Brooks
®
Model 5850i
4-18
Section 4 Maintenance
Installation and Operation Manual
X-TMF-5850i-MFC-eng
Part Number: 541B108AAG
November, 2008
Figure 4-4 Example Nomograph
If these conditions do not exist, pressure drop equals the inlet pressure
minus the outlet pressure.
Then
Δ
p = 64.7 - 44.7 = 20 psi
Using the nomograph, locate the pressure drop (psi) on the vertical line
marked "
Δ
p" (Point A).
4. Using the nomograph, locate the pressure drop (psi) on the vertical
line marked "Dp" (Point A).
5. Locate the Nitrogen equivalent flow rate (sccm Nitrogen) on the
vertical line marked "Q
Nitrogen
" (Point B).
6. Draw a line connecting Dp and QNitrogen and extend it to the
baseline. Mark this point (Point C).
7. Locate inlet pressure (psia) on the vertical line marked "P
in
" (Point D).
8. Draw a line connection P
in
(Point D) and baseline (Point C) and then
extend this line to the vertical line marked D
o
(orifice diameter,
inches). (Point E).
9. This point on the line is the minimum orifice size for the given
