Overview
ISO 13879:1999 - Petroleum and natural gas industries - provides guidance on the content and drafting of a functional specification. It explains what a functional specification should contain, how it should be structured, and the drafting principles to ensure verifiable, unambiguous requirements. The standard clarifies when a functional specification is appropriate (e.g., for novel or performance-based procurements) and notes it may be unnecessary when acquiring known standard products or services.
Key topics and technical requirements
ISO 13879 outlines a clear framework and drafting rules, emphasizing that a functional specification must be:
- Verifiable - only include requirements that can be tested or demonstrated.
- Consistent and clear - use uniform terminology and avoid synonyms.
- Complete within scope - define limits of applicability and exclusions.
- Life-cycle aware - address operational, safety and maintenance aspects.
Core content elements recommended by the standard:
- Preliminary elements: title page, contents, foreword, introduction.
- Normative elements: scope, normative references (e.g., ISO 13880), terms and definitions.
- Functional normative elements:
- Functional requirements - performance parameters, acceptance criteria, handling, storage, transport, preservative needs.
- Operating environment - all known environmental conditions and constraints.
- Boundaries, limits and exclusions.
- Ergonomics (per ISO 6385) and safety/environment (per ISO/IEC Guide 51).
- Documentation - records, certificates, commissioning/maintenance manuals, trial programmes.
- Supplementary elements: informative annexes and operational experience data.
Applications and practical use
ISO 13879 is practical for procurement and specification development across the petroleum and natural gas sector:
- Preparing performance-based procurement documents for equipment, systems, processes or services.
- Guiding project engineers, procurement specialists and technical authors in writing clear, testable functional specifications.
- Supporting innovation where standard components are not directly applicable (pilot tests, trials, packaged systems).
- Defining acceptance criteria and the documentation required to demonstrate conformity.
Who uses it:
- User/purchasers drafting functional specifications
- Manufacturers/suppliers preparing technical specifications (see ISO 13880)
- Project managers, systems engineers, QA/QC and regulatory compliance teams in oil & gas projects
Related standards
- ISO 13880 - Drafting and content of a technical specification (normative reference)
- ISO 6385 - Ergonomics principles (referenced)
- ISO/IEC Guide 51 - Safety aspects (referenced)
- ISO/IEC Directives - guidance on standards structure and terminology
ISO 13879:1999 is a practical drafting guide for producing clear, life-cycle focused functional specifications in the petroleum and natural gas industries.
Open preview (PDF)Petroleum and natural gas industries — Content and drafting of a functional specification