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B: Mooring Chain [Table of Contents] Ch.3: Certification and Classification

DNV-OS-E302 Offshore Mooring Chain

[-] Ch.2: Technical Provisions
[-] Sec.2: Mooring Chain Cables and Accessories
[-] C: Chain Accessories

Ch.2 Sec.2
C. Chain Accessories

Ch.2 Sec.2
C 100   Scope

Ch.2 Sec.2 C
101   These requirements are supplementary to A and apply to chain accessories.

Ch.2 Sec.2 C
102   Where the manufacture of materials and accessories, heat treatments, machining, testing and inspections involve several parties, the purchaser should establish by contract agreement, at the time of ordering, the responsibility of the various parties for meeting the requirements.

Ch.2 Sec.2
C 200   Design

Ch.2 Sec.2 C
201   Accessories shall be manufactured in accordance with ISO 1704 or purchaser-approved drawings showing the finished dimensions and the surfaces that will be subjected to significant loading. Accessories of unconventional design shall have their drawings accompanied by calculations or design reports.

Ch.2 Sec.2 C
202   Detailed design of Kenter shackles shall be according to API Spec 2F. Machining of Kenter shackles shall result in fillet radius minimum 3% of nominal diameter.

Ch.2 Sec.2
C 300   Proof load testing

Ch.2 Sec.2 C
301   All accessories shall be proof load tested in the condition of supply and shall withstand without fracture the proof load prescribed in Table C1 for the stud link chain grade and size for which they are intended.

Ch.2 Sec.2 C
302   In the event of a test failure, the accessory shall be rejected. Testing of the remaining accessories shall be considered acceptable if they meet the requirement and if it has been determined by examination that the probable cause of failure is not present in any of the remaining accessories.

Ch.2 Sec.2
C 400   Breaking load testing

Ch.2 Sec.2 C
401   At least one accessory out of every test unit shall be breaking load tested in the condition of supply and shall withstand without fracture the breaking load prescribed in Table C1 for the chain grade and size for which they are intended. It shall be considered acceptable if the samples show no sign of fracture after application of the specified minimum load for 30 seconds.

Ch.2 Sec.2 C
402   A test unit shall consist of up to 25 accessories of the same type, grade and size, made from the same heat of steel, and heat treated in the same furnace charge.

Ch.2 Sec.2 C
403   For individually produced accessories or less than five produced accessories, alternative testing may be agreed between the manufacturer and purchaser.

Ch.2 Sec.2 C
404   Except as provided in 405, accessories that have been breaking load tested shall be discarded and not used as part of an outfit.

Ch.2 Sec.2 C
405   Accessories that have been breaking load tested may be used as part of an outfit provided that:
—the accessories are of increased dimensions or alternatively a material with higher strength characteristics is used, and
—it is verified by procedure test that such accessories are so designed that the breaking strength is not less than 1.4 times the breaking load of the chain cable for which they are intended.


Ch.2 Sec.2 C
406   In the event of a test failure, two further breaking load tests shall be made. The test unit shall be considered acceptable if both additional tests meet the requirement and if it has been determined by examination that the probable cause of failure is not present in any of the remaining accessories.

Ch.2 Sec.2
C 500   Mechanical testing

Ch.2 Sec.2 C
501   At least one accessory out of every test unit shall be tensile and impact tested in the condition of supply. Except as provided in 503, test pieces shall be taken from proof load tested or breaking load tested full size accessories. For each test unit, one tensile and three Charpy-V-notch test pieces shall be taken.

Ch.2 Sec.2 C
502   A test unit shall consist of up to 25 accessories of the same type, grade and size, made from the same heat of steel, and heat treated in the same furnace charge.

Ch.2 Sec.2 C
503   For individually produced accessories or less than five produced accessories, alternative to testing full size accessories may be agreed between the manufacturer and purchaser provided that:
—the alternative testing is described in a written procedure, and
—the separately forged coupon have a cross-section and a reduction ratio similar to that of the accessories represented, and
—it is verified by procedure test that coupon properties are representative of accessory properties.

Ch.2 Sec.2
C 600   Dimensions and tolerances

Ch.2 Sec.2 C
601   After proof load testing, at least one accessory out of every test unit shall be checked for dimensions. Where applicable, the measurements shall include detachable component parts.

Ch.2 Sec.2 C
602   The diameter must have no negative tolerance. Unless otherwise specified by the purchaser, the plus tolerance on diameter shall not exceed 5% and tolerances on other dimensions shall not exceed plus or minus 2.5%.

Ch.2 Sec.2 C
603   If an accessory fails to meet the tolerance requirements or if Kenter shackles or similar designs are loose upon re-assembly, it shall be rejected and all remaining accessories in the test unit shall be measured.

Ch.2 Sec.2
C 700   Inspection

Ch.2 Sec.2 C
701   After proof load testing, all accessories shall be visually inspected and non-destructive tested. Prior to inspection the non-machined surfaces shall be cleaned by shot or sand blasting. Where applicable, the accessories shall be dismantled for inspection of internal surfaces.

Ch.2 Sec.2 C
702   All accessible surfaces shall be visually inspected and be free from burrs, rough edges, cracks, dents, cuts, and other injurious imperfections.

Ch.2 Sec.2 C
703   All machined surfaces, fillets, abrupt changes in section, and surfaces that will be subjected to significant loading, as indicated on drawings, shall be magnetic particle tested (MT). Testing shall be performed in accordance with standards referenced in Sec.1 A600. Surfaces shall be free from:
—relevant linear indications exceeding 1.6 mm in transverse direction
—relevant linear indications exceeding 3.2 mm in longitudinal direction
—relevant non-linear indications exceeding 4.8 mm.


Ch.2 Sec.2 C
704   Requirements for ultrasonic testing are given in Sec.1 C600 (forgings) and D600 (castings).

Ch.2 Sec.2
C 800   Repair

Ch.2 Sec.2 C
801   Defects on non-machined surfaces may be removed by grinding to a depth of 5% of the nominal diameter. Grinding is not permitted on machined surfaces, except for slight inspection grinding on plane surfaces in order to investigate spurious indications.

Ch.2 Sec.2
C 900   Identification

Ch.2 Sec.2 C
901   Each accessory shall be identified in a low stress area with at least the following:
—identification number or other marking that will enable the history of the accessory to be traced
—chain grade designation.


Ch.2 Sec.2 C
902   Each detachable component part shall be marked with an identifying number to avoid mix-up of parts.

Ch.2 Sec.2 C
903   Accessories that have been breaking load tested and are used as part of an outfit, as permitted in C400, shall be marked with the grade of chain for which they are intended.

Ch.2 Sec.2 C
Table C1 Formulas for proof and breaking test loads, weight, and five link length 
 Grade R3 Grade R3S Grade R4 Grade R4S Grade R5 
Proof load, stud link (kN) 0.0156d2
(44-0.08d) 		0.0180d2
(44-0.08d) 		0.0216d2
(44-0.08d) 		0.0240d2
(44-0.08d) 		0.0251d2
(44-0.08d) 
Proof load, stud less (kN) 0.0156d2
(44-0.08d) 		0.0174d2
(44-0.08d) 		0.0192d2
(44-0.08d) 		0.0213d2
(44-0.08d) 		0.0223d2
(44-0.08d) 
Breaking load (kN) 0.0223d2
(44-0.08d) 		0.0249d2
(44-0.08d) 		0.0274d2
(44-0.08d) 		0.0304d2
(44-0.08d) 		0.0320d2
(44-0.08d) 
Weight, stud link (kg/m) 0.0219d2 
Five link length (mm) Minimum 22d and maximum 22.55d 
d is the chain nominal diameter 

Ch.2 Sec.2 C
Table C2 Frequency of breaking load and mechanical tests 
Nominal chain diameter (mm) Maximum sampling interval (m) 
74 - 85 152 
86 - 98 175 
99 - 111 198 
112 - 124 222 
125 - 137 250 
138 - 149 274 
150 -162 297 
163 - 175 322 
176 - 186 346 
187 - 199 370 
200 - 210 395 

Ch.2 Sec.2 C
Table C3 Minimum mechanical properties for chain cables 
Grade Yield stress Tensile strength Elongation Reduction of area Charpy V-notch 
     Base Weld 
Re Rm A5 Z Temperature 1) Average energy Single energy Average energy Single energy 
N/mm2 N/mm2 % % °C J J J J 
R3 410 690 17 50 2) 0 60 45 50 38 
-20 40 30 30 23 
R3S 490 770 15 50 2) 0 65 49 53 40 
-20 45 34 33 25 
R4 580 860 12 50 3) -20 50 38 36 27 
R4S 700 960 12 50 3) -20 56 42 40 30 
R5 760 1000 12 50 3) -20 58 44 42 32 

1) For grade R3 and R3S, testing may be carried out at either 0°C or -20°C.

2) For cast accessories, the minimum value shall be 40%.

3) For cast accessories, the minimum value shall be 35%. 

B: Mooring Chain [Table of Contents] Ch.3: Certification and Classification