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The Practical Pumping Handbook

involved and, with the destinations being at different distances, there
will also be different levels of friction losses.
The selection of a single pump for such a system will impose a different
flow rate for every system. The best pump selection for this ldnd of
operation is the one where the pump will operate closest to its best
efficiency point for the longest period of time. This will ensure that the
pump will not only require the lowest horsepower draw, but will also
operate quieter and smoother and with an increased level of reliability
throughout it's operational life.
Depending on the shape of the various system curves and the demands
of all the systems, it may be beneficial to consider using a Variable
Speed Drive on a pump in this kind of service.

5.3 Price evaluation

When we buy value instead of price for our own consumption, we only
have to justify the buying decision to ourselves, and that's usually an
easy thing to do. The justification of a higher priced pump to a
colleague is not always as straight forward. This is particularly so when
the other's function is perceived as being expenditure reduction. Such a
focus is likely to eliminate all other factors from consideration. The
difficulty is compounded if the colleague has limited knowledge of
pumps and the systems in which they operate. The easy way out is to
succumb to the simplistic justification that, if all the pumps meet the
specs, and the suppliers guarantee they will do the job, then they are all
acceptable and the cheapest pump is the best buy.
There are three problems with this assumption.
The pump may not fully meet the requirements of the
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specification.
Having witnessed the situation from both sides, I have rarely seen
a statement from a supplier to the effect that the equipment being
offered will fully meet the specification requirements. Instead, we
usually find a listing of comments pertaining to various para-
graphs within the specification. Frequently, many of the details
are left to the integrity of the relationship between the purchaser
and supplier. These details can often become the subject of
intense and acrimonious negotiations should a problem ever arise.

The specification is not appropriate.
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This is a more serious situation and happens frequently when
incomplete information is provided. This does not refer to any
vindictive withholding of data, but rather to the limitations of

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