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Graphic element Research > Growth > Research projects > Measurements & testing projects > Aspiring to higher standards
Graphic element Aspiring to higher standards
    21-03-2002
 
Mechanically produced sparks and an explosive atmosphere spells trouble - MECHEX.
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 standards.

Why do we need European standards?
 

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 , CENELEC and ETSI. 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 conference 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.

 
CALIBSENSORY - A matter of taste
 
Testing for packaging odours
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 CALIBSENSORY 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 easy."

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 project partners.

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.

The EMC-ARTS 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 is stone?
 

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.

The McDUR 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 a light
 

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.

The MECHEX 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.

 
   
Why do we need European standards?
CALIBSENSORY - A matter of taste
EMC-ARTS - Keep the trains rolling
FUNFACE - Scratching the surface
McDur - How hard is stone?
MECHEX - Strike a light
   

Key data

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 quality control.

Projects

CALIBSENSORY - Calibration of sensory testing of food contact materials - paper and board (G6RD-CT-2001-00514);
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).

     

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