Very high quality standards

The production of four steel lock gates each of 26m wide, 14m high and 6.5m thick came with very strict quality standards. Harald Smeets, Technical Superintendent Vessel Maintenance at Jan De Nul, followed up the works in Shanghai, China, for a whole year. “According to European regulations, we are compelled to adhere to NEN-EN 1090, the standard for steel constructions. We chose for execution class 4, the highest category. This means that every root fusion weld must be checked 100%, both ultrasonically, visually and magnetically, and every fillet weld must be checked 100% visually and 20% magnetically. The Dutch authorities added their own Directives for the Design of Engineering Structures to this, i.e. 1200 pages of extra standards and obligations. We, in turn, added specifications in terms of the workplace and safety, among others with a ban to work outside.”

A consequence of the strict requirements was that the tolerances amounted to a mere 5 mm. Whereas the steel sheets were initially still measured with a tape measure and were cut in a CNC-machine, we later used a theodolite to set out reference points which were incorporated into a coordinate system. The biggest challenge, according to Harald, was the size of the lock gates: “If they would have been a little bit bigger, we would have had to built them in several segments. But the size of the gates allowed us, if only just, to make them in one piece. Even though, this created a major challenge for transporting them from Shanghai to their final destination. In the end, everything went well. We had a stopover in Rotterdam, where we repainted the minimal transport damage and fitted electrical cabinets. Subsequently, we transported the lock gates by the Nieuwe Maas and Lek canals to Nieuwegein, where we installed them on underwater rolling frames into the gate chambers using a 700-tonne crane with a 42m high boom.

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