….let's share our railways knowledge

Failure of Stainless Steel Wire Ropes in in Automatic Tension Device

By on April 18, 2021

Introduction

On first hearing about this failure, my reaction was that of disbelief. How can a wire rope made of such strong material fail? Break? Particularly when the load supported did not appear to be heavy! Hence disbelief. I had never worked in the Traction distribution where such a device is used.

Having analysed the failure and suggested a solution (Let me add that it was implemented by RDSO a few years after this article was published), I have another reason for satisfaction. These (Pulley, wire- ropes) are among the most basic machine elements about which engineering students learn in the first year. The basic understanding of steady and alternating stresses can be obtained very well in this situation.  Indeed, it is such a slowly alternating stress! The accuracy with which failures could be predicted using simple Goodman’s diagram was amazing! Equally satisfying was the ability of the theory to explain the observations of various divisions regarding the performance of wire-ropes. I urge the young engineers to try and understand this case study as a textbook case at failure investigation. In the real-life situation, there are numerous complexities that cloud the basic mechanism from all sides confusing the responses of practicing engineers. The farther people are from the equipment, the more clouded their “views”. Very often high-level discussions turn out to be high “decibel” noise and problems continue. This case is a classic example where the problem survived for decades in spite of high-level discussions whereas a simple look at the basics solved the problem.

Story

I would like to share the story of this investigation. I was working as Professor (Loco) at IRIEEN. I was also the course coordinator for the JA grade course at IRIEEN. In one of the batches in 2002, most participants were from a Traction Distribution background. Usually, I would invite retired officers to share their experience with the working officers. This was a kind of established ritual at IRIEEN. Judging purely from the point of view of the depth of technical knowledge exchange, very few seniors had substantial contributions to make. Mr. Hattangadi, retired GM/CLW, was an honorable exception. This time as I telephoned him requesting him to deliver a lecture, he came up with a battery of questions regarding the ATD, Pulley, wire rope, winch, and so on. I collected some information from Shri O P Mittal, Prof. Traction Distribution, and passed it on to him not really concerned about it like a good railwayman who did not look at another side of the fence until asked to do so by the authority.

Eventually, the day of the lecture arrived. Mr Hattangadi stated he would like to focus only on the problem of breakage of wire-ropes that day. He tried his best to engage with the trainee officers with the words like “stress”, “strength” “tensile”, “alternating stress”, “incipient failure”, “cycles to failure”. But the officers chose instead to talk about “warranty”, “advance payment”, “RDSO not listening to feedback”, “single supplier”. The discussion went nowhere! I arranged for tea but the post-tea situation was worse. I and Natraj Sir (another retired AGM ) sat through the class helplessly. Finally, Hattangadi told me not to invite him again for a lecture. I promised him to analyze and solve this problem based on what I had understood. This article was the result. Please enjoy reading the article through the link.

An article by Sh Mahesh Chandra on

Failure of STAINLESS-STEEL WIRE ROPES in AUTOMATIC TENSIONING DEVICES 

When you read this article, you will not be prompted to understand the problem of breakage of stainless steel wire rope, but learn the methodical approach to solving the problem of material failure. Unless you find out the real problem behind any failure and keep the problem burning in your mind till a permanent solution is found, you should not feel satisfied. In most of the cases, as soon some reasons, appears to be be the cause of the failure, we stick to our solution start jumping ‘euraka-euraka’. Just think, is the time you start telling your success story?

Mahesh Kumar Jain-Retd. Director IRIEEN

 

Post a Comment

Your email address will not be published. Required fields are marked *

Top