prEN ISO 20815

SLOVENSKI STANDARD
01-julij-2025
Naftna in plinska industrija, vključno z nizkoogljično energijo - Zagotavljanje
proizvodnje in upravljanje zanesljivosti (ISO/DIS 20815:2025)
Oil and gas industries including lower carbon energy - Production assurance and
reliability management (ISO/DIS 20815:2025)
Öl- und Gasindustrie einschließlich kohlenstoffarmer Energieträger - Betriebsoptimierung
und Zuverlässigkeitsmanagement (ISO/DIS 20815:2025)
Industries du pétrole, de la pétrochimie et du gaz naturel - Assurance production et
gestion de la fiabilité (ISO/DIS 20815:2025)
Ta slovenski standard je istoveten z: prEN ISO 20815
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.

DRAFT
International
Standard
ISO/DIS 20815
ISO/TC 67
Oil and gas industries including
Secretariat: NEN
lower carbon energy — Production
Voting begins on:
assurance and reliability
2025-05-15
management
Voting terminates on:
2025-08-07
Industries du pétrole, de la pétrochimie et du gaz naturel —
Assurance production et gestion de la fiabilité
ICS: 75.180.01; 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
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Reference number
ISO/DIS 20815:2025(en)
DRAFT
ISO/DIS 20815:2025(en)
International
Standard
ISO/DIS 20815
ISO/TC 67
Oil and gas industries including
Secretariat: NEN
lower carbon energy — Production
Voting begins on:
assurance and reliability
management
Voting terminates on:
Industries du pétrole, de la pétrochimie et du gaz naturel —
Assurance production et gestion de la fiabilité
ICS: 75.180.01; 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 20815:2025(en)
ii
ISO/DIS 20815:2025(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 Abbreviations .19
4 Production assurance and decision support .21
4.1 Users of this document .21
4.2 Framework conditions . 22
4.2.1 General . 22
4.2.2 Sustainability and climate change considerations . 23
4.3 Optimization process .24
4.4 Production assurance programme . 25
4.4.1 Objectives . 25
4.4.2 Project risk categorization . 26
4.4.3 Programme activities .27
4.5 Alternative standards . 29
5 Production assurance processes and activities .29
Annex A (normative) Production assurance programme (PAP) and reliability management
programme (RMP) – Structure and content .31
Annex B (informative) Core production assurance processes and activities .33
Annex C (informative) Interacting production assurance processes and activities .43
Annex D (informative) Production performance analyses .48
Annex E (normative) Reliability and production performance data .55
Annex F (informative) Performance objectives and requirements .58
Annex G (informative) Performance measures for production assurance .62
Annex H (informative) Relationship to major accidents .69
Annex I (informative) Outline of techniques .71
Bibliography .97

iii
ISO/DIS 20815:2025(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.
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 abbreviations;
— Clause 4: changes in Clause 4.1, new Clause 4.2.2, revised Figure 5 and Table 2;
— Main clauses and Annex A: establishment and use of production assurance programme or reliability
management programme will both imply conformance of this document;
— Annex A: minor changes;
— Annex B and C: changes to align with production assurance processes for life cycle phases in revised
Table 2;
— Annex A and Annex E are made normative;
— Annex D: various new text and new figures;
— Annex F: revised figure in Clause F.2, new text in Clauses F.3 and F.4;
— Annex G: various changes made to reflect the relationship to 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 H: some changes;
— Annex I: various changes in Clauses I.1, I.7 to I.10, I.18, I.20 to I.26.
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/DIS 20815:2025(en)
Introduction
The oil and gas industries including petrochemical and lower carbon energy activities involve large capital
expenditure (CAPEX) as well as operating expenditure (OPEX). The safety and the profitability of the
associated assets are dependent upon the reliability, availability and maintainability of the systems and
components that are used. Therefore, for optimal production availability to deliver affordable energy in a
sustainable manner, standardized and integrated production assurance and reliability management are
essential.
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 and covers the activities implemented
to achieve and maintain a performance level that is at its optimum in terms of the overall economy and, at
the same time, consistent with applicable regulatory requirements and framework conditions.
The normative Annex A and Annex E, and the informative annexes support this standardization concept for
industry stakeholders.
v
DRAFT International Standard ISO/DIS 20815:2025(en)
Oil and gas industries including lower carbon energy —
Production assurance and reliability management
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
This document describes the concept of production assurance within the assets and operations associated
with exploration drilling, exploitation, processing and transport of petroleum, petrochemical and natural gas
resources. This document covers assets and associated activities for upstream, midstream, downstream and
petrochemical business categories. It focuses on production assurance of oil and gas production, processing
and associated activities and covers the analysis of reliability and maintenance of the components. This
includes a variety of business categories and associated systems/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.
This 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. This document provides processes and activities, requirements and guidelines for systematic
management, effective planning, execution and use of production assurance and reliability technology. This
is to achieve cost-effective solutions over the life cycle of an asset development project structured around
the following main elements:
— production assurance management for optimum economy of the facility through all of its life cycle
phases, while also considering constraints arising from health, safety, environment, and quality;
— planning, execution and implementation of reliability technology;
— application of reliability and maintenance data;
— reliability-based technology development, design and operational improvement.
The IEC 60300-3 series addresses equipment reliability and maintenance performance in general.
This document designates 12 processes, of which seven are defined as core production assurance processes
and addressed in this document. The remaining five processes are denoted as interacting processes and are
outside the scope of this document. The interaction of the core production assurance processes with these
interacting processes, however, is within the scope of this document as the information flow to and from
these latter processes is required to ensure that production assurance requirements can be fulfilled.
This document specifies how to establish and execute the production assurance programme (PAP) and/or
a reliability management programme (RMP). It is important to reflect the PAP and/or RMP in the overall
project management in the project for which they apply. The PAP is generally used for an entire asset or a
project by an operator. The RMP typically applies for a contractor or a vendor/manufacturer/supplier for
their scope of work in a project. See Annex A for further guidance for preparing PAP and/or RMP.
This document also recommends that the listed processes and activities be initiated only if they can be
considered to add value for the stakeholder (e.g. operator), but the selected process can depend on their
business strategy and application area.

ISO/DIS 20815:2025(en)
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 terminological 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 (3.1.28)
Note 1 to entry: The expectation of the effective time to repair is called MART (mean active repair time).
Note 2 to entry: ISO 14224:2016 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,
3.63, 3.64 and 3.61 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 adjusted, and Note 3 to entry has
been added.]
3.1.2
asset
item (3.1.28), 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’ (see ISO 55000:2024, 3.1.6) 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 plant/units, systems (3.1.72), equipment classes
(see ISO 14224, 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/DIS 20815:2025(en)
3.1.3
availability
ability to be in a state to perform as required
Note 1 to entry: For a binary item, the measure of the availability is the probability to be in up state (i.e. in a state
belonging to the up state class), see 3.1.76.
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 (3.1.73) or operational availability (3.1.49) can be used as derived performance
measures to reflect estimate availability. Case specific definition of system availability is needed to reflect the system
(3.1.72) being addressed.
Note 5 to entry: Further terms are given in ISO/TR 12489:2013.
Note 6 to entry: See Figure G.1 for further information.
[SOURCE: IEC 60050-192:2015, 192-01-23, modified — Notes 1 to 6 to entry have been added.]
3.1.4
average availability
mean availability
A(t , t )
1 2
average value of the instantaneous availability (3.1.25) 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 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 ] is equal to (δ + δ + δ + δ + δ + δ + δ + δ )/t , i.e., 1 ̶ δ /t where δ /t is the average unavailability
3 1 2 3 4 5 6 8 9 3 7 3 7 3
of the system. This formula is similar to the formula obtained for production availability calculations when only two
levels, 100 % and 0 %, are considered.
Note 2 to entry: The average availability may 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, 192-08-01, modified — Notes 1 and 2 to entry have been added.]
3.1.5
barrier
functional grouping of safeguards or controls selected to prevent a major accident (3.1.39) or limit the
consequences
[SOURCE: ISO 17776:2016, 3.1.1, modified — Notes to entry not included.]
3.1.6
binary item
item (3.1.28) with two classes of states
Note 1 to entry: The two classes can be up state (3.1.76) and down state (3.1.14) .
EXAMPLE 1 An item that only have 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, A and B, has four states: S (both A and B in up state),
S (A in up state and B in down state), S (A in down state and B in up state), S (both A and B in down state). If the
2 3 4
system is able to operate as required in states S , S and S and not able in state S , it is a binary item with the up state
1 2 3 4
class {S , S , S } and the down class {S }. This is illustrated in Figure 1.
1 2 3 4
ISO/DIS 20815:2025(en)
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, C.2.
[SOURCE: ISO 15663:2021, 3.1.7]
3.1.8
common cause failure
failures of multiple items (3.1.28), which would otherwise be considered independent of one another,
resulting from a single cause
Note 1 to entry: See also Notes to entry for common cause failures in ISO 14224:2016, 3.5.
[SOURCE: IEC 60050-192:2015, 192-03-18, modified — Note 1 to entry has been added.]
3.1.9
condition monitoring
obtaining information about physical state or operational parameters
Note 1 to entry: Condition monitoring is used to determine when preventive maintenance 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 added.]

ISO/DIS 20815:2025(en)
3.1.10
corrective maintenance
maintenance (3.1.35) carried out after fault 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 added.]
3.1.11
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 (3.1.16) buffer storage, is included
Note 1 to entry: See Figure G.1 for further information.
3.1.12
design life
planned usage time for the total system (3.1.72)
Note 1 to entry: It is important not to confuse design life with the ‘mean time to failure’ (MTTF), which is comprised
of several items that might be allowed to fail within the design life of the system as long as repair or replacement is
feasible.
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 activities or life cycle costing.
3.1.13
demand availability
ability of the production facility to satisfy the demand over a specified period of time
Note 1 to entry: This performance measure expressed 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.
3.1.14
down state
unavailable state
internally disabled state
internal disabled state
state of being unable to perform as required, due to internal fault (3.1.22), or preventive maintenance (3.1.54)
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.
Note 2 to entry: See also Notes to entry for down state in ISO 14224:2016, 3.15.
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 — Notes 1 and 2 have been added.]
3.1.15
down time
time interval during which an item (3.1.28) is in a down state (3.1.14)
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 Figure 4 and Table 4 in ISO 14224:2016), 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 1 and 2 have been added.]

ISO/DIS 20815:2025(en)
3.1.16
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]
3.1.17
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 (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 — Note 1 to entry has been added.]
3.1.18
failure cause
root cause
set of circumstances that leads to failure (3.1.17)
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 also 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.]
3.1.19
failure data
data characterizing the occurrence of a failure event
Note 1 to entry: See also ISO 14224:2016, Table 6.
[SOURCE: ISO 14224:2016, 3.25]
3.1.20
failure mode
manner in which failure (3.1.17) occurs
Note 1 to entry: See also the tables in ISO 14224:2016, B.2.6, 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 — Note 1 to entry has been added.]
3.1.21
failure rate
conditional probability per unit of time that the item (3.1.28) fails between t and t + dt, provided that it has
been working over (0, t)
Note 1 to entry: See ISO 14224:2016, C.3 for further explanation of the failure rate.
Note 2 to entry: This definition applies for the first failure of binary items (3.1.4).
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
divided by this accumulated up time. In this case this is the reciprocal of MTTF (3.1.40). 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 or calendar time.
[SOURCE: ISO/TR 12489:2013, modified — Notes 1 to 4 to entry have been added.]

ISO/DIS 20815:2025(en)
3.1.22
fault
inability to perform as required, due to an internal state
Note 1 to entry: A fault of an item results from a failure, 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).
The down states of items A, B and S in Figure 2 are examples of faults.
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 — Note 2 to entry has been added.]
3.1.23
fault tolerance
attribute of an item (3.1.28) that makes it able to perform a required function in the presence of certain
given sub-item faults (3.1.22)
3.1.24
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 [87].
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 to act where the limits
of performance are defined by the system (see Reference [84]).
Note 4 to entry: See also IEC 62508:2010 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 — Notes 1 through 5 to entry have been added.]
3.1.25
instantaneous availability
A(t)
probability that an item (3.1.28) is in a state to perform as required at a given instant
[SOURCE: IEC 60050-192:2015, 192-08-01]
3.1.26
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 (see
ISO/TS 3250:2021, 3.1.2), mechanical integrity, plant integrity, safety integrity (see ISO/TR 12489:2013, 3.1.2),
structural integrity (see ISO 19900:2019, 3.50), system integrity, technical integrity and well integrity (see
ISO/DIS 16530-1:2025, 3.73) . These integrity terms can encompass various failure 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 for onshore gas infrastructure in EN
17649:2022, 3.7. see also DNV-ST-F101:2017 and ISO 19345-1:2019, 3.1.32.
Note 3 to entry: The integrity can be expressed mathematically by using specific performance measures as described
in Annex G.
[SOURCE: EN 17349:2022, 3.7, modified — Notes 1 to 3 to entry have been added.]

ISO/DIS 20815:2025(en)
3.1.27
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 practises used in reliability
management. See e.g. ISO 19345-1:2019, 3.1.21.
3.1.28
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/unit and installation. See ISO 14224:2016, Figure 3.
[SOURCE: IEC 60050-192:2015, 192-01-01, modified — Note 3 to entry has been added.]
3.1.29
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/or qualitative assessment.
[SOURCE: ISO 15663:2021, 3.1.27]
3.1.30
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]
3.1.31
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 — Notes 1 and 2 to entry have been added.]
3.1.32
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 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 not been included, and new Note
1 to entry has been added.]
ISO/DIS 20815:2025(en)
3.1.33
maintainability
ability to be retained in, or restored to a state to perform as required, under given conditions of use and
maintenance (3.1.35)
Note 1 to entry: Given conditions would include aspects that affect maintainability, such as: location for maintenance,
accessibility, maintenance procedures and maintenance resources.
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.]
3.1.34
maintainable item
item (3.1.28) that constitutes a part or an assembly of parts that is normally the lowest level in the equipment
hierarchy during maintenance (3.1.35)
[SOURCE: ISO 14224:2016, 3.48]
3.1.35
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]
3.1.36
maintenance data
data characterizing the maintenance action planned or done
Note 1 to entry: See also ISO 14224:2016, Table 8.
[SOURCE: ISO 14224:2016, 3.51]
3.1.37
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]
3.1.38
maintenance supportability
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 (3.1.33), 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.
[SOURCE: IEC 60050-192:2015, 192-01-31, modified — Note 2 to entry has been added.]

ISO/DIS 20815:2025(en)
3.1.39
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
Note 1 to entry: Examples of large-scale impact on the environment are persistent and severe environmental
damage that can lead to loss of commercial or recreational use, loss of natural resources over a wide area or severe
environmental damage that will require extensive measures to restore beneficial uses of the environment.
Note 2 to entry: In ISO 17776:2016, a major accident (3.1.39) is the realization of a major accident hazard.
[SOURCE: ISO 17776:2016, 3.1.12]
3.1.40
mean time to failure
MTTF
expected time before the item (3.1.28) fails
Note 1 to entry: See further details in ISO/TR 12489:2013, 3.1.29.
Note 2 to entry: IEC 60050-192:2015 defines MTTF as ”expectation of the operating time to failure”.
Note 3 to entry: See also ISO 14224:2016, Annex C.
[SOURCE: ISO/TR 12489:2013, 3.1.29, modified — Notes 1 through 3 to entry have been added.]
3.1.41
midstream
business category involving the processing, storage and transportation sectors of the petroleum industry
Note 1 to entry: See ISO 14224:2016, A.1.4 for further details.
[SOURCE: ISO 14224:2016, 3.65]
3.1.42
modification
combination of all technical and administrative actions intended to change an item (3.1.28)
Note 1 to entry: In this document, the use of the term modification is primarily meant to cover major modification
activities. See further details in ISO/TS 3250:2021, 8.2.2 with respect to how such major modifications are reflected
in production efficiency reporting.
[SOURCE: ISO 14224:2016, 3.67, modified — Notes 1 to 3 to entry have not been included, and new Note 1 to
entry has been added.]
3.1.43
multi-state item
item (3.1.28) with more than two classes of states
Note 1 to entry: This is an extension of the binary items beyond the concepts of up and down states. This can
characterize single items with degraded states or systems made up of several components in a production facility.
EXAMPLE An oil production system comprising two wells, A and B, that can be considered as binary items (see
3.1.3) has four states: S (both A and B in up state), S (A in up state and B in down state), S (A in down state and B in
1 2 3
up state), S (both A and B in down state). If, when they are in up state, A produces 200 bpd (barrels per day) and B
produces 100 bpd, then the system has four classes of production 300 bpd, {S },200 bpd, {S }, 100 bpd, {S } and 0 bpd,
1 2 3
{S }. With regards to oil production, it is a multi-state item. This is illustrated in Figure 2.
ISO/DIS 20815:2025(en)
Figure 2 — Illustration of production availability behaviour of a multi-state system
3.1.44
observation period
time period during which production performance (3.1.59) and reliability data (3.1.64) are recorded
3.1.45
on-stream availability
ability of a production facility to deliver a volume above zero over a specified period of time
Note 1 to entry: This performance measure expresses the fraction of time or number of times produced volume is
above zero. See also Table G.1.
3.1.46
operating expenditure
OPEX
expenses used for operation and maintenance, including associated costs such as logistics and spares
Note 1 to entry: See further information regarding estimation of OPEX in ISO 15663:2021, C.3.
[SOURCE: ISO 15663:2021, 3.1.31]
3.1.47
operating state
state of performing as required
Note 1 to entry: See also ISO 14224:2016, Table 4.
Note 2 to entry: In some applications, an item in an idle state is considered to be operating.
Note 3 to entry: The state capacities of a multi-state item characterize various levels of operation and consequently,
the definition of the operating state of a multi-state item depends on the situation, for example, if:
— no other requirement is given, any state with a capacity greater than zero is an operating state;
— a minimum capacity is required, it provides the limit to split the states between up and down classes;
— a given capacity is specified, then only the states with this capacity are operating states;

ISO/DIS 20815:2025(en)
— no other requirement is given, any state with a capacity greater than zero is an operating state (300 bpd, 200 bpd
and 100 bpd in Figure 2);
— a minimum capacity is required, it provides the limit to split the states between up and down classes (300 bpd,
200 bpd in Figure 2, if the minimum allowed production is 200 bpd);
— a given capacity is specified, then only the states with this capacity are operating states (200 bpd in Figure 2 if and
only if 200 bpd are required).
[SOURCE: IEC 60050-192:2015, 192-02-04, modified — Notes 1 and 3 to entry have been added.]
3.1.48
operating time
time interval during which an item (3.1.28) is in an operating state (3.1.47)
Note 1 to entry: The accumulated times of various disjunct operating times interru
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