Snapping cable or chains.

[kthompson]

On another thread the danger of snapped cable was made very real. It made me wonder if there is difference in the way a cable and chain react when snapped.

It is my impression a cable will always whip when snapped. In my chain snapping experience have never had one to really whip, normally pull back just a little and drop. Is that due to the length of chain (20 feet max) compared to cables which often are much longer? It is my belief that are many things come into play here such as the lighter weight of cable to it's strength than the chain, also if on a drum (winch) it has stored up energy compared to a chain. It also seems you will more likely see a cable run higher in the air than a chain, guess due to weight factor.

 

[bill onthehill]

My experience a snapped chain tends to come right back in the line it was stretched on. Only cable I ever broke whipped around a tree but I would think it might have something to do with the way the strands are wrapped. Last chain I broke was pulling the neighbors Belarus tractor out of mud. 40 ft of chain went back toward him and hit the rear tire.

 

[qball]

the potential energy stored in a chain or cable under tension can be unbelievably dangerous. i have seen both fail. i had 100 ft of 3/4 cable part and whip violently during a recovery. i won't use chains for pulling. ever. seen far too many part and fly. i have big nylons and inch and a half tugboat hawser for unsticking. when nylon strap or hawser parts, it falls to the ground. way safer that way.

 

[d4c24a]

wow

they are all dangerous when under unknown loadings ,always keep clear and where possible hang something on chain/cable to help stop it flying
YouTube - oh ****!!!!!!!

 

[Bully]

Nylon rope is a killer. That stuff will stretch to 1/3 it's length when put to it's max load capacity. It will start groaning and singing when its put under a steadily increasing strain.I've been told that a nylon will snap back with the velocity of a .45 caliber bullet. That's about 845 fps. Now imagine that .45 cal is a 3" d towing hawser. Probably like being hit with a 12 pounder cannonball.
I have been hit with a polyproplyene line and it hurts like hell. Took a layer of skin off the back of my thigh( I was wearing jeans) and left a wicked welt/ bruise. I know a guy who had his wrist broken by a 1.5" polypropylene leaving line. The only kind of tow hawser i've seen that has not parted violently is Spectra. Good stuff, but beaucoup bucks, and very sensitive to abrasion.

Any US Navy vet will tell you about the "synthetic line snapback" training film you were forced to watch in Boot Camp. Gruesome.

Here's something I found...

Nylon line + morons =

YouTube - Snap Back


Chain won't snap back, but it won't warn you either. Usually it looks fine, then you drop a crane ramp onto the barge deck. Not that I've been any part of something like that....:beatsme Not like I'm talking like I rigged a ramp with an old chain..not me..never...

Snapped lots of cable in my days, some violent, some not, but all of it was old crane cable made into facing wire. It goes with the territory of tugboating. Thankfully never had any snap while being used properly on a crane. Hope to never see it.

 

[Squizzy246B]

I am rather amused by some of the comments on "stretching" chain and snap back of chains.

For proper Grade 70 or higher drag chain the elongations factors are 5/8th of nothing within the WLL. The elongation at destruction can be up to 25%. destruction occurs at more than 2.5 x WLL.

A grade 80 1/2" short link drag chain is good for 9 tonnes...so if you going to use a D8 to pull a 30 tonne excavator out of the mud with it your more than likely going to break it.

Loads in recovery situations can be very hard to estimate however, whether it be rope, wire or chain, if its not capable of meeting 75% of the DWT of the lightest machine used then you are going to break something. 100% is recommended although traction and angles need to be considered.

Within its WLL a chain failure ( ie damaged link or torn off tow point) will result in the chain dropping quickly to the ground.

If you are stretching a chain to the point that elongation occurs (plastic deformation of the links) then there is no point blaming the chain when somebody gets killed.

Rules for using chain in recovery:

Only use short link Grade 70 or above that is rated for the task. Do not use un-rated cheap galvanised chain.

A drag chain is just that...its not used for anything else other than recovery. Keep a dedicated drag chain for recovery and nothing else.

Inspect the chain before use

Keep the Goofers clear

If you can, use a shot mat, blast mat or even heavy conveyor belting no matter what you using for a tow medium.

There may be a sense of urgency to effect a recovery....but its only a machine...its not worth dying for.

and

Has anybody used the Dyneema ropes for recovery??

 

[ok dirt witcher]

I have a 150,000 pound tow (jerk) rope and a 100,000 pound cotton winch rope both are reliable. I have a winch on my dozer and know 1 thing for sure "it's a lot harder when the winch is on the piece of equipment that is stuck. I guess what i'm trying to say is it's easier to winch somebody out than it is to winch yourself out using another vehichle for a deadman". If chains are all you have, use 2 on the stuck vehichle and 2 on the puller, dont hook them to each other. find the middle distance and link everything together with a used tire. Chains may still break but the tire somehow keeps the chain lower and reduces recoil. bystanders any any angle or distance shouldn't be allowed. I always try to stay down as low as possible in the cab. luckily Ive never had one come through the window.

 

[kthompson]

Squizzy, what does WLL stand for?

Think some how it is for safe working load but..

 

[bill5362]

WLL Stands for Working Load Limit or rated capacity of chains and slings, is determined by the “grade” of the chain and its components. Hope this helps...

 

[td25c]

Nylon rope is a killer. That stuff will stretch to 1/3 it's length when put to it's max load capacity. It will start groaning and singing when its put under a steadily increasing strain.I've been told that a nylon will snap back with the velocity of a .45 caliber bullet. That's about 845 fps. Now imagine that .45 cal is a 3" d towing hawser. Probably like being hit with a 12 pounder cannonball.
I have been hit with a polyproplyene line and it hurts like hell. Took a layer of skin off the back of my thigh( I was wearing jeans) and left a wicked welt/ bruise. I know a guy who had his wrist broken by a 1.5" polypropylene leaving line. The only kind of tow hawser i've seen that has not parted violently is Spectra. Good stuff, but beaucoup bucks, and very sensitive to abrasion.

Any US Navy vet will tell you about the "synthetic line snapback" training film you were forced to watch in Boot Camp. Gruesome.

Here's something I found...

Nylon line + morons =

YouTube - Snap Back


Chain won't snap back, but it won't warn you either. Usually it looks fine, then you drop a crane ramp onto the barge deck. Not that I've been any part of something like that....:beatsme Not like I'm talking like I rigged a ramp with an old chain..not me..never...

Snapped lots of cable in my days, some violent, some not, but all of it was old crane cable made into facing wire. It goes with the territory of tugboating. Thankfully never had any snap while being used properly on a crane. Hope to never see it.

Agree Bully,Nylon rope with the metal hooks on the ends is a killer,far worse recoil then any chain or cable when it fails.Dang stuff otta be outlawed.

 

[td25c]

Yep bill5362,I always took WLL as meaning "working load limit".

 

[surfer-joe]

Well, chain will snap back to an extent, not near as much as synthetic slings or wire rope however.

Now wire rope, it's a killer. The amount of stretch in wire rope is unbelievable, and when it breaks, it's really torqued. Bad thing is, in these cases, ya never know exactly which way the tow gear is going to go. It can snap to to either side, forward, or back. If a man is in the way, he gonna be hurting -- or dead! Good friend of mine had a lung smashed by a 1" winch cable when it popped. He survived that, was off two years, three years later TB got him.

I've had wire rope up to 2" diameter separate on me, chain up to 1" link, and any number of synthetic tow or lift slings up to 10" wide. If this stuff didn't get ya, the load would you know.

Most of these situations happened because the tow or lift medium was undersize, or we had too much horsepower or weight attached to one end. In other words, whatever we were using at the time was too dern small. But as one survives the accident, one becomes smarter for the next time, eh?

 

[kthompson]

Bill thanks.

Something I think that is also missed is when a set of chains or even a chain is use to lift or pull something but not straight on. Such as in a "V" and it is easy to forget you loose some to a lot of the capacity of the two chains as they are also pulling against each other. Guess for most people this would be slings. (well the term I learned them by.)

 

[AtlasRob]

I know everybody knows but I will say it anyway

DO NOT lift with chains or slings that have been used for pulling/recovery.

You dont know what sort of strain they have had on them. If they then fail during a lift.................. just DONT do it. :drinkup