ENGINEMAN  1  &  C 3.   The   comminutor.   One   comminutor   is located in each soil drain or combined drain enter- ing each tank. set up to collect and hold the discharges from soil drains only. 4. The aeration supply system. 5.  The  firemain  flushing  connections  and spray cleaning nozzle for tank washdown. 6. The piping, valves, and fittings. 2. In Port. During in-port periods, the CHT system  collects,  holds,  and  transfers  to  shore sewage facility all discharges from soil and waste drains. Strainer 3.  At  Sea.  When  operating  at  sea  outside restricted areas, the CHT system is set up to divert discharges   from   both   soil   and   waste   drains overboard. The   strainer-type   system   incorporates   an overflow strainer within the CHT tank and an in- flow strainer mounted on the discharge side of each pump. The drain collection piping directs sewage flow through the overflow strainer where liquids may overflow into the CHT tank if the inflow strainer or the pumps become clogged. Solid and liquid wastes flow through the ball or plug  valve  and  the  check  valves  until  they  reach the pump discharge piping. At this junction, the sewage flow passes through the inflow strainer where large solids are collected, then through the pumps,  and  back  into  the  CHT  tank.  The  inflow strainer limits the flow of solids, but liquids are allowed to pass through the pump into the tank. Each time the pump operates, its inflow strainer is  cleaned  by  the  reverse  flow  of  liquid  being pumped  from  the  tank.  The  strainer-type  system components, shown in figure 8-6, include: Transmit Mode While transiting a restricted zone, soil drains are routed to the CHT tanks and the waste drains are diverted overboard. Both CHT pump controller switches are in the OFF position. Pump suction valves A and inflow stop valve G (for strainer system only). are open (see figure 8-6). Pump discharge  valves  B  and  the  tank  washdown supply valve are closed. Soil drain diverter valves H are in the CHT COLLECTION position. Waste drain diverter valves J are in the OVERBOARD position,  discharging  through  the  gag  scupper valves. 1. The CHT tank. The capacity of each tank usually  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 plug or  ball  valves,  two  discharge  check  valves  (with hold-open device), a pump controller, a high level alarm, and an appropriate number of liquid level sensors. For systems equipped with a comminutor (see figure 8-5) and an aeration system (see figure 8-7), open  the  comminutor  isolation  valves,  D  and operate  the  comminutor.  The  tank  contents  must be aerated continuously. Operate the air blower and 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 aspirator pump should be activated. WARNING 3.  The  Firemain  flushing  connections  and spray cleaning nozzle for tank washdowns. 4. The piping, valves, and fittings. CHT OPERATIONAL MODES Whenever a high level alarm sounds, immediate action must be taken to close the isolation valves on drains below the overboard discharge and to divert upper level drains overboard to preclude flooding of spaces. The CHT system can be used in any of three district modes of operation in accordance with any one of the following situations: 1. Transiting Restricted Zones. When tran- siting restricted zones, the CHT system must be After sewage transfer hose connections are completed, both soil and waste drains are routed to the CHT tank and then discharged to a shore receiving facility, nested ship, or barge receiving station.  When  connecting  the  sewage  transfer hose, proper chafing gear and supporting lines 8-16