Failure Analysis of a Failed Steel Rope

What is the diameter of the cable?

the diamater of the steel rope is 5mm.

What is the load weight, and the travel of rope daily average.....the composition of the wire and pulley...??

Find a link such as this one, then check out 'bend fatigue'. The ratio of rope to drum diameter you mention doesn't look too good.

Could be plenty of other reasons.....

Agreed: he needs a bigger pulley, plus a contact with the manufacturer (or maybe a tables book) to see how big the pulley needs to be.

Possibility that the steel rope was manufactured or imported from China which products normally are under specifications size-wise and metal composition-wise..

That is sensible enough.

Exactly. The 50.8MM pulley is much too small for the wire diameter.

Fatigue is high on the list. Another possibility is a nick or other roughness on the pulley or other surface in contact with the wire rope.

Why does it sound like a homework question?

What is your proposal why does the rope fail?

Effort man, just a bit of effort!

I bet you was bold already before that!

Did you finish your studies and this is a real life question?

hoe often is the cable inspected? what is its load rating and how much was it lifting?

You would do well to develop a resource that is not.anonymous.

When you graduate, clients will expect you to know these answers.

You will have to affirm that your work is accurate.

For now, you have excellent tutors guiding you.

Trying to lift 50,000 kilograms with an average velocity of 340 m/sec for an elevation change of 1.2 kilometers, it is truly amazing that you achieved this once let alone for several months. What grade of steel alloy did you use? What was the weave pattern for the cable and were any man made polymers (Aramid) woven into this cable?

He's a student.

Gravity

Hola! This is the Eureka moment. Of course this is the reason that load made its downward movement! Gravity must have been pulling too hard and with more strength then the cable could offer as resistance . .

Nah, I think the load is just a diversion. This is some sort of very deep tunnel being built for critters......just got to a depth where the weight of unwound rope was too much for it's own good.

You bringing up a good point!

but

weight and gravity are connected over the mass!

So there mus have been this MASSiv impact on the rope . . .

Anyone knows that a piece of chain spliced in is a far better thing than bending a steel cable over a pulley!

several years ago a friend if mine was working at Boeing at Cape Canaveral. his assistant was operating the winch controls as a multi-million dollar satellite was being loaded on a Delta rocket. it crashed to the floor when the cable snapped. after disassembling the hoist they found after years of service it had simply worn and the cable was not tracking properly for a long time and this accelerated uneven wear on the cable. light loads never revealed a problem. it came down to a piece of equipment that had never been inspected(since its always up high)and lax maintenance protocol.

There are no unimportant parts:
Where do you use your least reliable piece of equipment?
Where do you place your least competent employee?

I am not sure that I understand your questions, but there are always more mission critical parts in any assembly just as there are more important employees in a company.

A simple FMEA is all you need to see what components are more important.

From: Midnight Cowboy -

Possibility that load is very near the maximum the stated/tested/certified weight-handling limit.

That combined with the stress of being bent over your 50.8mm pulley, is just enough to exceed the limits of the outer steel strands, at the moment the straight line is changed.

This partial parting of one or more strands, during each passage over the pulley, further reduces the overall weight handling of the cable, until the straight line weight-limit is grossly exceeded.

Age and overall condition are important factors to take into consideration!

I'll not detract from the GA's you have, but that is a load of rubbish.

Apart from lube (and the OP will need plenty after the rogering he's getting here), how on earth do you arrive at such advice ? Ratio of rope/pulley has already been covered. Is there some universal standard that can be applied ? We don't even know what kind of lay he's got on the, presumably, unlubed/nserviced rope.

The OP may as well have asked 'how long should a piece of string be'.

Are you expert on Wire Ropes? then you should have known the information I have provided is as per Indian/British Standards for the Wire ope. I do not speak the lingo you have learned so bye.

Voting me OT because you dislike my comment is childish. That's just a few seconds of your life lost foever. As it happens, I know more about wire rope than you can imagine. The question is about, semingly, small size, so I'm sure you know much more about that than I.

I had tried to be polite in my previous, and clearly failed. It's not a good idea to pick a fight when you have your head up your arse. That's unfair of me - how else could you speak at the same time.

There is some linguistic/semantic problem here. If you don't like my comments, then either do a Burt Bacharch - walk on by - or PM me so we can sort any misunderstandings outrside of the discussion. See, even I can fail to cmmunicate. To use an American expression, 'chill'.

Removed Cus

As I stated earlier, just before someone wiped out 8 more of my GA's for spite, if the OP weren't such a lazy, worthless bum they could have looked on the web for help with this simple homework question.

Depending on the application the sheave to wire rope diameter ratio could be 35:1.

I've lost 20 GA's lately to some flaming little piece of shit!

I can't resist, that desrves a GA .

Thanks.

Hear here!

I'm still curious if people think my absurd comment about Jimbo highlighted or obfuscated the lack of information in this question.

I'm not here for the GA's, why would anybody be.

What pisses me off is that anybody can cancel out your GA by simply voting it OT.

As they have done to me, and others. Voting something GA does not lock that GA in. Any jerk can cancel them, out of spite.

Some GA's are voted because of sound technical answers that were posted. For some twit to come along and maliciously cancel those out is childish.

Also, as I said, this homework question is a joke!!

But not in the quantity you mentioned surely.....

Everyone here has lost GAs to that, but who the hell cares......maybe you gained some somewhere else....

Andy, I agree with you fully. I just participated in discussion with no desire of getting GA but some one liked my comment and gave me GA and some one disliked it and made hue and cry.

Lyn mate how is it possible the your GA's are wiped off?

I don't really understand how that happened. Am sorry but this problem was taken from a text book and I just posted it for general discussion. It has no intention for members to get GA's wiped. I don't know how that happens and it wasn't the intention of this post.

Now that was a really stupid homework question to my mind. Please desist from posting such things.....

For sure wont occur again....

Any wire rope web site can provide far better information on the subject than you will get here.

So far, with the exception of one technical web site provided by Kris, all you have gotten here are opinions from people who may, or may not, have ever used wire rope.

If you wanted a general discussion on the subject, you should have called together a group of your fellow students. At least you know their real qualifications.

Actually the problem was Jimbo. Jimbo means well but he doesn't think clearly. You see the day before the accident Jimbo noticed that some of the cable threads had snapped. Jimbo knew that a critical lift had to be done the next day or the project would be delayed, so he had to do something. Instead of pointing out this damage out to the boss, Jimbo welded the tiny strands at the damaged site together into a hardened solid rod about 50mm long with an oxy-acetylene torch. When the rigid portion of the cable tried to move over the pulley the steel couldn't handle the strain and snapped.

That brings to mind my favourite US TV Gal!!

J.J.

ever so interesting

Dear Mr.hubertooru,

You have mentioned the Pulley Dia. is 50.8 MM, and in your reply - vide Post No.2, below (for the quiery in Post No.1), you have replied Rope Dia. is 5 MM.

For the good functioning of wire rope, there are few factors that are important, and one such important factor is D/d Raio, and it should be 16 to 20 as MINIMUM for smaller dia. 24 to 28 for medium size wire, and 36 to 42 for bigger size wire rope, where D = dia. of Pulley, and d = dia. of Rope. This ratio will help to keep higher bending circle/curvature for the wire rope, over the pulley. But, in your case D/d = 10.16. This is one of the reasons for failure of the rope.

If this ratio is less, as in your case, the severity of bending of wire will be more and move away from HOOK's LAW.

Other parameter, the malleability and ductility of the steel used for rope should be high. Greasing of wire rope should be properly done.

DHAYANANDHAN.S