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................................ Troubleshooting

combinations of symptoms identify the underlying cause of the
problem.

1.4.1 Speed of problem occurrence
An effective troubleshooting tool will always begin with the question,
'How fast did it show up?'. If the problem has only suddenly appeared,
it is likely to have a different cause than a similar problem that has been
developing over time. It is also fairly obvious that a sudden appearance
of the problem is probably caused by a sudden change in the condition
that created the problem. Therefore it is highly unlikely that such a
problem can be attributed to normal wear and tear. It is much more
probable that an inappropriate action has taken place quickly.
The exception to that concept is where wear gradually takes place until
the point at which failure suddenly occurs. In such an event however,
the wear is usually indicated by a gradual reduction in performance
until the breaking point is reached; thus providing some prior
notification of imminent failure. This type of condition underscores the
need for constant measurement of performance as it relates to
temperature, pressure, flow, vibration and power draw.

11.4.1.1 Excessive power consumption
For example, some of the more frequent causes of excessive power
consumption are as follows:
9 Flow rate is higher than expected
9 System pressure is lower than expected

9 Pump speed is too high
9 Impeller diameter is too big
9 Rotating element is binding somewhere
9 Impeller is rubbing on the casing
9 Wear rings are touching
9 Packing is too fight

9 High load on beatings
9 Pumpage has changed to higher density
Many of these causes can happen abruptly, while others can occur
gradually.

11.4.2 Frequency of problem occurrence
A typical example of this problem is when a mechanical seal in a
particular pump fails every six months, regardless of the type of seal

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