VAT Series 651 - Page 22

Installation, Operating & Maintenance Instructions
Series 651 DN 320-400 (I.D. 12“ - 16”), Logic
VAT Vakuumventile AG, CH-9469 Haag, Switzerland
Tel +41 81 771 61 61 Fax +41 81 771 48 30 CH@vatvalve.com www.vatvalve.com
267736ED
2008-02-26
22/53
Gasflow calculation for LEARN:
Do not apply a different gasflow for learn than determined below. Otherwise pressure control
performance may be insufficient.
Note: Required pressure / flow regime must be known to calculate the most suitable learn gas flow for a specific
application.
1. At first it is necessary to find out about the required control range respectively its conductance values. Each working
point (pressure / flow) must be calculated with one following formulas.
Choose the applicable formula depending on units you are familiar with.
1000 • q
WP
C
WP
=
p
WP
C
WP
required conductance of working point [l/s]
q
WP
gasflow of working point [Pa m
3
/s]
p
WP
pressure of working point [Pa]
q
WP
C
WP
=
p
WP
C
WP
required conductance of working point [l/s]
q
WP
gasflow of working point [mbar l/s]
p
WP
pressure of working point [mbar]
q
WP
C
WP
=
78.7
•
p
WP
C
WP
required conductance of working point [l/s]
q
WP
gasflow of working point [sccm]
p
WP
pressure of working point [Torr]
2. Out of these calculated conductance values choose the lowest.
C
R
= min(C
WP1,
C
WP2, . . . ,
C
WPn
)
C
R
required lower conductance [l/s]
C
WPx
required conductance of working points [l/s]
Note: To make sure that the valve is capable to control the most extreme working point verify that
C
R
≥ C
min
of the valve (refer to «Technical data»).
3. Calculate gasflow for learn. Choose the applicable formula depending on units you are familiar with.
p
max
• C
R
q
L
=
20
00
q
L
gasflow for learn [Pa m
3
/s]
p
max
max. pressure to control [Pa]
C
R
required lower conductance [l/s]
p
max
• C
R
q
L
=
2
q
L
gasflow for learn [mbar l/s]
p
max
max. pressure to control [mbar]
C
R
required lower conductance [l/s]
q
L
= 39.4 • p
max
• C
R
q
L
gasflow for learn [sccm]
p
max
max. pressure to control [Torr]
C
R
required lower conductance [l/s]