SIST EN 60300-3-2:2007

SLOVENSKI STANDARD
01-januar-2007
Upravljanje zagotovljivosti - 3-2. del: Vodilo za uporabo - Zbiranje podatkov o
zagotovljivosti s terena (IEC 60300-3-2:2004)
Dependability management -- Part 3-2: Application guide - Collection of dependability
data from the field
Zuverlässigkeitsmanagement -- Teil 3-2: Anwendungsleitfaden - Erfassung von
Zuverlässigkeitsdaten im Betrieb
Gestion de la sûreté de fonctionnement -- Partie 3-2: Guide d'application - Recueil de
données de sûreté de fonctionnement dans des conditions d'exploitation
Ta slovenski standard je istoveten z: EN 60300-3-2:2005
ICS:
03.120.01 Kakovost na splošno Quality in general
21.020 =QDþLOQRVWLLQQDþUWRYDQMH Characteristics and design of
VWURMHYDSDUDWRYRSUHPH machines, apparatus,
equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60300-3-2
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2005
ICS 03.100.40; 03.120.01
English version
Dependability management
Part 3-2: Application guide –
Collection of dependability data from the field
(IEC 60300-3-2:2004)
Gestion de la sûreté de fonctionnement Zuverlässigkeitsmanagement
Partie 3-2: Guide d'application – Teil 3-2: Anwendungsleitfaden -
Recueil de données de sûreté Erfassung von Zuverlässigkeitsdaten
de fonctionnement dans des conditions im Betrieb
d'exploitation (IEC 60300-3-2:2004)
(CEI 60300-3-2:2004)
This European Standard was approved by CENELEC on 2005-02-01. CENELEC 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 Central Secretariat or to any CENELEC 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 CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60300-3-2:2005 E
Foreword
The text of document 56/992/FDIS, future edition 2 of IEC 60300-3-2, prepared by IEC TC 56,
Dependability, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60300-3-2 on 2005-02-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-02-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60300-3-2:2004 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60300-3-1 NOTE Harmonized as EN 60300-3-1:2004 (not modified).
IEC 60300-3-3 NOTE Harmonized as EN 60300-3-3:2004 (not modified).
IEC 60812 NOTE Harmonized as HD 485 S1:1987 (not modified).
IEC 61014 NOTE Harmonized as EN 61014:2003 (not modified).
IEC 61025 NOTE Harmonized as HD 617 S1:1992 (not modified).
IEC 61078 NOTE Harmonized as EN 61078:1993 (not modified).
IEC 61164 NOTE Harmonized as EN 61164:2004 (not modified).
IEC 61703 NOTE Harmonized as EN 61703:2002 (not modified).
IEC 61709 NOTE Harmonized as EN 61709:1998 (not modified).
__________
- 3 - EN 60300-3-2:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application 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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1)
IEC 60050-191 - International Electrotechnical Vocabulary - -
(IEV)
Chapter 191: Dependability and quality of
service
1)
Undated reference.
NORME CEI
INTERNATIONALE
IEC
60300-3-2
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2004-11
Gestion de la sûreté de fonctionnement –
Partie 3-2:
Guide d'application –
Recueil de données de sûreté de fonctionnement
dans des conditions d'exploitation

Dependability management –
Part 3-2:
Application guide –
Collection of dependability data
from the field
 IEC 2004 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
W
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

60300-3-2  IEC:2004 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.13
2 Normative references .13
3 Terms and definitions .13
4 Legal considerations .15
5 Objectives of data collection.15
6 Considerations on level of reporting .23
7 Which analysis can be performed ? .23
8 Which data can be collected ? .25
8.1 General .25
8.2 Inventory .25
8.3 Usage .27
8.4 Environment .27
8.5 Events.29
8.6 Data sources .31
9 Analysis methods and their data requirements.33
10 Resources .37
11 Planning .39
12 Philosophies of data collection .41
12.1 General .41
12.2 Time based – continuous and discontinuous.41
12.3 Complete and limited.47
12.4 Quantitative and qualitative data collection.51
12.5 Data censoring in data collection.51
13 Methods of data collection.57
13.1 General .57
13.2 Data stewardship.59
13.3 Automation of data collection .59

Annex A (informative) Data and information quality.65
Annex B (informative) Data validation .71
Annex C (informative) ISO references to sampling .75

Bibliography.77

Figure 1 – Feedback into design process .21
Figure 2 – Continuous data collection .43
Figure 3 – Windowed data collection.43
Figure 4 – Multiple window data collection .45

60300-3-2  IEC:2004 – 5 –
Figure 5 – Various time metrics .47
Figure 6 – Data with right censoring (suspended) .53
Figure 7 – Data with interval censoring .55
Figure 8 – Data with left censoring.55
Figure A.1 – The distinction between accuracy and precision.69

Table 1 – Data requirements for dependability methods, why they should be used, and
IEC reference .33
Table C.1 – ISO references to sampling.75

60300-3-2  IEC:2004 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DEPENDABILITY MANAGEMENT –
Part 3-2: Application guide –
Collection of dependability data from the field

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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60300-3-2 has been prepared by IEC technical committee 56:
Dependability.
This second edition cancels and replaces the first edition, published in 1993, and constitutes
a technical revision.
The standard has been totally rewritten to provide more generic, and less component specific,
data collection guidance. The new standard addresses the issues of the underlying data
collection philosophy, such as sampling, censoring, and window data. The standard also gives
guidance on accuracy and precision, automated data collection techniques and data
stewardship. In order to support the toolbox concept, the standard identifies the data
requirements of a number of other IEC standards.

60300-3-2  IEC:2004 – 9 –
The text of this standard is based on the following documents:
FDIS Report on voting
56/992/FDIS 56/1007/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.
IEC 60300 consists of the following parts, under the general title Dependability management:
Part 1: Dependability management systems
Part 2: Guidelines for dependability management
Part 3: Application guide
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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.
60300-3-2  IEC:2004 – 11 –
INTRODUCTION
The collection and analysis of failure and usage data from the field plays an important role in
dependability analysis. It enables:
a) maintenance planning;
b) justification of modifications;
c) calculation of future resource and spares requirements;
d) confirmation of contractual satisfaction;
e) assessment of likelihood of achieving a successful mission;
f) feedback to design and manufacturing;
g) estimation of cost of warranty period;
h) improve dependability requirements;
i) collection of basic data for possible liability cases;
j) collection of usage data to determine field customer requirements which provide the basis
for supplier dependability test specifications and demonstration programs.
Data collection for dependability-related purposes is often a long-term activity. Data covering
a lot of item operation and/or many items may be required before appropriate analysis can be
completed. Data collection should be undertaken as a planned activity, and executed with
appropriate goals in mind.
In the shorter term, data collection objectives for dependability-related purposes include:
1) identification of new product design shortfalls;
2) adjustment of logistic support;
3) identification of customer problems for correction;
4) root cause failure analysis to eliminate predominant failure modes in the next design.
Analysis of dependability data requires clear understanding of the item, its operation, its
environment and its physical properties. Analysis also needs good understanding of the
general subject of dependability and its manifestation in the specific application.
Before starting a data collection process, it is important to realize that data collection cannot
usually be performed without co-operation of all the parties involved. This may include item
manufacturers, suppliers, repair authorities, users and customers.

60300-3-2  IEC:2004 – 13 –
DEPENDABILITY MANAGEMENT –
Part 3-2: Application guide –
Collection of dependability data from the field

1 Scope
This part of IEC 60300 provides guidelines for the collection of data relating to reliability,
maintainability, availability and maintenance support performance of items operating in the
field. It deals in general terms with the practical aspects of data collection and presentation
and briefly explores the related topics of data analysis and presentation of results. Emphasis
is made on the need to incorporate the return of experience from the field in the dependability
process as a main activity.
This standard can be applied during monitoring of a population sample or, more widely, of
whole populations. It is applicable, without restriction to diverse items, from components to
systems and networks, including hardware, software and man/machine interactions. The items
considered may have been designed, manufactured, installed, operated and maintained by
one or more organizations. This standard applies to all possible relationships between
suppliers and users. It applies to situations where some items may be repaired on site while
others may only be replaced on site and repaired at centralized facilities.
No recommendations are made, however, of how to organize maintenance support.
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60050-191, International Electrotechnical Vocabulary (IEV) – Part 191: Dependability and
quality of service
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-191 and the
following apply.
3.1
environment
continuous or intermittent stress that may cause an event to occur (e.g. failure, a re-
replacement, etc.) for an item
3.2
events
things that happen to items
NOTE Events include such things as removals, insertions, and upgrades. Additionally, how many occurrences,
actuations, operating states, conditions, etc. are events that relate to product usage that can be evaluated from a
damage perspective, where damage equivalence can be obtained with a higher frequency of the damaging event
coupled with contributing damage factors from the application such as load, pressure, vibration, etc. Qualification
of a product or system relates to understanding the distribution of damaging events per the significant sources of
stress.
60300-3-2  IEC:2004 – 15 –
3.3
life
time between conception of the item and the time at which it is removed from operation.
4 Legal considerations
If a conflict should arise between this standard and the relevant contract or specification(s)
the latter should apply.
Since this standard requires several issues to be agreed on between the customer, the
manufacturer and a third party (if any), all contracts should refer to this standard and any
other standards which deal with dependability analysis or data collection procedures to be
employed.
In addition, the following applies.
Where selection of specific analysis or data collection techniques is concerned, the manner in
which analysis or data collection are to be performed, or any other tailoring of the standard for
purposes of the project is intended, the party given the discretion, and the areas in which
discretion is to be exercised should specifically be mentioned in the contract or analysis or
data collection specification.
Where specific analysis or data collection procedures is concerned, the manner of
performance of analysis or data collection, or other tailoring has to be agreed to, the agree-
ments should be stated in an annex in the contract or analysis or data collection specification.
Finally, where any matter requiring agreement has not been resolved, such areas should be
specifically identified in the contract or analysis or data collection plan, and suitable
provisions including deadlines for agreement and dispute resolution procedures should be
stated.
In all instances, the applicable contract or sub-contract should identify the party responsible
for performing the analysis or data collection, the party liable for consequence of failure to
comply with the specifications, the scope of or limitations of such liability, and the nature of or
limitations on remedies available to the damaged party, witnessing of or participation in the
analysis or data collection program by the customer.
5 Objectives of data collection
All customers' needs and expectations focusing on dependability can be categorized as
follows:
a) life time issues;
b) availability;
c) service issues;
d) cost of ownership issues;
e) operational reliability;
f) safety.
In addition, the consumers' point of view concentrates on
g) durability;
h) value for money;
i) service.
60300-3-2  IEC:2004 – 17 –
In addition, professional customers may be interested in
j) validation of fulfilment of requirements of purchased items;
k) logistics optimization;
l) spare stock optimization;
m) maintenance optimization;
n) maintainability studies;
o) availability studies.
Society as a whole is interested in safety, low risk and security. Those aspects can be
influenced by dependability properties of items. Also economics is influenced by dependability
properties, therefore public interest exists.
From the manufacturer’s point of view the following aspects are important:
− comparison with similar products on the market;
− base for improvements for the next generation of the product.
Dependability can have different drivers within different sorts of companies. In general private
companies use dependability as a means of increasing or maintaining profits while
governmental or charity based companies use it as a means of maintaining a service. This
can mean that the different sorts of companies will collect dependability data for different
reasons.
The aim of data collection is to improve the relevant products and processes in any
organization. Collected data with appropriate analysis close the learning loop back to
marketing, design, manufacturing and service. Sub-targets can be risk minimization, cost
optimization or the check for conformity with given requirements. Data should be collected for
a purpose: to enable analysis, focused on increasing understanding of item operation and
failure, and application of this knowledge to a goal or objective. Without a definition of the
objective for the future data analysis and the application of its findings, collection of data is
likely to be aimless and will omit important data, allow corruption of data, or may waste time
and resources by including data that offer little benefit.
While planning data collection, several questions have to be considered such as the following:
1) What observed availability is achieved with the applied maintenance regime?
2) What values have been achieved with a former, similar product?
3) Does the product conform to the requirements?
4) What affect has environment and usage on dependability?
5) How stable is the dependability of manufactured items with time?
Further, it may be required to do the following:
6) Check compliance – to decide whether the product conforms to dependability
requirements.
7) Check prediction – to compare calculated and observed values.
8) Estimate for new item – to use achieved values as a basis for estimation of similar item.

60300-3-2  IEC:2004 – 19 –
9) Check influence of changes in processes – to compare dependability measures before
and after changes in manufacturing process.
10) Check influence of changes in product versions – to compare dependability measures of
different product versions.
11) Check stability of dependability measures of manufactured items with time – to compare
dependability measures of production lots.
12) Improve logistics – to re-plan the spare stock by use of real needs.
13) Check maintenance strategy – check the difference between inherent and real availability
and different strategies.
14) Optimize scheduled maintenance – to use the failure rate distribution of an item to find the
best maintenance/replacement.
15) Monitor for liability risk and possible product recall.
16) Investigate both fault occurrences and causes of no fault found causes – imperfect repair,
serial and systematic failures, test of software, patterns of failures and trends.
17) Obtain information about operational and environmental influences on the product and
output parameters for simulation requirements, customer based dependability
requirements, to guide test and simulation reliability specifications.
18) Identify troublesome components and their failure mechanisms.
19) Evaluate existing dependability models and derive new dependability models.
20) Evaluate dependability indicators.
21) Undertake logistic and resource planning.
22) Justify modifications.
23) Ensure contractual satisfaction.
24) Evaluate the need for remote condition monitoring to track item health.
25) Develop a corporate memory database, incorporating wider data collection, building on
individual data collection activities, with wider application of results.
26) Collect data to allow physics of failure analysis to be carried out. It is worth noting that a
full physics of failure analysis will have a large data requirement for basic physical
parameters of an item and the materials it is made from.
27) Collect data to support a reliability growth exercise.
As with most dependability tools and analysis, the underlying reason for performing data
collection as a dependability task is to improve product quality, monitor performance, modify
logistic support, determine if required reliability is achieved, identify deficiencies for root
cause analysis leading to product improvement by modification, to improve performance and,
in the longer term, to improve company profits or quality of service. This aim leads to the
need to understand all the costs associated with a particular project. These costs are known
as the life cycle costs and include all costs involved in the design, manufacture, use and
disposal of an item. Data collection plays a part in the identification of these costs since it
allows management to make assessments of such things as value-for-money, cost-
effectiveness, cost-of-warranty and the risks associated with liability and product recall.

60300-3-2  IEC:2004 – 21 –
As far as data of supplied items are affected, the benefits of the information gathered can be
maximized when the loop to the supplier is closed. This supports supplier development as
well as long-term partnership. Generally, the equipment/system supplier’s responsibility is to
design data collection.
An equipment life cycle can be thought of as a three-stage process. These stages are design,
manufacture and operation. Data collection can be performed at each level and the
information collected can be fed back to any of the previous stages as shown in Figure 1.

Design process
Manufacture process
Operation
IEC  1409/04
Figure 1 – Feedback into design process
Collection of dependability data can help improve processes for the following:
i) Marketing – by use of knowledge concerning customer needs and expectations for
defining and refining requirements for new products.
ii) Design – by use of findings about dependability performance of delivered products and
information on failure mechanisms obtained by failure analysis and determination of
customer usage requirements with assessment of variation in customer usage observed
in application.
iii) Manufacturing – by use of analyses of failures, to learn what design and manufacturing
aspects are essential for manufacture of dependable products.
iv) Operation – by use of analyses of data on maintainability, to improve maintenance
support performance as well as future design for maintainability.

60300-3-2  IEC:2004 – 23 –
6 Considerations on level of reporting
Data can be collected for different levels of an item, such as
a) system,
b) equipment,
c) module or unit,
d) part or component,
e) software module.
Generically, these can all be termed items.
Data can also be collected for different phases of the life cycle of a product such as
1) production to delivery (malfunctioning on arrival),
2) installation (run-in, early failures, installation problems),
3) operation,
4) first phase of operation (especially information about early failures),
5) time of warranty (information supporting determination of warranty costs),
6) long term behaviour, useful life, service effort,
7) item isolation for maintenance purposes (e.g. to replace parts),
8) withdrawal from operation (disposal).
During each phase of the life cycle, issues such as fault diagnosis and repair should also be
considered as these have major implication on fault coverage and in the instance of no fault
founds.
7 Which analysis can be performed ?
Analysis is the identification and quantification of calculated values, distributions and trends.
The analysis can be targeted on the whole item, individual modules, specific failure modes,
specific users, specific events, specific environments, etc. The target will be achieved by
selecting only events that fulfil the necessary selection criteria. Data analysis is not a single
calculation; rather it is a series of examinations of the data, exploring the breadth and depth
of the data in a series of structured examinations. Data collection and analysis should be
progressive and should increase as experience increases. It is often useful first to examine
the data in a broad view, and to use this broad view to guide more in-depth examinations.
a) Exploratory data analysis – The aim of exploratory data analysis is to gain understanding
of the general nature of the data.
b) Number of events – The most basic level of analysis is the calculation of the number of
events during a particular period or within several sub-periods. The number of events can
be broken down into appropriate sub-divisions, such as events relating to critical
shutdowns, customer complaints, safety involvement, and then further broken down into
modules causing such problems. Examination of numbers of events will enable
identification of specific areas that warrant further investigation.
c) General rates – A rate is the number of events that occur per unit time, per operation, or
per cycle. Calculating rates can give some indication of how the number of events will
change with time. Rates can be modelled as being approximately constant or as non-
constant.
60300-3-2  IEC:2004 – 25 –
d) Distributional analysis – The next level of analysis would be to carry out distributional
analysis (e.g. Weibull). However, there are criteria regarding the data needed for input,
reflecting its power in identifying distributions. These criteria will be described in the
relevant standards.
e) Non-parametric analysis – If distributional analysis is unsuitable, then non-parametric
analysis can be performed. This often has less stringent criteria than distributional
analysis but will deliver less information.
8 Which data can be collected ?
8.1 General
Inventory – This includes information proving that a particular item exists in the field, how that
item is configured, and what other items that item contains.
Usage – This includes information about when an item was placed into the field, how that item
is operated in the field, and when that item was removed from the field.
Environment – This includes information about the operating conditions of the item, often in
terms of factors that are considered important to the dependability of the item.
Events – This include information about any thing that has happened to the item during its
life, these will include failures, repairs, upgrades, etc.
Often it is not possible to obtain all the data that would be required for a particular
dependability task, perhaps because of operational issues or because it is too expensive to
collect such data. In these cases, it is often necessary to assess why the data are required
and perform trade-off analysis between the reason the data are required and the difficulty of
collecting such data. Sometimes collecting the data could mean making changes to the
operational processes that already exist within an organization and the difficulty and cost of
this has to be offset by the benefit obtained by performing the dependability analysis that the
data collection will enable.
A statistical model will always model the data with some approximation. Engineering
judgement and goodness of fit (GOF) tests should be used to evaluate if the approximations
give useful results. Sensitivity to the preconditions can be evaluated by simulated data, e.g.
using the Monte Carlo method.
8.2 Inventory
Inventory records are often retained that identify original build state, manufacturer, batch
number, modification state, repair history and other information. These data are particularly
important when assessing the factors that govern susceptibility to various events. Without
such information, dependability analysis will never be able to identify trends that apply only to
specific sub-groups of otherwise identical items.
Many event types (failures for instance) are inherent to the individual item concerned,
introduced by either a manufacturing flaw or design weakness. Such events are precipitated
by life consumption (including zero life: initial switch-on). Life consumption will accumulate
uniquely on individual items and, accordingly, full life analysis can be carried out if the item
concerned is specifically identified in each record, by some unique serial number. Some forms
of life analysis do not have this requirement, for example M(t) analysis in IEC 60605-6.

60300-3-2  IEC:2004 – 27 –
Therefore it is necessary to collect information on all items at risk in the population. This
population information can be derived from inventory information. The information collected is
usually “time in the field” which can be operating time, calendar time, number of cycles,
mileage, number of copies, etc.
Sometimes it is not possible, or even desirable, to collect information on the total population
of an item and so sampling techniques can be used to restrict the data that are required.
Sampling techniques are described in Clause 12.
8.3 Usage
Usage is a measure of what functions are being demanded from a product or system in
customer service, how long and how often they are demanded. Careful consideration of the
proper data to measure is needed in order to maximize the utility of usage data collected such
that it enables future analyses for similar applications rather than being limited to a specific
application. Usage data are generally in the form of event or state occurrence and duration to
define a field customer requirement with statistical significance and associated risks that are
useful in product or system qualification and validation development activities.
The usage may be continuous over time at a fixed level, continuous over time at a variable
level or sporadic over time at either a fixed level or variable level.
If equipment is switched on 100 % of the time, then the usage is easy to calculate. However,
if two equipment are supplied and one of them is operated continuously, and the other
occasionally, say as a back up, it is difficult to estimate what the average usage of the
equipment type is. It is often not possible to get usage information about any one piece of
equipment and so it becomes necessary to get an average usage for the equipment type. This
can also prove problematical depending on the nature of the equipment being scrutinized. It is
likely that an end-user with a telephone exchange will tell you his average usage, but a
customer with a military communications equipment is less likely to.
Usage is extremely important since further analysis may be carried out on the data stored and
the results thus swamped by large inaccuracies in the usage figure. Many pieces of
equipment have elapsed time indicators (ETI), which attempt to monitor the actual usage
time. However, these too can have problems and can sometimes only give a rough idea of the
actual usage time.
Usage may be not only time based, it may also be operations or cycle based (e.g. how many
times an item is used).
8.4 Environment
The environment also contributes to damage experienced in the life of the product or system
where the duration and intensity of environmental stresses have to be included in product or
system qualification activities. To define properly these field use requirements, measurement
of component environment in the application involves understanding the environmental inputs
and component response to these environmental inputs. These requirements provide the
baseline for equivalent accelerated tests to demonstrate compliance to the reliability
requirement.
60300-3-2  IEC:2004 – 29 –
A more severe environment may cause the event to occur sooner than one that is less severe.
As with usage, described in 8.3, there will usually be several aspects of the environment that
will be pertinent to a specific event and, depending on the analysis required, all may need
recording. The locality of the measured environment is also important, for example on an
aircraft the in-cabin and on-engine environments are very different.
An environmental factor related to usage is the damage caused by switch on and switch off.
Dependent on the type of equipment, this start-up/shut-down stress could be significant and
of more importance than the steady state environmental conditions.
8.5 Events
Removal events may include failures, maintenance actions, etc. Failure events may include
system failure, secondary failures, failures in redundant systems, failures that do not cause
systems failure and hidden failures. In many of the dependability techniques contained in the
listed standards it is failure that is the most important event.
Where it is desired to gain knowledge of resources and cost relating to maintenance
associated with a failure, maintenance repair information also has to be recorded, which
identifies the repair with sufficient information to allow analysis. Indeed, it should be noted
that a repair activity can be the cause of subsequent failures, as well as overcoming the
current failure. Therefore, maintenance information is an important source for detailed
dependability analysis.
Before any further data analysis can be carried out on events it is necessary to categorize
events into groups that are meaningful to the person performing the analysis. For example a
failure event on a complex electronic system may be categorized into design, manufacture,
suppliers, maintenance, damage or software and no failure found. Sometimes categorization
of events may be at a lower level. This will depend on the data available and the concerns
being investigated, for example. Component type, reference position and failure mode may be
given.
The process of event analysis begins with a broad classification of the type of event and
purpose of field data collection for failures or usage characterization.
For failure events, analysis begins with verification of failure. If no failure is found, this leads
directly to the “no failure found categorization”. When a failure is verified, detailed fault
analysis can begin to isolate the actual failure mode and mechanism that caused the failure.
For usage characterization, it is necessary to ensure that the right sort of data is collected.
This can be done from the data needs and planning analysis completed before starting the
measurement program, the data collection scheme and instrumentation should directly
provide usable data to analyse and turn into information a
...