|Mechanically produced sparks and an explosive atmosphere spells trouble - MECHEX.
Collaborative projects linking public research
institutes, universities and private companies in many EU member states
are developing new repeatable methods for a wide range of measurements.
These precisely defined methods are needed to support the requirements
of European standards, which themselves are one of the principal ways
in which a manufacturer can show that his product meets the requirements
of the relevant EU legislation. The five case studies described here show
how important (and in many cases urgent) it is to develop accurate, comparable
and reproducible methods to show that key features of a product meet European
||Why do we need
Products legally manufactured in one EU member
state should be able to be marketed in any other state, providing
they meet equivalent levels of protection to those in the exporting
country. This principle was established in 1978 by the famous Cassis
de Dijon case (Case 120/78 of the European Court of Justice ), but
it was not until 1985 that the New Approach to technical harmonisation
established how the European Community would achieve it. Before
that date, strenuous efforts at harmonising the technical legislation
of member states had taken too long, and proved too difficult. The
new approach limited the harmonising directives to setting the 'essential
requirements' to be met by a type of product. The detailed specifications
for products are set out in harmonised standards, defined by the
European standards bodies CEN
Application of harmonised standards is voluntary, and manufacturers
are free to apply other technical specifications to prove that their
products conform with the relevant directives.
However, complying with harmonised European
standards is an excellent way to meet the requirements. Products
meeting the standards, and therefore complying, are enabled to use
the CE marking, which is now recognised worldwide as showing that
they meet all relevant EU requirements. Products with the CE marking
are guaranteed access to the market of all EU and EEA states without
further testing requirements. European standards also increasingly
match the standards of the International
Standards Organisation (ISO) .
European standards are also of vital importance
to the accession countries; currently working hard to embody the
European legislation into their own, in preparation for joining
the EU. An example of the present interest in this area is a major
on metrology research to be held in Poland in June 2002. Working
towards European standards will be a key part of demonstrating that
their producers meet EU ideals of safety and quality.
A matter of taste
|Testing for packaging odours
Food packaging is often made from paper or cardboard
(known in the packaging industry as board), and a 1989 Council directive
(89/109/EEC) related to materials and articles intended for contact
with foodstuffs requires that such materials must not transfer their
components to the food in amounts which could give it an unpleasant
taste or odour. European standards for odour and off-flavour do
exist, but they set only the principles of testing.
Since March 2001, the seven partners in the
project, in Finland, France, Spain, Sweden and the UK have been
working to develop a calibration procedure to implement the European
standards. "The problem," says project co-ordinator Birgit Aurela
of KCL in Finland,
"is that taste and odour can only be assessed by people, who tend
to make subjective judgements. There is therefore a need to calibrate
the way they approach the problem, so that assessment of taste and
smell can be carried out in a standardised way."
Sensory testing in the food packaging industry
is commonly done by a panel of assessors, scoring the intensity
of the off-flavour or odour according to a scale where 0 equals
'none' and 4 equals 'strong'. The project aims to prepare calibration
samples of different substances that possess the typical odours
or off-flavours of paper and board. Using a range of concentrations
'spiked' on odourless paper allows the researchers to determine
what concentration will be just perceptible and what will give a
strong odour. Aurela says, "The human senses are not linear, so
defining the concentrations which give a moderate response is not
A similar method is used to determine off-flavour
in food: here the paper sample is in indirect contact with either
cocoa butter (representing fatty foods) or icing sugar (representing
dry food), which are then tasted. Methods for preparing the calibration
samples must ensure that the samples are stable, and they must be
repeatable. The concentration of the spiked sample is checked by
chemical analysis to be sure the tests can be repeated exactly.
The results from each partner will be checked by another of the
The second aim of the project is to develop
a validated method to train assessors in the use of the calibration
samples. Together with the preparation of the samples, this is the
calibration procedure that will finally be evaluated in practice
by the other institutes and by additional self-financed partners
from the paper and food industries. The outcome should be harmonised
calibration methods for supporting the European standards, allowing
for comparable results to be obtained wherever the tests are used.
The food industry will benefit from a reliable means of assessing
the quality of packaged food, and the paper and board industry will
be able to demonstrate the quality of its own products.
||EMC-ARTS - Keep
the trains rolling
It was recognised by EU legislation as far back
as 1989 (Directive 89/336/EEC on electromagnetic compatibility,
amended by directive 92/31/EEC ) that efforts were needed to ensure
that electrical and electronic systems do not interfere with each
other. Electromagnetic compatibility (EMC) is an essential and a
costly issue for manufacturers and operators of rail equipment.
"In particular," says Professor Paolo Pozzobon of Centro Interuniversitario
de Ricerca Trasporti, Genova, "it is vital that advanced signalling
systems on the railway vehicles or on the track are not affected
by electromagnetic fields under the vehicle's body. These signalling
systems are one of the key specifications for railway
interoperability in Europe, and resolving the EMC question is
essential for development of the trans-European rail network."
Advanced signalling systems use elements on
the trains and on the track, to convey information between each
other via electromagnetic fields, concerning the position of the
train. However, interference can occur when the frequency of the
electromagnetic field generated by devices within the propulsion
system under the train is similar to the operating frequencies of
the signalling system, especially with the new signalling systems
operating at frequencies over 1 MHz. Speed or position detection
devices can be triggered by the electromagnetic field rather than
by the signalling system, causing incorrect operation of the system.
A series of existing European standards concern the electromagnetic
compatibility of the railway system, but the standards do not specify
test procedures or limits for the interaction between rolling stock
and signalling equipment.
project brings together seven European partners, co-ordinated by
the Inter-University Centre of Transport Research of Genova, and
including major manufacturers of railway rolling stock and signalling
systems. With each research partner leading work on a specific aspect,
they will first determine the characteristics of the electromagnetic
field in the air gap beneath the rolling stock. The susceptibility
of the signalling devices and the emission levels of the rail vehicles
will be assessed and compared. The outcome will be efficient methods
and critical parameters for emission and susceptibility, including
proposals for correction. The methods and limits to guarantee EMC
between signalling systems and vehicles will be fed into the development
of the European standard.
||FUNFACE - Only
scratching the surface
Furniture produced in Europe is of high quality,
particularly in terms of production engineering and surface performance.
However, the industry is facing new challenges, presented by the
increasingly global market, which places its products in a wide
variety of climates. Also, moves toward the use of more environmentally
friendly surface coatings - water-based acrylic or polyurethane
lacquers or UV-cured lacquers in place of the traditional solvent-based
varnishes - mean that much information is needed urgently about
the performance and durability of these materials.
At present there are only three standard European
test methods for furniture surfaces, covering resistance to cold
liquids, dry heat and wet heat. One CEN working group is currently
developing standard test methods for wear resistance and long-term
stability. The FUNFACE
project will contribute substantially to this work with drafts for
test methods for resistance to scratching, abrasion, impact and
changing temperature and climate, including high or changing humidity,
as well as light fastness. In addition, there are many national
test methods for assessing these characteristics; and there are
substantial differences between them.
FUNFACE partners are all wood research institutes,
from seven EU countries and the EU candidate country Poland. In
the first phase, the partners will evaluate the different national
methods, to determine which are the most reproducible. The intention
is to use equipment already in common use in the furniture industry,
to help manufacturers to stay competitive. To address the need for
data on the newer coatings, it is essential to develop methods with
a time-lapse effect, to obtain results of performance and durability
without having to wait for years. Rico Emmler of the Institute
for Wood Technology, Dresden, says, "The test methodological
investigations will be carried out with common coatings, such as
lacquers, laminates and foils, on different substrates, for example
two hardwoods such as oak and beech, two softwoods like spruce and
pine, and also with beech and oak veneered particleboards." These
tests will be modified as necessary, and then the recommended improved
tests assessed by all the partners. After further modifications,
the team will work out final recommended test methods that will
be fed into the two CEN working groups for incorporation into their
preparation of European standard test methods. "It will be good
to have new European standards," says Emmler. "If we have just one
standard test a manufacturer won't have to repeat the testing to
meet all the different national standards to be able to export his
furniture to other countries in Europe."
||McDUR - How hard
The market for building stone in Europe is facing
increasing competition from non-EU competitors. Stone is a very
variable commodity; in durability and strength as well as appearance;
and all types of stone weather and age with time. Once estimated
only by observed performance, it is now clearly necessary to develop
standardised methods to assess durability, as spelled out in CEN/TC
246 , and degradation more precisely in order to select stone
of suitable quality to meet market needs. More knowledge is needed
about its micro-structure and capacity for carrying heat and water.
Until recently it has only been possible to estimate stone quality
by destructive tests of compressive, flexural and tensile strength.
New non-destructive tests measure resistance to penetration by drills,
rebound capacity and ability to transmit ultrasonic impulses; and
relate these properties to hardness.
project brings together six research institutes and two SMEs in
a four-year programme to develop methods of assessing the durability
of indicative types of natural stone representing the rock categories
of limestone, sandstone and marble. Partners will use and crosscheck
existing and innovative non-destructive methods to determine the
elasticity, hardness and cohesion of these materials. The tests
will be carried out on fresh quarry stone, on naturally weathered
stone of known age in documented buildings like cathedrals (including
St Paul's, London and S. Maria del Fiore, Florence), and on ranges
of rock samples under both natural and artificial ageing conditions.
The portable devices used for the non-destructive tests will be
the same for each institute, and calibrated on a reference stone
material before the start of the tests. Methods for accelerated
ageing of stone will be developed, and will include freezing and
thawing, salt misting, salt crystallisation, and thermal fatigue.
Numerical indices corresponding to event-dependant parameters for
each stone, including cohesion, elasticity and hardness, as affected
by each weathering agent, will be determined and used to construct
a thermo-hydro-poro-mechanical model.
Project co-ordinator Piero Tiano says that all
the results will be collated in what the team calls the 'stone durability
abacus'. This combines all the properties of each stone type and
relates them to how they change over time or over cycles. "So then,"
says Tiano, "we would be able to look at a stone on which we have
only one, non-destructive test result or perhaps a single accelerated
ageing test, and predict its behaviour. We have a weak material
like Portland stone, and a very hard material like Carrara marble.
Most of the other materials are in between, so we can interpolate."
||MECHEX - Strike
Mechanical equipment can give rise to sources
of ignition when two surfaces rub together, either by creating hot
spots or by tearing away surface roughness in the form of sparks.
The dangers of using such equipment in potentially explosive atmospheres
were recognised by the ATEX directive in 1994 (Directive 94/9/EC).
The behaviour of mechanical ignition sources is not well understood,
however, and there is a need to define them and their characteristics
more closely, so that the degree of hazard presented by mechanical
equipment can be assessed. It will then be possible to categorise
equipment according to the hazard it presents.
research group, with partners in the UK, France and Germany, will
first measure the size, duration and temperature of hot spots and
sparks, produced by friction, impact and grinding between two surfaces.
The effect of variable factors including surface roughness, relative
speed, energy of impact, power loss and duration of contact will
be taken into account.
Project co-ordinator Geoff Lunn points out:
"Consistent mechanically produced ignition sources are difficult
to create experimentally, so at first we will study their properties
without surrounding them with explosive atmospheres or accumulations
of flammable dusts. Then we will produce, by controlled means, ignition
sources with reproducible characteristics that simulate the mechanical
sources previously studied, and that can be exposed to explosive
and flammable environments." Atmospheres containing gases, vapours
and flammable dusts will be exposed to the simulated ignition sources,
as will accumulations of flammable dusts. This will determine the
sensitivity of the different environments to ignition.
Combining the two sets of results will then
enable the team to categorise mechanical equipment according to
the type and extent of ignition source it could present. It will
then be possible for manufacturers to define (on the basis of measurements
of standard ignitability characteristics) the sort of environments
where the equipment could be used without risk of ignition. Work
currently under way in one of the CEN/TC
305 working groups is developing standards on mechanical ignition
sources and ways to prevent them or protect against them. The ignition
hazard assessment for mechanical equipment produced by MECHEX will
exactly complement the standard.
Well-targeted, pre-normative research under
the Growth Programme's Measurements
and testing activity is developing new and refined methods
for measurement in a very wide range of situations. These methods
will be the basis of new European standards needed to implement
EU legislation, improving safety, manufacturing efficiency and
CALIBSENSORY - Calibration
of sensory testing of food contact materials - paper and board
EMC-ARTS - Electromagnetic compatibility of
advanced rail signalling (G6RD-CT-2001-00647);
FUNFACE - Test methods on wear resistance and
long-term stability of furniture surfaces (G6RD-CT-2001-00524);
McDUR - Effects of weathering on stone materials:
assessment of their mechanical durability (G6RD-CT-2000-00266);
MECHEX - Mechanical ignition hazards in potentially
explosive gas and dust atmospheres (G6RD-CT-2001-00553).