at the gauge glass fittings may indicate a false liquidlevel.Brine DensityProper brine density should be maintained at 1.5/32.If the brine concentration is too low, there will he a lossin capacity and economy. If the brine concentration istoo high, there will an increase in the rate of scaling ofthe evaporator heating surfaces.FLASH-TYPE DISTILLING PLANTSMany maintenance procedures for flash-typedistilling plants are similar to the maintenanceprocedures required for submerged-tube distillingplants. Both types of plants are subject to air leakage,saltwater leakage, and malfunctioning of pumps andother auxiliary equipment.HEAT-RECOVERY DISTILLING PLANTSHeat-recovery distilling plants are single-effectdistilling plants with a submerged-tube heat exchanger.This heat exchanger uses heat energy contained in thejacket cooling water circulated through diesel mainpropulsion engines and ship’s service diesel generators.This unit requires no steam for air ejectors because feedis used as the motive power to operate eductors for airand brine removal To supplement the heat in the jacketcooling water when engines are running at low rates, theplant has electric heating modules and steam heaters.This ensures that the jacket cooling water will be at therequired temperature when it enters the submerged-tubeheat exchanger. The jacket water passes through all theheat exchangers (whether energized or not) to the inletof the submerged-tube bundle. Here the heat istransferred through the tubes to the feed in the boilingcompartment. The jacket water then exits the tubebundle and returns to the engine. The heat-recoverysystem is fitted with a circulating pump and anexpansion tankMost heat-recovery distillers aboard Navy shipshave a secondary heat exchanger between the enginejacket cooling water system and the distiller unit. Thisheat exchanger isolates the engine coolant, with all itschemical additives, from the distiller. Systems nothaving this secondary heat exchanger get heat directlyfrom the engine coolant to support the distiller. This iscalled a single-loop system. A single-loop system mustbe monitored continuously to ensure that no enginecoolant leaks through the distiller submerged-tube heatexchanger. For more information on the monitoringrequirements, refer to NSTM Chapter 233, “DieselEngines.” For cleaning heat-recovery plants, follow theapplicable instructions as you would for cleaning thesubmerged-tube or the flash-type distilling plants. Formore detailed information concerning the distilling unitsthe Navy uses, refer to the manufacturer’s manual andNSTM, Chapter 531, Volumes 1, 2, and 3, “DesalinationLow-Pressure Distilling Plants.”HYDRAULIC SYSTEMSThe overall efficiency of the hydraulic installationsused to control or drive auxiliary machines is basicallydependent upon the size, oil pressure, speed, and strokeof the hydraulic installation. The efficiency of thehydraulic speed gears and the components of the systemwill depend upon the care that is given to them. Exceptfor piping and fittings, major repairs of hydraulic gearare generally done in a naval shipyard or by themanufacturers. This section will deal primarily withtroubleshooting and preventive maintenance ofhydraulic systems, including external hydraulics.Hydraulic transmissions are sturdy, service-provenmachines, inspected and tested with such care thatcasualties seldom occur. When casualties do occur it isusually the result of faulty assembly, installation, ormaintenance. A correctly installed hydraulic system,operated regularly and serviced with proper care, willretain its design characteristics of power, speed, andcontrol. The need for costly repair and replacement willseldom occur if the equipment has been maintainedproperly.TROUBLESHOOTINGTroubleshooting an electrohydraulic systeminvolves the systematic elimination of the possiblecauses, one by one, until the actual cause of a casualtyis found. In attempting to locate the source of any troublein an electrohydraulic system, remember that alltroubles fit into one of three categories. It is eitherhydraulic, electrical, or mechanical. Isolating a troubleinto one of these categories is one of the main steps infinding the source of trouble.Hydraulic TroublesCasualties in a hydraulic system are generally theresult of low oil levels, external or internal leakage,clogged lines or fittings, or improper adjustment ofvalves and other working parts. Do NOT disassemble aunit unless you are certain that the trouble exists withinthat unit! Unnecessary disassembly may create8-6
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