Coating mills apply
pipe coatings to protect the line pipe from corrosion. Often, the
coating mill is located adjacent to the pipe mill, so line pipe moves
directly from the pipe manufacturer to the coating facility.
The natural gas industry uses several different
types of pipe coatings. Historically, pipeline companies coated pipe
with coal tar enamel or an enamel tape wrap. Today a fusion bond epoxy
(FBE) coating is used most widely. FBE coating can be recognized by its
light blue color, often seen on pipe being transported by rail or
truck. Regardless of the type of coating used, the purpose is the same:
Prevent external corrosion by prohibiting moisture from coming into
direct contact with the metal.
To prepare for fusion bond epoxy coating, the
external surface of the pipe is thoroughly cleaned with a shot-blast
process. The pipe is then heated to a prescribed temperature and an
epoxy powder is applied. The powder "melts" onto the heated pipe and
forms a water tight barrier. Prior to transporting the pipe to the job
site, the mill tests the coated pipe with high voltage electricity to
evaluate the coating's insulating effectiveness.
Sumber : http://www.ingaa.org/Topics/Pipelines101/109/4063/112/127.aspx
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