Bulletin 1008A/1010A
Page 2
CORRECT VALVE SIZING
Made Easy
Curtain ½ open
Core full open
Curtain ¾
open
Core rotated ¼
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.
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
fl ow patterns: In their lower parts, change of fl ow is too fast,
causing an "over correction;" while at the upper end there is
practically no fl ow change in response to valve movements.
Shape of a fl ow curve depends (1) on valve
area characteristic
,
and (2) on size of valve port relative to downstream resistances
(piping, orifi ces, and burners), the sum of which is diffi
cult to
predict.
An Adjustable Port Valve solves the problem. Its linear area
characteristic permits proper "sizing" of valve
aft er installation
without involved calculations.
Figure B.
Flow characteristics of valves installed in systems with downstream
resistance. The three solid linesrepresent characterizable adjustable port valves.
0
20
40
60
80
100
Valve position, % of rated travel
100
80
60
40
20
0
Flow rate, % of rated capacity
Fixed
port valve
Quick
opening
Linear
Adjustable Port
valves can be
characterized to
a variety of curves
to match system
requirements.
Product Overview | 1008A Valve
GENERAL INFORMATION
Adjustable Port Valves are ideal for automatic control of fuel or
air fl ow to meet the requirements of modern instrumentation in
combustion systems. The adjustable port feature permits sizing
the valve to fi t the application, aft er valve has been installed.
Linkages can be adjusted for full or limited valve travel.
Number of turns from full
open to fully closed
3⁄8
" and ½ "
11
¾
"
14
1" 16
1¼ " and 1½ "
23
2" 30
2½ "
35
3" 43
4" 60
6v 87
Valve Size
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 fl ow response to movements of the
control motor.
Linkage between motor and valve can be "characterized" to
produce the desired fl ow curve, e.g., linear or equal percentage.
1008A
Pipe
Cv Valve
1010A
Size Coe
ffi
cient
-02
(
3⁄8
") 2.0
-01
(
½
") 2.0
-0
(
¾
") 7.9
-1
(1")
12.5
-2
(1
¼
") 19.7
-3
(1
½
") 28
-4
(2")
49
-5
(2
½
") 71
-6
(3")
111
-7
(4")
191
-8
(6")
433
