When
steel pipe is forged, a black oxide scale forms on its surface to give
it the finish which is seen on this type of pipe. Because steel is
subject to rust and corrosion, the factory also coats it with protective
oil. Those black steel are used for manufacturing pipe and tube, which
will not rust for a long time and requires very little maintenance. It
is sold in standard 21-foot lengths TBE.
Black steel pipes and tubes are cut and threaded to fit the job.
Fittings for this type of pipe are of black malleable (soft) cast iron.
They connect by screwing onto the threaded pipe, after applying a small
amount of pipe joint compound on the threads. Larger diameter pipe is
welded rather than threaded. Black steel pipe is cut either with a
heavy-duty tube cutter or cutoff saw or by hacksaw.
Widely applicable for ordinary uses in water, gas, air and steam, black
steel tubes and pipes are utilized for gas distribution inside and
outside the house and for hot water circulation in boiler systems. It is
also used for line pipes in oil and petroleum industries, for water
wells and for water, gas and sewage purposes. It is not used for potable
water or for drain waste or vent lines.
