Product Overview | 1008A Valve
GENERAL INFORMATION Adjustable Port Valves are ideal for automatic control of fuel or air flow to meet the requirements of modern instrumentation in combustion systems. The adjustable port feature permits sizing the valve to fit the application, after valve has been installed. Linkages can be adjusted for full or limited valve travel.
Recommended procedure is to open valve control handle and valve curtain wide, then close curtain until pressure drop across valve is 1⁄5 to 1⁄6 of total system pressure drop. Flow characteristics shown as solid lines in Figure B can be realized with full valve stroke, enabling desired flow response to movements of the control motor.
CORRECT VALVE SIZING Made Easy
Linkage between motor and valve can be "characterized" to produce the desired flow curve, e.g., linear or equal percentage.
Curtain ½ open Core full open Curtain ¾ open Core rotated ½ Figure A. Turning curtain adjusting knob changes port opening so valve can constitute optimum resistance in the system for good control. Curtain ¾ open Core rotated ¼ For a valve operated by a modulating type control, either a linear or an equal percentage characteristic is preferred for most applications. These characteristics are shown in Figure B, together with two curves indicating very common but usually undesirable flow patterns: In their lower parts, change of flow is too fast, causing an "over correction;" while at the upper end there is practically no flow change in response to valve movements. Shape of a flow curve depends (1) on valve area characteristic , and (2) on size of valve port relative to downstream resistances (piping, orifices, and burners), the sum of which is difficult to predict. An Adjustable Port Valve solves the problem. Its linear area characteristic permits proper "sizing" of valve after installation without involved calculations.
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Figure B. Flow characteristics of valves installed in systems with downstream resistance. The three solid linesrepresent characterizable adjustable port valves.
1008A 1010A
Pipe Size ( 3⁄8 ") ( ½ ") ( ¾ ")
Cv Valve Coe ffi cient
-02 -01
2.0 2.0 7.9
-0 -1 -2 -3 -4 -5 -6 -7 -8
Number of turns from full open to fully closed
Valve Size
(1")
12.5 19.7
(1 ¼ ") (1 ½ ")
3⁄8 " and ½"
11
28 49 71
¾ "
14 16
(2")
1"
(2 ½ ")
(3") (4") (6")
111 191 433
1¼" and 1½"
23 30 35 43 60 87
2"
2 ½ "
3" 4" 6v
Bulletin 1008A/1010A Page 2
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