Chapter  7—AUXILIARY  MACHINERY other light oils that vaporize easily and that, under compression, form a highly explosive mixture. 4. Use only the minimum amount and the proper grade of oil for cylinder lubrication. 5. Secure a compressor immediately if there is  an  abnormal  rise  in  the  temperature  of  air discharge from any stage. 6. Be sure a relief valve is installed between a compressor and a stop valve, or a check valve is installed between a compressor and the receiver. If there is no relief valve and the compressor is started against a closed valve or a deranged check valve, the air will not be able to escape and an explosion  will  result. 7. Do not leave a compressor station after starting  a  compressor,  especially  a  new  com- pressor or one that has been idle for some time, until you are positive that the control, unloading, and governing devices are working properly. 8.  Do  not  disconnect  any  part  of  a  com- pressor if the system is under pressure. To avoid serious   accidents,   the   following   precautions should be taken before working on, or removing, any part of a compressor: a. Leave all pressure gages open. b. Be sure the compressor is actually secured and   cannot   be   started   automatically   or accidentally. c.  Be  sure  the  compressor  is  completely blown  down. d. Be sure all valves, including the control or unloading valves, between the compressor and the receiver are closed. 9.  Operate  a  compressor  at  recommended speeds  and  maintain  proper  cooling  water  circula- tion   to   prevent   damage   from   excessive temperatures. 10. Drain the circulating water system of a compressor if it is to remain idle for an extended period,  or  if  it  is  to  be  exposed  to  freezing temperature. AUXILIARY BOILERS Information about the operation, maintenance,   and   safety   regarding   auxiliary boilers  in  this  chapter  supplements  that  given  in Engineman 3 & 2, NAVEDTRA 10541 (current edition). Detailed information on construction, operation, and maintenance of auxiliary boilers must   be   obtained   from   the   manufacturer’s technical manual. OPERATION The  operation  of  auxiliary  boilers  used  on diesel-driven ships is under the supervision of an ENC or EN1. You should ensure that personnel charged with the operation and maintenance of an auxiliary boiler are thoroughly familiar with the boiler and its associated equipment. Satisfac- tory operation of the boiler depends on proper care and maintenance. Specific attention must be paid  to  maintaining  automatic  regulating,  control, and safety devices in proper operating condition. Failure  of  these  devices  may  lead  to  a  major casualty, damage to equipment, and injury to per- sonnel;  therefore,  continuous,  alert  watchstanding should be maintained while the auxiliary boiler is  in  semiautomatic  or  manual  operation.  An operating auxiliary boiler should never be left unattended. TROUBLESHOOTING Faulty   operation   of   auxiliary   boilers   is indicated by various symptoms. These symptoms may indicate one or more conditions in the boiler. Each condition must be corrected. Consult the manufacturer’s  technical  manual  for  detailed information   on   troubleshooting   a   particular boiler. Knowing the probable causes of a par- ticular  symptom  can  assist  you  in  correcting  any trouble  quickly  and  efficiently.  Some  of  the troubles encountered in the operation of auxiliary boilers and their causes are listed in figure 7-2. AUXILIARY BOILER WATER  TREATMENT The auxiliary boiler feedwater is exposed to the same contaminants as the propulsion boiler feedwater. Auxiliary boilers are generally used for hotel  service  loads,  and  shore  water  used  for feedwater  is  usually  the  prime  source  of  con- tamination. The shore water may contaminate the feedwater system by leakage through malfunction- ing galley mixing valves, laundry equipment, and 7-7