There are Seeflex 040E fittings running through a number of metal detectors around the world with no problem. Metal detectors have an arc in which there can be no metal, you just need to ensure the spigots are welded outside of this arc (ie. welded to the pipe both above and below the metal detector). The BFM® connector then runs right through the metal detector. In the very unlikely event Seelfex 040E were to have any problems with false results, then the Seelfex 040AS could be used without issue. The metal detector specs will often tell you what ohm resistance the material needs to be within, you could check these.