"Barath" > wrote in message
oups.com...
Thanks a lot guys for your inputs.Paul can you please elaboarate more
on Black Iron.
Never heard of it bfore...

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Black iron is about like cast iron. It is used in making pipe,etc, and is
cheap.
It is not overly hard (therefore is not likely to become embrittled like
high strength steels in the presence of sulfur components or acids).

It has been used for years in sewer pipes, but has been supplanted by
PVC, etc.

In service to the oil industry, thousands of tons of diesel are stored in
tanks, onshore, to be transported offshore for use. I believe these tanks
are stainless steel, since there is always a layer of water on the bottom.
(Water is used to displace the diesel from the ships to the tanks)

There isnt normally MUCH water, but it is essentially always there, and has
to be dealt with by centrifugation, filtration, etc so that it does not
enter the
engines.

We treat the water layer with a chemical to decrease microbial activity and
corrosion. The microbes, principally Cladisporium resinae and others, cause
severe problems in the fuel, especially when used in turbines.

The supply vessels, etc, often use the same sort of treatment in their fuel
tanks. Having contaminated fuel, or corroded injection parts, is not fun
when you offshore.

In short, if you cant afford anything but iron or steel tanks, then take the
time to design
the tanks so that stresses are minimized, welds are of high quality and
normalized, and the
shape factor of the tank is designed not to hold up water. (Water which
passed through
the system and is caught in an external separator/filter might even help.)