| Summary: | With increasing energy costs and competitive pressures, interest has increased
in surveying installed pumps for potential energy savings. Field pump efficiency
tests are required to assess pumping performance and help to identify
improvement opportunities.
This work concerns the on-site measurements of pulp-suspension pumping
efficiency. This involves the measurement of pump head, flow rate and power
consumption. Provided that consistent flow measurements are available, it is
possible to reliably and non-invasively measure actual pump system efficiencies
in pulp suspension flow, with a minimum process disturbance.
As part of a most appropriate measurement-procedure study, four portable nonintrusive
flow meters were evaluated on site for pulp suspension flow. The Fast
Fourier Transform Doppler was found to be the most suitable for a pulp mill pump
survey.
Efficiency measurements were performed on six pump systems with motors
between 100 and 700 HP. It is shown that as-installed pump efficiency can be
used to help predict the degradation of the pump and also its effect on the
pumping system’s operation. A system approach analysis was performed in each
case, which can be effective in assessing system performance and finding
potential enhancements.
The use of variable speed drives allows the operating point to move along the
system curve, requiring less energy to drive the pump. VSD of larger motors are
expensive and their profitability compared to other modification alternatives
should always be carefully checked by calculations based on accurate on site
measurements and life cycle costs.
Finally, in this survey of six pump systems, significant potential savings of around
30% of present power consumption were found.
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