0027-nd rev 11.2 8-jul-16 guidelines for marine lifting and lowering operations
Static Hook load = (Design Weight) + (Rigging Weight) + (Additional Loads)
Dynamic Hook load = Static Hook load x DAF
For Additional Loads, clarification is given in Section 5.7.1.
6.2.3
For twin hook lifts whether cranes are on the same vessel, or multiple vessels, or the structure is
suspended from two hooks on the same crane on the same vessel, the load to each hook shall be
based on the Design Weight (see Section 6.2.1) proportioned by the geometric distance of the centre
of gravity from each of the hooks allowing for the effect of the module tilt / hook elevation tolerances
given in Section 5.4. Where a CoG envelope is used (see Section 8.3 of 0001/ND, Ref. [1]), the hook
loads should be calculated for a CoG position at the extremes of the CoG envelope. Where no CoG
envelope is used, the hook loads are to be increased by the factor given in Section 8.3.3 of 0001/ND,
Ref. [1].
The final static hook load is then determined by the additional rigging weight connected to the hook
and the addition of additional loads in accordance with Section 5.7.1.
The dynamic hook load is then determined in a similar way to the formula for the dynamic hook load in
Section 6.2.2.
6.2.4
Rigging weight includes all items between the lift points and the crane hook, including slings, shackles,
lifting tools and spreader bars or frames as appropriate.
6.2.5
For lifting operations involving pivoting and/or upending manoeuvres (e.g. roll-up operation, jacket
upending operation etc.), an adequate number of steps shall be analysed to ensure that the critical
load cases for the derivation of hook loads are identified. Where it is noted that there is the possibility
for higher loads to occur between the angles selected, then intermediate steps between the selected
angles should be considered.
6.2.6
The calculated hook loads are to be checked against the crane capacities - see Section 10.3.
6.2.7
Beware of different approaches to crane capacity for land-based cranes, which typically specify the
maximum load below the boom-head pulleys, and offshore cranes which typically specify the maximum
hook load for a given radius. This is due to land-based cranes being more often re-reeved with
different blocks to optimise crane capacity but requires the deduction of hook block and rope weight to
find the hook load. For further details, see Section 13.7.
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