Ladder held with magnets

[apsix]

I am scheduled to inspect fabrication of wind generator towers next week, height; 80 metres.
I haven't received any drawings yet but have been told the (internal?) ladder is held on by magnets, presumably to avoid any adverse effects due to welding.
Has anyone any experience with this form of fixing? I am thinking the magnets are possibly for lateral restraint only, vertical support is provided at the top and/or bottom of the ladder.
Any thoughts would be appreciated.

 

[AggieYank]

It sounds like a mechanical engineer was being creative.

Take this with a huge grain of salt, as I'm not someone who inspects things like that, and have no familiarity with using magnets, but I'd require a bolted/welded connection at the top and bottom for vertical and lateral support. It's boring, but boring is safe. Maybe you could ask them for the design drawings, or to speak with the manufacturer of the ladder. If they're worried about having a slip joint because of expansion/contraction of the ladder, I'd recommend a slotted hole and bolt(s).

My general inspection rule is, if it doesn't look right, it probably isnt, and an 80' ladder supported by magnets seems very not right.

 

[Bagman2524]

Agree with AggieYank. Don't think this is a good idea.

 

[Bagman2524]

Also, Don't think complies with OHSA.

 

[rb1957]

if it is, i won't climb up it

 

[JStephen]

This does sound like a poor idea. Suction cups would be much more economical.

 

[UcfSE]

It seems like a magnet would hold basically through friction. I would want more than friction holding my ladder on, even just horizontally.

 

[sundale]

Gorilla Glue would be far more economical than suction cups or magnets.

 

[Vaporware]

If it's supported by fixed connections at the top and bottom, then the magnets are only keeping the ladder from flexing off the wall, right? Sounds fine to me as long as the ladder is securely bolted at the top and bottom

Oh yeah, and if they specced the magnets out right.

 

[JStephen]

Seriously, I think the magnets would work if they had vertical support at the top of the ladder. You can get magnets pretty cheaply that will have a couple of hundred pounds of holding power against a steel plate. I wouldn't want to hang from magnets like that, but they should work fine to hold a ladder in place laterally. I would expect some more solid connection at the top, though.

 

[Loui1]

If I remember correctly in school. Permanent magnets lose their strength when they are dropped, vibrated, or struck. It disorients the dipoles....the things that make magnets do what they do.

You're putting a moment on the ladder as you climb it. if the magnets fail, you bend the ladder stringers. I'd be pretty afraid unless they provided upfront documentation from the installer.

 

[mcutchi]

Presumably this is not in the USA. Still, 80m is a long way to fall ! Make sure someone else has climbed this before, as take your fall restraints with you !

 

[MagMike]

I work in the permanent magnet industry and while I can envision a couple of magnet assemblies that'll hold the weight & stress, I would never spec something like that in such a critical application.

 

[apsix]

Thanks to those who commented.
AggieYank said; "if it doesn't look right, it probably isn't". I was sceptical but now that I've seen it, it doesn't look wrong.
Vertical load is taken by bolted connections at the top of each +/- 25 m ladder segment. There are pairs of magnets attached to the wall every few metres providing horizontal restraint. Each magnet is about 250 x 50 x 50 mm, with a reported holding power of 300 kg (TBC).
This ladder system has been used in similar towers around the world and will be certified by the supplier. We still have to decide on the form of documentation we require (if any) showing the adequacy of the magnets.

 

[rb1957]

i reckon the bolts make all the difference ...

the magnets are only there to stop the ladder swaying

 

[Tomfh]

I like the sound of this system. As you guys have pointed out the magnets only need to handle horizontal forces. I would expect 3 kN strength magnets will easily take care of this. Besides, even if the magnets did fail you still have a "rope" ladder.

 

[MJR2]

I agree with MagMike. We both work in the magnet industry and do not trust magnets where safety is involved. Not a good idea. I would not climb it.

Mike

 

[EdStainless]

This I could live with. I have (inadvertantly) hung from magnet assemblies. Using them as stiffeners with no load sounds fine to me.
My thought on evaluation is, will the ladder work with only half of the magnets? I trust that these are assemblies of permanent magnets with steel pole pieces, and that the shape of the poles matches the shape of the steel surface.

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