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APPLICATIONS: The Hersey® Meters FM³ fire service meter is designed for combined fire service and domestic water where a single supply line supports both fire and domestic or process needs. The meter may be utilized in automatic sprinkler systems and fire service, as a master meter for an entire water system, as a master meter for zoned systems, and for domestic or processed water where accuracy across a broad range of flows is critical. The FM³ meter eliminates the need for secondary service lines, saving time and reducing installation expenses and is compliant for FM® fire service meter applications.
CONSTRUCTION: Every Hersey FM³ meter is manufactured with epoxy coated ductile iron construction which eliminates additional gaskets and fasteners, reducing ongoing maintenance costs. The unique, Hersey strainer design protects the horizontal turbine meter measuring element in a unibody construction that reduces meter vault and installation costs due to its compact size and reduced weight while providing four times the inlet pipe diameter of strainer surface area. The unitized horizontal turbine measuring element is easily accessed through the top case of the meter and o-ring seals simplify field service. A Hersey EDCIV™ detector check provides proven backflow protection with a spring loaded clapper assembly that is mounted to the top case of the check valve for ease of service. Bypasses consist of an appropriately sized positive displacement or residential fire line meter for low flow accuracy. Dual ball valves permit isolation of the meter and a swing check prevents backflow through the bypass. Stainless steel and bronze fasteners are used throughout the meter where required.
REGISTER: Separate mainline and bypass registers provide visibility of performance and field testing opportunity. The permanently sealed registers use proven magnetic drive design and the exclusive Hersey triple seal provides clarity and error free meter reading. Internal gears are self lubricating, molded plastic for minimal friction and a long service life. Standard visual read and electronic Translator® registers offer odometer wheels with a totalizing display, 360° degree test circle with center sweep hand and a low flow indicator. All Hersey FM³ models are available with electronic meter reading system components to meet any utility AMR/AMI requirement and all registers are protected by the unique Hersey locking pin which requires no special removal tools for field service.
OPERATION: During normal low flow operation, all water flows through the sensitive bypass meter for accurate registration. As flow and pressure loss through the bypass increases, the mainline clapper assembly automatically opens, permitting water to flow through the horizontal turbine measuring element and the bypass meter for accurate combined registration of all flows. The element employs Hersey’s unique Retro-Thrust® feature to divide wear across multiple points, increasing accuracy, reducing friction and extending the life of the measuring element. Integral flow straightening vanes on the inlet and outlet sides of the measuring element contribute to the long term accuracy of the meter. As flow and pressure loss through the bypass meter decrease, the clapper assembly once again closes, redirecting all water through the bypass. Higher demand instances include master meter supply applications and fire suppression requirements.
INSTALLATION: Hersey FM³ meters are designed for horizontal installation with a minimum of five times the inlet pipe diameter of straight pipe prior to the meter and a minimum of three times the pipe diameter after the meter.
MAINTENANCE: All service components for the FM³ are unitized for easy replacement. Access to components is accomplished through the top side of the meter for full in-line service. Drop In Measuring Elements (DIMES) are available in pre-tested configurations which include a new measuring element, top case, register and o-ring for utilities that require quick field replacement. A calibration vane permits field adjustments to ensure accurate registration and extend the service life of the measuring element. The calibration vane is protected by the register and the locking pin for added security. For additional information regarding Hersey’s unitized replacement options, please contact the Hersey Meters Sales and Technical Support Group at 800-323-8584.
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