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

  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

Catalog Combustion 2021 - Page 1265

Fives Group
FIVES GROUP
FIVES GROUP-FIVES GROUP-1265-1251

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