One of the two sump elevations used may be at the specified
elevation.][ The sump elevations used shall be those specified in
paragraph CAPACITIES.] The test results with this sump elevation shall
meet all specified conditions of capacity, head, and brake kilowatt
horsepower. Submit curves indicating test results.
c. Tests Results - Plot results of tests to show total head,
[[static][pool-to-pool][bowl] heads], brake kilowatt horsepower and
efficiency as ordinates; all plotted against pump discharge as the
abscissa. Plot curves showing prototype performance to a scale that
will permit reading head directly to [60] [150] mm [.2] [.5] foot,
capacity to [190][380][760][1900] L/min [50][100][200][500] gpm,
[0.14][0.28][1.4] m3/s [5][10][50] cfs, efficiency to 1 percent, and
power input to [3.7][7.5][18.6][37.2] kW [5][10][25][50] horsepower.
d. Demonstration.-.Contractor shall demonstrate to Government witness
that the blade templates fit the tested pump. Demonstration shall be
done immediately after testing is completed. Contractor shall retain
all templates for the tested pump , and shall furnish them to
Government upon request of Contracting Officer, to permit Government to
verify geometric similarity with the manufacturer's pump. In addition
to providing templates, furnish dimensioned drawings of impeller, which
contain all dimensions needed to manufacture it. Tested impeller shall
be stamped with identification marks. Provide necessary facilities and
instruments needed to permit Government to verify that pump[s]
[is][are] in complete geometric similarity with the tested pump.
2.5.3.6
Cavitation Tests
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NOTE: Alternate 2.
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a.
Model Test - The model test shall include the determination of net
positive suction head required (NPSHR) at five or more points on
[the constant speed curve][each constant speed curve when more
than one speed is involved]. NPSHR shall, as a minimum, be
determined for five or more capacities corresponding to prototype
capacities over the total range of specified operating conditions.
If the pump has a capacity greater than that specified for the
lowest and/or highest operating condition, then these
over-capacity conditions shall be used. The other test capacity
points shall be equally spaced between the highest and lowest
capacities.
b.
NPSHR - NPSHR shall be determined on a constant-capacity,
constant-speed basis, using arrangement Figure 2.62 or 2.63 as
described under paragraph "Net Positive Suction Head Required
Test" in HI 2.6. Suction conditions shall be varied to produce
cavitation. NPSHR shall be the maximum value at which any one or
all of the plotted curves, head, kilowatt horsepower, and
efficiency depart from the constant values (point of tangency). A
sufficient number of points to accurately locate the departure
point shall be obtained.
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NOTE: The amount head margin used to determine
adequacy of NPSHR is determined during the design of
the pumping station as indicated in Engineering
SECTION 15131A
Page 45
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