Satellite-based data, control depend on reliable flowmeters

Securing flowmeter data and controlling valves and pumps via satellite is better than doing so by driving trucks through the Arizona desert. However, if this information isn’t based on accurate, reliable flowmeter performance, users may end up on the road again, doing repairs instead of monitoring and adjusting.

Dependable flowmetering was crucial when Salt River Project (SRP, Phoenix, Ariz.) switched its numerous water transmission sites from a manual to a satellite-based data communications system three years ago. One of the Southwest’s largest water and power utilities, SRP delivers nearly 1 million acre/ft of water annually to a 240,000-acre service area in Phoenix. SRP cooperatively manages a 13,000-mi

Dependable data delivery

To preserve network accuracy, SRP’s satellite-based data system is founded on flowmeters at 30 application sites throughout the utility’s jurisdiction. These include 10 propeller meters from Water Specialties (Porterville, Calif.), connected to deep-well pumps in the desert and to some city-based constituent pumps.

‘We need highly reliable water flowmeters with our satellite monitoring system,’ says Lee Ester, SRP’s field services manager. ‘If we can’t rely on flowmeters to provide data, then there’s no reason to be tied into a sophisticated satellite system.’

Flowmeter information is handled by Spatia, a data processing package SRP helped develop. Spatia includes a bundled network of earth-to-satellite-to-earth communications and back-end data support functions.

Designated flow-rate data is displayed via LCDs, while built-in indicator-totalizers connect to transmitting units that send Spatia’s proprietary signals to one of a series of 28 low-earth orbit (LEO) satellites supported by OrbComm (Reston, Va.). Spatia’s communicator-data logger consists of a fiberglass-enclosed VHF radio powered by a 12-V solar array backed up by a 7-A-hour battery. This communicator-logger needs only 5 W to reach the LEO satellites because they orbit at only 500 mi.

SRP-related messages are rebounded to one of OrbComm’s four ground-based earth stations; routed through OrbComm’s network control center in Virginia; and encapsulated and delivered via frame-relayed format to clients, such as SRP. The entire roundtrip usually takes two minutes or less. SRP collects its information from the Spatia Data Center’s web site, and then configures it into graphs, tables, or text on water use, flow, storage volume, and quality.

Using this web site, SRP can even control equipment at remote field locations. For example, SRP can send a Spatia-encoded e-mail back through Virginia and one of the satellites to a designated earth station. The message is then forwarded via a twisted-pair cable to a programmable logic controller on SRP’s transmission line, which can instruct specific equipment to open and close valves or perform other operations.

‘There’s a definite dollar savings over operating a supervisory control and data acquisition system using cell phone coverage or fixed-wire modems for sending and receiving data,’ says Mr. Ester. ‘However, the real value of the new system is almost immediate access to data because all our back office functions are now performed in real time.’ Mr. Ester adds SRP will eventually use the immediate reporting capabilities of its satellite-based system to monitor river, watersheds, and other recharge basins, which it helps maintain through intergovernmental cooperative agreements with many other local agencies and companies.

For more information, visit www.controleng.com/freeinfo .

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