by air in lines, or by binding of some part of the equipment. SQUEALS  or  SQUEAKS  indicate  that  the packing is too tight around some moving part or that  a  high-frequency  vibration  is  occurring  in  a relief valve. Electrical Troubles Even though troubles occurring in electrical equipment are the responsibility of the Electri- cian’s   Mate,   the   Engineman   can   facilitate maintenance of such equipment by making a few simple  checks  when  electrical  troubles  occur. Failure to have a switch in the ON position will cause unnecessary delay in operating electrical equipment. If the switch is closed and the equip- ment still fails to operate, check for blown fuses and tripped circuit breakers. Troubles of this type are 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.  Check for visual indication of open or shorted leads, faulty switches, and loose connections. Do not make repairs to the electrical equipment or system and do not open enclosures of electrical equip- ment, but report the condition to the Electrician’s Mate when evidence of electrical failure is found. Mechanical  Troubles When  an  electrohydraulically  driven  auxiliary becomes  inoperative  because  of  a  mechanical failure, a check should be made for improper ad- justment or misalignment of parts; shearing of 7-17