ENGINEMAN 1 & Can air test or a hydrostatic test, in accordance withthe recommended procedure in the manufac-turer’s instructions. Blueprints should also be usedto study the construction details of the individualheat exchanger.As soon as a leaky tube has been located, itshould be plugged at both ends. Special composi-tion plugs are provided in the allowance repairparts and should be used.Since plugging the tubes reduces the amountof heating surface, the heat exchanger will fail togive satisfactory performance after a number oftubes have been plugged. It will then becomenecessary to retube the heat exchanger. Undernormal conditions, this work should beaccomplished by a naval shipyard or tender.However, repair parts and a number of specialtools are included in the Ship’s Allowance Listto permit emergency repairs to the heat exchangersand to other parts of the distilling plant.To find which of the tubes within aREMOVABLE TUBE BUNDLE is leaking, it isnecessary to test the individual bundleshydrostatically. If the leak is in a removable bun-dle (vapor feed heaters when within an evaporatorshell, evaporator tube nests, distilling condenserson Solo-shell end-pull plants), the bundle mustbe withdrawn and a hydrostatic test at fullpressure (50 psi) must be applied on the tube side.If a leak occurs in a NONREMOVABLETUBE BUNDLE (distillate coolers, air ejectorscondenser, external vapor feed heaters), the tubenest covers must be removed, and the full testpressure (50 psi) applied on the shell side of theunit.If a nonremovable distillate condenser bun-dle is within an evaporator shell, the tube nestcovers must be removed and a full test pressureof 30 psi should be applied to the evaporator shell.If the distilling condenser is fitted with adiaphragm-type (Goubert) expansion joint, a testring will be required to replace the tube nest coverfor testing.Air Ejector OperationIn operation, air ejectors require little atten-tion. However, the following points should benoted.1. The steam pressure at the nozzle inlet mustnot be less than that for which the ejector isdesigned (stamped on the nameplate). Pressuresat the air ejector nozzle may be 10 to 15 psighigher than the minimum specified by themanufacturer.2. The primary causes of air ejector troubleare low steam pressure, wet steam, obstructednozzle, or a clogged steam strainer. Such troubleis indicated by failure to obtain or to maintainthe required vacuum. If the trouble is due to lowsteam pressure or to wet steam, it will be necessaryeither to increase the steam pressure or to pro-vide suitable drainage by installing a trap or byusing manual means. If the nozzle or steamstrainer is clogged, it must be removed andcleaned. Most plants are provided with two setsof air ejectors; this permits the use of the planton one unit while the second is being cleaned orrepaired. However, some of the latest plants haveonly one set of air ejectors.When it becomes necessary to clean air ejec-tor nozzles, they should be cleaned with the specialnozzle reamers furnished to each ship for this pur-pose. Sharp-edged tools should never be used forcleaning nozzles because the nozzle surfaces willbe damaged and the efficiency of the air ejectorswill be impaired.Procedures for testing air ejectors can befound in the manufacturer’s technical manual. Ingeneral, the same maintenance procedures shouldbe followed for distilling plant air ejectors as forair ejectors for main condensers.Since the air ejector strainer is usually anintegral part of the air ejector inlet, it should beinspected and cleaned in accordance with thePMS. When a new plant is first put into opera-tion, the strainer may require cleaning once a dayor even more frequently. Failure to keep thestrainer clean will cause a reduced or fluctuatingvacuum. When a strainer or a nozzle becomesdamaged, it should always be replaced with a newone.Insufficient Circulating WaterAn insufficient flow of circulating water isindicated if the temperature of the water risesmore than 20°F in passing through the condens-ing section of the distiller condenser. The last-effect shell pressure is directly dependent upon the7-26
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business