SIST EN ISO 20815:2026

• Abstract:

  This document specifies requirements and guidance for production assurance and reliability management as applicable to the assets and operations associated with exploration drilling, exploitation, processing and transport of petroleum, petrochemical and natural gas resources. It covers the assets and associated activities for upstream, midstream, downstream and petrochemical business categories. It focuses on the production assurance of oil and gas with respect to production and associated activities and covers the analysis of reliability and maintenance of the equipment. This includes a variety of associated systems and equipment in the oil and gas value chain. Production assurance addresses not only hydrocarbon production, but also associated activities such as drilling, pipeline installation and subsea intervention.; The document also supports production assurance and reliability management for lower carbon energy assets and associated operations, e.g. carbon capture and storage (CCS), hydrogen, ammonia, and wind energy. It describes the processes, activities, requirements and guidelines for systematic management, effective planning, execution and use of production assurance and reliability technology.; This document defines 12 processes, of which seven are denoted as core production assurance processes and addressed in this document. The remaining five processes are denoted as interacting processes and while they are outside the scope of this document, information is provided as to how they relate to production assurance and reliability management. The relationship of the core production assurance processes with these interacting processes, however, is within the scope of this document as the flow of information to and from these latter processes is required to ensure that production assurance requirements are fulfilled.; The document specifies how to establish and execute a production assurance programme (PAP) and a reliability management programme (RMP).; This document lists processes and activities that can be initiated to add value for the stakeholder (e.g. operator), where the selected process can depend on their business strategy and application area.; This document is intended for the following users and associated activities by their personnel:; Operators: Production assurance and reliability management activities. Related activities include project management and control, technology development, technology qualification, concept and system design, risk management (including HSE), integrity management, and maintenance management.; Contractors: Activities by the main contractor for engineering, procurement, construction, drilling, installation, operation, maintenance services, etc.; Vendors: Activities by manufacturer or supplier related to equipment design and quality management, technology development and qualification.; Authorities: Activities by regulatory bodies to ensure HSE, resource utilization and economic efficiency in operations.; Consultants: Consultancy services aimed at supporting production assurance and reliability management.; Universities: Activities associated with educating industry professionals, as well as conducting fundamental or applied research projects, when related to production assurance, reliability management, and technology development. This includes improvement of the methods and frameworks described herein.; Research institutions: Research activities related to production assurance, reliability management, and technology development. This includes equipment qualification testing and advanced engineering assessments using the methods and frameworks described herein.

• Status: Published
• Public Enquiry End Date: 30-Jul-2025
• Publication Date: 13-Jul-2026
• ICS: 03.100.01 - Company organization and management in general
• ICS: 75.020 - Extraction and processing of petroleum and natural gas
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 09-Jul-2026
• Due Date: 13-Sep-2026
• Completion Date: 14-Jul-2026
• Ref Project: EN ISO 20815:2026 - Oil and gas industries including lower carbon energy - Production assurance and reliability management (ISO 20815:2026)

• Revises: SIST EN ISO 20815:2019 - Petroleum, petrochemical and natural gas industries - Production assurance and reliability management (ISO 20815:2018)
• Effective Date: 12-Mar-2025

Overview

SIST EN ISO 20815:2026 provides internationally recognized requirements and guidance for production assurance and reliability management in the oil and gas industries, including lower carbon energy sectors. The standard targets the full oil and gas value chain, covering upstream (exploration, drilling), midstream (processing, transport), downstream (petrochemical processing), and emerging low-carbon energy operations such as carbon capture and storage (CCS), hydrogen, ammonia, and wind energy.

This document is intended for operators, contractors, vendors, authorities, consultants, universities, and research institutions seeking to ensure asset performance, safety, and economic efficiency across project lifecycles. The standard emphasizes systematic management practices, effective planning, and data-driven reliability and maintenance strategies suited to both traditional hydrocarbons and evolving energy resources.

Key Topics

• Production Assurance: Outlines methods to achieve consistent, optimum production throughout the lifecycle of assets, focused on reliability, availability, and maintainability in line with safety and regulatory requirements.
• Reliability Management: Presents a framework to analyze, manage, and improve the reliability of systems, equipment, and processes across oil, gas, and lower carbon energy operations.
• Lifecycle Approach: Guidance covers all major phases, from project conceptualization and design, through operational management to decommissioning.
• Core and Interacting Processes: Defines 12 processes, with seven core production assurance processes detailed, and describes the relationships to five interacting processes to ensure integration within broader organizational practices.
• Planning and Execution: Details how to establish and implement a Production Assurance Programme (PAP) and Reliability Management Programme (RMP), integrated into project and asset management strategies.
• Value Addition and Stakeholder Engagement: Encourages the selection of processes and activities that best fit organizational strategy and add value for all stakeholders, including operators and authorities.

Applications

SIST EN ISO 20815:2026 has broad practical applications for:

• Operators: Enhancing production uptime and operational reliability across facilities, supporting project management, technology qualification, risk, and maintenance management.
• Contractors and Vendors: Ensuring engineering, procurement, construction, and equipment supply meet rigorous reliability and quality benchmarks.
• Regulatory Authorities: Benchmarking compliance on health, safety, environment (HSE), resource utilization, and economic efficiency in oil, gas, and low carbon energy sectors.
• Consultants and Researchers: Utilizing a unified framework for production assurance, reliability assessment, and risk-based decision-making-key for technology development and system optimization.
• Education and Training: Serving as a foundation for university curricula and research projects on reliability, maintenance, and production optimization for energy industry professionals.

These applications support cost-effective, sustainable operations, addressing both existing and future challenges in energy production and climate-focused projects.

Related Standards

The standard identifies and aligns with other key international references for best practices in reliability and maintenance:

• ISO 14224:2016: Collection and exchange of reliability and maintenance data for equipment in petroleum, petrochemical, and natural gas industries.
• ISO/TS 3250:2021: Calculation and reporting of production efficiency in the operating phase.
• ISO 15663:2021: Lifecycle costing for petroleum, petrochemical, and natural gas industries.
• IEC 60300-3 series: Guidelines for equipment reliability and maintenance performance.

Organizations implementing SIST EN ISO 20815:2026 will benefit from integrating these standards, resulting in robust, efficient, and forward-looking asset management across a diverse and transitioning energy landscape.

SLOVENSKI STANDARD
01-september-2026
Naftna in plinska industrija, vključno z nizkoogljično energijo - Optimizacija
proizvodnje in upravljanje zanesljivosti (ISO 20815:2026)
Oil and gas industries including lower carbon energy - Production assurance and
reliability management (ISO 20815:2026)
Öl- und Gasindustrie einschließlich kohlenstoffarmer Energieträger - Betriebsoptimierung
und Zuverlässigkeitsmanagement (ISO 20815:2026)
Industries du pétrole, de la pétrochimie et du gaz naturel - Assurance production et
gestion de la fiabilité (ISO 20815:2026)
Ta slovenski standard je istoveten z: EN ISO 20815:2026
ICS:
03.100.01 Organizacija in vodenje Company organization and
podjetja na splošno management in general
75.020 Pridobivanje in predelava Extraction and processing of
nafte in zemeljskega plina petroleum and natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 20815
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2026
EUROPÄISCHE NORM
ICS 75.180.01; 75.200 Supersedes EN ISO 20815:2018
English Version
Oil and gas industries including lower carbon energy -
Production assurance and reliability management (ISO
20815:2026)
Industries du pétrole et du gaz, y compris les énergies Öl- und Gasindustrie einschließlich kohlenstoffarmer
à faible teneur en carbone - Assurance production et Energieträger - Betriebsoptimierung und
gestion de la fiabilité (ISO 20815:2026) Zuverlässigkeitsmanagement (ISO 20815:2026)
This European Standard was approved by CEN on 20 May 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20815:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 20815:2026) has been prepared by Technical Committee ISO/TC 67 "Oil and
gas industries including lower carbon energy" in collaboration with Technical Committee CEN/TC 12
“Oil and gas industries including lower carbon energy” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2026, and conflicting national standards
shall be withdrawn at the latest by December 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 20815:2018.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20815:2026 has been approved by CEN as EN ISO 20815:2026 without any modification.

International
Standard
ISO 20815
Third edition
Oil and gas industries including
2026-06
lower carbon energy — Production
assurance and reliability
management
Industries du pétrole et du gaz, y compris les énergies à faible
teneur en carbone — Assurance production et gestion de la
fiabilité
Reference number
ISO 20815:2026(en) © ISO 2026
ISO 20815:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 20815:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions .2
3.2 Abbreviated terms . 22
4 Production assurance and decision support .23
4.1 Framework conditions . 23
4.1.1 General . 23
4.1.2 Sustainability and climate change considerations . 25
4.2 Optimization process . . 26
4.3 Production assurance programme .27
4.3.1 Objectives .27
4.3.2 Project risk categorization . 28
4.3.3 Programme activities . 29
4.4 Alternative standards .31
5 Production assurance processes and activities .32
Annex A (normative) Production assurance programme (PAP) and reliability management
programme (RMP) — Structure and content .34
Annex B (informative) Core production assurance processes and activities .36
Annex C (informative) Interacting production assurance processes and activities . 47
Annex D (informative) Production performance analyses .52
Annex E (normative) Reliability and production performance data .58
Annex F (informative) Performance objectives and requirements . 61
Annex G (normative) Performance measures for production assurance .65
Annex H (informative) Relationship to major accidents .72
Annex I (informative) Outline of techniques . 74
Bibliography .101

iii
ISO 20815:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 67, Oil and gas industries including lower carbon
energy, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/
TC 12, Oil and gas industries including lower carbon energy, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 20815:2018), which has been technically
revised.
The main changes are as follows:
— Clause 3: several new terms, definitions and abbreviated terms added;
— Clause 4: 4.1 updated, new subclause 4.1.2 added, Figure 5 and Table 2 revised;
— Main clauses and Annex A: text updated to clarify that establishment and use of production assurance
programme or reliability management programme both imply conformity to this document;
— Annex B and Annex C: text updated to align with production assurance processes for life cycle phases in
the revised Table 2;
— Annex A, Annex E, and Annex G: status changed to normative;
— Annex D: new text and figures added;
— Annex F: Figure F.1 revised, new text added in Clauses F.3 and F.4;
— Annex G: text updated to reflect the relationship between this document and ISO/TS 3250:2021; some
text in the second edition (ISO 20815:2018) has been removed since the next edition of ISO/TS 3250 is
planned to cover production loss categories for also midstream, downstream and petrochemical;
— Annex I: sequence of clauses changed; text updated in Clauses I.1, I.8 to I.9, I.14, I.16 to I.18.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 20815:2026(en)
Introduction
The oil and gas industries, including petrochemical and lower carbon energy activities, involve large capital
expenditure (CAPEX) and operating expenditure (OPEX). The safety and profitability of the associated assets
are dependent upon the reliability, availability and maintainability of the systems and components that are
used. Therefore, production assurance and reliability management are essential for optimal production
availability. This contributes to delivering affordable energy in a sustainable manner.
The concept of production assurance, introduced in this document, enables a common understanding
with respect to use of reliability technology in the various life cycle phases. Production assurance covers
the activities implemented to achieve and maintain an optimal performance level in terms of the overall
economy, which is consistent with applicable regulatory requirements and framework conditions.

v
International Standard ISO 20815:2026(en)
Oil and gas industries including lower carbon energy —
Production assurance and reliability management
1 Scope
This document specifies requirements and guidance for production assurance and reliability management
as applicable to the assets and operations associated with exploration drilling, exploitation, processing
and transport of petroleum, petrochemical and natural gas resources. It covers the assets and associated
activities for upstream, midstream, downstream and petrochemical business categories. It focuses on the
production assurance of oil and gas with respect to production and associated activities and covers the
analysis of reliability and maintenance of the equipment. This includes a variety of associated systems and
equipment in the oil and gas value chain. Production assurance addresses not only hydrocarbon production,
but also associated activities such as drilling, pipeline installation and subsea intervention.
The document also supports production assurance and reliability management for lower carbon energy
assets and associated operations, e.g. carbon capture and storage (CCS), hydrogen, ammonia, and wind
energy. It describes the processes, activities, requirements and guidelines for systematic management,
effective planning, execution and use of production assurance and reliability technology.
This document defines 12 processes, of which seven are denoted as core production assurance processes and
addressed in this document. The remaining five processes are denoted as interacting processes and while
they are outside the scope of this document, information is provided as to how they relate to production
assurance and reliability management. The relationship of the core production assurance processes with
these interacting processes, however, is within the scope of this document as the flow of information to and
from these latter processes is required to ensure that production assurance requirements are fulfilled.
The document specifies how to establish and execute a production assurance programme (PAP) and a
reliability management programme (RMP).
This document lists processes and activities that can be initiated to add value for the stakeholder (e.g.
operator), where the selected process can depend on their business strategy and application area.
This document is intended for the following users and associated activities by their personnel:
— Operators: Production assurance and reliability management activities. Related activities include project
management and control, technology development, technology qualification, concept and system design,
risk management (including HSE), integrity management, and maintenance management.
— Contractors: Activities by the main contractor for engineering, procurement, construction, drilling,
installation, operation, maintenance services, etc.
— Vendors: Activities by manufacturer or supplier related to equipment design and quality management,
technology development and qualification.
— Authorities: Activities by regulatory bodies to ensure HSE, resource utilization and economic efficiency
in operations.
— Consultants: Consultancy services aimed at supporting production assurance and reliability management.
— Universities: Activities associated with educating industry professionals, as well as conducting
fundamental or applied research projects, when related to production assurance, reliability management,
and technology development. This includes improvement of the methods and frameworks described
herein.
ISO 20815:2026(en)
— Research institutions: Research activities related to production assurance, reliability management,
and technology development. This includes equipment qualification testing and advanced engineering
assessments using the methods and frameworks described herein.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 14224:2016, Petroleum, petrochemical and natural gas industries — Collection and exchange of reliability
and maintenance data for equipment
ISO/TS 3250:2021, Petroleum, petrochemical and natural gas industries — Calculation and reporting
production efficiency in the operating phase
ISO 15663:2021, Petroleum, petrochemical and natural gas industries — Life cycle costing
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
active repair time
effective time to achieve repair of an item (3.1.29)
Note 1 to entry: The expectation of the effective time to repair is called MART (mean active repair time).
Note 2 to entry: ISO 14224 distinguishes between the terms mean active repair time (MART), mean time to repair
(MTTR), mean time to restoration (MTTRes), and mean overall repairing time (MRT). See ISO 14224:2016, 3.59, 3,61,
3.63 and 3.64 for further details.
Note 3 to entry: The mean active repair time (MART) is defined as “expected active repair time” in ISO/TR 12489:2013,
3.1.34. See also ISO/TR 12489:2013, Figures 5 and 6.
[SOURCE: ISO 14224:2016, 3.2, modified — Notes 1 to 2 to entry have been added; notes 1 and 2 to entry
have been consolidated to become note 3 to entry.]
3.1.2
asset
item (3.1.29), thing or entity that has potential or actual value to an organization
Note 1 to entry: Assets can be physical or non-physical.
Note 2 to entry: A grouping of assets referred to as an "asset system," can also be considered as an asset.
Note 3 to entry: In this document, "asset" only refers to the physical assets, which are tangible assets. An organization
can also operate assets that are wholly owned or partly owned through joint ventures or other arrangements.
Typically, an asset is a facility or an installation, or a group of facilities. The facility corresponds to an installation
category in ISO 14224:2016, Table A.1. These installations can be subdivided into plants or units, systems (3.1.75),
equipment classes (see ISO 14224:2016, 3.18), subunits, components, etc. as described in ISO 14224:2016, Table 2.
[SOURCE: ISO 55000:2024, 3.1.1, modified — Note 3 to entry has been added.]

ISO 20815:2026(en)
3.1.3
availability
ability to be in a state to perform as required under given conditions
Note 1 to entry: For a binary item (3.1.6), the measure of the availability is the probability of being in up state (3.1.79)
(i.e. in a state belonging to the up state class).
Note 2 to entry: Figure 1 shows a system that is available at time t and unavailable at time t .
1 2
Note 3 to entry: See ISO 14224:2016, Annex C for a more detailed description and interpretation of availability.
Note 4 to entry: Technical availability (3.1.76) or operational availability (3.1.50) can be used as derived performance
measures (3.1.51) to reflect estimated availability. Case specific definition of system availability is needed to reflect
the system (3.1.75) being addressed.
Note 5 to entry: Further terms are given in ISO/TR 12489.
Note 6 to entry: See Figure G.1 for further information.
[SOURCE: IEC 60050-192:2015, 192-01-23, modified — Notes to entry have been replaced by the new notes 1
to 6 to entry.]
3.1.4
average availability
mean availability
Ā(t , t )
1 2
average value of the instantaneous availability (3.1.26) over a given time interval (t , t )
1 2
Note 1 to entry: The average availability is the ratio between the accumulated time spent in up state (3.1.79) and the
length of the considered period of observation. For example, Figure 1 shows the average availability of the system
over the interval [0, t ] which is equal to (δ + δ + δ + δ + δ + δ + δ + δ )/t , i.e. 1 ̶ δ /t where δ /t is the average
3 1 2 3 4 5 6 8 9 3 7 3 7 3
unavailability of the system. This formula is similar to the formula obtained for production availability (3.1.59)
calculations when only two levels, 100 % and 0 %, are considered.
Note 2 to entry: The average availability can be interpreted as the long-run proportion of time where the item is able
to function. Mathematically speaking, the average availability is the mathematical expectation of the term availability
(3.1.3), as this term does not have the mathematical property of a normal probability and cannot be handled as such.
[SOURCE: IEC 60050-192:2015, 192-08-05, modified — Note 1 to entry has been replaced by the new notes 1
and 2 to entry.]
3.1.5
barrier
functional grouping of safeguards or controls selected to prevent a major accident (3.1.40) or limit the
consequences
[SOURCE: ISO 17776:2016, 3.1.1, modified — Notes to entry have been removed.]
3.1.6
binary item
item (3.1.29) with two classes of states
Note 1 to entry: The two classes can be up state (3.1.79) and down state (3.1.15).
EXAMPLE 1 An item that only has an up state and a down state is a binary item. Components A and B in Figure 1 are
binary items.
EXAMPLE 2 A system made up of two redundant binary items, components A and B, has four states: φ (both A and
B in up state), φ (A in up state and B in down state), φ (A in down state and B in up state), φ (both A and B in down
2 3 4
state). If the system is able to operate as required in states φ , φ and φ and not able in state φ , it is a binary item
1 2 3 4
with the up state class {φ , φ , φ } and the down class {φ }. This is illustrated in Figure 1.
1 2 3 4
ISO 20815:2026(en)
Key
A component A
B component B
S system
δ period of time
t time
X state of component A (binary item)
A
X state of component B (binary item)
B
φ state of the system S (multi-state item)
C class of states of system S (binary item)
NOTE The two components each have states 1 (Up) and 0 (Down). System S as a binary item has classes 1 (Up)
and 0 (Down).
Figure 1 — Illustration of availability behaviour of an 1oo2 system
3.1.7
capital expenditure
CAPEX
investment used to purchase, install and commission an asset (3.1.2)
Note 1 to entry: See further information regarding estimation of CAPEX in ISO 15663:2021, Clause C.2.
[SOURCE: ISO 15663:2021, 3.1.7]
3.1.8
common cause failure
failure of multiple items (3.1.29), which would otherwise be considered independent of one another, resulting
from a single cause
Note 1 to entry: Common cause failures can also be common mode failures (3.1.9).

ISO 20815:2026(en)
Note 2 to entry: The potential for common cause failures reduces the effectiveness of system redundancy.
Note 3 to entry: It is generally accepted that the failures occur simultaneously or within a short time of each other.
Note 4 to entry: Components that fail due to a shared cause normally fail in the same functional mode. The term
common mode is therefore sometimes used. It is, however, not considered to be a precise term for communicating the
characteristics that describe a common cause failure.
Note 5 to entry: Explicit and implicit common mode failures are defined in ISO/TR 12489:2013, 5.4.2.
Note 6 to entry: Regarding interpretation rules for common cause failure parameters, see also ISO 14224:2016, C.1.6.
[SOURCE: IEC 60050-192:2015, 192-03-18, modified — Notes 3 through 6 to entry have been added.]
3.1.9
common mode failures
failures of different items characterized by the same failure mode
Note 1 to entry: Common mode failures can have different causes.
Note 2 to entry: Common mode failures can also be common cause failures (3.1.8).
Note 3 to entry: The potential for common mode failures reduces the effectiveness of system redundancy.
[SOURCE: IEC 60050-192:2015, 192-03-19]
3.1.10
condition monitoring
obtaining information about physical state or operational parameters
Note 1 to entry: Condition monitoring is used to determine when preventive maintenance (3.1.57) may be required.
Note 2 to entry: Condition monitoring may be conducted automatically during operation or at planned intervals.
Note 3 to entry: Condition monitoring is part of condition-based maintenance. See also ISO 14224:2016, Figure 6.
[SOURCE: IEC 60050-192:2015, 192-06-28, modified — Note 3 to entry has been replaced.]
3.1.11
corrective maintenance
maintenance (3.1.36) carried out after fault (3.1.23) detection to effect restoration
Note 1 to entry: See also ISO/TR 12489:2013, Figures 5 and 6, which illustrate terms used for quantifying corrective
maintenance.
[SOURCE: IEC 60050-192:2015, 192-06-06, modified — Note 1 to entry has been replaced.]
3.1.12
deliverability
ratio of deliveries to planned deliveries over a specified period of time, when the effect of compensating
elements, such as substitution from other producers and downstream (3.1.17) buffer storage, is included
Note 1 to entry: See Figure G.1 for further information.
3.1.13
design life
planned usage time for the total system (3.1.75)
Note 1 to entry: It is important not to confuse design life with the mean time to failure (MTTF) (3.1.41). Several items
can fail within the design life of the system. As long as repair or replacement is feasible, the design life of the system is
not affected by such failures.
Note 2 to entry: The design life is decided during the life cycle phase "Define". Design life in this document can thus
mean a lifetime that can change and that can be chosen based on production assurance (3.1.58) activities or life cycle
costing (3.1.30).
ISO 20815:2026(en)
3.1.14
demand availability
ability of the production facility to satisfy the demand over a specified period of time
Note 1 to entry: This performance measure (3.1.51) expresses the fraction of time or number of times the produced
volume that is exported is equal to or above demand. See also Table G.1.
3.1.15
down state
state of being unable to perform as required, due to internal fault (3.1.23), or preventive maintenance (3.1.57)
Note 1 to entry: This concept is related to a binary item (3.1.6), which can have several down states forming the
down state class of the item. All the states in the down state class are considered to be equivalent with regard to the
unavailability of the considered item.
EXAMPLE In Figure 1, the down state class of the system S comprises only one state {S } and the system S is in
down state at time t .
[SOURCE: IEC 60050-192:2015, 192-02-20, modified — Note 1 to entry has been replaced, and note 2 to entry
has been removed; EXAMPLE has been added.]
3.1.16
down time
time interval during which an item (3.1.29) is in a down state (3.1.15)
Note 1 to entry: The down time includes all the delays between the item failure and the restoration of its service.
Down time can be either planned or unplanned (see ISO 14224:2016, Table 4).
Note 2 to entry: Down time can be equipment down time (see ISO 14224:2016, Figure 4 and Table 4), production down
time (see Figures I.1 and I.2) or down time for other operations (e.g. drilling). It is important to distinguish between
the equipment down time itself and the down time of the plant to which the equipment belongs.
[SOURCE: IEC 60050-192:2015, 192-02-21, modified — Notes to entry have been replaced.]
3.1.17
downstream
business category most commonly used in the petroleum industry to describe post-production processes
Note 1 to entry: See ISO 14224:2016, A.1.4 for further details.
[SOURCE: ISO 14224:2016, 3.17, modified — EXAMPLE has been removed.]
3.1.18
failure
loss of ability to perform as required
Note 1 to entry: A failure of an item is an event that results in a fault (3.1.23) (i.e. a state) of that item. This is illustrated
in Figure 2 for a binary system S comprising two redundant components A and B.
[SOURCE: IEC 60050-192:2015, 192-03-01, modified — The notes to entry have been replaced by a new note
1 to entry.]
3.1.19
failure cause
root cause
set of circumstances that leads to failure (3.1.18)
Note 1 to entry: A failure cause can originate during specification, design, manufacture, installation, operation or
maintenance of an item.
Note 2 to entry: See ISO 14224:2016, B.2.3 and Table B.3, which define failure causes for all equipment classes.
[SOURCE: IEC 60050-192:2015, 192-03-11, modified — Note 2 to entry has been added.]

ISO 20815:2026(en)
3.1.20
failure data
data characterizing the occurrence of a failure (3.1.18) event
Note 1 to entry: See ISO 14224:2016, Table 6.
[SOURCE: ISO 14224:2016, 3.25]
3.1.21
failure mode
manner in which failure (3.1.18) occurs
Note 1 to entry: See ISO 14224:2016, Tables B.6 to B.15, on the relevant failure modes, which define failure modes to
be used for each equipment class.
[SOURCE: IEC 60050-192:2015, 192-03-17, modified — The notes to entry have been replaced by a new note
1 to entry.]
3.1.22
failure rate
conditional probability per unit of time that the item (3.1.29) fails between t and t + dt, provided that it
works over (0, t)
Note 1 to entry: See ISO 14224:2016, Clause C.3 for further explanation of the failure rate.
Note 2 to entry: This definition applies for the first failure (3.1.18) of binary items (3.1.6).
Note 3 to entry: Under the assumptions that the failure rate is constant and that the item is as good as new after
repairs the failure rate can be estimated as the number of failures relative to the corresponding accumulated up time
(3.1.80) divided by this accumulated up time. In this case this is the reciprocal of MTTF (3.1.41). In some cases, time
can be replaced by units of use.
Note 4 to entry: The estimation of the failure rate can be based on operating time (3.1.49) or calendar time.
[SOURCE: ISO/TR 12489:2013, 3.1.18, modified — The symbol "λ(t)" has been removed; the notes to entry
have been replaced by the new notes 1 to 4 to entry.]
3.1.23
fault
inability to perform as required, due to an internal state
EXAMPLE Down states (3.1.15) of items A, B and system S is illustrated in Figure 2.
Note 1 to entry: A fault of an item results from a failure (3.1.18), either of the item itself, or from a deficiency in an earlier
stage of the life cycle, such as specification, design, manufacture or maintenance. See latent fault (ISO 14224:2016,
3.44).
Note 2 to entry: An item made of several sub-items (e.g. a system) which continues to perform as required in presence
of faults of one or several sub-items is called fault tolerant.
Note 3 to entry: See also ISO/TR 12489:2013, 3.2.2.
[SOURCE: IEC 60050-192:2015, 192-04-01, modified — EXAMPLE has been added; the notes 2 to 4 to entry
have been replaced by the new notes 2 and 3 to entry.]
3.1.24
fault tolerance
attribute of an item (3.1.29) that makes it able to perform a required function (3.1.69) in the presence of
certain given sub-item faults (3.1.23)

ISO 20815:2026(en)
3.1.25
human error
discrepancy between the human action taken or omitted and that intended
EXAMPLE Performing an incorrect action; omitting a required action.
Note 1 to entry: Discrepancy with intention is considered essential in determining human error; see Reference [91].
Note 2 to entry: The term "human error" is often attributed in hindsight to a human decision, action or inaction
considered to be an initiator or contributory cause of a negative outcome such as loss or harm.
Note 3 to entry: In human reliability assessment, human error is defined as any member of a set of human actions or
activities that exceeds some limit of acceptability, this being an out of tolerance action or failure (3.1.18) to act where
the limits of performance are defined by the system (see Reference [88]).
Note 4 to entry: See IEC 62508 for further details.
Note 5 to entry: See also ISO/TR 12489:2013, 5.5.2.
[SOURCE: IEC 60050-192:2015, 192-03-14, modified — The words "or required" have been removed at the
end of the definition; in the EXAMPLE, "miscalculation; misreading a value" have been removed; notes 1 to 5
to entry have been added.]
3.1.26
instantaneous availability
A(t)
probability that an item (3.1.29) is in a state to perform as required at a given instant
[SOURCE: IEC 60050-192:2015, 192-08-01, modified — The admitted term "point availability" has been
removed; the symbol "A(t)" has been added.]
3.1.27
integrity
condition in which an asset (3.1.2) is safe and reliable for its purpose
Note 1 to entry: For some application areas, more specific terms and definitions exist, such as asset integrity,
mechanical integrity, plant integrity, safety integrity (see ISO/TR 12489:2013, 3.1.2), structural integrity (see
1) 2)
ISO 19900:— , 3.58), system integrity, technical integrity and well integrity (see ISO 16530:— , 3.73). These integrity
terms can encompass various failure (3.1.18) consequences (e.g. safety, environmental, production, and operation; see
ISO 14224:2016, Table C.2).
Note 2 to entry: Integrity is also defined for use in pipeline integrity management (3.1.28) for onshore gas infrastructure
in EN 17649:2022, 3.7. see also DNV -ST -F101: 2021 and ISO 19345-1:2019, 3.1.32.
Note 3 to entry: The integrity can be expressed mathematically by using specific performance measures (3.1.51) as
described in Annex G.
[SOURCE: EN 17649:2022, 3.7, modified — Notes 1 to 3 to entry have been added.]
3.1.28
integrity management
set of processes and procedures used to proactively manage the safe, environmentally responsible and
reliable service of an asset (3.1.2) throughout its life cycle
Note 1 to entry: The integrity management program covers a set of processes and practices used in reliability
management (3.1.68). See e.g. ISO 19345-1:2019, 3.1.21.
1) Under preparation. Stage at the time of publication: ISO/DIS 19900:2026.
2) Under preparation. Stage at the time of publication: ISO/DIS 16530:2026.

ISO 20815:2026(en)
3.1.29
item
subject being considered
Note 1 to entry: The item can be an individual part, component, device, functional unit, equipment, subsystem, or
system.
Note 2 to entry: The item may consist of hardware, software, people or any combination thereof.
Note 3 to entry: In this document, item can also be plant or unit, or installation. See ISO 14224:2016, Figure 3.
[SOURCE: IEC 60050-192:2015, 192-01-01, modified — In note 1 to entry, "material", "product" and "service
or process" have been removed; in note 2 to entry, "can" has been changed to "may"; note 3 to entry has been
added.]
3.1.30
life cycle costing
process of evaluating the difference between the life cycle cost of two or more alternative options
Note 1 to entry: Life cycle costing can involve quantitative and qualitative assessment.
[SOURCE: ISO 15663:2021, 3.1.27, modified — Note 1 to entry has been adjusted.]
3.1.31
life cycle phase
discrete stage in the life cycle with a specified purpose
Note 1 to entry: The different life cycle phases are further described in ISO 15663:2021, 4.5.
[SOURCE: ISO 15663:2021, 3.1.28]
3.1.32
logistic delay
delay, excluding administrative delay, incurred for the provision of resources needed for a maintenance
action to proceed or continue
Note 1 to entry: Logistic delays can be due to, for example, travelling to unattended installations, pending arrival of
spare parts, specialists, test equipment and information, and delays due to unsuitable environmental conditions (e.g.
waiting on weather).
Note 2 to entry: See also ISO/TR 12489:2013, Figure 5.
[SOURCE: IEC 60050-192:2015, 192-07-13, modified — Note 1 to entry has been replaced by the new notes 1
and 2 to entry.]
3.1.33
lost revenue
LOSTREV
income loss that occurs when generated income are less than expected due to external or internal factors
Note 1 to entry: Production loss (3.1.61) categories are defined in ISO/TS 3250:2021. Time loss categories are described
in Clause G.3.
[SOURCE: ISO 15663:2021, 3.1.29, modified — Notes 1 and 2 to entry have been replaced by the new note 1
to entry.]
3.1.34
maintainability
ability to be retained in, or restored to a state to perform as required, under given conditions of use and
maintenance (3.1.36)
Note 1 to entry: Given conditions would include aspects that affect maintainability, such as: location for maintenance,
accessibility, maintenance procedures and maintenance resources.

ISO 20815:2026(en)
Note 2 to entry: Maintainability can be quantified using appropriate measures. See IEC 60050-192:2015, 192-07,
Maintainability and maintenance support: measures.
Note 3 to entry: See Figure G.1 for further information.
[SOURCE: IEC 60050-192:2015, 192-01-27, modified — Note 3 to entry has been added.]
3.1.35
maintainable item
item (3.1.29) that constitutes a part or an assembly of parts that is normally the lowest level in the equipment
hierarchy during maintenance (3.1.36)
[SOURCE: ISO 14224:2016, 3.48]
3.1.36
maintenance
combination of all technical and management actions intended to retain an item in, or restore it to, a state in
which it can perform as required
[SOURCE: IEC 60050-192:2015, 192-06-01, modified — Note 1 to entry has been removed.]
3.1.37
maintenance data
data characterizing the maintenance action planned or done
Note 1 to entry: See ISO 14224:2016, Table 8.
[SOURCE: ISO 14224:2016, 3.51, modified — The notes 1 and 3 to entry have been removed; new note 1 to
entry added.]
3.1.38
maintenance management
all activities of the management that determine the maintenance requirements, objectives, strategies, and
responsibilities, and implementation of them by such means as maintenance planning, maintenance control
and the improvement of maintenance activities and economics
[SOURCE: EN 13306:2017, 2.2]
3.1.39
maintenance supportability
ability to be supported to sustain the required availability (3.1.3) with a defined operational profile and
given logistic and maintenance resources
Note 1 to entry: Maintenance supportability of an item result from the inherent maintainability (3.1.34), combined with
factors external to the item that affect the relative ease of providing the required maintenance and logistic support.
Note 2 to entry: See ISO 14224:2016, Annex C for further details regarding the interpretation of maintainability.
3.1.40
major accident
hazardous event that results in
— multiple fatalities or severe injuries; or
— extensive damage to structure, installation or plant; or
— large-scale impact on the environment (e.g. persistent and severe environment
...