The main revisions in the Rules for Classification of Sea-going Steel Ships 2026 Revision Circular include:

Part 1 — Rules for Classification

• Added additional notations for digital delivery, re-liquefaction systems, gas combustion units, yield strength assessment of Type C independent tanks based on the Load and Resistance Factor Design (LRFD) method, enhanced fire protection for the carriage of lithium-battery electric vehicles, hull monitoring and decision support systems for ice operations, and sewage discharge control;
• Adjusted the wording of the floating dock lifting capacity notation, the technical requirements of the fishing vessel notation, and the description of the LNG carrier notation;
• Revised the notations for oil well stimulation vessels, maximum cargo density, and multi-port loading/discharging of cargo;
• Adjusted the scope of vessels eligible for the "ESP" notation;
• Further clarified the inspection requirements for thermal oil heaters; adjusted the list of products requiring certification.

Part 2 — Hull

• Revised the definition of the bracket arm length for end connections of secondary structural members;
• Supplemented and refined the modelling requirements for structural details based on actual structural configuration, and added the submission requirements for typical joint detail drawings;
• Deleted the duplicated provisions regarding the use of high-performance anticorrosive coatings for underwater hull parts where underwater surveys are adopted;
• Clarified the application scope of three additional notations, including cargo density, for ordinary dry cargo ships, and deleted the corresponding descriptions in the original bulk carrier chapter;
• Further refined the web opening requirements for deck web frames;
• Updated content in accordance with IACS Unified Requirements; corrected the hatch cover requirements, the definition of rudder horn area, and the submission requirements for container lashing calculation programs;
• Clarified the towing point arrangement requirements for tugs engaged in stern towing;
• Deleted the technical requirements for pontoons;
• Revised the rule length determination, the wave coefficient calculation formula, and the diagonal brace cross-sectional area requirements for box-shaped barges, and deleted the requirement for maintaining zero trim under the minimum draught control of box-shaped barges;
• Added the application scope and additional notation descriptions for salvage vessels and pile-driving vessels;
• Added requirements for the corners of mud door openings or slits in the bottom shell of dredgers, and supplementary requirements for deck openings.

Part 3 — Machinery

• Clarified the formula values under positive and negative manufacturing tolerances;
• Clarified the design requirements for pressure vessels carrying alternative fuels;
• Revised the technical requirements for alternative fuel engines: clarified that the requirements of Chapter 9 for diesel engines apply to all alternative fuels, provided definitions for revised and extended dual-fuel engine types, and provided subsystem approval design proposals;
• Adjusted the piping requirements for alternative fuel engines, harmonizing the technical requirements for methanol and ammonia engines with those for natural gas engines;
• Deleted the longitudinal vibration requirements for turbines.

Part 4 — Electrical

• Revised the overcurrent capability indicators of AC generators and the long-time delay overload protection requirements; clarified the closing provisions for galley range exhaust duct fans;
• Incorporated updates to the IACS Unified Requirements regarding battery ventilation and "spaces of higher fire risk";
• Harmonized with IEC standards: revised the minimum electrical clearance values for AC high-voltage electrical installations, and revised the corresponding requirements for cable conductors and sheaths.

Part 6 — Fire Protection

• Modified the standard referenced for the wall thickness parameters of CO₂ piping;
• Deleted the requirements on paint colour for CO₂ cylinders;
• Modified the material names used for cylinder head valves and the sampling inspection quantities.

Part 8 — Supplementary Provisions

• Revised the supplementary provisions for fishing vessels in Chapter 5, harmonizing them with our Rules for Construction of Ocean-going Fishing Vessels;
• Corrected the arrangement area of the anti-racking brackets in Chapter 9;
• Harmonized the additional notations in Chapter 10 with Part 1;
• Incorporated the technical revisions of UR I2 Rev.5 into Chapter 13 to facilitate practical shipboard application;
• Supplemented Chapter 21 with the HMS-ICE and HMS-ICE (×) additional notations, harmonized with Part 1;
• Revised the requirements for life-saving appliances and arrangements in Chapter 23 to facilitate specific arrangement measures on board;
• Clarified that the requirement "windows shall be fitted from outside" in Chapter 24 applies only to bolted fixed windows and no longer to welded windows;
• Added a new Chapter 40, "Supplementary Provisions for Ships with Oil Well Stimulation Systems", specifying clear requirements for hazardous zones, design and arrangement, carriage of chemicals, personnel protection and surveys for ships fitted with oil well stimulation systems, with two additional notations applicable respectively to newbuildings with permanently installed oil well stimulation equipment and to conversion ships with such equipment temporarily arranged on deck; the relevant technical and survey requirements for stimulation systems are to follow the supporting guidelines.

Part 9 — Bulk Carrier and Oil Tanker Structure (CSR)

Incorporated the IACS 2024 CSR errata, including:

• The welded lower knuckle of hopper tanks may be assessed for fatigue using the screening method;
• Clarification of the plate thickness exponent for post-weld treatment;
• Updated fatigue assessment formulae and descriptions of related parameters;
• Clarification that the number of wave cycles experienced by a ship refers to the total number of stress cycles induced by wave loads;
• Clarification of the proportionality factor diagram for the allowable vertical still water bending moment;
• Clarification that deck longitudinals need not consider the static and dynamic pressures induced by liquids in topside tanks;
• Clarification of the definition of the attached plate width used for calculating moments of inertia and section moduli;
• Clarification of the definition of the "b" type hot spot stress read-out points;
• Clarification of the butt weld distance requirements for deck stiffeners;
• Updated diagrams of the design standards for oil tanker transverse bulkheads, bulk carrier transverse bulkheads and bulk carrier side frames;
• Updated diagrams of the welding requirements for transverse bulkhead supporting structures.

The effective date of this Revision Circular is 1 July 2026.