Stud link anchor chain cables, grade K4 - End links; Text in German and English
1Key Takeaways
This standard applies to the end connectors of Gütegrad K4 (K4 grade) anchor chains, which are components of a three-section transition joint conforming to DIN 81854.
2Expert Interpretation
This article provides an in-depth analysis of the DIN 81850:2007 standard for marine anchor chain end rings, covering the dimensional specifications, material requirements, and testing standards for K4 grade end rings, as well as an analysis of the technical differences with ISO 1704. It also details the geometric calculation formulas for end rings, including w²=3.3d² and p²=3.65d², and provides implementation recommendations and a standard comparison table.
DIN 81850 Standard Overview and Technical Background
DIN 81850 is a specialized standard for marine anchor chain end rings developed by the German Institute for Standardization. It specifically applies to the end ring components of three-link adapters for K4-grade anchor chains. This standard, jointly developed by the DIN Standards Committee for Ship and Marine Technology (NSMT) and the DIN Standards Committee for Round Chains (NRK), represents the internationally advanced technology for key components of marine anchor chain systems.
Detailed Explanation of Standard Technical Parameters
The core technical parameters of the DIN 81850 standard are calculated based on strict geometric relationships:
| Parameter | Calculation Formula | Explanation | Difference from ISO 1704 |
|---|---|---|---|
| d2 | d2 = 1.2d | End Ring Nominal Diameter | Change in Reference Parameters |
| p2 | p2 = 3.65d2 | End Ring Pitch | ISO 1704: 4.35d |
| w2 | w2 = 3.3d2 | End Ring Width | ISO 1704: 4d |
Where d represents the nominal thickness of a typical chain link according to DIN 81848. The standard requires that the cross-sectional area of the end ring crown must not be less than the cross-sectional area calculated based on the nominal diameter d2 to ensure consistent mechanical properties.
Material and Manufacturing Requirements
According to DIN 17115, the end ring must be made of high-strength alloy steel 1.6758 (23MnNiMoCr5-4). This material offers an excellent combination of strength and toughness to meet the corrosion requirements of marine environments. Manufacturing process requirements include:
- Butt welds must be longitudinally deburred
- Dimensional tolerances are strictly controlled in accordance with the limit deviations in Table 1
- Mass is calculated using the formula G = 73.46 × d2³ × 10⁻⁶ kg
Technical Difference Analysis with ISO 1704:1991
There are significant technical differences between DIN 81850 and ISO 1704:1991, which are mainly reflected in the change of dimensional datums:
| Standard | w2 calculation formula | p2 calculation formula | Base diameter |
|---|---|---|---|
| ISO 1704:1991 | 4d | 4.35d | d |
| DIN 81850:2007 | 3.3d2 | 3.65d2 | d2 |
The main reason for this benchmark change is to maintain a similar geometric proportion relationship between the end ring, transition ring and ordinary ring, so as to improve the coordination and reliability of the entire anchor chain system.
Quality Control and Testing Requirements
Quality control of end rings must comply with the requirements and testing specifications of DIN 81841, including:
- Dimensional accuracy testing
- Material chemical composition analysis
- Mechanical property testing
- Non-destructive testing requirements
Test force and breaking force requirements refer to the provisions of DIN 81846-1 and DIN 81846-2 to ensure the safety of end rings in actual use.
Standard Implementation Recommendations
Design and Selection Recommendations
When selecting end ring specifications, the appropriate d value should be selected, ranging from 19mm to 58mm, based on the requirements of the actual anchor chain system. For large ships, end rings with a d ≥ 38mm are recommended to ensure sufficient strength reserve.
Manufacturing Process Control
The heat treatment process must be strictly controlled during the manufacturing process to ensure the optimal metallographic structure and mechanical properties of the 23MnNiMoCr5-4 material. The welding process must comply with the requirements of ship welding regulations and undergo corresponding process assessment.
Inspection and Certification
All end ring products must be certified by a third-party inspection agency and obtain the corresponding classification society certificate. Inspection should include multiple steps such as dimensional inspection, material verification, non-destructive testing, and mechanical property testing.
Standard Evolution and Version Changes
The DIN 81850 standard has undergone multiple revisions:
- DIN V 81850:1999-03 - Initial Version
- DIN 81850:2007-12 - Major Revision
- Major changes in the current version compared to the 2007 version include:
- a) Revision of the values in Table 1
- b) Adaptation of the standard structure to the latest formatting rules
These revisions reflect the continuous advancement of ship anchor chain technology and the ongoing improvement of standardization.
Application Case Analysis
Taking a 32mm end ring as an example, its complete identification is: Endglied DIN 81850 — K4 — 32. In actual ship anchor chain systems, this type of end ring is usually used in conjunction with a three-link adapter according to the DIN 81854 standard to form a complete anchor chain connection system.
In offshore platform mooring systems, K4 grade end rings are widely used due to their high strength properties. They can withstand dynamic loads in extreme marine environments and ensure the safety and reliability of the mooring system.