Table 14 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.18 Direct Actuator, 3 to 15 psi Spring Allowable Pressure Drops (PSI) Air Leakage Supply Trim Size Class Pressure 1" 1.5" 2" 3" 4" 6” 8” 18 18 18 20 20 20 22 22 22 24 24 24 27 27 27 30 30 30 33 33 33 36 36 36
II IV & VI V II IV & VI V II IV & VI V II IV & VI V II IV & VI V II IV & VI V II IV & VI V II IV & VI V
1,103 924 56 1,896 1,717 911 2,689 2,510 1,704 3,482 3,303 2,497 4,671 4,492 3,686 5,861 5,681 4,876 7,050 6,871 6,065 7,843 7,664 6,858
998 749
949 654
865 481
679 230
311
175
1,752 1,502 381 2,505 2,256 1,134 3,259 3,009 1,887 4,389 4,140 3,018 5,519 5,270 4,148 6,649 6,400 5,278 7,403 7,153 6,031
1,688 1,393
1,584 1,201
1,301 859
671 283
455 24
2,427 2,132 804 3,166 2,871 1,543 4,275 3,980 2,652 5,384 5,089 3,761 6,492 6,197 4,870 7,232 6,937 5,609
2,304 1,920 171 3,023 2,639 914 4,102 3,719 1,993 5,181 4,798 3,072 6,260 5,877 4,151 6,980 6,596 4,871
1,922 1,481
1,031 643
735 323
2,544 2,103 79 3,477 3,036 1,050 4,410 3,969 1,983 5,343 4,902 2,916 5,965 5,524 3,538
1,391 1,003
1,015 603
1,930 1,542
1,435 1,023
2,470 2,082 336 3,010 2,622 876 3,369 2,982 1,236
1,854 1,443 2,274 1,862 2,554 2,142 290
Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column.
ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.18 Reverse Actuator Allowable Pressure Drops (PSI) Initial Leakage Air Trim Size Class Pressure 1" 1.5" 2" 3" 4" 6” 8” 3 3 3 6 6 6 9 9 9 12 12 12
II IV & VI V II IV & VI V II IV & VI V II IV & VI V
1,103 924 56 2,292 2,113 1,307 3,482 3,303 2,497 4,671 4,492 3,686
998 749
949 654
865 481
679 230
311
175
2,129 1,879 757 3,259 3,009 1,887 4,389 4,140 3,018
2,057 1,762 435 3,166 2,871 1,543 4,275 3,980 2,652
1,944 1,560
1,611 1,170
851 463
595 183
3,023 2,639 914 4,102 3,719 1,993
2,544 2,103 79 3,477 3,036 1,050
1,391 1,003
1,015 603
1,930 1,542
1,435 1,023
The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 315 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures.
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10/10/2008