Capacities | Valve
CAPACITIES scfh air with curtain and valve wide open
Graph 1.
Valves are designed for control of combustion air at line pres- sures up to 3 psi. Due to their non-airtight nature, they are not for tight shutoff and cannot be used for fuel gases. This is because they just have a metal to metal sealing surface on the shaft. See Bulletin 1008A for adjustable port valves designed for fuel gas use.
C v cœfficients 4272
700 000 600 000 500 000 400 000 300 000 200 000 150 000 100 000 80 000 60 000 50 000 40 000 30 000
Maximum air temperatures: 1004 (formerly Fig. 4).......................300°F 1014 (formerly Fig. 14) ......................900°F Minimum ambient temperature ............-20°F
1677
Adjustable Port Valve flow characteristics can be set in the field after valve has been installed in the pipe. This is desirable to achieve linear, equal percentage, or other control characteristic. VALVE SELECTION Use North American's COMBUSTION HANDBOOK, or other source to determine the pipe size for the required flowing volume, piping configuration and allowable pressure loss. Table A lists available valve/body sizes for selected pipe size. Graph 1 is used to determine pressure drop when valve is wide open. As long as valve body is large enough, its curtain can be adjusted for optimum drop under field conditions. Valve sizes 1 1 ⁄ 2 " through 8" are provided with threaded adapter flanges while optional 8" and 10" through 14" have welding adapters. PREHEATED AIR When using 1004 (300°F maximum) or 1014 (900°F maximum) Valves with hot air, multiply scfh by Table B correction factor and use resultant figure for valve sizing from Graph 1. Table A. Pipe Size Valve/Body Sizes 1½" -3-B 2" -4-B, -4-C 2½" -5-C 3" -6-C, -6-D
585
355
122
20 000 15 000
77
10 000 8 000 6 000 5 000 4 000 3 000
2 000
0.4 .5 .6 .8 1.0 1.5 2
3 4 5 6 8 10
pressure drop, osi
Temp. (F) 300 400 500 600 700 800 900 Factor 1.21 1.29 1.36 1.43 1.49 1.56 1.62 Table B. Air temperature correction factors
Example: Select Adjustable Port Valve for application requiring 3,000,0000 Btu/h HHV input using 600°F air, with available hot air pressure 10 osi or more: 3,000,000 Btu/h HHV requires 30,000* scfh air. 600°F factor is 1.43: 30,000 × 1.43 = 42,900 (equivalent 60°F air). Graph 1 indicates an E body would have a 1.5 osi pressure drop or a D body a 4 osi pressure drop. Usual selection would be an E body which is available in only a 6" pipe size. *Excess air requires an additional multiplier (1.1 for 10% XSAir).
4" 6" 8"
-7-D
-8-D, -8-E -9-F, -9-FW
10"* 12"* 14"*
-10-FW, -10-GW
-12-GW -14-GW
* Size "G" has been discontinued.
Bulletin 1004/1014 Page 3
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