SUBJECT : A new way to troubleshoot centrifugal pumps and mechanical seals. 5-6

One of the U. S. based Japanese automobile manufacturers has a unique method of troubleshooting any type of mechanical failure. The system is called the "Five Whys". It is a simple but powerful concept, nothing has been solved until the question "why ?" has been asked at least five times and a sensible answer has been given for each of the "why" questions. As an example:

1. Why did the seal fail?

2. Why did the faces open?

3. Set screws are not supposed to slip. Why did the set screws slip?

4. Why was the seal installed on a hardened sleeve?

5. Why couldn't the mechanic tell the difference between a hardened sleeve and a soft one?

6 Why were they stored in the same bin?

7. Why did they have the same part number?

Now you get the idea! Needless to say you may have to go further than just five "whys". Let's try another example:

1. Why did the seal fail?

2. Why was the pump cavitating?

3. Why didn't it have enough suction head?

4. Why did the level in the tank get too low?

You have not finished five "whys" so you better go find out why the level in the tank got too low, or the problem is going to repeat its self. In the above example the float became stuck on a corroded rod, giving an incorrect level indication.

One more example should do it:

1. Why did the seal start to leak?

2. Why did the elastomer get hard and crack?

3. Why did it get too hot?

4. Why did the stuffing box run dry?

5. Why was it running under a vacuum?

6. Why was it adjusted backwards?

This is a powerful trouble shooting technique. I hope you make good use of it.

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