Three principal factors have caused this
dramatic switch in materials selection by offshore engineers:
Firstly, as highly disruptive failures of stainless steel and copper based
alloys have increased, concerns have grown for plant safety and protection of
the environment at the lowest practicable life cycle cost.
Secondly, titanium continues to be available at competitive and relatively
stable prices, and with this has come supporting growth of fabrication
experience and capability to supply a wide range of titanium products, particularly
pipes, fittings and systems required by the offshore industry. Since 1990,
fifteen Norwegian fabricators have developed the capability to supply titanium
taking only a relatively short time to become skilled in all aspects of
machining, bending, and welding. The development of cold bending of thin wall
titanium pipework has provided a breakthrough in the overall competitiveness of
titanium systems.
The third factor in the increased specification and use of titanium has
been the improved availability of information to design engineers and offshore
operators of the useful combination of properties which titanium uniquely
possesses, together with the practical aspects of specifying and using titanium
cost effectively. The Titanium Information Group, collaborating with the
Norwegian Titanium Technology Forum, has contributed significantly to this
achievement. Offshore the cost of replacement is 27 times higher than for
similar onshore work. The specification of titanium at the outset, coupled with
cost effective design, fabrication, installation and use is seen as wholly
appropriate for off shore installations which are now being designed with life
cycles of 30 to 50 years. Titanium will frequently be competitive on first
cost, and will always be the winner in the life cycle cost contest.
A pilot project in 1994 by Elf Petroleum
Norge for the Frigg platform produced results showing that the installed cost
of titanium on a 200m by 15cm 2MNm-2 sea water line was 20% below that of
carbon steel. The use of cold bending, eliminated more than 80% of the welding
work. Fewer bends and fittings were needed and there was less welding. Flanged
joints were made by cold flaring of the pipe ends.
The low weight of the titanium pipe
considerably eased installation - one man can handle a 6m length of 15cm
diameter schedule 10s pipe without assistance. Post installation surface
treatments, shot blasting and painting of the titanium were not required.
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