2.9 Ships engaged in lifting operations
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Statutory Documents - IMO Publications and Documents - International Codes - 2008 IS Code – International Code on Intact Stability, 2008 - Part B – Recommendations for ships engaged in certain types of operations, certain types of ships and additional guidelines - Chapter 2 – Recommended design criteria for ships engaged in certain types of operations and certain types of ships - 2.9 Ships engaged in lifting operations

2.9 Ships engaged in lifting operations

2.9.1 Application

2.9.1.1 The provisions given hereunder apply to ships the keel of which is laid or which is at a similar stage of constructionfootnote on or after 1 January 2020 engaged in lifting operations and to ships converted to carry out lifting operations after this date.

2.9.1.2 The provisions of this section should be applied to operations involving the lifting of the ship's own structures or for lifts in which the maximum heeling moment due to the lift is greater than that given in the following:

  • ,

where:

  • ML = Threshold value for the heeling moment, in (t.m), induced by the (lifting equipment and) load in the lifting equipment;

  • GM = The initial metacentric height, in (m), with free surface correction, including the effect of the (lifting equipment and) load in the lifting equipment;

  • f = the minimum freeboard, in (m), measured from the upper side of the weather deck to the waterline;

  • B = the moulded breadth of the ship, in (m); and

  • Δ = the displacement of the ship, including the lift load, in (t).

The provisions of this section also apply to ships which are engaged in lifting operations where no transverse heeling moment is induced and the increase of the ship's vertical centre of gravity (VCG) due to the lifted weight is greater than 1%.

The calculations should be completed at the most unfavourable loading conditions for which the lifting equipment shall be used.

2.9.1.3 For the purpose of this section, waters that are not exposed are those where the environmental impact on the lifting operation is negligible. Otherwise, waters are to be considered exposed. In general, waters that are not exposed are calm stretches of water, i.e. estuaries, roadsteads, bays, lagoons; where the wind fetchfootnote is six nautical miles or less.

2.9.2 Load and vertical centre of gravity for different types of lifting operations

2.9.2.1 In lifting operations involving a lifting appliance consisting of a crane, derrick, sheerlegs, a-frame or similar:

  • .1 the magnitude of the vertical load (PL) should be the maximum allowed static load at a given outreach of the lifting appliance;

  • .2 the transverse distance (y) is the transverse distance between the point at which the vertical load is applied to the lifting appliance and the ship centreline in the upright position;

  • .3 the vertical height of the load (KGload) is taken as the vertical distance from the point at which the vertical load is applied to the lifting appliance to the baseline in the upright position; and

  • .4 the change of centre of gravity of the lifting appliance(s) need to be taken into account.

2.9.2.2 In lifting operations not involving a lifting appliance consisting of a crane, derrick, sheerlegs, a-frame or similar, which involve lifting of fully or partially submerged objects over rollers or strong points at or near a deck-level:

  • .1 the magnitude of the vertical load (PL) should be the winch brake holding load;

  • .2 the transverse distance (y) is the transverse distance between the point at which the vertical load is applied to the ship and the ship centreline in the upright position; and

  • .3 the vertical height of the load (KGload) is taken as the vertical distance from the point at which the vertical load is applied to the ship to the baseline in the upright position.

2.9.3 Stability criteria

2.9.3.1 The stability criteria included herein, or the criteria contained in paragraphs 2.9.4, 2.9.5 or 2.9.7, as applicable shall be satisfied for all loading conditions intended for lifting with the lifting appliance and its load at the most unfavourable positions. For the purpose of this section, the lifting appliance and its load(s) and their centre of gravity (COG) should be included in the displacement and centre of gravity of the ship, in which case no external heeling moment/heeling lever is applied.

2.9.3.2 All loading conditions utilized during the lifting operations are to comply with the stability criteria given in sections 2.2 and 2.3 of part A. Where the ship's characteristics render compliance with section 2.2 of part A impracticable, the equivalent stability criteria given in chapter 4 of the explanatory notes to the 2008 IS Code should apply. During the lifting operation, as determined by paragraphs 2.9.1, the following stability criteria should also apply:

  • .1 the equilibrium heel angle, φ1, shall not be greater than the maximum static heeling angle for which the lifting device is designed and which has been considered in the approval of the loading gear;

  • .2 during lifting operations in non-exposed waters, the minimum distance between the water level and the highest continuous deck enclosing the watertight hull, taking into account trim and heel at any position along the length of the ship, shall not be less than 0.50 m; and

  • .3 during lifting operations in exposed waters, the residual freeboard shall not be less than 1.00 m or 75% of the highest significant wave height Hs, in (m), encountered during the operation, whichever is greater.

2.9.4 Lifting operations conducted under environmental and operational limitations

2.9.4.1 For lifting conditions carried out within clearly defined limitations set forth in paragraph 2.9.4.1.1, the intact criteria set forth in paragraph 2.9.4.1.2 may be applied instead of the criteria included in paragraph 2.9.3.

  • .1 The limits of the environmental conditions should specify at least the following:

    • the maximum significant wave height, HS; and

    • the maximum wind speed (1 minute sustained at 10 m above sea level).

      The limits of the operational conditions should specify at least the following:

    • the maximum duration of the lift;

    • limitations in ship speed; and

    • limitations in traffic/traffic control.

  • .2 The following stability criteria should apply with the lifted load is at the most unfavourable position:

    • .1 the corner of the highest continuous deck enclosing the watertight hull shall not be submerged;

    • .2 ARL ≥ 1.4 × AHL

    • where:

      • ARL = The area under the net righting lever curve, corrected for crane heeling moment and for the righting moment provided by the counter ballast if applicable, extending from the equilibrium heeling angle, φ1, to the angle of down flooding, φF, the angle of vanishing stability, φR, or the second intersection of the righting lever curve with the wind heeling lever curve, whichever is less, see figure 2.9-1;

      • AHL = The area below the wind heeling lever curve due to the wind force applied to the ship and the lift at the maximum wind speed specified in paragraph 2.9.4.1.1, see figure 2.9-1.

Figure 2.9-1 – Intact criteria under Environmental and Operational limitations

    • .3 The area under the net righting lever curve from the equilibrium heel angle, φ1, to the down flooding angle φF, or 20°, whichever is less, shall be at least 0.03 m rad.

2.9.5 Sudden loss of hook load

2.9.5.1 A ship engaged in a lifting operation and using counter ballasting should be able to withstand the sudden loss of the hook load, considering the most unfavourable point at which the hook load may be applied to the ship (i.e. largest heeling moment). For this purpose, the area on the side of the ship opposite to the lift (Area 2) should be greater than the residual area on the side of the lift (Area 1), as shown in figure 2.9-2, by an amount given by the following:

  • Area 2 > 1.4 × Area 1, for lifting operations in waters that are exposed.

  • Area 2 > 1.0 × Area 1, for lifting operations in waters that are not exposed.

Figure 2.9-2

where:

  • GZ1 = net righting lever (GZ) curve for the condition before loss of crane load, corrected for crane heeling moment and for the righting moment provided by the counter ballast if applicable;

  • GZ2 = net righting lever (GZ) curve for the condition after loss of crane load, corrected for the transverse moment provided by the counter ballast if applicable;

  • φe2 = the angle of static equilibrium after loss of crane load;

  • φf = the angle of down-flooding or the heel angle corresponding to the second intersection between heeling and righting arm curves, whichever is less; and

  • The term "net righting lever" means that the calculation of the GZ curve includes the ship's true transverse centre of gravity as function of the angle of heel.

2.9.6 Alternative method

2.9.6.1 The criteria in paragraph 2.9.6 may be applied to a ship engaged in a lifting operation, as determined by paragraph 2.9.1, as an alternative to the criteria in paragraph 2.9.3 through paragraph 2.9.5, as applicable. For the purpose of this section and the stability criteria set out in paragraph 2.9.7, the lifted load which causes the ship to heel is translated for the purpose of stability calculation to a heeling moment/heeling lever which is applied on the righting lever curve of the ship.

2.9.6.2 The heeling moment applied to the ship due to a lift and the associated heeling lever should be calculated using the following formulae:

HMφ = PL · y · cos φ

HLφ = HMφ ÷ Δ

where

  • HMφ = the heeling moment, in (t·m), due to the lift at φ;

  • PL = the vertical load, in (t), of the lift, as defined in 2.9.2.1.1;

  • y = the transverse distance, in (m), of the lift, metres, as defined in 2.9.2.1.2;

  • φ = angle of heel;

  • HLφ = the heeling lever, in (m) due to the lift at φ; and

  • Δ = the displacement, in (t) of the ship with the load of the lift.

2.9.6.3 For application of the criteria contained in paragraph 2.9.7 involving the sudden loss of load of the lift in which counter-ballast is used, the heeling levers that include the counter-ballast should be calculated using the following formulae:

where

  • CBM = the heeling moment, in (t·m), due to the counter-ballast;

  • CHL1 = combined heeling lever, in (m), due to the load of the lift and the counter-ballast heeling moment at the displacement corresponding to the ship with the load of the lift; and

  • CBHL2 = heeling lever, in (m), due to the counter-ballast heeling moment at the displacement corresponding to the ship without the load of the lift.

2.9.6.4 The equilibrium heel angle φe referred to in 2.9.7 means the angle of first intersection between the righting lever curve and the heeling lever curve.

2.9.7 Alternative stability criteria

2.9.7.1 For the loading conditions intended for lifting, but before commencing the operation, the stability criteria given in sections 2.2 and 2.3 of part A should be complied with. Where a ship's characteristics render compliance with section 2.2 of part A impracticable, the equivalent stability criteria given in chapter 4 of the explanatory notes to the 2008 IS Code should apply. During the lifting operation, as determined by paragraph 2.9.1, the following stability criteria should apply:

  • .1 the residual righting area below the righting lever and above the heeling lever curve between φe and the lesser of 40° or the angle of the maximum residual righting lever should not be less than:

  • 0.080 m rad, if lifting operations are performed in waters that are exposed; or

  • 0.053 m rad, if lifting operations are performed in waters that are not exposed;

  • .2 in addition, the equilibrium angle is to be limited to the lesser of the following:

    • .1 10 degrees;

    • .2 the angle of immersion of the highest continuous deck enclosing the watertight hull; or

    • .3 the lifting appliance allowable value of trim/heel (data to be derived from sidelead and offlead allowable values obtained from manufacturer).

2.9.7.2 A ship engaged in a lifting operation and using counter ballasting should be able to withstand the sudden loss of the hook load, considering the most unfavourable point at which the hook load may be applied to the ship (i.e. largest heeling moment). For this purpose, the area on the side of the ship opposite from the lift (Area 2) in figure 2.9-3 should be greater than the residual area on the side of the lift (Area 1) in figure 2.9-3 by an amount given by the following:

Area 2 – Area 1 > K,

where:

  • K = 0.037 m rad, for a lifting operation in waters that are exposed; and

  • K = 0.0 m rad, for a lifting operation in waters that are not exposed.

Figure 2.9-3

  • GZ(1) = The righting arm curve at the displacement corresponding to the ship without hook load;

  • GZ(2) = The righting arm curve at the displacement corresponding to the ship with hook load;

  • Area2 = residual area between GZ(1) and CBHL2 up to the lesser of the down-flooding angle or the second intersection of GZ(2) and CBHL2;

  • Area1 = residual area below GZ(1) and above CBHL2 up to φe.

2.9.8 Model tests or direct calculations

2.9.8.1 Model tests or direct calculations, performed in accordance with a methodology acceptable to the Administration, that demonstrate the survivability of the ship after sudden loss of hook load, may be allowed as an alternative to complying with the requirements of paragraph 2.9.5 or 2.9.7.2, provided that:

  • .1 the effects of wind and waves are taken into account; and

  • .2 the maximum dynamic roll amplitude of the ship after loss of load will not cause immersion of unprotected openings.

2.9.9 Operational procedures against capsizing

2.9.9.1 Ships should avoid resonant roll conditions when engaged in lifting operations.

Parent topic: Chapter 2 – Recommended design criteria for ships engaged in certain types of operations and certain types of ships
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