Teledyne 6200E - Sulfides Analyzer - Manual (Page 215)

Model 6200E Instruction Manual Theory Of Operation
M6200E Rev: A1 215
SPRING
O-RINGS
FILTER
CRITICAL
FLOW
ORIFICE
AREA OF
LOW
PRESSURE
AREA OF
HIGH
PRESSURE
Sonic
Shockwave
Figure 10-8: Typical Flow Control Assembly with Critical Flow Orifice
The actual flow rate of gas through the orifice (volume of gas per unit of time), depends on the
size and shape of the aperture in the orifice. The larger the hole, the more gas molecules, moving
at the speed of sound, pass through the orifice.
The result is that he flow rate of the gas is unaffected by degradations in pump efficiency due to
age.
The critical flow orifice used in the Model 6200E is designed to provide a flow rate of 650 cm 3 /min.
10.3.4. Sample Particulate Filter
To remove particles in the sample gas, the analyzer is equipped with a Teflon membrane filter of
47 mm diameter (also referred to as the sample filter) with a 1 µm pore size. The filter is
accessible through the front panel, which folds down, and should be changed according to the
suggested maintenance schedule in Table 9-1.
10.3.5. Hydrocarbon Scrubber (Kicker)
It is very important to make sure the air supplied to sample the chamber is clear of hydrocarbons.
To accomplish this task the M6200E uses a single tube permeation scrubber. The scrubber
consists of a single tube of a specialized plastic that absorbs hydrocarbons very well. This tube is
located within the outer flexible plastic tube shell. As gas flows through the inner tube,
hydrocarbons are absorbed into the membrane walls. and transported through the membrane wall
and into the hydrocarbon free, purge gas flowing through the outer tube. This process is driven by
the hydrocarbon partial pressure gradient between the inner and outer tubes.