(a) Each vessel equipped to counterballast while lifting must be shown by design calculations to be able to withstand the sudden loss of the hook load, in each condition of loading and operation and at each combination of hook load and crane radius.
(b) When doing the calculations required by this section, the hook load and counterballast heeling arms and vessel righting arms, as plotted on graph 173.025, must define areas that satisfy the following equation:
Area II >Area I + K
Where—
(1) K = O for operation on protected waters and 7 foot-degrees (2.13 meter-degrees) for operation on partially protected and exposed waters.
(2) Areas I and II are shown on graph 173.025.
(c) Each heeling arm curve must be defined by—
HA = HAO cos (T)
Where—
HA = heeling arm.
HAO = heeling arm at 0 degrees of heel.
T = angle of heel.
Where—
GZ(1) is the righting arm curve at the displacement corresponding to the vessel without hooking load.
GZ(2) is the righting arm curve at the displacement corresponding to the vessel with hook load.
HA(1) is the heeling arm curve due to the combined heeling moments of the hook load and the counterballast at the displacement with hook load.
HA(2) is the heeling arm due to the counterballast at the displacement without hook load.
Theta(c) is the angle of static equilibrium due to the combined hook load and counterballast heeling moments.
Theta(f) is the downflooding angle on the counterballasted side of the vessel.
[CGD 79-023, 48 FR 51045, Nov. 4, 1983, as amended by CGD 85-080, 61 FR 945, Jan. 10, 1996]
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