MODEL MFM II FIRE LINE AND MASTER DETECTOR METERS

APPLICATIONS: The Hersey Model MFMII ® was designed for use as a combined fire and domestic service meter where one water line serves both fire and domestic, or process needs. Also as a master meter for an entire water system; for water system zones; automatic sprinkler systems and fire services; for domestic or process water systems where low pressure loss and dependable accuracy over a very wide flow range are essential. Hersey MFM II Water Meters will measure accurately at full pipe capacity, and have the highest flow capability available.

CONSTRUCTION: Hersey MFM II Water Meters consist of a mainline meter to measure high flow rates, a bypass meter to measure the lower flow rates, and a weight and lever valve (mainline valve) to automatically control the point at which the larger mainline meter registers. The valve is self-aligning and self-adjusting. The bypass includes a resilient seated isolation valve, a swing check valve, and depending upon the bypass meter, either a Hersey MCT II ™ Compound Meter, Hersey Model MVR ™ Meter or Hersey Horizon ™ Meter. The mainline meter maincase is cast iron with epoxy coating inside and out.

The MFMII is designed with an unobstructed full flow that eliminates the need for an external strainer. An internal strainer protects each measuring element.

REGISTERS: Separate mainline and bypass registers are provided. Permanently sealed registers use proven magnetic drive design and the exclusive Hersey triple seal to provide clarity and error free meter reading. Internal gears in all assemblies are self-lubricating, molded plastic for long life and minimum friction. The standard registers include a straight reading, odometer- type, totalization display, a 360 degree test circle with center sweep hand, and a low flow indicator. The Calibrator Gear Train permits accuracy calibration on MFMII mainlines and MCTII bypasses. For accuracy calibration on MVR and Horizon bypasses, consult the appropriate meter sections. All Hersey models are available with electronic meter reading systems for increased meter reading efficiency. ( See Automatic Meter Reading Equipment )

OPERATION: In normal operation, during low flow rates all water flows through the bypass section and is registered by a sensitive model MCT II compound, model MVR vertical turbine meter or a Hersey Horizon Meter (see separate data pages for description of these meters). When pressure loss through the bypass section approaches 4 psi, the mainline lever valve automatically opens permitting the torrent proportional mainline meter to measure flow. When flow rate decreases sufficiently, the mainline lever valve closes, and all lower flows are again measured by the bypass meter.

The exclusive automatic lever valve is controlled by a specially designed weight which locks the valve in the closed position until a predetermined pressure loss overcomes the weight and opens the valve. A venturi effect causes a precise portion of the total volume to pass through the torrent proportional mainline meter. The self-aligning rubber-faced valve clapper assures a positive seal for accurate bypass meter registration.

MAINTENANCE: The Hersey MFM II and bypass meters are designed and manufactured to provide long service life with low maintenance. All parts are accessible for in-line service if needed.

CONNECTIONS: ANSI class 125 flanges standard.

Model Designation
MFM II

Sizes
3"*, 4", 6", 8", 10", 12"

Standards
Manufactured and tested to meet or exceed all applicable parts of AWWA C703, FM approved mainline; UL listed, ULC classified.

Installation
Horizontal only with 8x pipe diameter of straight pipe (same size as meter) on inlet side of meter.

Operating Flow Range
See Catalog PDF below

Accuracy
See Catalog PDF below

Maximum Working Pressure
175 PSI

Temperature Range
33F to 100F

Measuring Elements
Mainline = Torrent wheel. Bypass: MCT II = Torrent Wheel and Nutating Disc. MVR = Rotor. Horizon = Rotor

Register Type
Permanently sealed, straight reading, magnetic drive with low flow indicator. Remote reading units optional.

Meter Connections

ANSI class 125 standard end flanges.

Materials
Maincase - epoxy-coated cast iron; Bypass meter case - bronze UNSC84400; valve weight, swing arm and seats - bronze UNSC84400; Valve discs - elastomer; Casing bolts - steel

Options
AMR Reading Systems.
* 3" size is MFM design, not MFM II.  


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