The circuit isn't protected by a leakage current trip.
A small pinhole opened near the neutral end of the element. This would
have tripped a leakage breaker - but not blown a fuse.
Water worked its way along inside the tube.
The element wire corroded and went open circuit - creating an arc which
turned the water inside the tube and near the arc into high pressure steam.
The expanding high pressure steam split the tube open from end to end.
The fuse blew.
Suggestion ends..
Of course forget I wrote that lot if there is a leakage breaker
protecting the circuit..
Otherwise, you may be able to detect the pinhole..
It may not be a pinhole but a deep scratch* or other site for crevice
corrosion, exacerbated by the thermal cycling. But careful examination
should find it.
* Which may be tiny and nowhere near the split.
The element may have come with a one or two year warranty - but it would
have been invalidated if it had suffered a deep scratch during installation.
If you can find a pinhole, you can argue that it was a defect in
manufacture and demand a replacement. If it was a scratch, then proving
it was there when purchased is going to be a bit difficult..
Whether it is worth arguing, I leave to you...
--
Sue
The explanation is more or less what I had assumed, but there is no scratch.
Some sort of leak which allowed water in is obvious, but not seen. It is
also possible that the seam weld along the tube was not done as well as it
might, and since this is what has split open, the original fault will be
hidden.
The one we have in our house is used daily, and is 10 years old at least.
BTB No I don't buy from 'wikes' anymore and No I didn't get a refund ,not
even a sorry.
CJ