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Mike Duffy, Professional Electrical Engineer for Tacoma Water, invited us to tour one of the city’s reservoirs to learn more about their infrastructure issues and to hear how Seametrics meters and controllers are meeting specific needs. The Tacoma water system includes a network of mountain watersheds and reservoirs, pumped well water, chlorine treatment and monitoring, city reservoirs and distribution channels, and on-site hydroelectric generation. Historically, Tacoma Water has measured flow at various points in the system using a combination of full bore magmeters and Seametrics TX insertion turbine meters.

 

Mike installed a Seametrics EX215 stainless hot-tap insertion magmeter with bidirectional sensor in a 42” pipe supplying water to the hydrogenerator. The meter is housed in an underground vault, and the sensor measures forward flow to the generator and reverse flow when, with changing system demands, booster pumps send water out to other distribution zones. This meter replaced a competitor’s aging full bore magmeter. When asked why he chose the Seametrics meter over replacement with the full bore, Mike said, “It’s very simple. Cost.” Not only is the EX215 itself far less expensive than his other alternatives, but the hot-tap installation saves significant excavation and downtime costs. Added to cost considerations is the convenience of wall-mounting the FT420 display in a nearby building (as compared to meter-mounting the display underground, as was the only option with the competitor’s meter).

 

When asked, “Why a magmeter?”, Mike’s emphatic answer was “No moving parts”. Though the possibility is remote, a mechanical meter failure that might result in plastic parts breaking free and traveling down the supply line to the generator would have catastrophic results. The magmeter avoids this problem entirely.

 

Mike likes the low maintenance, improved accuracy, and simple installation of the EX hot-tap meter so well that he and the city’s Principal Electrical Engineer maintain a stock of these meters and the corresponding FT420 and FT520 displays for retrofit projects and new pump station applications as they arise. They have also developed applications where the flow signal is fed directly into a PLC, cutting the cost of the display.