ISO 13729:2020
(Main)Ships and marine technology — Ship's mooring and towing fittings — Closed chocks
Ships and marine technology — Ship's mooring and towing fittings — Closed chocks
This document specifies the types, nominal sizes, dimensions and materials, as well as construction, manufacturing and marking requirements, 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 — Chaumards fermés
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INTERNATIONAL ISO
STANDARD 13729
Second edition
2020-08
Ships and marine technology —
Ship's mooring and towing fittings —
Closed chocks
Navires et technologie maritime — Corps-morts et ferrures de
remorquage de navires — Chaumards fermés
Reference number
©
ISO 2020
© ISO 2020
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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 closed chocks . 9
Bibliography .14
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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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
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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.
The committee responsible for this document is Technical Committee ISO/TC 8, Ships and marine
technology, Subcommittee SC 4, Outfitting and deck machinery.
This second edition cancels and replaces the first edition (ISO 13729:2012), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— technical guidelines have been added in 7.2and 7.3;
— the definition of SWL (3.1) has been reworded;
— the extension lines and dimension line in Figures 1 and 2 have been amended;
— technical information on FEM has been added in A.3.2.
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 closed chock is a 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.
The closed chocks are normally adopted for ships which use wire ropes. The radius of chock surface
was designed based on the bending ratio of rope through the chock of not less than twelve times the
wire rope diameter.
INTERNATIONAL STANDARD ISO 13729:2020(E)
Ships and marine technology — Ship's mooring and towing
fittings — Closed chocks
1 Scope
This document specifies the types, nominal sizes, dimensions and materials, as well as construction,
manufacturing and marking requirements, 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 closed chock shall be classified by its installation site as belonging to one of the following types:
a) Type A: deck-mounted closed chock;
b) Type B: bulwark-mounted closed chock.
4.2 Nominal sizes
The nominal sizes, L × H × D, of closed chocks are denoted by reference to the width and height of the
opening and the depth of the chock, in millimetres. For the closed chocks having the same size, the
letter of the alphabet, i.e. A or B, is followed by the nominal size for the different 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 closed chocks shall have dimensions and particulars in accordance with Tables 1, 2, 3 and 4, and
Figures 1 and 2.
6 Materials
The following material shall be used for manufacturing the closed chocks:
— steel casting material, having a yield point of not less than 235 N/mm or equivalent.
The carbon contents of the steel casting shall not be more than 0,23 % considering weldability.
7 Construction
7.1 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.
7.2 The selection of ship’s mooring fittings and mooring lines should take into account the diameter, D,
of surfaces of mooring fittings that are in contact with the mooring line diameter, d, (D/d ratio) to reduce
or mitigate bend ross of strength.
7.3 The tensile strength of mooring rope may be reduced depending on bend radius (D/d ratio)
through the mooring fittings, in accordance with the rope manufacturer’s guidelines.
8 Manufacturing and inspection
8.1 All surfaces of the 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 closed chocks shall be coated externally with an anti-corrosion protective finish.
9 Marking
9.1 The SWL for the intended use of the 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 the foundation and under deck
reinforcement, and it shall be marked on the towing and mooring plan. The actual SWL shall not be over
the SWL indicated in this document.
9.3 The closed chocks shall be clearly marked with their SWL by weld bead or equivalent. The SWL
shall be expressed in tonnes (symbol 't') and be placed so that it is not obscured during operation of the
fitting.
EXAMPLE SWL XXX t
9.4 The SWL mark shall be provided on the foundation of the chock or on the deck.
2 © ISO 2020 – All rights reserved
9.5 The radii of edges and corners not shown in Figure 1 shall be of minimum 25 mm.
Dimensions in millimetres
Key
1 closed chock
a
Alternative welding method.
Figure 1 — Type A — Deck-mounted closed chocks
Table 1 — Dimensions of Type A — Deck-mounted closed chocks
Dimensions in millimetres
Nominal size
l l l l H H H R R R R
1 2 3 4 1 2 3 1 2 3
L × H × D
250 × 200 × 214 488 453 76 265 427 368 108 100 219 160 108
300 × 250 × 286 614 565 89 330 551 481 144 125 282 212 144
350 × 250 × 333 716 660 114 403 601 525 168 125 308 232 168
400 × 250 × 381 820 754 139 475 652 553 192 125 335 236 192
450 × 250 × 381 870 804 164 524 652 553 192 125 335 236 192
500 × 250 × 381 920 854 189 574 652 553 192 125 335 236 192
400 × 250 × 428 870 796 139 500 701 609 216 125 360 268 216
450 × 250 × 428 920 846 164 550 701 609 216 125 360 268 216
500 × 250 × 428 970 896 189 600 701 609 216 125 360 268 216
500 × 400 × 428 970 896 176 600 851 759 216 200 435 343 216
500 × 250 × 525A 1 068 1 000 190 652 798 675 264 125 409 286 264
500 × 400 × 525A 1 068 1 000 193 652 948 825 264 200 484 361 264
500 × 250 × 525B 1 074 1 000 176 652 801 680 264 125 412 291 264
500 × 400 × 525B 1 074 1 000 179 652 951 830 264 200 487 366 264
4 © ISO 2020 – All rights reserved
Table 2 — Dimensions (continued) and SWL of Type A — Deck-mounted closed chocks
Dimensions in millimetres
Welding
Wire rope
Calculated
b
leg SWL c
Nominal size diameter d
weight
R R R d T a
4 5 6 1
length
L × H × D (recommend-
kg
ed)
z kN t
250 × 200 × 214 86 150 128 108 22 6 226 23 18 73
300 × 250 × 286 118 180 154 144 26 6,5 422 43 24 142
350 × 250 × 333 138 200 170 168 30 7,5 549 56 28 222
400 × 250 × 381 156 250 214 192 36 9 687 70 32 310
450 × 250 × 381 156 250 214 192 36 9 706 72 32 322
500 × 250 × 381 156 250 214 192 36 9 765 78 32 337
400 × 250 × 428 178 250 212 216 38 9,5 883 90 36 434
450 × 250 × 428 178 250 212 216 38 9,5 912 93 36 452
500 × 250 × 428 178 250 212 216 38 9,5 932 95 36 472
500 × 400 × 428 178 250 212 216 38 9,5 893 91 36 528
500 × 250 ×
224 320 280 264 40 10 1 148 117 44 657
525A
500 × 400 ×
224 320 280 264 40 10 1 158 118 44 724
525A
500 × 250 ×
218 320 274 264 46 11,5 1 413 144 44 753
525B
500 × 400 ×
218 320 274 264 46 11,5 1 383 141 44 825
525B
a
The welding method may be changed based on the same welding volume/strength.
b
SWLs shown a
...
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