Dr. Horst Grothus

Don't take Deterioration and Defects for granted
Consider simultaneously their frequency, probability, detectability, potential consequences, and - most important - why do they occur at all?



[Download of detailed Systen description]

[Eliminate the real root causes of all defects]

[Pure chances control your quality - right?]
[History doesn't always tell you where to watch out]
[Analyze the character of you quality defects]
[Permanent failures plus momentary faults simultaneously]
[Fault trees unmask the mechanism behind defects]

[Systemize the root causes of your quality defects

[Six Sigma = Measuring quality quantitavely]

[Many different promises to achieve improvements]

[Re-active evolution to Zero Defect Management]
[You cannot predict results from linear actions]
[Here you see what to improve with your organization]

[Proper plant design is not meant just to produce repairs]
[Your Maintenance policy might be entirely wrong] 

[Don't take deterioration and defects for granted]
[Defects; permissible, detectable, controllable?]
[Just these few components may detteriorate repeatedly] 

[Just tell me your problems- I may help you - free!]
[Publications and support for Zero Defects Management]

[About myself]

Dr. Horst Grothus, Wettring 4,
D-46284 Dorsten/Germany
Tel: +49 (0)2362-61144,
Fax: +49 (0)2362-699497

Click here for contacting me!



Download of Detailed System Description  (If you have not yet installed Acrobat Reader, first download now)

What are Defects?

Components of your plant equipment might deteriorate (e.g. wear, corrode, contaminate, break etc.).

When this deterioration has reached an amount, you cannot further tolerate, you call this a "Defect".

Classifying "Defect Symptoms"

A "Defect Symptom" is what you see when looking at a defective component.

You can define certain capacities of these Defect Symptoms and specify their "Admissability" and "Controllability"

My "Defect Standard" is based on the analyses of several hundred thousands of defects occurring in many different kinds of industrial plants.

Most defects do not "develop" but are provoked by faults!

About 30% of all defects occur in a plant more or less regularly ("Chronically"), namely

  • predictably about 10% at "short-life components", the life time of which had been anticipated to be much shorter than that of the entire equipment, because there had not been a more economical alternative
  • and unintentionally about 20% at "Weak Components" because they had been design not according to the actual stress or they are more roughly stressed than properly (similar components at other pieces of equipment would not develop these defects at all).

However about 70% of all defects never occur repetitively at the same component at the same location, but only one single time. These "Sporadic Defects"

  • also fail unintentionally (most similar components at other positions never fail)
  • do not deteriorate normally
  • but are just being singularly provoked.

Which defects can be detected in time and repaired, before causing break downs?

Some Defect Symptoms develop rather steadily and could be detected before causing the piece of equipment to break down.

The "Defect Standard" indicates, which defects symptoms technically could thus be properly controlled.

Out of all defects actually triggering an equipment break down you could control 

  • at mechanical components only about 50%
  • and at electrical components even less: about 10%.

When considering a "normal" production plant, where break downs triggered by defects occur roughly evenly at mechanical and electrical components (50% each), your inspections just can control only (50% of mechanical plus 10% of electrical, i.e. 0,5*50% + 0,1*50%=) 30% of your break downs. This is very unfortunate, but true!

Preventive and Condition Based Maintenance work - unfortunately - rather poor!

Ideally you would presume to inspect literally all components developing defects and thereby triggering break downs. You would need to inspect 

  • not only all components, developing Chronic Defects (contributing to about 30% of all breakdowns)
  • but also those ones developing Sporadic Defects (contributing to about 70% of all breakdowns); these Sporadic Defects by definition might occur at any time at any spot.

Even applying devices automatically monitoring these components would (except at extremely dangerous pieces of equipment, like Nuclear Power Plants) hardly be economical, because 

  • they had to be installed at each individual element (e.g. each individual bearing etc.)
  • and their investment amounts to about 500 US$ for each element o be checked.

Inspections and other means of Condition Based Maintenance can therefore only be economical and efficient caring for those elements

  • (not being "Weak Components", which rather should be eliminated
  • but) intentionally suffering from Chronic Defects (mainly, but not exclusively the short-life components)
  • the Defect Symptoms of which can be detected in time (which is mainly but not always the case only at short-life components).

Your only alternative: Avoiding defects, not inspecting them.

If you can - as demonstrated - control Loss Events triggered by defects only to a very limited amount, you must avoid the defects. This you will do

  • with Chronic defects (about 30% of all)
    • by identifying and eliminating substandard defects at Weak Components
    • and with your "Zero Defects  Management" (because the real causes of Weak Components  do not lie in the technical design but in the Organization, i.e. in Basic Risk Factors)
  • and with Sporadic Defects again with "Zero Defects Management"

Look at defects quite differently from now on: They do not develop automatically, but are being produced by faults in you organization!

If you have any questions: Just tell me. I shall be glad to assist you.