Table of Contents
Advertisement
14
Calculations
Sample Calculation
Concentration of the permeant compound in the span outlet stream is inversely
proportional to the carrier flow rate through the chamber. It is determined using
the following equation:
Concentration (ppm) =
Where:
K = 24.45 / molecular weight of gas
P = permeation rate in ng/min (information included with
the permeation device documentation)
F = Chamber carrier flow (ml/min)
If the permeation rate is known for some reference temperature, the rate at a
second temperature can be estimated as follows:
log P = log P
Where:
P
= Permeation rate at reference temperature T
O
P = New permeation rate at temperature T
Certified devices should be used only at the temperature
specified on the certificate.
Using any permeation device beyond its recommended tem-
perature range could result in the destruction of the device
by explosion and/or changes in the membrane characteris-
tics. If in doubt, contact VICI Metronics with the part number
of the device to determine its maximum temperature limit.
Given:
Permeation rate: 21,000 ng/min Cl
Carrier flow: 500 ml/min
Then:
Concentration (ppm) =
For zero reference measurement, remove the permeation device from the
chamber.
K * P
F
+ 0.034 (T - T
)
O
O
@ 30°C
2
K * P
F
(0.346)(21,000)
=
= 14.5 ppm
500
O
Advertisement
Table of Contents
