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Field reports of problems with irrigation systems have led to a
new testing protocol being developed at the Center for Irrigation
Technology (CIT).
"Recent field experience has noted
serious deterioration in micro-jet performance when particulate matter
is present in the water," explained Ed Norum, special projects engineer
for CIT. "Micro-jets designed to give 5-10 years of satisfactory field
performance have failed in several months under adverse conditions,"
he said.
In the wake of these problems, CIT was asked by a
micro-jet vendor to develop a test jig and protocol to provide
accelerated testing of various designs and materials. The goal is to
improve the tolerance of micro-jets to the problem of particles in the
water.
Norum directed design and construction of a test jig
capable of circulating aluminum oxide grits through a manifold on
which micro-jets were mounted. Aluminum oxide was selected because
of its inherent hardness and the sharp rugged shape.
Grit
designations varying in size from No. 10 (0.0937 in.) to No. 100 (0.0059
in.) are being used in initial system tests. Water pressure and particle
concentrations have been set to achieve erosion of micro-jet material in
a relatively short time.
Results of initial testing have been
characterized primarily by surface changes in the contour of the splash
plates of several different micro-jet sprayers, explained Norum. Short of
catastrophic failure, these changes suggest only a deterioration in
pattern performance, with changes difficult to quantify.
The formal testing procedure still has not been finalized.
Norum said another abrasive material may be tried to see if its erosive
power is greater than that of aluminum oxide.
The
problem of micro-jet deterioration is further complicated by a general
lack of understanding of the importance of uniformity of application
under such systems, said Norum. Nevertheless, equipment performance
under adverse conditions is of critical importance to manufacturers.
As an independent testing agency, CIT works closely
with irrigation equipment manufacturers from California and across the
globe in testing all types of irrigation products. In the case of the micro-
jet testing, "the procedure is of importance to product engineers
interested in understanding the degree of forgiveness inherent in their
designs," Norum said.
For more information on this
project, Norum may be contacted through CIT at (209) 278-2066.
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