IEC 62550:2017

IEC 62550 ®
Edition 1.0 2017-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Spare parts provisioning
Approvisionnement en pièces de rechange

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IEC 62550 ®
Edition 1.0 2017-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Spare parts provisioning
Approvisionnement en pièces de rechange

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 03.120.01; 21.020 ISBN 978-2-8322-3834-9

– 2 – IEC 62550:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 11
4 Overview . 12
4.1 Participants and major steps in the spare parts provisioning process . 12
4.2 Types of spare parts . 14
4.3 Identification of spare parts as integral part of the level of repair analysis
(LORA) . 14
4.4 Overall spare parts provisioning process . 16
5 Demand forecast . 17
5.1 General . 17
5.2 Forecast based on consumption data . 18
5.2.1 General . 18
5.2.2 Procedures for forecast . 18
5.3 Initial determination of demand . 19
5.3.1 General . 19
5.3.2 Prediction of failure rates and failure intensities . 19
5.3.3 Calculation of demand rates . 20
6 Spare parts quantification . 20
6.1 General . 20
6.1.1 Process overview . 20
6.1.2 Probability distributions for spare parts quantification . 22
6.1.3 Measures of effectiveness (MoE) . 23
6.1.4 ABC-analysis (Pareto analysis) . 24
6.1.5 Quantification of repairable items . 26
6.1.6 Quantification of non-repairable items . 26
6.2 Strategic (critical, insurance) spare parts . 28
6.3 Inventory systems . 28
6.4 Inventory optimization . 30
7 Spare parts documentation . 32
7.1 Principles and objectives . 32
7.2 Illustrated parts catalogue (IPC) . 32
7.3 Parts catalogue . 35
8 Supply management . 35
8.1 General . 35
8.1.1 Activities . 35
8.1.2 Economic provisioning . 36
8.2 Sources for spare parts . 36
8.3 Supply policies . 37
8.3.1 Insourcing . 37
8.3.2 Outsourcing . 37
8.3.3 Single sourcing . 37

8.3.4 Global sourcing . 38
8.3.5 Concurrent sourcing . 38
8.3.6 Obsolescence management . 39
8.4 Planning and control of the flow of repairable spare parts . 39
Annex A (informative) Prognosis of demand . 40
A.1 General . 40
A.2 Synthetic determining of demand . 40
A.3 Prognosis based on consumption data . 41
A.3.1 Overview . 41
A.3.2 Forecast on the basis of the moving average . 41
A.3.3 Forecast on the basis of the weighted moving average . 42
A.3.4 Forecast on the basis of exponential smoothing . 42
A.3.5 Forecast on the basis of regression analysis . 43
Annex B (informative) Measures of effectiveness . 44
B.1 General . 44
B.2 Stock-related measures of effectiveness . 44
B.2.1 Fill rate (FR) and risk of shortage (ROS) . 44
B.2.2 Expected backorders (EBO). 46
B.2.3 Mean waiting time (MWT) . 47
B.3 System-related measures of effectiveness . 48
B.3.1 Operational system availability (A ) . 48
op
B.3.2 Number of systems not operationally ready (NOR). 49
Annex C (informative) Example: Quantification of spare parts and optimization of
inventory stocks . 50
C.1 General . 50
C.2 Product breakdown structure . 50
C.3 Calculation of spare parts quantities and costs . 52
Bibliography . 54

Figure 1 – Participants and major steps in the spare parts provisioning process . 13
Figure 2 – Identification of spare parts . 16
Figure 3 – Spare parts provisioning process during design and development . 17
Figure 4 – Spare parts provisioning process during utilization . 21
Figure 5 – Principle of an ABC-analysis . 25
Figure 6 – Inventory control policies . 27
Figure 7 – Hierarchically structured inventory system . 28
Figure 8 – Single-product-single-inventory models . 30
Figure 9 – Idealized inventory model for non-repairable items . 31
Figure 10 – Supply management activities . 36
Figure A.1 – Procedures of demand forecast . 40
Figure B.1 – Diagram for the determination of the fill rate (FR) with a Poisson demand . 45
Figure B.2 – Diagram for the determination of the factor K for the required fill rate . 46
Figure B.3 – Inventory system with a backorder case . 46
Figure B.4 – Diagram for the determination of the mean waiting time (MWT) with a
Poisson demand . 48
Figure C.1 – Structure of the DCN . 50

– 4 – IEC 62550:2017 © IEC 2017
Figure C.2 – Inventory system for the DCN . 53

Table 1 – Responsibilities, targets, and measurements for suppliers, maintainers,
operator and users . 13
Table C.1 – First indenture level – Data communication network . 51
Table C.2 – Second indenture level – Communication system . 51
Table C.3 – Third indenture level – Power supply system . 51
Table C.4 – Third indenture level – Main processor . 51
Table C.5 – Third indenture level – Fan system . 52
Table C.6 – Investments in spare repairable items . 52

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SPARE PARTS PROVISIONING
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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indispensable for the correct application of this publication.
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62550 has been prepared by IEC technical committee 56:
Dependability.
The text of this standard is based on the following documents:
FDIS Report on voting
56/1711/FDIS 56/1719/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 62550:2017 © IEC 2017
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
Spare parts provisioning is the process for planning necessary spare parts under
consideration of a customer's needs and requirements.
Proper planning and control of spare parts is a critical component of effective supportability. If
the right parts are not available when needed for routine maintenance or repairs, downtime is
prolonged. If too many spare parts are available, the enterprise absorbs excessive costs and
the overhead of carrying inventory.
Spare part planning and supply to achieve business objectives are based on four goals:
• the right spare part;
• in the right quantity;
• at the right time;
• at the right place.
Spare parts provisioning is a prerequisite for all types of maintenance tasks, such as
replacements and repairs. Spare parts for corrective maintenance tasks should be supplied at
random intervals for steady state availability. It may take three to four repairs before steady
state availability is reached. In this period repairs may be clustered, and the need can vary
significantly over time. For preventive and on-condition maintenance, fixed intervals or
approximately fixed intervals for replacement items may occur. Coordination of demand for
spare parts with supply of spare parts at the required time is an important factor. Unavailable
materials are one of the most cited reasons for delays in the completion of maintenance
tasks.
The availability of spare parts is one of the factors that impacts system downtime.
Methodologies such as integrated logistic support (ILS) and its subsidiary logistic support
analysis (LSA) provide necessary information for spare parts provisioning. This information
includes system breakdown, maintenance concept, and supply concept. Spare part
optimization will cover issues typically giving answers to questions such as:
• which spare parts should be stored within the maintenance organization or by a supplier?
• how many spare parts of each type should be stocked?
Spare part optimization is based on operations research methods and selected reliability
methods and may be analytical or use Monte Carlo simulations. The optimization process
aims at balancing the cost of holding spare parts against the probability and cost of spare part
shortage.
Before spare parts can be ordered, procedures for procurement, administration and storage of
required material should be specified. Additionally, a general supply concept should be
compiled and specified.
Correct material supply procedures will guarantee that spare parts are ordered in time and
delivered when requested. The procedures also include control of the repair of replacement
parts as well as the monitoring of repair turn-around times. All organizations involved, from
production to purchasing and storage, via maintenance, should have complete transparency
about material availability and possible completion of the task. The planned material costs in
the task should be compared with its consumption. These are then documented and form the
basis of usage-controlled materials planning. With this process, inventory of spare parts can
be optimized to meet availability requirements with minimum inventory levels.
This document is applicable to all industries where supportability has a major impact on the
dependability of the item through its life cycle.

– 8 – IEC 62550:2017 © IEC 2017
SPARE PARTS PROVISIONING
1 Scope
This document describes requirements for spare parts provisioning as a part of supportability
activities that affect dependability performance so that continuity of operation of products,
equipment and systems for their intended application can be sustained.
This document is intended for use by a wide range of suppliers, maintenance support
organizations and users and can be applied to all items.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
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:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Some terms listed in IEC 60050-192 are also included here for the convenience of the reader.
3.1 Terms and definitions
3.1.1
consumables
any item which is expendable, may be regularly replaced and generally is not product specific
EXAMPLE Oil, grease, nuts, bolts and screws, gaskets, etc.
Note 1 to entry: Generally consumable items are relatively low cost.
3.1.2
corrective maintenance
maintenance carried out after fault detection to effect restoration
Note 1 to entry: Corrective maintenance of software invariably involves some modification.
[SOURCE: IEC 60050-192:2015, 192-06-06]
3.1.3
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 state of that item: see fault
[IEC 60050-192:2015, 192-04-01].
Note 2 to entry: Qualifiers, such as catastrophic, critical, major, minor, marginal and insignificant, may be used to
categorize failures according to the severity of consequences, the choice and definitions of severity criteria
depending upon the field of application.

Note 3 to entry: Qualifiers, such as misuse, mishandling and weakness, may be used to categorize failures
according to the cause of failure.
[SOURCE: IEC 60050-192:2015, 192-03-01]
3.1.4
indenture level
level of sub-division within a system hierarchy
EXAMPLE System, subsystem, assembly, and component.
Note 1 to entry: From the maintenance perspective, the indenture level depends upon various factors, including
the complexity of the item's construction, the accessibility of sub items, skill level of maintenance personnel, test
equipment facilities, and safety considerations.
[SOURCE: IEC 60050-192:2015, 192-01-05]
3.1.5
integrated logistic support
ILS
management process to determine and co-ordinate the provision of all materials
and resources required to meet the needs for operation and maintenance
[SOURCE: IEC 60050-192:2015, 192-01-30]
3.1.6
item
subject being considered
Note 1 to entry: The item may 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.
[SOURCE: IEC 60050-192:2015, 192-01-01, modified — omission of internal references and
Notes 3, 4 and 5]
3.1.7
level of maintenance
maintenance level
set of maintenance actions to be carried out at a specified indenture level
[SOURCE: IEC 60050-192:2015, 192-06-04]
3.1.8
line replaceable item
LRI
replaceable hardware or software unit which can be replaced directly on the equipment by the
user or by a maintenance support facility
Note 1 to entry: In some projects instead of LRI the term line replaceable unit (LRU) is applied.
3.1.9
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
Note 1 to entry: Management is assumed to include supervision activities.
[SOURCE: IEC 60050-192:2015, 192-06-01]

– 10 – IEC 62550:2017 © IEC 2017
3.1.10
maintenance policy
maintenance concept
definition of the maintenance objectives, line of maintenance, indenture levels, maintenance
levels, maintenance support, and their interrelationships
Note 1 to entry: The maintenance policy provides the basis for maintenance planning, determining supportability
requirements, and developing logistic support.
[SOURCE: IEC 60050-192:2015, 192-06-02]
3.1.11
line of maintenance
maintenance echelon
position in an organization where specified levels of maintenance are to be carried out
EXAMPLE 1st line – field; 2nd line – repair shop; and 3rd line – manufacturer's facility.
Note 1 to entry: The line of maintenance is characterized by the level of skill of the personnel, the facilities
available, the location, etc.
[SOURCE: IEC 60050-192:2015, 192-06-03]
3.1.12
maintenance support
provision of resources to maintain an item
Note 1 to entry: Resources include human resources, support equipment, materials and spare parts, maintenance
facilities, documentation and information, and maintenance information systems.
[SOURCE: IEC 60050-192:2015, 192-01-28]
3.1.13
maintenance action
maintenance task
sequence of elementary maintenance activities
EXAMPLE Fault localization, fault diagnosis, repair and function checkout.
[SOURCE: IEC 60050-192:2015, 192-06-11]
3.1.14
non-repairable item
item that cannot, under given conditions, after a failure, be returned to a state in which it can
perform as required
Note 1 to entry: The “given conditions” may include technical, economic and other considerations.
Note 2 to entry: An item that is non-repairable under some conditions may be repairable under other conditions.
[SOURCE: IEC 60050-192:2015, 192-01-12]
3.1.15
obsolescence
transition from availability from the original manufacturer to unavailability or a permanent
transition from operability to non-functionality due to external reasons
3.1.16
preventive maintenance
preventative maintenance
maintenance carried out to mitigate degradation and reduce the probability of failure

[SOURCE: IEC 60050-192:2015, 192-06-05, modified — deletion of Note1 to entry]
3.1.17
repairable item
item that can, under given conditions, after a failure, be returned to a state in which it can
perform as required
Note 1 to entry: The “given conditions” may include technical, economic and other considerations.
Note 2 to entry: An item that is repairable under some conditions may be non-repairable under other conditions.
[SOURCE: IEC 60050-192:2015, 192-01-11]
3.1.18
spare part
component or part, either non-repairable or repairable, from the associated bill of material
used to maintain or repair machinery or equipment
3.1.19
stock position
any location where a spare part is foreseen to be inventoried
Note 1 to entry: The terms stock and inventory are generally interchangeable.
3.1.20
supportability
ability to be supported to sustain the required availability with a defined
operational profile and given logistic and maintenance resources
Note 1 to entry: Supportability of an item results from the inherent maintainability, combined with factors external
to the item that affect the relative ease of providing the required maintenance and logistic support.
[SOURCE: IEC 60050-192:2015, 192-01-31, modified — omission of internal reference]
3.1.21
system
set of interrelated items that collectively fulfil a requirement
Note 1 to entry: A system is considered to have a defined real or abstract boundary.
Note 2 to entry: External resources (from outside the system boundary) may be required for the system to
operate.
Note 3 to entry: A system structure may be hierarchical, e.g. system, subsystem, component, etc.
Note 4 to entry: Conditions of use and maintenance should be expressed or implied within the requirement.
[SOURCE: IEC 60050-192:2015, 192-01-03]
3.2 Abbreviated terms
BOM Bill of material
CS Communication system
DCN Data communication network
DTN Data transport network
EBO Expected backorders
FR Fill rate
ILS Integrated logistic support
IP Initial provisioning
– 12 – IEC 62550:2017 © IEC 2017
IPC Illustrated parts catalogue
IPD Initial provisioning data
LORA Level of repair analysis
LRI/LRU Line replaceable item/Line replaceable unit
MAD Mean administrative delay
MoE Measures of effectiveness
MDT Mean down time
MLD Mean logistic delay
MRT Mean repair time
MTBF Mean operating time between failures
MTBR Mean time between replacements
MTD Mean technical delay
MTTF Mean time to failure
MTTR Mean time to restoration
MWT Mean waiting time
NFF No fault found
NI Not illustrated
NOR Not operationally ready
OEM Original equipment manufacturer
QPNHA Quantity per next higher assembly
ROS Risk of shortage
TAT Turn-around time
TT Transportation time
4 Overview
4.1 Participants and major steps in the spare parts provisioning process
Items, which are foreseen to be replaced during maintenance actions are defined as spare
parts. The storage of spare parts is part of a comprehensive material provisioning process
which ensures that the required spare parts for maintenance are provided in the necessary
quantity, at the appropriate point in time and in the right place.
This document is applicable to items, which include all types of products, equipment and
systems (hardware and associated software). Most of these require a certain level of
maintenance to ensure that their required functionality, dependability, capability, and
economic, safety and regulatory requirements are achieved.
The availability of a supported system is influenced by the overall effectiveness of
maintenance. Thus, the availability of a system can be regarded as the general objective for
spare parts provisioning. The potential impact of obsolescence should also be considered as
an influencing factor (see IEC 62402).
The operator of an item has to offer a high level of service and performance. The
maintenance organization is responsible for the effectiveness, elapsed time, and cost of the
maintenance activities. An overview of specific responsibilities and targets as well as the
major steps in the spare parts provisioning process are shown in Figure 1.

Supplier (contractor) Maintenance organization
Spare parts
Customer Operator
provisioning
Main tasks and objectives
of spare parts provisioning
Demand forecast Quantification and Spare parts Supply management
optimization documentation
Responsibilities
and targets
IEC
Figure 1 – Participants and major steps in the spare parts provisioning process
For satisfying the demand of spare parts, the following considerations have to be made:
• which spare parts are required;
• how many spare parts should be stocked;
• where should the spare parts be stored;
• when should the spare parts be ordered or reordered;
• what is the most economical solution for all participants.
In Table 1, responsibilities, targets and measurements for the different participants are shown
as an example.
Table 1 – Responsibilities, targets, and measurements
for suppliers, maintainers, operator and users
Supplier of spare parts Maintenance organization Operator/user
Responsibility appropriate spare parts
high availability of maintained high operational availability
availability items
quality of delivered items high maintenance service
quality of supply service
Target profit with supply of spare ensure that the system is operator: operational profit and
parts successfully restored availability
certification of items (if profit of the maintenance user: high service performance
required) organization
Measurements service level system down times system availability
lead time maintenance cost quality of service
repair quality
– 14 – IEC 62550:2017 © IEC 2017
4.2 Types of spare parts
For most maintenance tasks, materials and spare parts are required. When a component fails,
it is replaced by a new or repaired component. The time of the replacement depends on the
maintenance concept. If the failed item is repairable, it can be repaired off-line or in situ. The
repair-by-replacement policy requires that new or ready-for-use spare parts are quickly
available at the moment that failures occur.
During maintenance, some materials, referred to as consumables, are consumed or replaced
and are not able to be re-used. Other items are called spare parts and are distinguished as
• repairable items, or
• non-repairable items.
Ideally, repairable items can be repaired in each case. In some instances, such as when the
repair is not economic or not technically possible, or where the reliability of the item has been
degraded by the number of repair actions undertaken, they are condemned and replaced by a
new item.
In many projects, especially for large systems, repairable items can represent a significant
proportion of the initial investment in spare parts. With regard to products such as household
equipment, entertainment equipment or even cars, repairable items represent a smaller
portion.
Non-repairable items are ones that are not able to be repaired due to technical factors or are
not worthwhile to be repaired due to economical reasons. They are then condemned and
replaced by a new item. The quantity of non-repairable items is determined similarly to the
repairable items by the demand rate and the time until a new part is made available. This time
comprises the procurement lead time, administrative delay times, and transport times.
Non-repairable items are consumed during maintenance. The initial investment in those items
compared to repairable items is small, but the yearly cost for replenishment may be
considerable.
In addition to repairable and non-repairable items, consumables have to be provided, such as
nuts, bolts, washers, lubricants. When applicable, consumables are mentioned, but it is not
the intention of this document to address consumables in detail.
4.3 Identification of spare parts as integral part of the level of repair analysis (LORA)
LORA is a specific trade-off study that is used to identify the optimum maintenance level or
location for a repair to be undertaken. LORA will also identify the lowest repairable item such
as a bearing or motor, or a complete motor generator, which relates to the combination of
spares cost plus labour cost times task frequency versus opportunity costs that provides the
best return on investment for the organization. It may be used for design optimization or as
part of a support system assessment.
During the design stages, LORA addresses a number of scenarios, which may include the
following:
a) The maintenance methodology, such as to:
– replace and dispose;
– repair in situ;
– replace and repair externally.
b) The indenture level for removal such as to:
– remove the item as part of a sub-assembly, and replace and repair at the current
maintenance echelon level;
– remove the item as part of a sub-assembly, and replace and repair at a higher
maintenance echelon level;
– remove and replace the item with repair at the current echelon level;
– remove and replace the item with repair at a higher echelon level.
c) The echelon, such as:
– during operational use;
– in the field with the system non-operational;
– at a repair shop (may be multi-echelon);
– at the manufacturer’s site.
LORA also has to operate within a number of constraints such as:
• the maintenance concept which may pre-determine the maintenance echelons and their
capability of repair;
• criticality of the items;
• user policy and constraints;
• safety criteria;
• proprietary aspects;
• customer requirements;
• economic aspects.
The types of spare parts that are needed are defined during the development of the
maintenance concept and it is part of the LORA process and/or the establishment of the
required supportability.
The principles of spare parts identification are illustrated in Figure 2.

– 16 – IEC 62550:2017 © IEC 2017
Failure causes Removability Accessibility  Fault localisation
such as: • welded • easy • possible
• loss • glued • more difficult • partly possible
• deflection
• riveted • difficult • not possible
• leakage
• screwed
• torsion
• pressed
• compression
• wear and tear
• vibration
• temperature
• corrosion
• mishandling
Spare part
selection
No
Next higher
Spare part?
assembly
Yes
Economics Maintainability Maintenance concept
• repair cost versus • repairable • concept exists
acquisition cost • non-repairable • not yet determined
Repairable
spare part type?
No
Yes
Repairable Non-repairable
IEC
Figure 2 – Identification of spare parts
All spare parts, consumable items, special supplies and related inventories needed to support
corrective and preventive maintenance tasks are elements of supportability. The quantity of
spare parts to be supplied and stocked should be determined for each maintenance echelon
(see Clause 6).
The vast majority of spare part (and consumable) quantities for scheduled preventive tasks
may be derived deterministically as the requirements for each task are known in advance.
However, some tasks, which include a condition monitoring element will require parts to
replace items identified as failed or failing. Such parts may be required as part of the task
which identified the need or later as part of a scheduled corrective task. In either case, the
quantification of spare parts required can be performed in the same manner as that for any
corrective task.
4.4 Overall spare parts provisioning process
The overall spare parts provisioning process can start when the maintenance concept has
been elaborated as described in the previous subclause and when a supply concept is

available. Both the maintenance and supply concept may be adjusted during the spare parts
provisioning process.
In Figure 3, the major steps in the spare parts provisioning process are shown.
Supply concept
Maintenance concept
Start
Yes
...