The Irrigation Training & Research Center (ITRC) of Cal Poly San Luis Obispo tested 28 different pressure-compensating models of microirrigation emitting devices from a total of nine manufacturers in order to compare independent laboratory testing with manufacturer specifications.
The test results indicate that:
The majority of ~0.5 gallon-per-hour emitters (drippers), regardless of manufacturer exhibited:
Good uniformity of manufacturer
Had excellent response to pressure variation
Had consistent flow rates within the nominal operating pressure range
But that the percentage of well-performing products decreased as the designed flow rate increased. Many of the emitters designated as microsprinklers or sprayers, although pressure compensating did not compensate at the normal operating pressures. Often the pressure compensating feature did not start performing until much higher pressures were achieved. Often this occurred when clogging occurred and this clogging often occurred where the pressure diaphragm was located and was not performing. Sediment would get in back of the diaphragm. Effectively the emitters were not pressure compensating. The testing procedure of numerous medium and high flow models also found individual pieces were found to be defective. These faulty emitters had a measurable effect on the evaluation for those models.
Read more at: http://www.itrc.org/reports/pdf/emitters.pdf
Sand media filters are commonly used in agricultural microirrigation systems. They have the advantages of simplicity and large capacities and are favored by many farmers and designers over other filtration hardware when there is a lot of organic matter in the water. The Irrigation Training and Research Center (ITRC) at Cal Poly San Luis looked at sand filters to see if it were possible to use lower-than-accepted backflush pressure and thereby reduce the total pressure required for irrigation systems. By lowering backflush pressure it would be possible to design a system that could run at an overall lower pressure and hence cost. The various components of microirrigation systems run at lower pressures than the backflush pressures recommended for most sand media filters.
The conclusions are:
There are substantial pressure differences amongst different models and designs during backflush and filtration
The main pressure loss is at the backflush valves
If designed right large backflush flow rates can be accomplished at low backflush pressures (this is critical for proper detritus removal).
There are substantial differences among underdrains of various models which affects pressure requirements
No large intimal high pressure was necessary to break up the media bed, a common practice.
Different underdrain designs create different patterns of cleaning the media.
There were substantial differences among models in the amount of sand discharged from the system at backflow rate of 190 GPM. Sand discharge should actually be avoided since it's an indication of preferential flow and poor cleaning.
These are some new ideas, and even though they are meant to reduce pressure and energy use, they are also good management suggestions.
If this strikes your fancy, read more at http://www.itrc.org/reports/mediafilters.htm
A microirrigaiton workshop on use and maintainence of systems in Spanish is being held on three successive dates in San Luis Obispo, Ventura and Fallbrook. These are the same workshop held on July 23, 24 and 25 in the respective areas. The workshops are intended for Spanish speaking workers who maintain and use microirrigation systems. The classes are free and no registration is required. These and future workshops are funded by USDA. For more information contact Lesa Scarborough at:
Click on the flyer below for more details