f. For strainer-type systems, the inflow
3. Energize the high-level alarm circuit at the
stop valves (G) should be open.
IC switchboard to continuously monitor the tank
level.
4. Call main control and request that the CHT
pump-room power panels be energized.
4. Secure both the air blower and the
comminutor power supply switches at the local
5. Check the comminutor belt tension.
power panel.
6. For comminutor-type systems, once the
During the at-sea mode, you must flush the
power panels are energized, open the comminutor
holding tank for 30 minutes each week, and pump
isolation valves (D) and start up the comminutor.
it down even when the tank is not in use. Keep the
Observe the comminutor to ensure that it is
pump rooms clean and dry. Make sure that the
operating properly.
pump-room sumps are clean and pumped down.
De-energize the pump-room power panels at the
7. Notify DC central (or main control) that the
main switchboards.
CHT system is ready to be shifted to the transit
mode.
Transit Mode
The engineering officer of the watch (EOOW)
The OOD should inform the engineer officer 1
will report to the OOD that the CHT system is
hour before the ship enters restricted waters.
ready to be shifted.
(Restricted waters are the waters within 3 miles of
land.) The engineer officer will then have personnel
When the ship is 4 miles out from land, the
in charge of the CHT system start switching the
OOD will direct the EOOW to have the CHT
system over from the at-sea mode to the transit
system shifted. The EOOW will, in turn, direct the
mode.
CHT personnel to make the shift. The EOOW will
also inform DC central when the shift is to be
To change the system over to the transit mode,
made.
follow these preliminary procedures first:
When you are notified to shift the CHT system
1. Make sure the tanks are pumped down.
to the transit mode, follow these procedures:
2. Check the pump-room power panels to
1. Shift the soil drain diverter valves (H) to the
ensure that all switches are in the OFF position,
CHT collection position.
including the pump selector switches.
2. Check the waste drain diverter valves (J) to
3. Verify that these valves are in their proper
ensure that they are still in the overboard position.
positions:
3. Inform DC central that the system is in the
a. The pump suction valves (A) should be
transit mode.
open.
DC central will then inform the EOOW that the
b. The pump discharge valves (B) should
switch has been completed. DC central will then
be closed.
update the valve positions on the valve status board.
c. The tank washdown supply valve (L)
When the ship is going into anchorage,
should be closed.
arrangements for a sewage barge will be required.
The sewage barge is normally furnished by the host
d. The air blower discharge valve (M)
activity or by a civilian contract.
should be open.
In-Port Mode
e. The ship's service air supply valves (N)
should be open.
While the ship is entering port, the CHT system
stays in the transit mode. Once the ship moors to
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