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1. Diaphragm Meters

1. Diaphragm Meters. Principles of Operation. 1. Diaphragm Meters. 1. Diaphragm Meters. Residential Meters AC-175 AM-250 AT-210/250 AC-250 AT-350 AL-425. 1. Diaphragm Meters. 1. Diaphragm Meters. B109.2 (Over 500 CFH) Flow Rates for each Class (CFH) Class Minimum Maximum

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1. Diaphragm Meters

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  1. 1. Diaphragm Meters • Principles of Operation

  2. 1. Diaphragm Meters

  3. 1. Diaphragm Meters • Residential Meters • AC-175 • AM-250 • AT-210/250 • AC-250 • AT-350 • AL-425

  4. 1. Diaphragm Meters

  5. 1. Diaphragm Meters • B109.2 (Over 500 CFH) • Flow Rates for each Class (CFH) • Class Minimum Maximum • 500 500 899 • 900 900 1399 • 1400 1400 2299 • 2300 2300 3499 • 3500 3500 5599

  6. 1. Diaphragm Meters • Commercial • AC-630 • AL-800 • AL-1000

  7. 1. Diaphragm Meters • Industrial • AL-1400 • AL-2300 • AL-5000

  8. 1. Diaphragm Meters

  9. 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.

  10. 1. Diaphragm Meters • Capacity of diaphragm meter at elevated pressure Qr = Qi x {( Pg + Pa ) / Pb } 3/4

  11. 1. Diaphragm Meters • Qr = Qi x {( Pg + Pa ) / Pb } 3/4 • Where: • Qr = Rated Capacity at elevated pressures • Qi = Rated Capacity at 0.25 psig • Pg = Gage Pressure • Pa = Atmospheric Pressure • Pb = Base Pressure

  12. 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?

  13. 1. Diaphragm Meters Capacity at Elevated Pressure Qr = Qi x {(PG+Pa)/Pb}3/4 Qr = 3000x {(15+14.4)/14.73}3/4 =5000 SCFH

  14. 1. Diaphragm Meters

  15. 1. Diaphragm Meters • Size of diaphragm meter operating at elevated pressure needed for a load. • Qi = Qr / {(PG+Pa)/Pb}3/4 • Where: • Qi = Rated Capacity at 0.25 psig • Qr = Load in SCFH • PG = Gage Pressure • Pa = Atmospheric Pressure • Pb = Base Pressure

  16. 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?

  17. 1. Diaphragm Meter • Meter Sizing Based on Load • Solution • Qi = Qr / {(PG+Pa)/Pb}3/4 = 3500/{(15+14.4)/14.73} 3/4 = 3500/ {1.9959} 3/4 = 3500/1.679 = 2084 CFH • Use an AL-2300

  18. 1. Diaphragm Meter

  19. 1. Diaphragm Meter

  20. 1. Diaphragm Meter • Options • Pressure Compensating Index

  21. 1. Diaphragm Meter • Options • Temperature Compensation

  22. 1. Diaphragm Meter • Options • AMR (Automatic Meter Reading) Compatible

  23. 1. Diaphragm Meters • Accuracy

  24. 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

  25. 1. Diaphragm Meters • 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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