Author
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Replogle, John |
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Wahlin, Brian |
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Submitted to: American Society of Civil Engineers Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/11/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Irrigation wells and drainage pumps are widely used to lift water into canal systems. These wells usually spill directly into the canal as a free outfall. Effective irrigation water management would be enhanced if these wells were measured economically, but many conditions can arise that make this task difficult. For example, the pipes sometimes do not flow full, which most metering systems require, or the pipe is old and rusted with a jagged end, limiting the use of many end-attachment meters. The well pump itself, or the pipe bends upstream in the pipe frequently produce a distorted flow profile that is detrimental to the proper installation and operation of common meters that fit into the pipe. Laboratory and field tests of a Pitot-static tube system for measuring velocity profiles near the discharge outlet of pump systems are presented. The device can be constructed using common shop techniques and standard small pipe fittings. It is portable and disassembles to fit into a standard business brief case Its application is relatively straightforward and does not require drilling holes in the well pipe. It provides irrigation district technicians a convenient and needed tool for evaluating existing meter installations and for measuring discharges from previously unmeasured wells. Technical Abstract: Pumps are widely used to lift water into canal systems. These usually spill directly into the canal as a free outfall. Upstream elbows or other pipe fittings frequently produce a distorted flow profile that is detrimental to the proper installation and operation of commonly available pipe meters. When less than recommended pipe lengths exist upstream of the emetering device, an economical method of field-evaluating the result of an installed meter in this compromised situation is needed. A conveniently fashioned pitot-tube system that can be clamped to the pump discharge pipe was built and tested. It is used to detect quickly the velocity at several points across the pipe diameter. Distorted profiles can be measured. Using this information, the meter technician can determine whether a correction in the meter coefficient will suffice; or if flow conditioning equipment is needed; or whether flow conditioning equipment, if already installed, is working effectively. The Pitot impact tube, with its static pressure companion tube, can be constructed using common shop techniques and standard small pipe fittings. Previous Pitot tube systems have long been used in pipe flows. Most require that special pipe ports be drilled and threaded. Some use special double-tube constructions that are difficult to build using simple machine shop procedures. |
