Section 7 Wing tank structure

7.1.1 The wing tank structure is generally to comprise the double skin side and topside structure. On a self-unloading bulk carrier, a hopper side structure may be incorporated, see Figure 4.1.2 Typical Great Lakes Bulk Carrier without self-unloading equipment.

7.1.2 Requirements given in this Section are for longitudinal or transverse framing of the side shell and longitudinal bulkhead.

7.1.3 The buckling strength requirements of Ch 4, 3.6 Hull buckling strength are to be satisfied.

7.1.4 The minimum thickness of structural members in the wing tank structure is to be 9,5 mm.

7.2.1 Hopper side structure is typically arranged in self-unloading bulk carriers.

7.2.2 The sloped hopper structure, clear of the hopper side tank structure, on self-unloading bulk carriers, is not normally included in the longitudinal strength calculations. Where it is included in the longitudinal or transverse strength calculations, the structure is to be specially considered.

7.2.3 Where the structure is longitudinally framed, transverses are to be arranged in the hopper side structure in alignment with the double bottom floors to ensure continuity of transverse strength.

7.2.4 The scantlings of hopper structures are to be determined to satisfy the following:

1. Deep tank requirements if applicable.

2. Cargo loading requirements.

The deep tank requirements are given in Rules for Ships, Table 1.9.1 Watertight and deep tank bulkhead scantlings. The cargo loading requirements are to be specially considered.

7.2.5 The scantlings of the sloped hopper bulkhead transverses are to comply with the requirements of Table 7.9.1 Hopper tank primary structure of the Rules for Ships, with a maximum stowage rate of 1,00 m³/tonne. Alternative scantlings may be considered based on direct calculations.

7.2.6 Where the breadth of the double bottom structure exceeds the breadth of the hopper tank structure over the breadth of the ship, suitable scarphing of the inner bottom plating is to be arranged into the wing bottom structure by horizontal scarphing brackets, fitted in line with the inner bottom plating at each transverse. These brackets are to be arranged on each side of the transverse, see Figure 4.7.1 Scarphing of inner bottom plating into the wing/hopper side structure.

7.2.7 Where the bottom and side shell structure and the sloped longitudinal bulkhead are transversely framed, the transverse web frames are to be in line with the double bottom floors and the single bottom floors integrated into the double bottom structure, see Figure 4.8.1 Floor.

Figure 4.7.1 Scarphing of inner bottom plating into the wing/hopper side structure

7.2.8 The scantlings of the sloped longitudinal bulkhead are to be in accordance with the greater of Table 7.8.1 Strengthening for heavy cargo requirements of the Rules for Ships, using a head of cargo measured vertically from the location under consideration to the strength deck at side or underside of topside tank with a maximum stowage rate not exceeding 1,00 m³/tonne. The scantlings are also to comply with Table 1.9.1 Watertight and deep tank bulkhead scantlings of the Rules for Ships and are to be maintained throughout the cargo region.

7.3.1 The double skin and vertical longitudinal bulkhead may be either longitudinally or transversely framed.

7.3.2 Where the side shell and the vertical longitudinal bulkhead are transversely framed, the transverse web frames are to be in line with floors in the double bottom. The single bottom floors in the side structure are to be arranged with the free edge suitably stiffened.

7.3.3 Where the double skin structure is longitudinally framed, the transverses are to be in line with the transverses below and horizontal stringers are to be arranged at the upper and lower knuckle connections of the longitudinal bulkhead. The stiffening of the knuckle connection is to be specially considered.

7.3.4 The scantlings of the vertical longitudinal bulkhead are to be in accordance with Table 1.9.1 Watertight and deep tank bulkhead scantlings of the Rules for Ships and are to be maintained throughout the cargo region.

7.4.1 The topside structure is to be longitudinally framed.

7.4.2 The thickness of the sloped longitudinal bulkhead plating is to be in accordance with Pt 4, Ch 7, 7.2 Bulkhead plating 7.2.1.(b) of the Rules for Ships.

7.4.3 The section moduli of the longitudinal bulkhead stiffeners, are to be in accordance with Pt 4, Ch 7, 7.3 Bulkhead stiffeners of the Rules for Ships, with h ₄ value, the greater of the distance in metres from the middle of the effective length to the top of the tank, or half the distance to the top of the overflow or 1,5 m, whichever is the greatest.

7.4.4 Transverse web frames are to be in line with the transverses in the double skin structure below and transverse arch webs in the cargo holds under the cross deck strips and are to be suitably stiffened.

7.5.1 The scantlings of the tank end bulkheads are to comply with the requirements for deep tanks in Table 1.9.1 Watertight and deep tank bulkhead scantlings of the Rules for Ships.

7.5.2 Where possible, the location of the transverse tank end bulkheads are to be in line with the transverse screen bulkheads in the cargo holds.