Section 2 Lifting capacity

2.1.1 For the purposes of classification or certification, each shiplift and transfer system facility will be designated a lifting capacity on the following basis:

1. Maximum distributed load (MDL):

   1. This is the maximum load, in tonnes/metre, without any wind loading, which can be uniformly distributed along the centreline of the platform, or where docking is only via transfer cradles which are evenly distributed along the inner longitudinal transfer rails over the maximum docking length of the platform or which has been used in establishing the scantlings of the platform and capacity of the hoist units. It is to be taken as:

      (Capacity of one pair of hoists minus deadweight of the length of pontoon associated with these hoists) divided by the hoist spacing.

   2. For transfer systems that incorporate trestles and independent bogies, special attention is to be given to the local platform structure supporting any load concentrations from the trestle legs.

   3. The maximum distributed load (MDL) on the platform includes the weight of cradles, trestles or blocks used for supporting the ship.

   4. In addition, the MDL may also be expressed as being exclusive of the transfer system and this would relate directly to the weight distribution of the ships being docked.

2. Maximum lifting capacity (MLC):

   1. This is the maximum theoretical load, in tonnes, without wind loading, which can be lifted on the platform. It is to be taken as:

      MDL x maximum effective docking length.
      This capacity takes no account of dynamic loading or uncertainties in the weight distribution of the ship being docked and consequently this will not be used for operational purposes. Where specially requested, this value may be included in the certification issued for information purposes only.

3. Nominal lifting capacity (NLC):

   1. This is the maximum displacement, in tonnes, of a ship of normal form which can be lifted without exceeding the maximum distributed load for which the platform is designed, and is to be taken as:
      NLC = MDL x maximum effective docking length x a distribution factor.

   2. The NLC is calculated to provide Operators with a guide of the load to which the platform may be subjected from a ship of normal form, so that the MDL is not exceeded at any point on the platform during docking or transfer operations. This may be used, for example, when the weight distribution of the ship being docked is not accurately known.

   3. Normal form is taken to differentiate between conventional mono-hull ships, which would usually dock along the keel block centreline of the platform, and other ship forms such as catamarans, trimarans, swaths, semi-subs, ships with moonpools, etc. which would require specific blocking arrangements.

2.2.1 The distribution factor is to ensure that the maximum distributed load is not exceeded anywhere along the effective length of the platform and to allow for dynamic factors. The following values are generally to be adopted:

1. Platforms of articulated design (that have no longitudinal stiffness or bending rigidity) and incorporating conventional block, cradle or trestle arrangements :0,67.

2. Platforms of articulated design incorporating flexible (fluid bed) cradles, or platforms of rigid design (a rigid design is one where moments are carried through the platform structure) incorporating flexible or rigid cradles: 0,83. Distribution factors in excess of 0,83, requested by the designer, will be specially considered.

2.2.2 Special consideration may be given to platforms with a fluid bed transfer system which is used to redistribute local peak ship loadings in excess of the MDL. Calculations in support of these requests must be submitted for consideration by LR.

2.3.1 For ships with direct blocking, the maximum effective docking length on the platform is taken as the total length between hoists plus the length of end cantilevers. Each of these cantilevers is to be taken as not greater than 0,4 times the hoist spacing.

2.3.2 Special consideration will be given to cantilever overhangs that are greater than 0,4 x hoist spacing, where they are supported by the dockside during transfer operations.

2.3.3 For shiplifts where vessels dock directly on to transfer cradles, the docking length is typically less than the effective docking length where ships dock directly on the platform centreline. The effective docking length when docking directly on to the transfer system (cradles or trestles) occurs may be determined by:

• the number of cradles x cradle spacing; or
• the number of trestles x trestle spacing.

2.4.1 The MDL and the NLC will appear on the certification issued. Where requested, the MLC will also be included in the certification for information purposes only.

2.4.2 The lifting capacities will be specially considered in cases where:

1. The block or cradle arrangement is such that the loads are not applied along the centreline of the platform, i.e. asymmetric loading.

2. The design incorporates different maximum distributed loads along the length of the platform.