# 1. Diaphragm Meters n Principles of Operation. 1. Diaphragm Meters.

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1. Diaphragm Meters n Principles of Operation

1. Diaphragm Meters

n Residential Meters –AC-175 –AM-250 –AT-210/250 –AC-250 –AT-350 –AL-425

1. Diaphragm Meters

n B109.2 (Over 500 CFH) n Flow Rates for each Class (CFH) –ClassMinimumMaximum » 500 500 899 » 900 9001399 »1400 14002299 »2300 23003499 »3500 35005599

1. Diaphragm Meters n Commercial –AC-630 –AL-800 –AL-1000

1. Diaphragm Meters n Industrial –AL-1400 –AL-2300 –AL-5000

1. Diaphragm Meters

Capacity at Elevated Pressure Diaphragm meter capacities at elevated pressures must be de-rated to limit differential pressure to a maximum of 8” w.c. This practice of limiting differential pressure extends service life of valves and diaphragms.

1. Diaphragm Meters n Capacity of diaphragm meter at elevated pressure Q r = Q i x {( P g + P a ) / P b } 3/4

1. Diaphragm Meters n Q r = Q i x {( P g + P a ) / P b } 3/4 n Where: –Q r = Rated Capacity at elevated pressures –Q i = Rated Capacity at 0.25 psig –P g = Gage Pressure –P a = Atmospheric Pressure –P b = Base Pressure

1. Diaphragm Meters Capacity at Elevated Pressure Example: What is the capacity of an AL-1400 diaphragm meter rated at 3000 SCFH at a 2” w.c. differential pressure when it is operating at 15 PSIG, an atmospheric pressure of 14.4 PSIA, and a base pressure of 14.73?

1. Diaphragm Meters Capacity at Elevated Pressure Q r = Q i x {(P G +P a )/P b } 3/4 Q r = 3000 x {(15+14.4)/14.73} 3/4 = 5000 SCFH

1. Diaphragm Meters

Size of diaphragm meter operating at elevated pressure needed for a load. Q i = Q r / {(P G +P a )/P b } 3/4 Where: Q i = Rated Capacity at 0.25 psig Q r = Load in SCFH P G = Gage Pressure P a = Atmospheric Pressure P b = Base Pressure

1. Diaphragm Meters Meter Sizing Based on Load Example: Connected load = 3,500 scfh Meter pressure = 15 psig Atmospheric pressure = 14.4 psia Base pressure = 14.73 psia What size meter should be used?

1. Diaphragm Meter Meter Sizing Based on Load Solution Q i = Q r / {(P G +P a )/P b } 3/4 = 3500/{(15+14.4)/14.73} 3/4 = 3500/ {1.9959} 3/4 = 3500/1.679 = 2084 CFH Use an AL-2300

1. Diaphragm Meter

n Options –Pressure Compensating Index

1. Diaphragm Meter n Options –Temperature Compensation

1. Diaphragm Meter n Options –AMR (Automatic Meter Reading) Compatible

1. Diaphragm Meters n Accuracy

1. Diaphragm Meters n Installation –Ship, store, and install in upright position –Keep dirt and water out –Level + 1/4” –No undue stress –Do not bury –Filter may be needed –Protect from damage –Hand tighten swivels first –Check for leaks –Slowly pressurize –Need for by-pass? –Cathodic Protection considerations

1. Diaphragm Meters n Factors that affect Accuracy –Internal friction that increases differential –Maintaining constant diaphragm displacement over a range of operating conditions –External leaks –Internal leaks –Wear

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