CCS issues Rule Change Notice for Materials and Welding

The China Classification Society (CCS) Rule Change Notice No. 1, effective from January 1, 2025, outlines updates to the CCS Rules for Materials and Welding. This notice addresses key changes in the rules related to metallic materials, welding, and non-destructive inspections.

Part One, which focuses on metallic materials, includes Chapter 6 on steel castings. The notice states that test material must be provided in sufficient quantities for required tests and potential retests, with test blocks representing the properties of the entire casting. The test sample thickness should be at least 30mm or equal to the ruling section of the casting, whichever is greater. For thin-walled steel castings, the thickness of the test sample must be at least 20mm. The test samples must be heat-treated along with the castings before detachment and must meet specific size and location requirements based on ISO standards. In the case of small batch testing, separately cast test samples may be used if they meet the minimum thickness specified by recognized standards like ISO 4990.

Chapter 9 addresses other non-ferrous materials, specifically copper alloy propellers. For these propellers, the standard practice is to cast separate keel block-type test samples. If the test bars are attached to the blades, they must be located between 0.5R and 0.6R of the propeller’s radius, with specific dimensions given for the keel block test samples.

Part Three, which covers welding, includes Chapter 8, focusing on welding important machinery components. Section 4 details non-destructive inspection and weld repairs of propellers. It explains how liquid penetrant testing is used to detect indications such as cracks or discontinuities in the material. These indications are classified as non-linear, linear, or aligned, based on their size and shape, and each category has specific limits regarding the size and number of indications allowed, depending on the severity zone (A, B, or C). For example, in Zone A, a maximum of 7 indications is allowed, with non-linear indications limited to 5.

In terms of repairs, weld repairs in critical areas (Zone A) are generally not allowed unless specially approved by CCS. If repairs are permitted, they must be stress-relieved through heat treatment, and the procedure must be approved by a CCS surveyor. The repairs must maintain the blade thickness as per the approved design, and defects deeper than the allowable limits may require special consideration. In some cases, propeller designers may submit detailed hydrodynamic load and stress analyses to propose modifications to Zone A, which would be subject to CCS approval.