ISO 19901-7:2013

Overview

ISO 19901-7:2013 specifies methodologies for the design, analysis and evaluation of stationkeeping systems for floating offshore structures and the assessment of stationkeeping for mobile offshore units. It covers mooring and positioning systems used in petroleum and natural gas offshore operations-supporting production, storage, drilling, well intervention, construction and pipelay activities. The standard defines functional, safety, planning, inspection and analytical requirements and includes informative guidance on typical system components.

Key topics and technical requirements

• Types of stationkeeping systems covered
  • Spread moorings (catenary, taut-line, semi-taut-line)
  • Single point moorings (anchored by spread mooring arrangements)
  • Dynamic positioning (DP) systems
  • Thruster-assisted moorings
• Design and analysis methodology
  • Definition of exposure levels, design situations and limit states
  • Environmental actions: wind, waves, current and indirect actions
  • Mooring analysis: offsets, motions, line response, anchor loads and line geometry constraints
  • Fatigue analysis procedure and fatigue safety factors
  • Transient and dynamic analyses (including thruster-assisted scenarios)
• Mooring hardware and materials
  • Guidance on mooring line components, winching and monitoring equipment
  • Specific guidance for synthetic fibre rope mooring systems (creep, stiffness, fatigue and model testing)
• In-service requirements
  • Inspection, monitoring and maintenance for mobile and permanent moorings
  • Operational and personnel considerations for DP systems
• Informative annexes
  • Descriptions of typical stationkeeping components and regional guidance
  • Annex A incorporates detailed guidance (including material aligned with API RP 2SK on anchor design and vortex-induced motions)

Practical applications and users

ISO 19901-7 is intended for engineers, designers, operators and regulators working with:

• Floating production, storage and offloading (FPSO) units, semi-submersibles, spars and ship-shaped structures
• Mobile offshore drilling units (MODUs), pipelay and construction units
• Mooring contractors, naval architects, offshore operations planners and maintenance teams

Practical uses include selecting appropriate mooring or DP solutions, performing site-specific mooring analyses, fatigue assessments, anchor and hardware specification, and developing inspection/maintenance programs.

Related standards

• ISO 19900 - General requirements for offshore structures
• Other parts of ISO 19901 (Metocean, seismic, topsides, geotechnical, marine operations)
• ISO 19904 / ISO 19905 series (floating structures and site-specific assessments)
• Informative alignment with API RP 2SK and API RP 2SM for anchor and synthetic rope guidance

Keywords: ISO 19901-7, stationkeeping systems, mooring analysis, dynamic positioning, floating offshore structures, synthetic fibre rope mooring, spread mooring, single point mooring, fatigue analysis.