ENGINEMAN  1  &  C an air test or a hydrostatic test, in accordance with the  recommended  procedure  in  the  manufac- turer’s instructions. Blueprints should also be used to study the construction details of the individual heat  exchanger. As soon as a leaky tube has been located, it should be plugged at both ends. Special composi- tion plugs are provided in the allowance repair parts and should be used. Since  plugging  the  tubes  reduces  the  amount of heating surface, the heat exchanger will fail to give satisfactory performance after a number of tubes  have  been  plugged.  It  will  then  become necessary to retube the heat exchanger. Under normal   conditions,   this   work   should   be accomplished  by  a  naval  shipyard  or  tender. However, repair parts and a number of special tools are included in the Ship’s Allowance List to permit emergency repairs to the heat exchangers and to other parts of the distilling plant. To  find  which  of  the  tubes  within  a REMOVABLE TUBE BUNDLE is leaking, it is necessary   to   test   the   individual   bundles hydrostatically. If the leak is in a removable bun- dle (vapor feed heaters when within an evaporator shell, evaporator tube nests, distilling condensers on Solo-shell end-pull plants), the bundle must be   withdrawn   and   a   hydrostatic   test   at   full pressure (50 psi) must be applied on the tube side. If  a  leak  occurs  in  a  NONREMOVABLE TUBE BUNDLE (distillate coolers, air ejectors condenser,  external  vapor  feed  heaters),  the  tube nest covers must be removed, and the full test pressure (50 psi) applied on the shell side of the unit. If a nonremovable distillate condenser bun- dle is within an evaporator shell, the tube nest covers must be removed and a full test pressure of 30 psi should be applied to the evaporator shell. If  the  distilling  condenser  is  fitted  with  a diaphragm-type  (Goubert)  expansion  joint,  a  test ring will be required to replace the tube nest cover for testing. Air Ejector Operation In operation, air ejectors require little atten- tion. However, the following points should be noted. 1. The steam pressure at the nozzle inlet must not  be  less  than  that  for  which  the  ejector  is designed  (stamped  on  the  nameplate).  Pressures at the air ejector nozzle may be 10 to 15 psig higher  than  the  minimum  specified  by  the manufacturer. 2. The primary causes of air ejector trouble are  low  steam  pressure,  wet  steam,  obstructed nozzle, or a clogged steam strainer. Such trouble is indicated by failure to obtain or to maintain the required vacuum. If the trouble is due to low steam pressure or to wet steam, it will be necessary either to increase the steam pressure or to pro- vide suitable drainage by installing a trap or by using  manual  means.  If  the  nozzle  or  steam strainer  is  clogged,  it  must  be  removed  and cleaned. Most plants are provided with two sets of air ejectors; this permits the use of the plant on one unit while the second is being cleaned or repaired. However, some of the latest plants have only one set of air ejectors. When it becomes necessary to clean air ejec- tor nozzles, they should be cleaned with the special nozzle reamers furnished to each ship for this pur- pose. Sharp-edged tools should never be used for cleaning nozzles because the nozzle surfaces will be damaged and the efficiency of the air ejectors will be impaired. Procedures  for  testing  air  ejectors  can  be found in the manufacturer’s technical manual. In general, the same maintenance procedures should be followed for distilling plant air ejectors as for air ejectors for main condensers. Since  the  air  ejector  strainer  is  usually  an integral part of the air ejector inlet, it should be inspected  and  cleaned  in  accordance  with  the PMS. When a new plant is first put into opera- tion, the strainer may require cleaning once a day or  even  more  frequently.  Failure  to  keep  the strainer clean will cause a reduced or fluctuating vacuum. When a strainer or a nozzle becomes damaged, it should always be replaced with a new one. Insufficient  Circulating  Water An insufficient flow of circulating water is indicated  if  the  temperature  of  the  water  rises more  than  20°F  in  passing  through  the  condens- ing section of the distiller condenser. The last- effect shell pressure is directly dependent upon the 7-26