ISO 19901-3:2024

Overview

ISO 19901-3:2024 - Third edition - specifies requirements and guidance for the design, fabrication and assessment of topsides structure for offshore structures (fixed platforms, topsides on floating units and mobile offshore units, and arctic topsides excluding winterization). The standard covers pre-service, in-service and post-service conditions and defines actions on topsides and resulting action effects for structural components. It also addresses prevention, control and assessment of fire, explosions and other accidental events affecting topsides and related hull areas that contain hydrocarbon processing or storage.

Key topics and technical requirements

• Scope of application: topsides of fixed structures; discrete topside units on floating hulls and mobile units; flare structures, helidecks, crane pedestals, bridges, masts and module support frames.
• Design philosophies: limit states and allowable stress options; use of national building standards with a correspondence factor for non-circular prismatic members.
• Actions and analysis: metocean (waves, current), wind, ice, seismic and extreme environmental actions; action factors for operational and extreme design situations.
• Serviceability and strength: vibration, deflection, load combinations, structural stability and robustness requirements.
• Fatigue and fracture: fatigue design guidance (in conjunction with ISO 19902) and measures to manage cyclic stresses in topsides components.
• Accidental hazards: structural design for fire, explosion, cryogenic spill, dropped objects, vessel collision and loss of buoyancy; interaction of explosion and fire.
• Fabrication, loadout and installation: design for fabrication, inspection, transportation, heavy lift and set-down operations.
• Materials and corrosion control: material selection, corrosion protection and inspection requirements for topsides environments.
• Lifecycle considerations: assessment of existing topsides, reuse, repair, refurbishment, decommissioning and structural integrity management (see ISO 19901-9).

Practical applications

• Use ISO 19901-3 for developing topsides structural design criteria, technical specifications and construction drawings.
• Apply the standard when assessing or retrofitting existing topsides for continued service, repurpose or transport/set-down operations.
• Integrate its fire/explosion provisions into topside layout, segregation and passive fire protection strategies for hydrocarbon processing areas.

Who should use this standard

• Offshore structural and mechanical engineers
• Naval architects and topsides designers
• Project managers, integrity engineers and fabrication yard leads
• Classification societies, regulators and operators planning or evaluating topsides

Related standards

• ISO 19901-1 (wind actions), ISO 19901-2 (seismic), ISO 19901-9 (structural integrity management)
• ISO 19902 (fixed platforms - fatigue design), ISO 19903, ISO 19904-1, ISO 19905-1, ISO 19905-3 and ISO 19906 (arctic structures) - referenced and used together when parts of topsides form primary global structure.