0027-nd rev 11.2 8-jul-16 guidelines for marine lifting and lowering operations
GUIDELINES FOR MARINE LIFTING & LOWERING OPERATIONS 0027/ND Rev 11 Page 27 of 84 5.6.12
For indeterminate 4-sling lifts using matched pairs of single laid slings, a Skew Load Factor (SKL) of
1.25 shall be applied to each diagonally opposite pair of lift points in turn provided the following are
applicable:
The slings are fabricated with a length tolerance of ±2.0d and the difference between a
matched pair of slings shall not be more than 1.0d where d is the sling diameter;
The slings are of a standard construction and meet the criteria of 230xW/d2 <1.0 where W is
the weight in kilograms (kg) per metre (m) of the sling and d is the sling diameter.
The slings are installed so that the longer slings of each matched pair are not on the same
diagonal.
Sling utilisation when checking with the splice efficiency factor (see Sections 7.3.1and 7.7.1)
and a skew factor of 1.25 should be more than 0.6.
Note, where utilisations are less than 0.6, whilst a higher skew factor will not overload the slings, the
load on the lift point may increase and the effect of this shall be included in the design for the lift points.
5.6.13
For indeterminate 4-sling lifts using four single laid slings of un-equal length, the skew load shall be
calculated using an elastic modulus, E, of 80,000 N/mm
2
with the sling area used based on a value of
0.785 x d
2
, where d is the sling diameter in mm, and the sling lengths based on the most onerous
fabrication tolerances.
5.7 ADDITIONAL FACTORS 5.7.1
When appropriate, allowances for special loads should be made in the derivation of loads on the lifted
structure, lift points and rigging system. These special loads may include tugger line loads, guide
loads, wind loads, hydrostatic and hydrodynamic loads.
