Section 3 Hull envelope plating
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 4 Ship Structures (Ship Types) - Chapter 4 Offshore Support Vessels - Section 3 Hull envelope plating

Section 3 Hull envelope plating

Parent topic: Chapter 4 Offshore Support Vessels

3.1 Hull envelope plating

3.1.1 Anchor handing activities often give rise to areas of high local loads and/or frequent impacts, such as in way of stern rollers and immediately adjacent to high duty bollards. The shell in way of high loads and/or frequent impacts is to be suitably reinforced by increasing shell plate thickness, additional stiffening support or other appropriate means.

3.2 Side shell

3.2.1 The thickness of side shell is to be that required by Pt 4, Ch 1, 5.4 Side shell but is not to be less than given by Table 4.3.1 Minimum side shell thickness

3.2.2 As an alternative, where over the length of a vessel, portions of the sheerstrake that are not protected by an efficient fender, the sheerstrake is to be increased by a minimum of 5 mm thickness. The increased thickness shall extend from the deck level to not less than 600 mm below the deck level.

Table 4.3.1 Minimum side shell thickness

Ship type Minimum thickness, mm
Offshore supply ships 9
Standby vessels 8
Anchor handler 9

3.3 Weather decks

3.3.1 Where cargo is to be carried on weather decks, the scantlings are to be suitable for the specified loadings. The thickness, t, of deck plating is to be not less than the greater of:

  1. t = 0,025L + 4.5 + ta mm

  2. t = mm

    Where

    P = specified design load for weather deck, in tonnef/m2
    =
    h = equivalent design head, in metres, not to be taken less than 3,5 m
    s = spacing of secondary stiffeners, in mm
    σ = yield stress of plating, in N/mm2
    fm = 0,75
    fy = 0,67
    ta = 2,5 mm, in general
    = 1,0 mm, for ships with dedicated class notation standby vessel.

3.3.2 Scantlings are to be increased locally where specialised cargoes are likely to induce concentrated loads that exceed the specified design load. Acceptable stress levels are given in Pt 4, Ch 3, 7.2 Towing equipment foundations 7.2.4.

3.3.3 Deck areas, where there are arrangements for the collection and handling of anchors and associated equipment, are to be protected by wooden sheathing. Alternatively, this can be omitted if the plate thickness is increased by 2,5 mm.

3.4 Cargo containment

3.4.1 Means are to be provided to enable deck cargoes to be adequately secured and protected. In general, suitable inner bulwarks, rails, bins or storage racks of substantial construction are to be provided and properly secured to adequately strengthened parts of the hull structure. Properly designed locking equipment or efficient means of lashing containers are to be fitted where appropriate. Small hatches (including escape hatches), valve controls, ventilators, air pipes, etc. are to be situated clear of the cargo containment areas.

Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.