ISO 23113:2020

Ships and marine technology - Ship's mooring and towing fittings - Seats for closed chocks

This document specifies the types, nominal sizes, dimensions and materials, as well as construction, manufacturing and marking requirements, for the seats for closed chocks installed to lead the mooring and towing rope of a ship,

Navires et technologie maritime — Corps-morts et ferrures de remorquage de navires — Sièges pour chaumards fermés

General Information

• Status: Published
• Publication Date: 27-Aug-2020
• ICS: 47.020.50 - Deck equipment and installations
• Technical Committee: ISO/TC 8/SC 4 - Outfitting and deck machinery
• Drafting Committee: ISO/TC 8/SC 4/WG 4 - Ship's mooring and towing fittings
• Current Stage: 9060 - Close of review
• Completion Date: 04-Mar-2031

Overview

ISO 23113:2020 - Ships and marine technology - Seats for closed chocks defines requirements for the seats that carry closed chocks used to lead mooring and towing ropes from a ship’s inboard to outboard. The standard specifies types, nominal sizes, dimensions, materials, and rules for construction, manufacturing, inspection and marking. It is intended to ensure safe, durable seats for closed chocks that transmit loads reliably to the hull without plastic deformation or cracking.

Key topics and technical requirements

• Classification and types
  • Type A: deck‑mounted closed chock seats
  • Type B: deck and side shell‑mounted seats
  • Type C: brackets for bulwark‑mounted closed chocks
• Nominal sizes and dimensions
  • Nominal sizes correspond to closed chock sizes (see ISO 13729). Examples in the standard include sizes such as 250 × 200 × 214 and 500 × 400 × 525B. Detailed tables and figures specify dimensional and welding requirements for each type.
• Materials
  • Seats shall be manufactured from weldable steel plates with a yield point of not less than 235 N/mm².
• Construction and strength
  • Foundations and welds must be designed for the actual load directions so that maximum loads are transmitted to hull structure without plastic deformation or cracks.
  • Annex A provides the basis for strength assessment using finite element analysis and defines horizontal and vertical load cases relevant to mooring/towing operations.
  • Stress criterion: combined stress under the SWL is limited (the standard sets allowable stress margins relative to material yield).
• Manufacturing and inspection
  • All surfaces, including welds, must be free of visible flaws.
  • Rope‑contact surfaces must be smooth to avoid abrasion damage.
  • External anti‑corrosion protective coating is required.
• Marking and documentation
  • Safe Working Load (SWL) must be recorded on the ship’s towing and mooring plan per IMO Circular MSC/Circ.1175 and clearly marked on the seat or deck (in tonnes, “t”).

Applications and users

• Practical uses: specifying and verifying seats for closed chocks during ship design, outfitting, refit and maintenance; ensuring compatibility with mooring/towing plans; guiding manufacturers in producing compliant fittings.
• Typical users:
  • Shipbuilders and shipyards
  • Naval architects and marine engineers
  • Manufacturers of mooring and towing fittings
  • Classification societies and surveyors
  • Ship operators and crew responsible for mooring/towing arrangements

Related standards

• ISO 13729 (closed chocks - nominal sizes/thickness)
• IMO Circular MSC/Circ.1175 (guidance on shipboard towing and mooring equipment)

Keywords: ISO 23113:2020, seats for closed chocks, ship mooring fittings, SWL, closed chock seats, marine technology, mooring and towing.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23113
First edition
2020-08
Ships and marine technology — Ship's
mooring and towing fittings — Seats
for closed chocks
Navires et technologie maritime — Corps-morts et ferrures de
remorquage de navires — Sièges pour chaumards fermés
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 1
4.1 Type . 1
4.2 Nominal sizes . 1
5 Dimensions . 2
6 Materials . 2
7 Construction . 2
8 Manufacturing and inspection . 2
9 Marking . 2
Annex A (normative) Basis for strength assessment of the seats for closed chocks .9
Bibliography .13
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www .iso .org/ iso/ foreword .html.
This document was prepared Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 4, Outfitting and deck machinery.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved

Introduction
The seat for closed chocks is a seat type of ship’s mooring and towing fitting installed on the shipside to
lead the mooring and towing rope from the ship’s inboard to outboard.
INTERNATIONAL STANDARD ISO 23113:2020(E)
Ships and marine technology — Ship's mooring and towing
fittings — Seats for closed chocks
1 Scope
This document specifies the types, nominal sizes, dimensions and materials, as well as construction,
manufacturing and marking requirements, for the seats for closed chocks installed to lead the mooring
and towing rope of a ship,
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
IMO Circular MSC/Circ.1175, Guidance on shipboard towing and mooring equipment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
safe working load
SWL
safe load limit (maximum permissible load) of the fittings used for mooring and towing
4 Classification
4.1 Type
The seat for closed chocks shall be classified by its installation site as belonging to one of the
following types:
a) Type A: seat for deck-mounted closed chock;
b) Type B: seat for deck and side shell-mounted closed chock;
c) Type C: brackets for bulwark-mounted closed chock.
4.2 Nominal sizes
The nominal sizes of seats for closed chocks are denoted by reference to the same nominal sizes of closed
chocks (ISO 13729). For the seats for closed chocks having the same size, the letter of the alphabet, i.e.
A, B or C, is followed by the nominal size for the different safe working loads (SWL).
The nominal sizes are:
250 × 200 × 214, 300 × 250 × 286, 350 × 250 × 333, 400 × 250 × 381, 450 × 250 × 381, 500 × 250 × 381,
400 × 250 × 428, 450 × 250 × 428, 500 × 250 × 428, 500 × 400 × 428, 500 × 250 × 525A, 500 × 400 ×
525A, 500 × 250 × 525B, 500 × 400 × 525B
5 Dimensions
The seats for closed chocks shall have dimensions and particulars in accordance with Tables 1, 2 and 3,
and Figures 1, 2 and 3.
6 Materials
Weldable steel plates having a yield point of not less than 235 N/mm shall be used for manufacturing
the seats for closed chocks.
7 Construction
The foundation of the closed chocks shall be determined by considering the actual load direction. The
foundation and welding connections to the hull shall guarantee a reliable transmission of the maximum
loading of the closed chocks to the hull construction without any plastic deformation or cracks.
8 Manufacturing and inspection
8.1 All surfaces of the seats for closed chocks, including welded surfaces, shall be free from any visible
flaws or imperfections.
8.2 All surfaces in contact with the ropes shall be free from surface roughness or irregularities likely to
cause damage to the ropes by abrasion.
8.3 The seats for closed chocks shall be coated externally with an anti-corrosion protective finish.
9 Marking
9.1 The SWL for the intended use of the seats for closed chocks shall be noted in the towing and
mooring plan available on board for the guidance of the shipmaster, as specified in IMO circular MSC/
Circ.1175.
9.2 The actual SWL on board shall be determined by considering
...