Fretting Corrosion

In a plant it so happened that a machine with its shaft and pulley assembly was kept idle for little over three years.

Then one day the engineers decided to run the machine. After two months of running, the pulley came loose on the shaft and started rattling – making just enough noise for the operator to notice it and promptly stop the machine thus averting a nasty accident.
This is a case of fretting corrosion. This happens when things are kept in assembled condition for long without running or components are assembled loosely. The asperities at the contact surface that help to hold two components together are lost; thus loosing the vital grip forcing the components to come loose. This wear process is accelerated in presence of low frequency vibration that usually travel to such joints por assemblies from other running machines. The confirmation of fretting corrosion lies in observing reddish coloured powder in between the closely fitting joint interfaces and assemblies.

The pictures of fretting corrosion as seen in this case are the following:

Ways to manage this failure mode:

1. Take care to assemble correctly

2. Don’t leave a machine idle for a long time.

3. Prevent, as far as possible, low frequency vibrations to travel to a machine.

4. If an idle machine is to be commissioned then take care to inspect the joints and interfaces and replace assemblies as found necessary.

5. May be monitored by Wear Debris Analysis for lubricated joints and interfaces and by vibration monitoring for dry joints and interfaces or simply by visual monitoring.

Doing Nothing yet Everything is Done

From 21st June to 23rd June I conducted a live workshop on Streamlined Reliability Centered Maintenance (SRCM) at the Power Management Institute (PMI) of National Thermal Power Corporation (NTPC).

But what the heck is SRCM?

It is a structured process of risk based decision making against black swans.

In brief, it is about:

  1. How to detect an incipient black swan in time?
  2. How to improve the stability of a system?
  3. How to improve the longevity of a system?
  4. How to mitigate consequences of failures?

When we are able to do all that to a system we may call it “smart maintenance.” After all as human beings we create, maintain and destroy systems. Given a system, smart maintenance is about doing all the three – create, maintain and destroy. Surely, it is one of the most complex project management we can engage with.

However, the smart maintenance can really happen when one simply does nothing yet everything is done.

Role of Critical Thinking in Solving Complex Problems

Within the next five years the ability to solve complex problems would be the number one skill people would be desperately looking for.

However, development of this skill rests on three fundamental pillars, which are:

  1. Critical Thinking 
  2. Creativity 
  3. Seeing” things differently

In this post, we focus on the skill of critical thinking. To do so, we draw inspiration from ten examples of critical thinking and critical thinkers that changed our world and our world views.

“Being bold enough to let your mind go where good arguments take you, even if it’s to places that make you feel uncomfortable, may lead you to discoveries about the world and yourself.”

(Critical Thinking: The Art of Argument, by George W. Rainbolt and Sandra L. Dwyer)

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