ISO 20438:2017

INTERNATIONAL ISO
STANDARD 20438
First edition
2017-06
Ships and marine technology —
Offshore mooring chains
Navires et technologie maritime — Chaînes d’amarrage en haute mer
Reference number
ISO 20438:2017(E)
©
ISO 2017

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ISO 20438:2017(E)

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ISO 20438:2017(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Grade . 2
5 Materials . 2
6 Shape, dimensions and tolerances . 3
Bibliography .22
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ISO 20438:2017(E)

Foreword
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This document was prepared by ISO/TC 8, Ships and marine technology, SC 4, Outfitting and deck
machinery.
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INTERNATIONAL STANDARD ISO 20438:2017(E)
Ships and marine technology — Offshore mooring chains
1 Scope
This document specifies the requirements for grades, materials, shapes, proportions, dimensions and
tolerances of offshore mooring chains.
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.
ISO 4967, Steel — Determination of content of non-metallic inclusions — Micrographic method using
standard diagrams
ASTM A255, Standard test methods for determining hardenability of steel
ASTM E112, Standard test methods for determining average grain size
ASTM E381, Standard method of macroetch testing steel bars, billets, blooms, and forgings
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 19901-7:2013 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
mooring chain
component used for positioning and mooring of offshore structures composed of chain links (3.2) and
accessories (3.3)
3.2
chain link
closed, link shaped components of mooring chain (3.1), including common stud link, common studless
link, enlarged link and end link
3.3
accessory
detachable connectors used for joining different chain components, including joining shackle(3.8) and
end shackle(3.9)
3.4
common stud link
common mooring chain link (3.2) with stud
3.5
common studless link
common mooring chain link (3.2) without stud
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ISO 20438:2017(E)

3.6
enlarged link
strengthened link that connects a common link and the end link (3.7)
3.7
end link
link that joins mooring chains (3.1) and shackles
3.8
joining shackle
accessories used for joining chain links (3.2) or other accessories, including “D” type LTM joining
shackle, “D” type LTM end joining shackle, Kenter type joining shackle and “H” type LTM joining shackle
3.9
end shackle
accessories used for attaching the mooring chain (3.1) to mooring equipment
Note 1 to entry: It usually refers to LTM end shackle.
3.10
LTM shackle
long term moored “D” type joining shackle, “D” type end joining shackle and end shackle with the bolt
fastened by nut
3.11
nominal diameter
diameter of the common link
4 Grade
4.1 The mooring chain is classified by tensile strength into five grades: R3, R3S, R4, R4S and R5.
4.2 The mechanical properties of mooring chain for each grade are given in Table 1.
4.3 The proof load and breaking load of mooring chains for each grade are given in Table 2.
5 Materials
5.1 The steel used for manufacturing of mooring chains is classified into five grades: R3, R3S, R4,
R4S and R5.
5.2 Mechanical properties for materials of each grade shall meet the requirements of base materials
specified in Table 1.
5.3 The steel shall be manufactured by an electric progress or one of the basic oxygen processes or any
other process involving secondary refining. The austenite grain size shall be 6 or finer in accordance with
ASTM E112.
5.4 Steel grades R4S and R5 shall be vacuum degassed.
5.5 For steel grades R4S and R5, the following test results shall be supplied by steel mills to the
mooring chain or accessory manufacturer:
a) Each heat shall be examined for non-metallic inclusions according to ISO 4967 or equivalent
standards.
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ISO 20438:2017(E)

b) A sample from each heat shall be macro etched according to ASTM E381 or equivalent standards to
ensure there is no injurious segregation or porosity.
c) Jominy hardenability data according to ASTM A255 or equivalent standards shall be supplied with
each heat.
5.6 Steel grades R4, R4S and R5 shall contain a minimum of 0,20 % molybdenum.
6 Shape, dimensions and tolerances
6.1 The shapes of common studless link, common stud link, enlarged studless link, enlarged stud link
and end link are indicated in Figures 1 to 5 and their dimensions are specified in Tables 3 to 7.
6.2 The shapes of kenter shackle, “H” type LTM joining shackle (sample), “D” type LTM end joining
shackle (sample), “D” type LTM joining shackle, LTM end shackle are indicated in Figures 6 to 10 and
their dimensions are specified in Tables 8 to 12.
6.3 Tolerances of common links, enlarged links and end links
The diameter shall be measured at crown, and the average value based on two perpendicular
measurements must have no negative tolerance and the plus tolerance shall not exceed 5 % of
nominal diameter. The minus tolerance for the diameter measured at crown shall meet the following
requirements:
— for nominal diameter from 50 mm to 84 mm: −2 mm;
— for nominal diameter from 85 mm to 122 mm: −3 mm;
— for nominal diameter from 123 mm to 152 mm: −4 mm;
— for nominal diameter from 153 mm to 184 mm: −6 mm;
— for nominal diameter from 185 mm to 210 mm: −7,5 mm;
— for nominal diameter over 210 mm: −8,5 mm.
The cross sectional area of the crown shall not be less than the theoretical cross section of the nominal
diameter.
The plus tolerance at weld shall not exceed 15 % of nominal chain diameter.
6.4 Length of five links
The five-link length of links shall be 5 × p + 2 d = 22 d measured from outside. The allowable
+25,
manufacturing tolerance on a length of five links is % .
0
6.5 All other dimensions
+5
The tolerances of the diameter: % .
0
The tolerances other than diameter: ± 2,5 %.
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ISO 20438:2017(E)

Table 1 — Mechanical properties of mooring chain
Grade Minimum Minimum Minimum Minimum Average impact energy J
yield tensile elongation reduction in
Temperature Base material Weld
strength strength area
%
°C Average Single Average Single
2 2
N/mm N/mm %
value value
0 60 45 50 38
R3 410 690 17 50
−20 40 30 30 23
0 65 49 53 40
R3S 490 770 15 50
−20 45 34 33 25
R4 580 860 12 50 −20 50 38 36 27
R4S 700 960 12 50 −20 56 42 40 30
R5 760 1000 12 50 −20 58 44 42 32
NOTE 1 Reduction of area of cast steel accessories is to be for Grades R3 and R3S: minimum 40 %; for Grades
R4, R4S, and R5: minimum 35 %.
NOTE 2 CVN Impact Test of R3 and R3S may be performed either at 0 Deg. C or at −20 Deg. C.
NOTE 3 Aim maximum hardness for R4S is HB330 and R5 HB340.
NOTE 4 For guidance only: Typical yield to tensile strength ration is in the range of 0,85 to 0,95.
Table 2 — Proof load and breaking load
Dimensions in KN
R3 R3S R4 R4S R5
2 2 2 2 2
0,0156d 0,0180d 0,0216d 0,0240d 0,0251d
Proof load of stud chain
(44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d)
2 2 2 2 2
0,0156d 0,0174d 0,0192d 0,0213d 0,0223d
Proof load of studless chain
(44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d)
2 2 2 2 2
0,0223d 0,0249d 0,0274d 0,0304d 0,0320d
Breaking load
(44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d) (44-0,08d)
NOTE   d is the nominal diameter.
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ISO 20438:2017(E)

Key
d nominal diameter of common link
l = 6d
1
p = 4d
1
w = 3,35d
1
NOTE For nominal dimensions, see Table 3.
Figure 1 — Common studless link
Table 3 — Dimensions of common studless link
Dimensions in millimeters
Nominal size d l p w Nominal size d l p w
1 1 1 1 1 1
50 300 200 168 120 720 480 402
52 312 208 174 122 732 488 409
54 324 216 181 124 744 496 415
56 336 224 188 127 762 508 425
58 348 232 194 130 780 520 436
60 360 240 201 132 792 528 442
62 372 248 208 137 822 548 459
64 384 256 214 142 852 568 476
66 396 264 221 147 882 588 492
68 408 272 228 152 912 608 509
70 420 280 235 157 942 628 526
73 438 292 245 162 972 648 543
76 456 304 255 165 990 660 553
78 468 312 261 168 1 008 672 563
81 486 324 271 171 1 026 684 573
84 504 336 281 175 1 050 700 586
87 522 348 291 178 1 068 712 596
90 540 360 302 180 1 080 720 603
92 552 368 308 182 1 092 728 610
95 570 380 318 185 1 110 740 620
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ISO 20438:2017(E)

Table 3 (continued)
Nominal size d l p w Nominal size d l p w
1 1 1 1 1 1
97 582 388 325 188 1 128 752 630
100 600 400 335 191 1 156 764 640
102 612 408 342 194 1 164 776 650
105 630 420 352 197 1 182 788 660
107 642 428 358 200 1 200 800 670
111 666 444 372 205 1 230 820 687
114 684 456 382 210 1 260 840 704
117 702 468 392
Key
d nominal diameter of common link
l = 6d
2
p = 4d
2
w = 3,6d
2
NOTE For nominal dimensions, see Table 4.
Figure 2 — Common stud link
Table 4 — Dimensions of common stud link
Dimensions in millimeters
Nominal size d l p w Nominal size d l p w
2 2 2 2 2 2
50 300 200 180 120 720 480 432
52 312 208 187 122 732 488 439
54 324 216 194 124 744 496 446
56 336 224 202 127 762 508 457
58 348 232 209 130 780 520 468
60 360 240 216 132 792 528 475
62 372 248 223 137 822 548 493
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ISO 20438:2017(E)

Table 4 (continued)
Nominal size d l p w Nominal size d l p w
2 2 2 2 2 2
64 384 256 230 142 852 568 511
66 396 264 238 147 882 588 529
68 408 272 245 152 912 608 547
70 420 280 252 157 942 628 565
73 438 292 263 162 972 648 583
76 456 304 274 165 990 660 594
78 468 312 281 168 1 008 672 605
81 486 324 292 171 1 026 684 616
84 504 336 302 175 1 050 700 630
87 522 348 313 178 1 068 712 641
90 540 360 324 180 1 080 720 648
92 552 368 331 182 1 092 728 655
95 570 380 342 185 1 110 740 666
97 582 388 349 188 1 128 752 677
100 600 400 360 191 1 146 764 688
102 612 408 367 194 1 164 776 698
105 630 420 378 197 1 182 788 709
107 642 428 385 200 1 200 800 720
111 666 444 400 205 1 230 820 738
114 684 456 410 210 1 260 840 756
117 702 468 421
Key
d nominal diameter of common link
d nominal diameter of enlarged studless link, d = 1,1d
3 3
l = 6d
3 3
p = 4d
3 3
w = 3,35d
3 3
NOTE For nominal dimensions, see Table 5.
Figure 3 — Enlarged studless link
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ISO 20438:2017(E)

Table 5 — Dimensions of enlarged studless link
Dimensions in millimeters
Nominal size Nominal size
d l p w d l p w
3 3 3 3 3 3 3 3
(d, common link) (d, common link)
50 55 330 220 184 120 132 792 528 442
52 57 342 228 191 122 134 804 536 449
54 59 354 236 198 124 136 816 544 456
56 62 372 248 208 127 140 840 560 469
58 64 384 256 214 130 143 858 572 479
60 66 396 264 221 132 145 870 580 486
62 68 408 272 228 137 151 906 604 506
64 70 420 280 235 142 156 936 624 523
66 73 438 292 245 147 162 972 648 543
68 75 450 300 251 152 167 1 002 668 559
70 77 462 308 258 157 173 1 038 692 580
73 80 480 320 268 162 178 1 068 712 596
76 84 504 336 281 165 182 1 092 728 610
78 86 516 344 288 168 185 1 110 740 620
81 89 534 356 298 171 188 1 128 752 630
84 92 552 368 308 175 193 1 158 772 647
87 96 576 384 322 178 196 1 176 784 657
90 99 594 396 332 180 198 1 188 792 663
92 101 606 404 338 182 200 1 200 800 670
95 105 630 420 352 185 204 1 224 816 683
97 107 642 428 358 188 207 1 242 828 693
100 110 660 440 369 191 210 1 260 840 704
102 112 672 448 375 194 213 1 278 852 714
105 116 696 464 389 197 217 1 302 868 727
107 118 708 472 395 200 220 1 320 880 737
111 122 732 488 409 205 226 1 356 904 757
114 125 750 500 419 210 231 1 386 924 774
117 129 774 516 432
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ISO 20438:2017(E)

Key
d nominal diameter of common stud link
d nominal diameter of enlarged stud link, d = 1,1d
4 4
l = 6d
4 4
p = 4d
4 4
w = 3,6d
4 4
NOTE For nominal dimensions, see Table 6.
Figure 4
...