Dropped gear - Safe to use?

[Cavedrone]

I was ascending a pitch and dropped my CS rack descender and krab 30 metres.

They look fine but my understanding is that the best advice is to bin and replace the krab
as you don't know whether it has internally weakened it. What about the descender?
They look pretty robust?

 

[Mike Hopley]

It's probably fine. Question is: are you happy with "probably"?

I would replace it. Just like the krab, it could be weakened from the fall.

 

[Daz_of_caving1]

My descender survied a drop down JH a bit ago, still works fine despite being slightly bent at the top  :read:

Daz :chair:

 

[potholer]

Presumably a lot comes down to the materials - must be some qualified people out there who could give suitable answers.

Personally, I'd generally worry rather less about steel-based devices than aluminium ones when it came to damage.
I'd guess the bars on a rack are relatively little-stressed compared to the likely failure points on an alloy krab - assume the krab was alloy?

 

[Mike Hopley]

Personally, I'd generally worry rather less about steel-based devices than aluminium ones when it came to damage.

I think that's correct. I believe steel is not subject to the hidden internal fracturing that can occur when aluminium kit is bashed.

If the rack frame is steel, then you're probably fine. Probably.

 

[Cavedrone]

Probably vs frugality means I will be investing in new gear whenever I next venture underground!!

 

[Pete K]

All the way through every outdoor qualification I've had reenforced that a significant impact or drop should cause a bit of kit to be retired. I am fairly certain I have seen the same advice directly from people like Petzl and DMM although I am not able to post a link currently.
This is what I teach when instructing in a vertical environment.

 

[potholer]

Though what does 'significant' mean?

Is it the same thing for a lightweight alloy krab and a 7mm steel maillon?

Is it easy (or even possible) to hidden-damage a steel maillon?

If someone wanders through a cave with a long cowstail swinging away, banging off walls and floor, how many little knocks equate to one significant one, or is there a level below which they don't count?

 

[TheBitterEnd]

I think it is likely that there is a level below which they don't count - i.e. elastic vs. plastic deformation. Think about trying to break a thin piece of metal by bending it backwards and forwards. it you only bent it within its elastic limits - i.e to a point where it would spring back to its original shape it would take a very long time to break*, if at all.

That said, I imagine what constitutes a "significant" impact depends on too many variables to determine as a rule of thumb.


*due to work hardening and other effects the elastic/plastic deformation boundary can change over time.

 

[robjones]

Re: steel equipment, just consider for a moment the lifespan of a hammer head, or a cold chisel in relation to significant impacts...

Alloy I'd be the first to admit is a very different material.