Basejumper.com - archive

The incident thread on the recent riser malfunction spawned a lot of interest in riser failure modes. Let me pose a few statements, feel free to disagree or agree, I'm curious why.

As I understand it, the weakest part of a riser is generally considered to involve the upper ring or yellow cable. Ring attachment failure, or yellow ring pulled through the grommet, to be specific. These spots, and also type 17 webbing sewn in a riser configuration, will all fail around similar load ranges... according to the Jump Shack tech article.

Degradation to the nylon webbing itself, can result in weak spots with unpredictable braking strength. ultraviolet light, acid exposure, high heat, history of severe openings... can render the riser material itself very weak. Car batteries make terrible packing weights. I heard rumor of a riser snapping after using that, way back in the day.

Some manufacturers of gear have put their risers under test equipment, and pulled-to-failure, with ample data resulting. Private companies in my experience tend to consider this data proprietary, and do not share it.

The spectra loop for trapping slider-down brake lines, on my old set of risers, broke at 3.6-3.8 kN. the lower end range was on a loop that was 40% worn through. I was really surprised that the intact loop was only slightly stronger. I can't recall what the typical force on a brake line is during opening, but it's usually a heck of a lot less than 3.6 kN. I believe there are case reports of brake lines releasing on opening, due to failure of this loop. Can anyone confirm?

example- http://www.basejumper.com/...est_case_1_2106.html

I've seen that happen twice. Both times resulting in water landing and no injury. In both cases _both_ loops failed, so both toggles were lost.

I'd guess this was a manufacturing error.

I suspect that we are on the same page here but I feel your wording could be misleading for some people.
Structurally I don't feel that the small ring is weak at all in terms of construction. But by default the loop/ring/grommet assembly is the weakest part of the system as it is what closes the entire system. And for obvious reasons the locking loop lacks durability.

P.S. Historically risers will snap the locking loop or shear off where it wraps around the harness ring. Of course people can always invent new failure modes.

But... I have L-bars...

Good point- and it raises another distinction:
what is the weakest point in a brand new set of risers, and is it different than in a, say, 15-year-old set.

My guess is, the individual components of a riser assembly do not age/weaken at the same rate, as it is heavily affected by each unique exposure, rust, repeated loads, etc.