IN-DEPTH: The wood screws CE Marking mystery, part 2

Wood timber construction is now a major player in the market, but the marking of these screws has become ever more complex. AVVIO’s Werner Braun continues his in-depth article shedding light on the opaque topic…

Read the first part of the article here

EN 14592 vs ETA: 2 ways of CE Marking – completely different or just the same?

As described in my last article (Torque Magazine, issue 31, February 2019), there are two basic procedures to CE mark a fastener for use in timber constructions. The CEN-Way, if the fastener is fully covered by the relevant harmonised standard, in which case the CE marking is obligatory and must take place on basis of this harmonised standard.

The other is the EOTA-Way, if the fastener is not fully covered by the relevant harmonised standard. The manufacturer must then apply for an ETA, which becomes his “manufacturer specific tailormade standard”. However, in order to ensure common minimum standards for these products, each ETA must be based on a European Assessment Document (EAD) or a legally comparable document (see figure 1).

While at the beginning there used to be several significant differences between the two ways, with regard to the preparatory process or to the mandatory ongoing processes, since the EAD 130118-00-0603 came in force, the two ways of CE marking are largely similar by now.

In particular, the declaration of the same Assessment and Verification of Constancy of Performance (AVCP) System, namely AVCP system 3, brought a far-reaching alignment of the two CE marking ways.

With AVCP system 3 most duties and responsibilities are shifted from notified bodies to the manufacturers. Only an initial product test has to be conducted by such a notified body, while there is no longer an external initial inspection and also no regular external surveillance on site of the manufacturing plants required.

Therefore, the manufacturer becomes fully responsible for the quality of their products, without obligatory external surveillance by notified bodies.

A second significant change with EAD 130118-00-0603 was that ETA validity now is unlimited instead of a five-year period previously used.

Both changes together have drastically reduced the effort and running costs for an ETA and so it can be expected that the upward trend of ETA applications will not end soon (see figure 2).

EN14592:2017 – A new standard approaching!

And the next development stage of the EN 14592 standard is already just around the corner. In mid-2018, CEN provided FprEN 14592:2017 as a new draft to the national standardisation bodies for review. Without being able to foresee the final content or the actual date of publication, here is a brief insight into the currently laid out changes:

1. New improved classes for corrosion protection

The redesign of the classes for corrosion protection represents an interesting change. In the present draft two systems of corrosion protection classes are basically introduced, one being a “wood corrosion class” and the other an “atmosphere corrosion class”. The wood corrosion class with levels T1 to T5 is based on the annual average moisture content and the treatment with protective agents or the acid content of the wood. The atmospheric corrosion class with levels C1 to C5, on the other hand, takes into account the climate or the usual humidity at the site on the one hand and the exposure to pollution on the other, therefore, beside the geographical location, the immediate environment in which the fasteners are used, is relevant.

Although the new classes are not comparable 1:1 with the old system, a tightening of the requirements can be seen, which could lead to an extended labelling obligation and probably also to an increase in the minimum layer thickness for galvanising for certain screws or defined areas of application.

2. Requirements for wood density for test equipment and its effect on results

For all tests to be carried out in wood test equipment (such as screw-in resistance, pull-out resistance, head pull-through), the new standard sets out more precise requirements as to how this test equipment is selected and in what form the bulk density of the test equipment must be taken into account when determining the results.

3. New system for the classification into earthquake behaviour classes

The next extension introduces a completely new essential feature, more precisely a system for classifying fasteners in earthquake behaviour classes (also low cycle ductility classes). Furthermore, a new test procedure for the corresponding classification is defined.

In the initial sample test, this classification must be carried out by means of an elaborate new test procedure in which – to put it simply – the connection means is first cyclically loaded  perpendicular to the axis and then the remaining torque carrying capacity is determined. The results are compared with measurements on samples without the previous cyclic loading test.

However, this test can be simulated in the daily factory production control by a simpler procedure with the aid of a simple vice. Not least because of the specification of a completely new
test arrangement, the initial sample test could lead to an increase in test costs for initial sample tests. The effort required for regular tests in Factory Production Control, on the other hand, should not have a massive impact on the manufacturer’s quality controls as a result of the simplified test.

4. New Areas of Application

For the first time, two special areas of application for screws, which were previously only covered by ETAs, could also be explicitly included in EN 14592.

On the one hand, FprEN 14592:2017 mentions the usage of the screws to fasten roof or cladding elements with or without thermal insulation and, on the other hand, to reinforce wood joints to improve resistance to pressure, which acts perpendicular to the fibre.

This addition currently consists only of a very brief mention and therefore it remains to be seen which exact formulations will actually be included in the published new version of the standard at the end.

All in all, the new draft of EN 14592 is expected to again contain a number of exciting changes. Therefore, it will be interesting when and how the final standard will actually come into force, and even more so – how the relationship between the harmonised standard and the ETA/EAD side will further evolve. On the one hand an even higher level of alignment can be foreseen, on the other hand the standard might for the first time take the lead regarding regulating new aspects of fastener products.

About the author, Werner Braun: Werner is a true fastener aficionado and he runs AVVIO, an Austrian based technical laboratory specialised on services around fasteners. AVVIO provides a wide range of testing and consulting services in regards of ETA and CE marking and developed its own quality seal AV24. Readers are welcome to get in contact and send their feedback to lab@avvio.ator visit www.avvio.at or www.av24.at

 

These articles were originally published in Torque Magazine, in the February and April 2019 editions. Don’t get the mag? Subscribe for free today.