For subsea installations where subsurface load
transfers from the initial handling crane to the
lowering winch are required (also known as the
"wet handshake"), specific gravity and flexibility
become issues. Samson’s high-performance
slings made with Dyneema® fiber are extremely
flexible and neutrally buoyant in seawater making
handling by ROVs for the load transfer much
faster and easier than extremely heavy and stiff
wire rope. With synthetic lines, there is no need
for the ROV to overcome the extreme weight
or account for the leverage of stiff, inflexible
wire slings.
Although Samson manufactures a full spectrum
of constructions from 6-, 8-, and 12-strand single
braids to double braids, jacketed ropes and
twisted ropes, the two best suited to fabricating
slings are 12-strand and 8-strand constructions.
For heavy lift situations, 12-strand constructions
provide the optimum level of strength to weight
with straightforward fabrication and resistance
to abrasion.
The size of the pins, trunnions, and rigging hooks
are important in designing the slings. Samson’s
R&D department has done extensive testing
of single-leg slings and grommets at various D/d ratios and splice placements to determine
the optimum design and the effective grommet
efficiency factor to predict working loads
for grommets.
The length of the eye and the diameter of the
pin or weight-bearing surface affects the angle
of the leg in relationship to the body of the rope,
and thus can have an affect on the strength
of the sling itself.
Synthetic ropes made with Dyneema® have an
inherently low coefficient of friction. Where a
higher COF is required or desirable, Samson
offers Quantum-12 and Quantum-8 ropes
incorporating DPX™ technology, which
increases the COF by adding spun polyester
fiber to the surface yarns of the rope. These
patented constructions show significantly
increased COF for more efficient splices or
handling by traction winches or capstans.
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