feedwater is required to compensate for these
You must ensure the minimum amount of
time possible elapses between sampling and receipt
system losses.
of the report of laboratory analysis. Ships have
Although the shipboard water cycle is
continuous, different terminology is used to
to use the test results to ensure clean fuel. Schedule
describe the water at different points. These
routine and monthly sampling for optimum
use of available transportation to fuel laboratory
distinctions are necessary because water quality
standards vary throughout the system. The
locations. Take samples immediately before enter-
following terms identify the water at various
ing port while the ship's aviation fuel system is
points:
in normal operating condition. Deliver the
samples by the quickest means possible to the
nearest fuel laboratory. For detailed information
1. Distillate--The evaporated water that is
on the sampling and testing requirements of JP-5
discharged from the ship's distilling plant. The
fuel, refer to Naval Ships' Technical Manual,
distillate is stored in the feedwater tanks which
are designated as the on-line feed tank and reserve
chapter 542.
feed tank by the chief engineer.
2. Feedwater--The term used to designate the
BOILER WATER/FEEDWATER.--On
water stored in the feed tanks.
ships with WHBs, you may be responsible for
3. Boiler water--The feedwater becomes
testing and treating the WHB with various
boiler water as it enters the boiler and boiler tubes.
chemicals to maintain the boiler water within
4. Condensate--After the steam has done its
prescribed limits. To be certified for boiler-water
work, it is returned to its liquid state by cooling
and feedwater testing, you must attend school,
in a condenser. The condenser is a heat exchanger
pass the course, and be certified by your ship's
in which seawater cools the steam and returns it
commanding officer as being qualified. In this
to liquid form. It is then returned to the feed tank.
section we will not attempt to go into detail as
to each individual test and requirement, but we
Contamination. --Boilers cannot be operated
will discuss the reasons for treating the WHB and
safely and efficiently without careful attention to,
your responsibilities for the necessary tests and
and control of, feedwater and boiler water quality.
administration.
With proper control of water chemistry, proper
plant operation, and proper lay-up during idle
Shipboard Water Cycle.--The overall ship-
periods, boilers should last the life of the ship with
board water cycle is a closed system in which feed-
no need to renew boiler tubes. If water conditions
water is fed to the boiler, the water is heated to
are not controlled within allowable limits, rapid
generate steam, the steam does work, and it is then
deterioration of waterside surfaces, scale forma-
condensed and returned to the feedwater system.
tion, and carry-over will occur. This leads to
Water for the cycle is obtained from seawater,
serious boiler casualties. Because boilers concen-
which is taken into a distiller and evaporated to
trate all feedwater contaminants as steam is
produce distillate. The distillate is stored in reserve
generated, boiler water quality and reliable boiler
feedwater tanks until needed as makeup feed.
operation depend directly upon control of feed-
When needed to replace system losses, it is
water quality.
pumped to the system. It is then pumped to the
Because of ship operations, propulsion
deaerating feed tank (DFT), if the ship is so
systems use water from two sources, seawater and
shore water. For boiler operations, these waters
equipped, where oxygen and other gases are
removed. This deaerated water, now called feed-
are considered contaminated due to various
water, is pumped to the boiler where heat is
chemicals in them. These chemicals can cause
applied. The boiler water is converted to steam,
serious boiler failures because of chemical
and then it is used to operate auxiliary equipment
reactions within the boiler. Some of the effects
and provide heat energy to different parts of the
of contamination of boiler water and feedwater
are as follows:
ship. When most of the heat energy has been
removed, the steam is condensed in the condenser.
Then it is ready to be recycled once again.
1. pH (acidic and caustic corrosion)-Failure
to maintain a correct pH balance can cause
Because the cycle is continuous and closed, the
same water remains in the system except for
corrosion. Excessive acidity causes the film on the
boiler tube metal to dissolve, resulting in corrosion
nonrecoverable losses, such as boiler blowdowns,
of the inner tubes of the boiler. Excessive
laundry presses, and miscellaneous leaks. Makeup
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