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]In ...... Troubleshooting

ocean, lake or river. Consequently it may be necessary to live with the
problem.
That does not mean to say that it is necessary to live with the
ramifications of the problem. If we can't cure the problem, we can
frequently make a difference to the damaging effects of the symptom.

For example, with a pump that is cavitating, there arc four identifiable
symptoms;
9 A peculiar rumble/rattling noise,

9 high vibration levels,
9 a pitted impeller, and
9 a slight reduction in total head.
The use of ear plugs is about the only relief that can be experienced
from the noise level, and a slight increase in impeller diameter or
rotational speed will take care of the total head.
The extent of the pitting damage can be frequently aleviated with the
use of a harder material for the impeller. For example, a stainless steel
impeller has been known to last 4-6 times as long as a bronze impeller
in the same adverse conditions.
The high vibration levels can sometimes be reduced with the use of a
stronger shaft as will be discussed in Chapter i 1.4.2.2.
While none of these options eliminates the problem, they may allow the
plant personnel to live with the reduced detrimental effects of the
symptoms.

11.3 Reliability problems

Reliability problems bring into question the length of time the pump
can be expected to continue running. While this would include the
damaging aspects of a cavitation type of problem as discussed in the
previous paragraph, a more typical example is when a pump is vibrating
as a result of a variety of mechanical conditions as identified in Figure
11.3.
Although there have been almost 100 different problems identified
with centrifugal pumps, many of which have more than one solution-
sometimes they have two, three, or even more solutions - it is
intcrcsting to note that thcrc are much fcwcr solutions. In fact, if you
scrutinize the accompanying tables, it is evident that there really arc
only 6 basic solutions to all pump problems.

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