Section 3 Materials
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 11 Transmission Systems - Chapter 2 Shafting Systems - Section 3 Materials

Section 3 Materials

Parent topic: Chapter 2 Shafting Systems

3.1 Materials for shafts

3.1.1 Components are to be manufactured and tested in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022 (hereinafter referred to as the Rules for Materials).

3.1.2 The specified minimum tensile strength of forgings for shafts is to be selected within the following general limits:

  1. Carbon and carbon-manganese steel − 400 to 760 N/mm2. See also Pt 11, Ch 2, 4.4 Screwshafts and tube shafts 4.4.3.

  2. Alloy steel main propulsion shafting:

    1. not exposed to seawater − not exceeding 800 N/mm2,

    2. for other forgings - not exceeding 1100 N/mm2.

3.1.3 Where it is proposed to use alloy steel forgings, particulars of the chemical composition, mechanical properties and heat treatment are to be submitted for approval.

3.1.4 Where shafts may experience vibratory stresses close to the permissible stresses for transient operation, the materials are to have a specified minimum tensile strength of 500 N/mm2.

3.1.5 Where materials with greater specified or actual tensile strengths than the limitations given above are used, reduced shaft dimensions or higher permissible vibration stresses are not acceptable when derived from the formulae used in sub-Sections Pt 11, Ch 2, 4.2 Intermediate shafts, Pt 11, Ch 2, 4.4 Screwshafts and tube shafts, Pt 11, Ch 2, 4.5 Hollow shafts and Pt 13, Ch 1, 3.2 Limiting stress in propulsion shafting unless, for intermediate shafts only, it is verified that the materials exhibit a similar fatigue life to conventional steels through compliance with the requirements in Pt 11, Ch 2, 7 Approval of alloy steel used for intermediate shaft material.

3.1.6 Unprotected screwshafts and tubeshafts exposed to sea-water are in general to be manufactured from materials that show improved corrosion resistance in seawater when compared to carbon steel and alloy steels, referred to in Pt 11, Ch 2, 3.1 Materials for shafts 3.1.1 and Pt 11, Ch 2, 3.1 Materials for shafts 3.1.3; examples of some such alloys are indicated in Table 2.4.1 `A’ Value for use in unprotected screwshaft formula . However, the selection of these alloys should carefully consider the level of corrosion resistance in relation to all the environmental service conditions and operational requirements applicable to the individual vessel.

3.1.7 In the selection of materials for shafts, keys, locking nuts etc. consideration is to be given to their compatibility with the proposed propeller material.

3.1.8 Where shafts are manufactured from composite material the process is to be approved.

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