Section 3 Hull Structures

301. General

Hull structuress are to be in accordance with this section in addition to relevant requirements in each chapter of Ch 3, Sec 2.

302. Supporting structures of anchor handling equipments

The surroundings of the supporting structures of anchor handling equipments and the part where an- chors are loaded must be ensured to be sufficiently strong.

303. Suitable construction for anchor handling operation

1. Ships are to have completely clear decks with no obstacles in order to effectively handle anchors.

2. In cases where anchor handling operations are conducted using after deck stern rollers, the aft ter- minals nearby the stern areas for anchor handling are to be round in shape.

304. Supporting structures of towing equipment

1. In principle, towing equipment is to be located on longitudinals, beams or girders, which are parts of the deck construction.

2. In case the towing equipment cannot be located as specified in 1. above, towing equipment is to be reinforced to the stiffener.

22 Guidance for Offshore Support Vessels 2015

3. The supporting structures of towing equipment are to be such to ensure sufficient strength.

4. The design load on fittings is to take into account all acting loads.

5. The design loads for the supporting structures of towing equipment are to be not less than the breaking strength of the towline system.

305. Side Shell and Frames

For vessels subject to impact loadings during anchor handling or towing operations, it is recom- mended that side frames and side shell plating comply with Ch 3, 203.

306. Work Deck

1. Reinforcement against Impact, Wear and Tear

Plating thickness at the aft portion of the work deck is to be increased to protect the structure against heavy impact loads and wear and tear. It is recommended that minimum plating thickness in this area be not less than 25 mm. Alternative arrangements will be considered on case by case basis for re-enforcement against impact and wear and tear. Where heavy anchors and/or chains are carried on deck, suitable means for distributing their weights properly to deck structures are to be provided. The stresses in deck members are not to exceed the following Table 5.2.

Table 5.2 The stresses in deck members

307. Work Deck Protection

The aft deck areas exposed to anchor drags should not be fitted with sheathings or if present, the sheathings are to be suitably protected. In addition, any protrusion above deck such as coamings, manholes, lashing pad eyes, etc. shall be avoided.

The deck plating thickness in these areas shall be suitably increased to allow for abrasion and me- chanical damage.

308. Anchors and Chains Securing Means

Pad eyes for securing and/or moving the anchors and/or chains are to be welded directly to the deck plating without doublers.. The deck in way of the pad-eyes is to be adequately reinforced. Removable pad eyes are to have firm attachment to the deck sockets or holdings. All pad eyes are to be permanently marked with bead welded SWL values.

309. Arrangements for Shifting Anchors and Chains

The foundations of tugger winches and/or capstans are to be welded directly to the deck plate and with adequate reinforcement underneath.

310. Deck Openings

Access openings, including emergency exits, are to be located clear off the towline sweep area.