Section 2 Stud link chain cables for ships

2.1.1 Provision is made in this Section for a range of grades, U1, U2 and U3, of stud link chain and fittings intended for anchor cables for ships.

2.1.2 The requirements for mooring chain cables are given in Ch 10, 3 Offshore Mooring chain cables.

2.1.3 The design of chain cables and fittings is to be to a Standard recognised by LR, such as ISO 1704.

2.2.1 All grades of chain cable and accessories are to be manufactured by approved procedures at works approved by LR. A list of approved manufacturers of stud link chain cables and fittings is published separately by LR.

2.2.2 The links may be made by the flash-butt or other approved welding process, or in the case of Grades U2 and U3 they may be flash-butt welded or drop forged, designated U2(a) or U3(a), or cast steel designated U2(b) or U3(b), see Table 10.2.5 Number of breaking tests from completed cables.

2.2.3 As far as practicable, consecutive links in all chain cable should originate from a single cast or batch of bar stock (see Ch 3, 9.6 Mechanical tests 9.6.1), and indicating marks should be stamped on the final link formed from one cast or batch and the first link formed from a separate cast or batch.

2.2.4 A length of chain cable is to measure not more than 27,5m and is to comprise an odd number of links. In this context, a length is a statutory term and is the basis for the number of test samples.

2.2.5 Where end links or enlarged links are manufactured and heat treated as part of and at the same time as the chain cable and are of the same cast heat of steel, they may be excluded from separate mechanical tests and break load tests.

2.3.1 Bar material is to comply with the requirements of Ch 3, 9 Bars for welded chain cables and may be heated either by electrical resistance or in a furnace. For electrical resistance heating, the process is to be controlled by an optical heat sensor. For furnace heating, thermocouples in close proximity to the bars are to be used for control. The temperature is to be continuously recorded. In both cases, the controls are to be checked at least once every eight hours and checks are to be recorded.

2.3.2 Mechanical properties testing of U1 cable is not required. For Grade U2 cable supplied in the as-welded condition, and Grade U3 in all conditions, one tensile and one set of three Charpy V-notch impact test specimens are to be taken at the side of a link opposite the weld from at least every fourth 27,5m length of cable. A further set of three impact test specimens is to be taken with the notch positioned at the centre of the weld, see Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings. The test specimens are not to be selected from the same length as that from which the breaking test sample is taken, unless breaking test samples are to be taken from every length of the batch. All test samples are to be correctly identified with the lengths of cable represented.

2.3.3 The test links from which the mechanical test specimens are prepared are to be made as part of the chain cable and are to be heat treated with it. They may be removed from the cable prior to heat treatment provided that each sample is heat treated with, and in the same manner as, the chain it represents prior to preparation of the mechanical test specimens.

2.3.4 The results of tests on specimens taken from the non-welded areas are to comply with the appropriate requirements of Table 10.2.1 Mechanical properties of finished chain cable and fittings. The results of tests on the welds are to comply with the requirements of Table 10.2.6 Mechanical properties of welds in chain cables.

2.4.1 The manufacture of cast steel chain cable is generally to be in accordance with the requirements of Ch 4, 1 General requirements, as appropriate.

2.4.2 The chemical composition of ladle samples is to comply with the specification approved by LR.

2.4.3 Separately cast test samples are to be provided from each cast. They are to be of similar dimensions to the links they represent and are to be heat treated together with, and in the same manner as, the completed chain cable, see Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings.

2.4.4 Tensile and Charpy V-notch impact test specimens are to be taken from each test sample and machined to the dimensions given in Ch 2, 3 Impact tests.

2.4.5 The results of all tests are to comply with the requirements given in Table 10.2.1 Mechanical properties of finished chain cable and fittings for the relevant grade.

2.5.1 The procedure for the manufacture and testing of drop forgings for chain cable will be specially considered, but is generally to be in accordance with the appropriate requirements of Ch 5, 1 General requirements.

2.5.2 The chemical composition is to comply with Table 10.2.2 Chemical composition of butt welded and forged chain cable.

2.5.3 The completed forgings are to be heat treated in accordance with Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings.

2.5.4 Test samples are to be provided in the form of forgings of similar dimensions to the links they represent. These test samples are to be from the same steel-making heat and heat treated together with the links they represent.

2.5.5 One tensile and three Charpy V-notch specimens are to be taken from each test sample.

2.5.6 The results of mechanical tests are to comply with the requirements of Table 10.2.1 Mechanical properties of finished chain cable and fittings for the relevant grade.

Table 10.2.1 Mechanical properties of finished chain cable and fittings

Grade	Yield stress N/mm2 minimum	Tensile strength N/mm2	Elongation on 5,65% minimum	Reduction of area % minimum	Charpy V-notch impact tests
					Test temperature °C	Average energy J minimum
U2	295	490 – 690	22	—	0	27
					(see Note 1)
U3	410	690 minimum	17	40	0	60
					–20 (see Note 2)	35
Note 1. When required see Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings. Note 2. Testing may be carried out at either 0°C or –20°C. Note 3. Mechanical testing is not required for finished chain cables and fittings in Grade U1.

2.6.1 Steel studs are to be used for all grades of welded chain cable. In general, the carbon content should not exceed 0,23 per cent but mechanical tests for acceptance purposes are not required.

2.7.1 Where studs are welded into the links this is to be completed before the chain cable is heat treated.

2.7.2 The stud ends must be a good fit inside the link, and the weld is to be confined to the stud end opposite the flash-butt weld. Welding of studs both ends is not permitted unless specially approved. The full periphery of the stud end is to be welded. If, however, it can be demonstrated to the Surveyor that the quality of welding is of a high standard then partial peripheral welding may be accepted provided that welds are made only at the sides of the stud and that each run extends continuously for at least 25 per cent of the stud periphery. Weld start/stop positions are not to be located in the plane of the chain cable.

2.7.3 The welds are to be made by qualified welders using an approved procedure and consumables approved to Grade 3 and low hydrogen, in accordance with Ch 11 Approval of Welding Consumables.

2.7.4 The welds are to be of good quality and free from defects liable to impair the proper use of the chain. Undercuts, end craters and similar stress raising defects shall, where necessary, be ground off.

2.7.5 All stud welds are to be visually inspected. At least one stud weld within each length of cable is to be inspected using magnetic particle inspection or dye penetrant testing in accordance with Ch 1, 5 Non-destructive examination after the chain has been proof loaded. If a crack is found, the stud welds in the adjoining links are to be inspected; if a crack is found in either link, all the stud welds in that length are to be inspected using magnetic particle inspection or dye penetrant testing.

2.8.1 The completed chain cable is to be heat treated in accordance with Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings for the appropriate grade of cable.

2.8.2 Special consideration will be given to the heat treatment of certain types of drop forged chain cable.

2.8.3 In all cases, heat treatment is to be carried out prior to the proof loading and breaking tests.

2.8.4 All test samples are to be heat treated with, and in the same way as, the chain cables they represent.

2.9.1 All chain cables are to be subjected to a Proof Load test and a Breaking Load test. In addition, mechanical tests should be carried out where required, see Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings.

2.9.2 All chain cables are to be tested in the presence of a Surveyor, at a proving establishment recognised by LR. A list of recognised proving establishments is published separately by LR. In addition to the requirements stated in this Chapter, attention must be given to any relevant statutory requirements of the National Authority of the country in which the ship is to be registered.

2.10.1 Each length of chain cable is to be subjected to a proof loading test in an approved testing machine and is to withstand the load given in Table 10.2.4 Test loads for stud link anchor chain cables for the appropriate grade and size of cable.

2.10.2 On completion of the test, each link is to be visually examined and is to be free from significant defects. Special attention is to be given to welds.

2.10.3 Should any link be found to be defective it is to be replaced by an approved connecting link (joining shackle or substitute link as detailed in Ch 10, 2.14 Substitute single links). The chain is then to be subjected to a repeat of the proof load test followed by re-examination.

2.10.4 If a link breaks during proof load testing, a sample consisting of three common links is to be taken from each side of the broken link and subjected to a breaking test as detailed in Ch 10, 2.12 Breaking load tests. If either of these samples fails, the length of cable is not to be accepted. A thorough examination of all broken links is to be made to determine the cause of failure and, after evaluation, LR will consider the extent of cable which is to be rejected.

2.11.1 The measurement of dimensions in Ch 10, 2.11 Dimensional inspection 2.11.2 and Ch 10, 2.11 Dimensional inspection 2.11.3 is to take place after the proof load has been applied to the chain and subsequently reduced to the load of 10 per cent of the proof load. All other dimensional checks are to be carried out without application of load.

2.11.2 On every 27,5 m length of chain, five links are to be selected for measurement of length to ensure that the maximum allowable tolerance on a length of five links is plus 2,5 per cent. No under-tolerance is permitted.

2.11.3 If a five-link length of chain exceeds the tolerance given in Ch 10, 2.11 Dimensional inspection 2.11.2, then the entire chain is to be checked for length, five links at a time with an overlap of two links, which is to include the first five links. Oversize links are to be removed and an approved connecting link inserted.

2.11.4 Checks of all other dimensions are to be made on three links from every four 27,5 m lengths. All measurements are to be made on links selected by the Surveyor and are to be carried out to the Surveyor’s satisfaction.

2.11.5 If one of the links detailed in Ch 10, 2.11 Dimensional inspection 2.11.4 fails to comply with the required tolerances, measurements are to be made on all four 27,5 m lengths.

2.11.6 If more than one link in a 27,5 m length of chain cable fails to meet the tolerance requirements, all the links in that length are to be measured.

2.11.7 Links that fail to comply with tolerance requirements are to be removed and approved connecting links inserted. Where a significant number of links fail to comply with the tolerance requirements the chain is to be rejected.

2.11.8 The form and proportion of links and shackles are to be in accordance with a standard recognised by LR, such as ISO 1704, see Figure 10.2.2 Common link to Figure 10.2.9 Lugless shackle of the Kenter type; alternatively, the design may be specifically approved by LR.

2.11.9 Manufacturing tolerances on stud link chain are to be within ±2,5 per cent (taking into account that all components of the chain are to be a good fit with one another), except for those detailed in Ch 10, 2.11 Dimensional inspection 2.11.10.

2.11.10 The nominal diameter, d, is to be the average of the diameters, measured in the plane of the link, d _c, and perpendicular to the plane of the link, d _p, see Figure 10.2.2 Common link. The negative tolerance on the nominal diameter is not to exceed the following:

1. Minus 1 mm when d ≤ 40 mm

2. Minus 2 mm when 40 mm < d ≤ 84 mm

3. Minus 3 mm when 84 mm < d ≤ 122 mm

4. Minus 4 mm when d > 122 mm

For diameters of 20mm or greater, the plus tolerance on the diameter at the crown measured perpendicular to the plane of the link, d _p, is not to exceed 5 per cent. For diameters less than 20mm, the plus tolerance is to be agreed between the chain manufacturer and bar material supplier.

2.11.11 The cross-sectional area is to be calculated using the nominal diameter, d. The cross-sectional area at the crown of the link is to have no negative tolerance.

2.11.12 The diameter measured at locations other than the crown is to have no negative tolerance. For diameters of 20mm or greater, the plus tolerance may be up to 5 percent of the nominal diameter except at the butt weld where it is to be in accordance with the manufacturer’s specification, which is to be agreed by LR. For diameters less than 20mm, the plus tolerance is to be agreed between the chain manufacturer and bar material supplier.

2.11.13 Studs must be located in the links centrally and at right angles to the sides of the link, although the studs at each end of any length may also be located off-centre to facilitate the insertion of the joining shackle. The following tolerances in Figure 10.2.1 Manufacturing tolerances will be accepted provided that the stud fits snugly and its ends lie practically flush against the inside of the link:

1. Maximum off-centre distance ‘X’: 10 per cent of the nominal diameter d

2. Maximum deviation ‘α’ from the 90° – position: 4°.

Figure 10.2.1 Manufacturing tolerances

2.11.14 All individual parts must have a clean surface consistent with the method of manufacture and the surface is to be free from cracks, notches, inclusions and other defects which could impair the performance of the product. Crack-like imperfections less than 3 mm in length can be ignored. The flash produced by upsetting or drop forging must be properly removed.

2.11.15 Minor surface imperfections may be ground off so as to leave a gentle transition to the surrounding surface provided that the cross-sectional area remains equal to or greater than the nominal cross-sectional area. Remote from the crown, local grinding up to 5 per cent of the nominal diameter may be permitted.

2.11.16 Paint or anti-corrosive coatings are not to be applied until these inspections are completed to the satisfaction of the Surveyor.

2.12.1 Breaking load tests are to be carried out on three-link samples selected by the Surveyor from the completed (including heat treatment) chain. The test links may be removed from the chain prior to heat treatment provided that each sample is heat treated with, and in the same manner as the chain it represents. They are to be properly identified with the lengths of chain they represent.

2.12.2 The number of tests required is to be in accordance with Table 10.2.5 Number of breaking tests from completed cables except that for chafing chain for Emergency Towing Arrangements (ETA), see Pt 3, Ch 13, 12.2 Chafing chain and wire or fibre rope for Emergency Towing Arrangements, one test is to be carried out on each 110 m of finished chains.

2.12.3 Breaking test specimens are to withstand the load given in Table 10.2.4 Test loads for stud link anchor chain cables for the appropriate grade and size of cable. The specimen is considered to have passed this test if it has shown no sign of fracture after application of the required load for a minimum of 30 seconds.

2.12.4 Where a breaking test specimen fails, a further specimen is to be cut from the same length of cable and subjected to test. If this re-test fails, the length of cable from which it was taken is to be rejected. When this test is also representative of other lengths, each of the remaining lengths is to be individually tested by taking a breaking test specimen from each length of the batch. If one of these further tests fails, the entire set of lengths represented by the original test is to be rejected.

2.12.5 For large diameter cables where the required breaking load is greater than the capacity of the testing machines, special consideration will be given to acceptance of an alternative testing procedure.

2.13.1 Cable fittings are to be manufactured at an approved works.

2.13.2 The materials from which the fittings are made are to be manufactured at approved works, in accordance with the appropriate requirements of Ch 4, 1 General requirements or Ch 5, 1 General requirements respectively. Alternative arrangements may be agreed provided that full details concerning the manufacturer are submitted to LR.

2.13.3 All fittings are to be manufactured to an approved manufacturing specification, and provision is to be made for tensile specimens and, where applicable, impact test specimens, see Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings. The mechanical test requirements are the same as those for the relevant grade of chain cable, see Table 10.2.1 Mechanical properties of finished chain cable and fittings.

2.13.4 The test samples are to be prepared in accordance with Ch 10, 2.4 Cast chain cables 2.4.3 or Ch 10, 2.5 Forged chain cables 2.5.4 as applicable. The test specimens are to be subjected to heat treatment with the fittings they represent.

2.13.5 For mechanical testing, a batch is defined as fittings of the same grade, size and heat treatment furnace load and is to have originated from a single cast heat of steel.

2.13.6 Mechanical tests of pins are to be taken in accordance with Ch 10, 4.6 Mechanical tests 4.6.7.

2.13.7 Fittings such as shackles, swivels and swivel shackles are to be forged or cast in steel of at least Grade U2. The welded construction of fittings may also be approved providing that full details of the manufacturing process and the heat treatment are submitted.

2.13.8 All chain cable accessories, including spares, are to be subjected to the proof loads appropriate to the grade and size of cable for which they are intended. These include shackles, swivels, swivel shackles, enlarged links and end links. Where swivel shackles are not permanently attached as part of an approved anchor design, then they shall be design approved and tested as a chain cable fitting. Shackles, including D shackles and swivels shackles, which are permanently attached to an anchor shank, are also to be tested in combination with the anchor assembly in accordance with the approved design, see Ch 10, 1.2 Design requirements.

2.13.9 The appropriate breaking load is to be applied for a minimum of 30 seconds to at least one item out of every batch of up to 25 detachable links, shackles, swivels, swivel shackles, enlarged end links and end links and at least one item out of every batch of up to 50 for lugless (Kenter) shackles. The item tested is to be destroyed and not used as part of an outfit. For the purposes of break load testing, a batch of accessories is to consist of:

1. the same accessory type, grade and size;

2. the same rolling or forging or casting process; and

3. accessories that are heat treated together in the same furnace.

2.13.10 Where a break load batch as defined in Ch 10, 2.13 Fittings for chain cables 2.13.9 requires a normalise or normalise and temper heat treatment, the size of accessories may vary within a batch provided that the heat treatment cycle is chosen to satisfy the accessory with the largest cross-section size. The batch may consist of more than one steel-making heat provided that the two accessories are break tested, one with the largest crosssection size and one with the smallest cross-section size.

2.13.11 Where a break load batch as defined in Ch 10, 2.13 Fittings for chain cables 2.13.9 requires a quench and temper heat treatment, the size of the accessories within the batch is to be the same and is limited to the same steel-making heat.

2.13.12 If the sample fails to withstand the breaking load without fracture, two more samples from the same batch may be tested. If either of these samples fails, the batch is to be rejected.

2.13.13 Fittings of increased dimensions or higher grade material may be used subject to approval by LR.

2.13.14 Where items of increased dimensions are used or if material of a higher grade than is specified is used, the breaking load is to be applied to each item, and the items so tested included with the outfit. For the purpose of this paragraph, items of increased dimensions are those so designed that their breaking strength is not less than 1,4 times the Rule minimum breaking load of the chain cable with which they are to be used.

2.13.15 LR may waive the breaking load test provided that:

1. the breaking load test has been completed satisfactorily during approval testing, and

2. the tensile and impact properties of each manufacturing batch are proved and

3. the accessories are subjected to suitable non-destructive testing.

2.13.16 All testing is to be carried out in the presence of the Surveyor and to his satisfaction.

2.13.17 The following tolerances are applicable to accessories:

1. Nominal diameter: plus 5 per cent, minus 0 per cent

2. Other dimensions: ±2,5 per cent

3. The radii of all machined corners are to be not less than 0,03 times the nominal chain diameter

2.13.18 All fittings are to be stamped in accordance with Ch 10, 2.15 Identification.

2.14.1 Single links to connect lengths of chain cable or to substitute for defective links, without the necessity for re-heat treatment of the whole cable length, are to be made by the chain manufacturer in accordance with an approved procedure. Separate approvals are required for each grade of chain cable and the tests are to be made on the maximum size of chain for which approval is sought. Re-approval is required annually.

2.14.2 Manufacture and heat treatment of the substitute link are not to affect the strength of the adjoining links. The temperature reached by these links is nowhere to exceed 250°C.

2.14.3 The steel bar used is to conform with the specification for the chain in accordance with Ch 3, 9 Bars for welded chain cables.

2.14.4 Details of the method of manufacture, including heat treatment, are to be submitted for approval, together with the results of a series of tests laid down by LR.

2.14.5 All links involved in the approval tests are to be destroyed and are not to be used as part of a chain cable.

2.14.6 Every substitute link included in a chain cable is to be subjected to the proof load appropriate to the grade and size of chain in which it is incorporated, as detailed in Table 10.2.6 Mechanical properties of welds in chain cables.

2.14.7 Each substitute link is to be stamped on the stud with the identification marks listed in Ch 10, 2.15 Identification 2.15.1 plus a unique number for the link. The adjoining links are also to be stamped on the studs.

2.15.1 All lengths of Grades U1, U2 and U3 cable and all fittings are to be stamped with the following identification marks:

1. LR or Clasifications Register and abbreviated name of LR's local office issuing the certificate.

2. Number of certificate.

3. Proof load and grade of chain.

4. Surveyor’s personal stamp.

5. Each length of chain cable is to be stamped on both ends.

2.16.1 An LR certificate is to be issued for chain cable only, fittings only or chain cable with associated fittings.

2.16.2 Each test certificate is to include the following particulars for all items included on the certificate:

1. Manufacturer’s name.

2. Purchaser's name and order number.

3. Description and dimensions.

4. Grade of chain cable.

5. Identification mark which will enable the full history of the chain or fitting to be traced.

6. Chemical composition.

7. Details of heat treatment.

8. Mechanical test results.

9. Breaking test load.

10. Proof load.

2.16.3 Where appropriate, the certificate is to include a list of all substitute links together with their grade of steel, the name of the steelmaker, the heat number and the purchase order number.

Figure 10.2.2 Common link

Figure 10.2.3 Enlarged link

Figure 10.2.4 End link

Figure 10.2.5 Dee shackle

Figure 10.2.6 End shackle

Figure 10.2.7 Lugless shackle

Figure 10.2.8 Swivel

Figure 10.2.9 Lugless shackle of the Kenter type