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OFFSHORE E-NEWS
May 2000
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INDUSTRY
TENDS TO OVER-APPLY
REGULATIONS TO GULF OF MEXICO SPARS
There is a natural
tendency in the industry to apply the severest existing requirements
to a floating offshore installation, especially when there are no
specific requirements published, according to Bret Montaruli, ABS
Manager of the Houston Engineering Services Department. In the course
of his work, Montaruli and his team have seen this occur on a number
of occasions. A notable example is related to Spar or Deep Draft
Caisson Vessel (DDCV) ballast systems. Often times, designers have
applied to Spars the same ballast system requirements of a column
stabilized drilling unit (CSDU). These stringent requirements can
add unnecessary cost and technical redundancies since the ballast
system on a production Spar is not as critical to the unit’s
safety as on a CSDU.
ABS has been
involved with production Spar/DDCV and Tension Leg Platform (TLP)
technology from their first introductions, and has been instrumental
in helping develop appropriate regulatory guidelines.
After recognizing
the need for surer regulation regarding such ballast systems, ABS
worked with the industry and the US Coast Guard (USCG) to develop
a new approach that considers the unique operational aspects of
Spars and associated level of risk involved. As a result, the USCG
now recognizes that this approach represents an equivalent level
of safety under the current regulations for ABS-classed Spars and
DDCVs.
An important
design consideration, critical to the safety of Spars, is the systems
requiring piping or cable runs in the hull. Runs require penetration
of numerous decks, increasing the risk of flooding. Additionally,
to prevent corrosion, it is critical to maintain a dry environment
in hull spaces. Penetrations of decks increase the possibility for
corrosion. Thus, best practice for reducing corrosion occurs in
initial design and, when inspections note otherwise, through prompt
repair.
Another important
aspect that can impact the safety onboard Spars is an abundance
of systems that must be inspected regularly and maintained. On a
Spar hull, tanks are often located several hundred feet below the
water surface, making access difficult. If an injury occurs, it
can be extremely difficult to extract the injured person from the
hull. Reducing the number of systems needing to be visited in the
hull will also significantly reduce the associated risk of such
injuries occurring.
"With
Spar and TLP technology rapidly expanding beyond the North Sea and
Gulf of Mexico, it is imperative for owners and operators to carefully
consider the experience that has been gained with existing offshore
structures," said Montaruli. "Our experience with Spars
and TLPs has helped us identify those areas that are critical to
the safety related to hull structures, marine systems and production
facilities."
Drawing on ABS’
significant experience in both new offshore construction and the
practical operating conditions of an installation, an ABS team of
engineers is in the process of developing ABS Rules for Spars
and TLPs. As always, ABS will work closely with industry and regulatory
bodies – particularly USCG relative to joint experience in
the Gulf – to ensure that rational and practical criteria are
developed. Said Montaruli, "The ABS requirements, specific
to these systems and based on our experience and that of owners
and operators, will provide the industry with much clearer guidance
in developing efficient and safe designs."
Based on experience
gained during a deepwater project with Petrobras, which used synthetic
rope for a taut-leg mooring system for its Campos Basin P-27 semisubmersible
floating production unit, ABS released ABS Guidance Notes for
Synthetic Ropes in Offshore Mooring Applications last year.
The Guidance Notes were developed to address specific industry
concerns, including non-linear stiffness or behavior, minimum tension
requirements, creep phenomenon and effective handling and storage
of rope which is more than seven inches in diameter for current
typical deepwater applications.
To learn more
about ABS experience on offshore projects, contact ABS Offshore
at ABS-Offshore@eagle.org
or tel: 1-281-877-6517 and fax: 1-281-877-6796.
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