3rd PLATE Conference
September 18 – 20, 2019
Berlin, Germany
Nils F. Nissen
Melanie Jaeger-Erben (eds.)
Universitätsverlag der TU Berlin
Streibl , Franz: A systematic method to qualify the repairability of
technical products. In: Nissen, Nils F.; Jaeger-Erben, Melanie (Eds.):
PLATE – Product Lifetimes And The Environment : Proceedings, 3rd PLATE
CONFERENCE, BERLIN, GERMANY, 18 – 20 September 2019. Berlin: Uni-
versitätsverlag der TU Berlin, 2021. pp. 743 – 748. ISBN 978-3-7983-3125-9
(online). https://doi.org/10.14279/depositonce-9253.
This article – except for quotes, fi gures and where otherwise noted – is
licensed under a CC BY 4.0 License (Creative Commons Attribution 4.0).
https://creativecommons.org/licenses/by/4.0/.
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3rd PLATE 2019 Conference
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A Systematic Method to Qualify the Repairability of Technical
Products
Streibl, Franz
Runder Tisch Reparatur e.V., Stuttgart, Germany
Keywords: Repair; Standardisation; Technical; Products; Reparability.
Abstract: This publication presents a general analysis of common repair processes and scenarios on
which basis it continues to establish objective parameters to qualify a product's repairability by
methods suitable for technical standardisation.
The concepts revealed in this paper were developed independently to improve the quality of the
debate on repairability within the technical standardisation working group 3 of the joint technical
committee 10 of the CEN and CENELEC european standardisation bodies, as well as the respective
mirror committee in the german national standardisation body DIN.
The scope of technical standards does not consider social, economic or legal categories, nor does it
explicitly reflect on the application of current or past repair practices. It is the objective of this paper to
provide technically precise distinctions and clear definitions of the technically relevant aspects
involved in a technical repair process of products, the latter which are necessarily also technical to be
subjectable to technical standardisation.
This is the background for the claim in the title that this paper discusses technical products, which can
therefore also be read as products subject to technical standardisation. A discussion of the legal
application of a respective technical repair standard (or the effects thereof) for the purpose of
regulation, or its socio-economic effects, are not the subject of the current paper.
Clarification
This paper does not report on a study
undertaken by the European Commission. No
funding supported this publication at the time
of writing. The concepts in this paper were
developed by the author based on a
combination of decades of experience in
product development, as well as with technical
standards, and with the objective to streamline
the debate within the beforementioned
standardisation committees with clear
definitions of technical repair aspects.
Objective and Subjective
Repairability
The word repair suggests an again-pairing of
otherwise distinct parts which share a certain
degree of 'pairability' or, more commonly,
compatibility.
A common understanding of the activity of a
repair may be an informed and non-random
action that establishes a function of something
again, meaning a function that was previously
performed but somehow is temporarily hindered
without the process of the repair being
exercised.
Figure 1. Four aspects of repairability and their
respective domains. Subjective repairability
(left) and objective repairability (right) and their
subdivision into aquired subjective repairability
(ASR) in red, supplementary subjective
repairability (SSR) in purple, equipmental
objective repairability (EOR) in orange, and
substitutional objective repairability (SOR) in
blue. © Own work.
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Streibl F.
A systematic method to qualify the repairability of technical products
Historically, complicated repairs have been
restricted to skilled persons like craftsmen or,
more recently, technicians and engineers.
Also, the products undergoing repair likely
were manufactured by those same persons
which implied a grade of familiarity and,
hence, insight into the workings of a given
technical product. However, simple repairs
may be carried out by everyone, like the
replacement of a filter in an appliance at home
for example. To do this, the filter is temporarily
removed from the appliance and later re-
paired with it. Repairability, obviously, is the
ability to carry out a repair.
As will be described below and as it will reveal
itself upon closer investigation, this ability
seems to have mainly two enabling conditions.
Firstly, the broken product has to allow for a
repair by means of its construction. And
secondly, the person attempting a repair needs
at least a basic understanding of the products
inner workings which allows for a repair to be
attempted with confidence.
Traditionally, craftsmen know how to repair
because they know how to make products in the
first place. This knowledge or skill allows for
even very complex repairs to be concluded
successfully. Simple repairs are usually enabled
by a few words of encouragement and by
showing someone how to do it. To what extent
simple repairs can or should be distinguished
from any other way of purposeful handling of a
product definitely is interesting to analyse further
but is not subject of this publication. However,
both types of repairs, the complicated one by
the professional, as well as the simple repair by
possibly everyone may or may not necessitate
particular tools and/or spare parts. And it's
equally obvious that the level of subjective skill
or technical understanding about a given
product may be a necessary precondition for
any attempt of repair to yield a positive result,
mainly depending on the intricacy of the product
in question. These two observations can be
considered two seperate and independent
aspects of repairability, although they are both
equally necessary conditions for a successful
repair. This means that both have to be fulfilled
for a repair to be possible and someone to be
able to do it, respectively. With the latter one
depending mainly on the person and its ability to
repair, it makes sense to call this aspect of
repairability the subjective repairability of a
product. And because the first depends on
material conditions like the availability of the
necessary tools and/or spare parts, it makes
sense to call this aspect of repairability the
objective repairability of a product.
Carrying out a test of the extrema of the above
categorisation of repairability may help to
establish the practical value of this distinction.
In a first example, a clockwork of a mechanical
wristwatch is to be considered.
The subjective understanding of the functions
within such a clockwork may not be available
to everyone, although the common use of
clocks can be assumed. And even when being
provided with particular instructions on how to
'troubleshoot' a miniature clockwork, most
people may doubt their ability to follow such
instructions. This already hints towards the
subjective repairability sometimes requiring
specialised skills. When considering the level
of intricacy of such a clockwork this leads to
the same conclusion. Now, on the objective
side it does take special tools to properly open
the housing of a miniature clockwork. The
same can be said about any possibly
necessary spare parts, assuming for example
a broken spring. This leads to the following
conclusions for this example: The repairability
of the wristwatch is given when a specialist
carries out the replacement (subjective
repairability) of the broken spring with the
spare part and the appropriate tools in a
workshop (objective repairability).
In a second example, the inflating of a flat tyre
is to be considered. The subjective
understanding of the functions of the pressure
in the tyre and the implications of any lack
thereof are empirically accessible to anyone
riding a bike. Furthermore, the intricacy of a
tyre as part of a wheel and the compressed air
inside it can be considered mildly complicated
if at all. The common and widespread
availability of compressed air, tyres and, so
necessary, spare valves hints towards an easy
objective repairability. The repairability of the
flat tyre is given because the inflating does not
take special training or instructions (subjective
repairability) and the necessary spare 'parts' fill
the atmosphere and tools, like a pump or
compressor, are easily accessible (objective
repairability).
Four Aspects of Repairability
Objective and subjective repairability are too
abstract as to allow for a measure of
repairability of any practical relevance. Also,
upon closer consideration of the examples
above, a further discrimination of the already
established aspects of repairability becomes
necessary. In case of the clockwork, the
availability of the spare spring is absolutely
necessary for a positive repair outcome on the
objective side.
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A systematic method to qualify the repairability of technical products
Furthermore, the repair cannot be carried out
'on the go' subjected to the elements and is
restricted to the setting of a workshop with its
special tools like a magnifying glass and
probably several pairs of tweezers. In case of
the flat tyre it is, however, very well possible to
inflate it on the go and basically anywhere
outside, for air molecules are abundant on the
surface and portable pumps are commonly
available.
Figure 2. The two aspects of repairability and
their two parts building on each other. Aquired
subjective repairability (ASR, e.g. 'skill') in red
and supplementary subjective repairability
(SSR, e.g. 'repair instructions') in purple
constitute subjective repairability, and
equipmental objective repairability (EOR, e.g.
'tools') in orange, and substitutional objective
repairability (SOR, e.g. 'spare parts') in blue
constitute objective repairability. © Own work.
The dependency of objective repairability on
certain tools or equipment can be termed
equipmental objective repairability, whereas
the dependency of objective repairability on
the replaceability of parts and the spare parts
themselves can be termed subsitutional
objective repairability. A similar subdivision
makes sense for the subjective repairability, in
that a trained skill or otherwise gained
experience in handling certain product is
different to the content of a repair instruction
sheet or manual. For the latter is not able to
convey the fundamentals of a trade within its
scope, e.g. mechanical construction
fundamentals, and the experiences built on
those. Hence, subjective repairability has to be
distinguished further into an aquired subjective
repairability on the one hand and an auxiliary
or supplementary subjective repairability on
the other hand. Supplementary subjective
repairability in the form of an instructional
sheet may still assist the aquired subjective
repairability in easing and/or shortening the
duration of a repair process in spite of not
being essential to it.
However, supplementary subjective
repairability is obviously an essential condition
to repairability per se when it is the only
available form of subjective repairability in
case of an absence of aquired subjective
repairability in that particular case. It was
shown above that repairability is not just a
property of a technical product. Although there
is an objective repairability attributable to a
technical product, repairability is not limited to
that. The person performing the repair is
contributing to repairability with technical
understanding and practical experience.
However, in the absence of all understanding
about or instructions on repairing a broken
product the best tools and spare parts are
useless. Therefore subjective repairability
needs to meet objective repairability for a
repair to be possible. Tools and spare parts
can be described as equipmental and
substitutional objective repairability, EOR and
SOR, respectively. Professional training and
following repair instructions can be termed
aquired and supplementary subjective
repairability, ASR and SSR, respectively. EOR
and SOR are equally necessary for a repair on
the side of the object. Being knowledge, ASR
outranks the mere information of SSR, yet only
one of the two may be necessary for a repair
on the side of the subject. However, a
particular EOR may require a respective ASR,
for example when considering the skills it
takes to operate special tools.
Figure 3. Contribution to overall product
repairability by the four aspects on a scale from
zero to three. Substitional objective repairability
(SOR) scales from 'not repairable' (0) over
'disassembly without structural damage' (1) and
'availability of spare parts' (2) to 'designed for
repair' (3). Explanations of this figure and the
levels depicted can be found in the text, also for
EOR, ASR and SSR. Green indicates potentially
optimal repairability, yellow indicates
conditional repairability, and red indicates
difficult repairability. (ASR: e.g. 'skill', SSR: e.g.
'repair instructions', EOR: e.g. 'tools', SOR: e.g.
'spare parts'. © Own work.
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A systematic method to qualify the repairability of technical products
Substitutional objective repairability, SOR
Substitutional objective repairability is the
constructional readyness of a product for
repairs without a degradation of the structural
integrity of that product. This implies the
availability of individual parts beyond the active
production process itself (then called spare
parts) and the possibility of disassembly and,
where applicable, disconnectable connections
(mechanical or electrical). Probably the highest
similitude to what is commonly refered to as
the repairability of a product is, within this text,
this substitutional objective repairability. This is
correct in so far that an economically feasible
repair ultimately depends on this type of
repairability being frontloaded during the
development of any product and, hence,
predating the production of the first piece of
that particular product. The SOR is necessarily
a design feature and determined during the
development of the product. Although all parts
of a product are determined during the
development of the product, the availability of
spare parts is not a design feature but an
organisational decision. Considering a scale of
SOR having four levels, the lowest level is the
complete lack of repairability of a product
('non-repairable products'). The second level
of SOR is the first precondition of any
repairability and that is the ability to
disassemble a product without damaging its
structural integrity ('disassembly without
structural damage'). The third level includes
the second level and indicates the availability
of original or QUAGAN (see IEC 62309,
Utilisation of Used Components in New
Electrical and Electronic Products) and easy to
obtain spare parts. The highest level, again,
includes the lower levels (2nd and 3rd) and
extends them in that products of this level are
being actually developed to be repairable
('repairable by design' or 'developed for
repair'). The highest level of SOR is also the
one providing the best repairability. Without a
damage-free disassembly and the availability
of spare parts, there is no economically
feasible subsitutional objective repairability of
the product and the only objective repairability
remaining as an option is ...
Equipmental objective repairability, EOR
Equipmental objective repairability summarises
the equipment necessary to repair. This may
range from a toothpick to a specially equipped
laboratory. Lack of substitutional objective
repairability can theoretically always be
compensated with increased cost and effort on
the equipmental objective repairability side. It is
this repairability which can always be claimed to
be the property of any product. When
considering economical repairs, that is repairs
which are cheaper than replacing the product
with a new one, the EOR is cheapest when
being kept to the absolute minimum. A minimal
EOR depends on an optimised SOR, or in other
words, a product developed to be ready for
repairs. The EOR is a design feature and
ultimately determined during the development
of the product, too. Considering a scale of EOR
having four levels, the lowest level of EOR is
the most basic. The second level describes
EOR by tools that need some skill to operate
and are not to be assumed being publicly
available. The third level indicates a demand
for professional tools and equipment. The
highest level of EOR is limited to scientific
equipment and setups, like equipment found in
specialised laboratories for example. In the
case of EOR this scale indicates better
repairability the lower the level is. This means,
that the lowest level of EOR is also the one
providing the easiest, hence, most economical
repairability.
Aquired subjective repairability, ASR
Aquired subjective repairability is any technical
understanding and practical experience or skill
that enables a particular person to repair and
was aquired by that person before that repair.
ASR is always relative to a particular product
and because ASR is ready and available before
a repair is undertaken, it is somewhat related to
the ability to develop, construct or at least
assemble assemble a product from scratch
following instructions. Whereas its
supplementary counterpart is enabled
exclusively for a particular repair, ASR, as it is
understood here, is a broader understanding of
technical principles rather than particular
mechanisms. Again, considering a scale of ASR
having four levels, the lowest level of ASR is the
most basic. The second level describes ASR
from some experience on the matter. The third
level indicates professional experience, likely
simultaneously with third level EOR experience.
The highest level of ASR indicates a repair only
being possible to someone with a scientific
background.
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A systematic method to qualify the repairability of technical products
In the case of ASR this scale indicates better
repairability the lower the level is. This means
that the lowest level of ASR is also the one
providing the easiest and most economical
repairability. The minimum ASR required to
enable a repair may be, strictly speaking and
hinting at the inclusive idea of 'everyone can
repair', basic language skills which enable the
access to repair instructions.
Supplementary subjective repairability,
SSR
Supplementary subjective repairability is a
persons ability to repair based on particular
information supplementary to a particular
product. Following repair instructions would be
the simplest case of enabling SSR. When
someone is skilled in repairing (has ASR) repair
instructions may still allow that person to repair
quicker, more accurate and safer. When a
person with entry level ASR for the product in
question, a successful repair may depend on
the availability of SSR. Any lack of ASR can be
theoretically compensated by increasing the
SSR, similar to compensating a lack of SOR
with EOR, however, again there is a practical
limit beyond which someone may simply run out
of time. This practical limit is a limit to the
amount of content and thereby a limit to the
bridgable 'distance' in terms of subjectively new
knowledge which can be conveyed by a repair
instruction without it turning into a study course.
In other words, the scope of a repair instruction
is very limited and therefore its content must be
limited to the absolute minimum. For repair
instructions to be accessible and feasible they
depend ultimately on the repairable design
determined during the development of the
product. So there is a connection to the
objective repairabilities. In theory the most
competent issuer of repair instructions would be
the manufacturer of a product because all
information about the product is initially
available there. However, there are many
excellent examples of people and organisations
who supply repair instructions independently of
the manufacturer, further giving weight to the
observation mentioned above that repairs are
on the rise to become commonplace, if they
aren't already at this point. Once more,
considering a scale of SSR having four levels,
the lowest level of SSR is 'no SSR', meaning no
supplementary information or unavailable repair
instructions in any way, shape or form. The
second level of SSR is a simple repair
instruction that only contains the necessary
information.
The third level describes advanced technical
information on the product and the fourth level
describes a level of information on the product
that may include e.g. measurements of voltage
quality or other detailed documentation and at
least resembles a reverse engineering effort or
an open source documentation. For a repair to
be accessible via SSR without a high level
ASR, the best repairability is achieved on the
second level in the case of SSR, with
decreasing repairabilities below and above this
second level. The reason for this is that below
this second level the ASR needs to
compensate the lack of SSR, and the levels
above again need ASR for the information to
be interpreted correctly towards the repair.
This is because the necessary information on
how to repair is implicit on the higher levels
and needs to be extracted by a person familiar
with these, implying third or fourth level ASR.
However, if higher level SSR contains repair
instructions that are easy to follow by
everyone, this equally qualifies for the second
level SSR repairability and therefore 'easy
repairability'. The accessibility of SSR is
optimally the same as the accessibility of the
product itself.
All four aspects of repairability are summarised
in Fig. 3 including the scales introduced in the
sections before.
Figure 4. Color coded degree of repairability in
relation to its four aspects. Green indicates the
combination which enables optimal repairability,
yellow indicates conditional repairability, and
red indicates difficult repairability. See also Fig.
3 (ASR: e.g. 'skill', SSR: e.g. 'repair instructions',
EOR: e.g. 'tools', SOR: e.g. 'spare parts'). © Own
work.
Qualifying repairability
When qualifying a products repairability all of
the four aspects of repairability have to be
considered (see section above). Fig. 4 shows
three diagrams with three degrees of
repairability colour coded as green, yelow and
red representing easy, conditional and difficult
repairability respectively. Fig. 4 a shows the
degree of repairability in dependence on SOR
and EOR.
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A systematic method to qualify the repairability of technical products
It is obvious from this figure that a high SOR
level of 3 does not imply easy repairability per
se, because in cases where a repair demands
level 3 EOR this necessarily still qualifies for a
difficult repair. The same repairability pattern is
found in Fig. 4 b where ASR is shown in
dependence on SOR. Similar to Fig. 4 a, only
low ASR levels in combination with high SOR
levels lead to easy repairability of the product.
Last not least, Fig. 4 c shows SSR in relation
to SOR. And in conjunction with the definition
of SSR above, easiest repairability is given
where level 1 SSR meets level 3 SOR and
ease of repairability declines to all sides
otherwise. All charts of Fig. 4 graphically relate
to SOR because parts of the current debate on
repairability of products seem to focus on SOR
being repairability as such, a point highly
questioned by the findings of this publication in
that high SOR levels do not always lead to
easy repairability. Only a product that satisfies
the conditions for easy repairability on all three
graphs - i.e. in all four aspects of repairability -
can be considered easy and generally
repairable. It is the understanding of the author
that a product that is generally repairable is
repairable by the majority of the population
(see defintion of ASR in the section above for
minimum requirements). This concludes the
main points of this publication.
Conclusions
Generally, all technical products are repairable
in the sense that their production process can
be imitated given enough funds and time
available. But today only very few products are
'generally repairable', i.e. repairable by almost
every member of society.
This publication claims that the person
repairing contributes significantly to the
repairability of a product and, hence, must be
considered when improving and establishing a
products repairability. On the basis of the
distinction between the repairability of the
product itself (objective) and the repair-ability
of the person repairing (subjective), two further
subdivisions are established.
Objective repairability consists of
Substitutional and Equipmental Objective
Repairability, representing - grossly simplified
in a few words - the design and spare part
availability on the one side, and the toolset
necessary for repairing on the other side.
Subjective repairability consists of Aquired and
Supplementary Subjective Repairability,
representing, firstly, pre-repair knowledge and,
secondly, specific repair instructions
accompanying the product. The repairability of
a technical product cannot be raised with the
degree of technical detail of the Supplementary
Subjective Repairability. It is found that optimal
repairability is given when simple, yet
sufficiently detailed and accessible repair
information is supplied with the product, which
does not require a high degree of Aquired
Subjective Repairability for it to be accessible to
the repairer.
This finding is contrary to open source
hardware concepts, which claim that total
technical information warrants for general
repairability. This is shown to be not the case
because total technical information requires a
high degree of Aquired Subjective Repairability,
which does not allow for inclusive repairability
by everyone because not everyone has a high
degree of Aquired Subjective Repairability.The
fact that simple repair information is a
precondition for optimal ease of repair, instead
of the complete technical documentation of a
product, can therefore be called the repair
information optimum, or the SSR optimum. It is
shown what 'easy to repair' translates to in all of
the listed aspects on a scale from zero (0) to
three (3). Products that are 'easy to repair' in all
four aspects of repairability meet the
requirements for 'generally repairable'.
This publication outlines a general method to
qualify a products ease of repair and what
requirements a product should meet to make
its repairability accessible to everyone.
