determine the space ventilation requirements and
under pressure. It is flammable with an ignition
ensure that the atmosphere in the tank is at 10
temperature of 651°C. The flammable limits are 16
percent or less than the lower explosive limit (LEL).
to 25 percent by volume.
Equipment can then be removed using an air-line
mask or other approved respirator. Openings
NH3 has a maximum safe level of 50 ppm.
should then be sealed using either blank flanges or
However, the acceptable safe limit is 25 ppm.
a suitable sealing device. Air-line masks or OBAs
Ammonia is toxic, and inhaling it in a high
can then be removed and work can be continued on
concentration can cause swelling of the respiratory
tract. It can also cause headaches, nausea, vomiting,
breathing difficulties, and coughing. If ammonia
gets into your eyes, it can cause a visual disorder.
If NH, gets into your eyes, wash your eyes with
large quantities of water and seek medical help.
In this chapter, you were introduced to the CHT
sewage system. There are other marine sanitation
CHT TANK MAINTENANCE NOT
devices in use. If your ship has a system that was
REQUIRING TANK ENTRY
not discussed here, refer to the manufacturer's
technical manual for that system. Keep in mind that
Tank maintenance sometimes calls for
there are regulations that govern the discharge of
equipment to be removed from the outside of the
sewage in navigable waters within 3 miles of the
tank so that an opening will be left in the tank.
coastline. For your health and the safety of others,
Some examples are the removal of level sensors,
follow the prescribed sanitation procedures.
washdown nozzles, or valves adjacent to the tank
Courses, PQS, and schools are available for sewage
and below the level of the tank overflow in the
systems maintenance and operation. See your
pump room. If this is done but the tank is not to
educational services officer or career counselor for
be entered, observe steps 1 through 9 of the
more information and class convening dates for
preceding discussion under Work Procedures
with this exception: The ship's gas-free engineer can