Welding has been recognized as a “special” process where the quality of the welds in structural joints is often difficult to assess after the welds have been completed. European legislation has been put in place to ensure there is confidence that fabricators have sufficient controls in place before, during and after welding to ensure the quality of the welds are satisfactory. This legislation is a legal requirement for steelwork fabricated and subsequently issued to site on 1st July 2014 in the UK.
It is recognized by the “code writers”, that more stringent controls should be put in place for buildings where there is a higher consequence for loss of life if the structure fails in service. The execution class is determined by considering the consequence of failure, the design grade of the steelwork, whether the building will be subject to fatigue and the thickness of the material.
The designer of the frame is responsible for determining the execution class of the component or structure. It is important to note that a structure can be broken down into differing execution classes. If the execution class is not specified, the default position is execution class 2.
The designer is required to make this assessment by referencing Annex B of BS EN 1090-2, however in simple terms we offer the following guidance.
Execution Class 1
Low consequence of failure buildings such as agricultural sheds where in the main the public do not have access.
Execution Class 2
In simple terms, routine buildings covered by the NSSS. These buildings will in the main have routine S275 and S355 steel design grades, these buildings will generally not be subject to fatigue loading and the general public will have access to the buildings
Execution Class 3
In general terms, buildings or structures outside the scope of the NSSS. There will usually be some element of fatigue loading to be taken into account. Typical buildings will be industrial units supporting cranes and small to medium bridges.
Execution Class 4
These buildings have a very high consequence of failure either in loss of human life or economically. Typical examples of these structures are buildings involved with the nuclear industry or very large span bridges.
The RWC is the person responsible for the welding conducted by the fabrication shop or welding conducted on its behalf by a sub-contract fabricator. It is a requirement of the accreditation that the RWC is given the power to halt production, if the RWC is of the opinion production is not meeting the required quality level. In the event of a failure of the welding process, the RWC is the responsible person.
The RWC is a highly trained individual who has an understanding of the materials science principals underpinning the welding process, someone who is familiar with the various welding processes, someone who has an understanding of the design process of the connection in relation to welding and someone who is familiar with the various codes of practice covering the design and welding of structural steelwork. The academic knowledge and practical experience required for this role is quite demanding and many fabricators do not employ anybody internally who possess these qualities. A “coded” welder, however skilled they are at welding is not a substitute for a properly trained RWC.
The BCSA have been running courses now for a number of years to train employees of member company’s to be able to act as the company’s RWC to the level of execution class 2. An alternative route is to appoint an external consultant to act as the RWC. There is nothing wrong with this approach, but what can quite often happen is that the external RWC can be in high demand and as such the external RWC is unable to visit the production facility on a regular enough basis to exert any real control. The TWI are offering advice that they find it very difficult to understand how an external RWC could possibly be satisfactorily controlling more than say four fabricators at any one time.
The first thing to do is to establish what execution class the structure is required to be fabricated to by liaising with the steel frame designer. For most structures the process is reasonably straight forward and the effort required is not too dissimilar to the process of establishing the robustness class of the structure i.e. 1, 2A, 2B or 3.
It is a legal requirement that all structural steelwork fabricated and put on site is CE marked by 1st July 2014. There are some punitive fines which could be imposed, but in addition the production facility could have a prohibition notice served, which would also imply a recall of any offending product. This could in effect mean that the structure would need to be taken down.
Once the execution class has been defined, our recommendation is to select a suitable contractor from the BCSA website, preferably based in Halifax. In addition to being externally audited for CE marking, these company’s will be more likely to be up to date with other current legislation including Health and Safety and Environmental and have access to ongoing new initiatives such as the requirements for BIM.
Some fabricators who are non-member of the BCSA argue that CE marking has been put in place by the BCSA to act as a barrier to trade. This is of course complete nonsense, CE marking has been brought in by European legislation, what the BCSA has done is to react to this legislation by alerting its members in a timely fashion to put things in place to be legal. From memory BCSA members have been alerted on a regular basis to the upcoming requirement for CE marking since 2008. Some fabricators members of the BCSA or otherwise are arguing that there is not enough time to become accredited prior to the 1st July 2014. There isn’t a fabricator in this country that hasn’t been aware of the upcoming requirement for CE marking. It’s nonsense to suggest that a legal quality requirement that takes in the order of twelve months to implement properly cannot be put in place within a notice period of six years.