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Introduction
2
CARRIER
STREAM
INPUT
SCRUBBER
SCRUBBER
DILUTION
STREAM
INPUT
As indicated in Figure 1, the carrier stream passes through scrubber #1 and
30-micron line filter LF1 to the differential pres sure regulator DPR1. The scrubber
contains spe cially-activated charcoal designed for broad-based scrubbing action.
This scrubbing medium is particularly effective in removing sulfur dioxide and
other sulfur compounds.
The differential pressure regulator and carrier flow restrictor FR1 together
provide a highly stable carrier stream flow rate to the permeation chamber.
The standard carrier flow restrictor consists of a disk with a 0.006" diameter
orifice. The flow rate through the orifice is a function of the pressure differential
across it and this differential is maintained at 3.2 psi by DPR1.
The output of the permeation chamber is fed to a mixing tee, where the calibrat-
ed dilution stream is added to set the final concentration. The combined stream
is then fed through another tee to the rear panel overflow vent and span outlet.
DIFFERENTIAL
PRESSURE
REGULATOR
DPR1
LINE FILTER
LF1
#1
RESTRICTOR
DIFFERENTIAL
PRESSURE
REGULATOR
FLOWMETER
DPR2
#2
DILUTION FLOW
CONTROL VALVE
FCV2
Figure 1: Model 340 plumbing schematic
For those analyzers sensitive to sample feed pressure, the overflow vent dumps
excess calibration gas to ensure that the analyzers receive span gas at near at-
mospheric pressure. The overflow vent is usually left open, but can be plumbed
to an external exhaust point. Any exhaust plumbing must be sized so as not to
increase pressure into the analyzer under calibration.
Referring again to Figure 1, note that the dilution stream passes through
scrubber #2 and feeds into differential pressure regulator DPR2. The differential
pressure regulator maintains a fixed pressure differential across dilution flow
control valve FCV2 and dilution flowmeter FM2.
CHAMBER
FLOWMETER
FM1
PERMEATION
TEE
CHAMBER
CARRIER
FLOW
FR1
DILUTION
FM2
TEE
NO
SOLENOID
C
CONTROL
VALVE
NC
SV1
MIXING
TEE
TEE
CHAMBER
VENT
OVERFLOW
VENT
SPAN/STREAM
OUTLET
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