ENGINEMAN 1 & C3. The comminutor. One comminutor islocated in each soil drain or combined drain enter-ing each tank.set up to collect and hold the discharges from soildrains only.4. The aeration supply system.5. The firemain flushing connections andspray cleaning nozzle for tank washdown.6. The piping, valves, and fittings.2. In Port. During in-port periods, the CHTsystem collects, holds, and transfers to shoresewage facility all discharges from soil and wastedrains.Strainer3. At Sea. When operating at sea outsiderestricted areas, the CHT system is set up to divertdischarges from both soil and waste drainsoverboard.The strainer-type system incorporates anoverflow strainer within the CHT tank and an in-flow strainer mounted on the discharge side ofeach pump. The drain collection piping directssewage flow through the overflow strainer whereliquids may overflow into the CHT tank if theinflow strainer or the pumps become clogged.Solid and liquid wastes flow through the ball orplug valve and the check valves until they reachthe pump discharge piping. At this junction, thesewage flow passes through the inflow strainerwhere large solids are collected, then through thepumps, and back into the CHT tank. The inflowstrainer limits the flow of solids, but liquids areallowed to pass through the pump into the tank.Each time the pump operates, its inflow straineris cleaned by the reverse flow of liquid beingpumped from the tank. The strainer-type systemcomponents, shown in figure 8-6, include:Transmit ModeWhile transiting a restricted zone, soil drains arerouted to the CHT tanks and the waste drains arediverted overboard. Both CHT pump controllerswitches are in the OFF position. Pump suctionvalves A and inflow stop valve G (for strainersystem only). are open (see figure 8-6). Pumpdischarge valves B and the tank washdownsupply valve are closed. Soil drain diverter valvesH are in the CHT COLLECTION position. Wastedrain diverter valves J are in the OVERBOARDposition, discharging through the gag scuppervalves.1. The CHT tank. The capacity of each tankusually is less than 2000 gallons.2. The CHT pump set; one pump set per tank.A pump set consists of two motor-driven pumps,two suction plug or ball valves, two discharge plugor ball valves, two discharge check valves (withhold-open device), a pump controller, a high levelalarm, and an appropriate number of liquid levelsensors.For systems equipped with a comminutor (seefigure 8-5) and an aeration system (see figure 8-7),open the comminutor isolation valves, D andoperate the comminutor. The tank contents mustbe aerated continuously. Operate the air blowerand open discharge valve M (shown in figure 8-7).Air also can be supplied by opening the ship serv-ice air supply valve N (also shown in figure 8-7).If an aspirator system is employed, the aspiratorpump should be activated.WARNING3. The Firemain flushing connections andspray cleaning nozzle for tank washdowns.4. The piping, valves, and fittings.CHT OPERATIONAL MODESWhenever a high level alarm sounds,immediate action must be taken to closethe isolation valves on drains below theoverboard discharge and to divert upperlevel drains overboard to preclude floodingof spaces.The CHT system can be used in any of threedistrict modes of operation in accordance with anyone of the following situations:1. Transiting Restricted Zones. When tran-siting restricted zones, the CHT system must beAfter sewage transfer hose connections arecompleted, both soil and waste drains are routedto the CHT tank and then discharged to a shorereceiving facility, nested ship, or barge receivingstation. When connecting the sewage transferhose, proper chafing gear and supporting lines8-16
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