0027-nd rev 11.2 8-jul-16 guidelines for marine lifting and lowering operations
Figure 6-1 Resolving Sling Loading 6.3.3
For lift points where double trunnions or double padears are connected to a structure and are
considered as a single lift point when determining loads, such as a double trunnion connected to the
apex chord of a flare, the following effects of tilt and rotation shall be considered in the design of both
structure and slings or grommets.
a)
Tilt can cause uneven loading unless there is means to ensure that the load on the two sides
of the trunnion or padear is equalised.
b)
Tilt can also cause the rigging to shift along the bearing surface of the trunnion or padear
such that increased moment is introduced into the trunnion or padear.
c)
As a result of friction, rotation of the sling eye or grommet round the padear or trunnion can
result in significant torque on the padear or trunnion (and unequal loading in the legs of a
grommet or doubled sling).
The use of a “matched pair” of slings or grommets connected to a double trunnion or double padear
should be avoided as they are rarely adequately matched. If they are used, then the slings or
grommets must have identical lengths when measured under the same tension. Where there are
differences in the lengths, the effect of unequal lengths shall be considered in the design (see Section
5.8.5 for further details).
6.4 SLING LOADS 6.4.1
The sling load is the vertical lift point load resolved by the sling angle to determine the direct (axial)
load in the sling and lift point using the minimum possible sling angle.
6.4.2
The sling angle should not normally be less than 45º to the horizontal although for lifts that are installed
at an angle this may not be the case, e.g. flare booms installed by a single crane, the upper rigging
may be less than 45º.
Sling IP
`