Special Operating Conditions | Metering Orifice
IF LIMITED PRESSURE IS AVAILABLE If 31/2"w.c. cannot be spared for metering, larger orifice plates can be selected to take less pressure drop. (See charts on page 5 and 6).
Part of the pressure drop across an orifice may be recovered. Net recovery, in % of the drop, varies from about 15% for the small- est orifice for any pipe size to about 33% for the largest orifice .
Chart 1. Temperature Correction Factor
Chart 2. Pressure Correction Factor
1.1
2.2
1
2
0.9
1.8
0.8
1.6
0.7
1.4
0.6
1.2
0.5
1
0
200
400
600
800
1000
1200
0
5 10 15 20 25 30 35 40 45 50 Pressure, psig
Temperature, F
ALTITUDE CORRECTION FACTOR FOR AIR OR GAS
Altitude
Altitude
feet 1500 2000 2500 3000 3500 4000 4500
meters
Factor = √ G
feet
meters
Factor = √ G
457.2 609.6 762.0 914.4
0.983 0.975 0.965 0.958 0.947 0.939 0.932
5000 5500 6000 6500 7000 7500 8000
1524 1676 1829 1981 2133 2286 2438
0.921 0.913 0.905 0.898 0.886 0.878 0.870
1067 1219 1372
Bulletin 8694A Page 11
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