Doppler Flowmeter Helps Measure Flow of the Rio Grande

Delta Lake Irrigation District is one of the oldest pumping stations located on the Rio Grande River, just south of Weslaco, Texas. Established in 1940 to provide water for agricultural irrigation and municipal needs, this station was state-of-the-art with its Fairbanks Morse 55 in. pumps and piston engines.

At this time, the Rio Grande Valley area was very sparsely populated and water for any need was abundant. The only provision for measurement back then was a rectangular concrete gate marked in feet and inches - located downstream about 100 yards from the discharge.

Rapid growth in the past 20 years has brought about a greater demand for water and a new attitude toward conservation and measurement of these precious natural resources.

It gradually became evident that such a simple thing as river or canal water was extremely difficult to measure. The engineers of the COMPU-FLOW Doppler ultrasonic flowmeter by Teksco USA had developed a new unit to better deal with these environments and provide all the necessary engineering units that would be required. The clamp-on sensors worked well, as long as the pipe wall was smooth and parallel. However, when the pipe material became old, cracked, or rusted, it was virtually impossible to obtain repeatable data.

After an unsuccessful attempt at measuring river water in 55-in. steel lines with clamp-on sensors, Teksco engineers drilled into the pipe to examine the conditions. Visual inspection revealed rust pits 1/2-in. deep and flakes of corrosion banding half the circumference. This was almost as bad a conductor of sound as concrete. They then designed a very universal set of wetted stainless steel sensors that mounted directly into the pipe wall. They found the wetted sensors would work in an unlimited number of harsh problem environments from canals to sewer plants. Repeatable readings were now the norm regardless of the pipe material.

The next hurdle was to address the ever-changing consistency of the river water and its contaminants. These often consisted of hydrilla, moss, sand, algae, fish, plastic bottles, tractor tires, palm tree trunks, and even a 55-gallon steel barrel. Particle count would change daily due to rainfall or rate of release from the reservoir. The pH also varied greatly depending upon the tidal backflows or the amount of toxins industry dumped into the river upstream. Without the wetted transducer and the new CLT-V4 circuitry with automatic gain control, it would have been nearly impossible to obtain consistent data.

Delta Lake Irrigation District has had its Doppler system in place since 1990. The system has no moving parts and is virtually maintenance-free. There are four of the flowmeters in a row, and the transducers are located about 300 ft. from the displays.

The plant operator tells Teksco that he can almost tell what size of object is in the pump by watching the display. The wetted sensors track so well that the plant operator just one-quarter mile up the river, where ten of the COMPU-FLOW systems have been in place for more than six years, is able to detect when one of the natural gas pumps is off pace by glancing at his display.

Teksco USA, Combes, TX

Phone 800-649-5331

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