In reply to Martin1978:
> (In reply to crayefish)
>
> When are you EVER going to put 15kn through a belay loop?
Right. The answer is never in any belay situation, including factor 2 falls, because the maximum impact load for climbing ropes is typically well under 10 kN and is required by UIAA standards to be under 12 kN, and to even see those loads you'd have to tie the climbing rope to the belay loop rather than using a belay device.
It isn't inconceivable that you might attain loads above 15 kN if you girth-hitch a sling to the belay loop, clip to an anchor, and then take a factor 2 fall on it. If the sling is dyneema, it would probably break, but if not the maximum impact load would probably be over 15 kN. I read some years ago that Petzl tested the maximum impact load of one of their nylon runners in a factor 2 fall and came up with 18 kN, so a nylon runner would probably do the trick too.
Of course, pulling a loop to something above 15 kN is not the same as dropping an 80 kg weight on it in a factor 2 fall. My guess is that since the nylon runner doesn't break (for example, the Sterling Chain Reactor tether withstands three factor-2 falls), there is no way the much burlier belay loop would break, even in these extreme circumstances.
It is well past time to stop citing the Todd Skinner tragedy as any kind of evidence for concerns about belay loop strength. (And the poster who suggested "several deaths" was, of course, unable to come up with any others.) Anything will break if you neglect it for long enough, and there was, sadly, abundant visual evidence that his harness was way, way past the retirement point.