The how and why of damage investigation

During the RailTech Europe event, DEKRA Rail has organised a workshop on damage investigation. A great opportunity to share our expertise with rail professionals. When damage occurs, every effort is made to repair the damage as soon as possible. What is often forgotten, is the careful understanding of the cause of the damage. This provides essential information to prevent damage in the future. In this article we will first go deeper into the importance of damage investigation. Then we will tell you more about the most common causes of damage and discuss two methods to determine the cause of damage.

The importance of damage investigation
We use damage investigation to determine the cause of the damage. Is the damage caused by corrosion, overloading or any other mechanism? If you know the cause of the damage, you also know how to prevent it in the future. In addition, the extent of the damage provides important information. For example: how big is the crack? And what is the tenacity? Based on this information you can determine whether the part needs to be repaired or replaced.

Margreet, Expert Mechanics at DEKRA Rail: "An extensive damage investigation also provides important information for specifications when renewing the assets. In addition, It provides information about the remaining life of systems that have not yet failed.”

Potential causes of damage
Most damage is caused by an unfortunate combination of loads. For example, by a combination of mechanical forces and chemical influence. Other forms of stress that can lead to damage are friction, heating and electrical effects. Margreet: "A common cause of damage is corrosion. This is an example of chemical influence and has to do with the chemical attack on materials because their environment affects them. For example, we receive corroding clamps, bolts and springs from clients. The corrosion and subsequent cracking can be caused by incorrect use of materials or by coating that has not been applied properly.” In order to find the cause, close collaboration with the customer is important. Sometimes there are changes in the process that give clues to the cause. How is the system maintained? How was it used? What load has it undergone? What were the specifications?

The most common mechanisms that DEKRA Rail has encountered over the years have been schematically mapped out. This results in the The DEKRA Damage Map.

Methods to identify the cause of damage
Depending on the complexity of a damage, different methods can be used to identify the cause of damage. Two examples are Root Cause Analysis (RCA) and the Kepner & Tregoe approach.

Root Cause Analysis
RCA is used when there are multiple possible causes, and causes and consequences are difficult to distinguish. The practice of an RCA is based on the belief that the best way to solve the problems is to eliminate the causes. Instead of dealing with the symptoms.

Kepner & Tregoe
The Kepner & Tregoe method is a problem analysis model in which the 'problem' is disconnected from the 'decision'. This method is used when deviations from normal use play a role in the search for a problem that is difficult to understand. The emphasis is on visualizing the process of the customer. In which the past and the future are included in the analysis.

Voorbeeld schadeonderzoek: scheurende isolatie van kabels
Hoe ziet een schadeonderzoek er dan in de praktijk uit? Op de afbeelding bij dit artikel zie je beschadigde elektriciteitskabels uit een trein. Vrij kort na vervanging van deze kabels zijn er scheurtjes geconstateerd in het isolatiemateriaal. Bovendien is er roest aangetroffen. DEKRA Rail heeft allereerst de feiten verzameld. Wat houdt de schade precies in? Hoe zijn de kabels gemaakt? Welke materialen zijn daarbij gebruikt? Is er iets veranderd in het proces? Vervolgens hebben we geconstateerd dat het glijmiddel dat gebruikt is om de kabels in het isolatiemateriaal te krijgen, veranderd is. Dat middel heeft de kabelmantel doen krimpen en heeft ook roestvorming veroorzaakt, wat vervolgens tot scheurtjes heeft geleid. De conclusie was dat zowel de veranderingen in werkwijze en in gebruikte materialen oorzaak waren van de schade.

Cracking insulation of cables
How does damage investigation work out in everyday life? The picture in this article shows damaged power cables from a train. Shortly after replacing these cables, cracks were found in the insulation material. Moreover, rust was found. First of all, DEKRA Rail collected the facts. What exactly is the damage? How were the cables made? What materials were used? Has anything changed in the process? We have noted that the lubricant has changed. This lubricant is used to get the cables into the insulation material. This lubricant shrunk the cable sheath and also caused corrosion, which subsequently led to cracks. The conclusion is that the damage was caused by: the changes in working methods and the changing in material use.

Do you want more information about damage investigation? Please us.

April 2019

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