Beware of oil in the
boilers feed water system.
The steam boilers on board in ships
nowadays have become a less evident part of the engine room than they were in
the old days. However, the steam boilers are still important parts of the
system, especially if the main engines are running on heavy fuel oil that need
to be heated. I dont want to go through the entire instruction book for
the marine boiler but just point out one important matter.
As we all know, a very thin layer of oil on the surface of the boiler tubes
or any of the direct heated surfaces of a boiler might cause local overheating
of the material and possible damage to the boiler. What we maybe not know is
how very small quantity of oil it requires to get a dangerous situation. A tube
break in a fuel oil heat exchanger is very easy to detect, a simple detector in
the hotwell will manage that, but a small crack in a tube may cause you an even
more serious problem.
A tiny oil leakage giving some 15 to 25 ppm of oil in the boiler feed water
would not be visible; the water is still limpid. Yet this apparently
insignificant oil pollution might causes sever danger to the boiler.
If a boiler has a capacity of 20 tons of steam per hour at full load and the
feed water is polluted with 25 ppm of oil, then it will accumulate approximately
12 kg oil in the steam drum per day. A bucket of oil in the boiler every day; I
suggest that you buy yourself a sensitive oil detector.
It will cost you, but it might save you from some future cost of repairs.
An oily ring inside the water gauge glasses
at the water level is a serious warning.
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