Manual EM 1110-2-3105.
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c.
Value of NPSHR - The value of NPSHR shall be [300][600][900] mm
[1][2][3] feet less than the corresponding available net positive
suction head (NPSHA). NPSHA shall be determined using the
temperature of the water in the model at the time the tests are
run and the datum shown on Figure 3 at the end of this section.
The water elevations specified in paragraph CAPACITIES shall be
used to determine the NPSHA for the pumps.
d.
Plotting Test Results - The test results shall be plotted to the
scales determined by the Contracting Officer at the time of the
test. Curves showing [static][pool-to-pool][total] head, brake
kilowatt horsepower, and [pool-to-pool] efficiency as ordinates
and NPSH as the abscissa shall be drawn. In addition, curves
showing NPSHR versus capacity shall be drawn with NPSH as the
ordinate and capacity as the abscissa. NPSHA points shall be
shown on the curves.
e.
Curves - Should it be considered necessary by the Contractor to
take into account measurement inaccuracies when drawing the curve
needed to determine NPSHR in accordance with paragraph NPSHR, the
following method shall be used. No other method will be
acceptable. The inaccuracy shall be determined by the Contractor
for each parameter, and the calculations shall be furnished to the
Contracting Officer for approval. Using the calculated inaccuracy
as the radius and the test point as the center, a circle shall be
drawn for each test point. Two curves, one a maximum and the
other a minimum, shall be drawn and shall pass through or touch
each circle. The maximum curve shall touch the top and the
minimum curve shall touch the bottom of as many circles as is
practicable while maintaining smooth curves. Should the plot
indicate that a test point is obviously erroneous, it may be
ignored by mutual consent or the test may be rerun. Halfway
between the maximum and minimum curves, another curve (the mean)
shall be drawn. The point at which the mean curve departs from
the constant values (point of tangency) shall be considered to be
the NPSHR of the pump for the capacity at which the test was run.
2.5.3.7
Witness Test
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NOTE: The time to review test data should be 2
week. Longer times may be used when the District
has staffing difficulties or special arrangements
are required to have data reviewed by others. The
shortest period id preferred since this may permit
the pump tested to remain in place during the review
period. If the pump/test instruments are not moved,
then the possibility of changes to the test results
for the witness test are less likely to occur. The
cost of the tests would be less also.
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When the Contractor is satisfied that the tested pump performs in
accordance with the requirements of the specifications and the guaranteed
values, the Contractor shall notify the Contracting Officer that the
witness tests are ready to be run and shall furnish two copies of the
SECTION 15131A
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