ISO 19901-5:2021

Overview

ISO 19901-5:2021 - "Petroleum and natural gas industries - Specific requirements for offshore structures - Part 5: Weight management" defines requirements for weight management and centre of gravity (CoG) control of offshore facilities throughout their lifecycle. It applies to both fixed and floating facilities, for new (greenfield) projects and modifications (brownfield), and covers all phases from conceptual design, FEED and detailed engineering, through construction, installation, operations and decommissioning. The standard addresses static mass only (snow and ice are excluded). Dynamic load topics are covered in related standards.

Key technical topics and requirements

• Mass management across lifecycle phases: requirements for predicted, conceptual, FEED and detailed weight control and tracking.
• Control weights: definitions and use of budget weights, not-to-exceed (NTE) weights, and reserves to manage design margins.
• Weight and CoG interfaces: managing interfaces between modules, assemblies and the global facility CoG to protect stability and structural integrity.
• Weighing procedures and equipment: requirements for weighing tagged equipment, discipline bulks and major assemblies, including calibration, capacity, uncertainty and witnessing of weighings.
• Reporting and databases: specifications for supplier weight data submission, weight databases, documentation, verification and change control.
• Operational and decommissioning management: weight control during operations, modifications, laydown/storage planning and removal.
• Standardized terminology: common definitions for estimating, reporting and verification of weight and CoG.

Note: the standard excludes dynamic loads (see ISO 19904-1, ISO 19901-6, ISO 19901-7).

Practical applications and users

ISO 19901-5 is used to:

• Provide a basis for costing, scheduling, construction planning and installation strategy.
• Serve as a contract reference for supplier weight deliverables and acceptance criteria.
• Support structural integrity management (SIM) by ensuring accurate mass and CoG data feed into structural models.
• Refine structural analysis/model inputs by providing validated control weights and CoG information.

Primary users include:

• Offshore structural and mechanical engineers
• Weight/CoG engineers and specialists
• Project managers (concept, FEED, detail engineering)
• Procurement and suppliers (weight data submission)
• Construction yards, installation contractors and operations/decommissioning teams

Related standards

• ISO 19904-1 (dynamic loads / offshore mooring systems)
• ISO 19901-6 and ISO 19901-7 (dynamic loading aspects)

ISO 19901-5:2021 is essential for reliable, auditable weight management for offshore structures, improving safety, installation predictability and lifecycle cost control.