21:39 Feb 9 

finding "emergency release/shut-off" within the proper context on the net. "fuse" would probably be a false friend here. "coupling" does NOT fit the bill, as there is only one coupling involved, not two as use of your own suggestion would imply. Although I can not know your text I doubt the author of a technical document would use a variety of terms for one defined piece of equipment in the same document, as that would be against the rules of technical authoring. Regards.

17:12 Jan 25 

Hi, thanks for the answers, but this is not really to do with electrical components. I finally found an answer and it is a breakaway unit or emergency release coupling (Nottrenkupplung). As usual the German writer uses many possible words for the same thing! = a mechanical device uncoupling the gas/liquid conveying lines in case of an emergency.