1-8 | Model 888 ATEX IECEx Tail Gas Analyzer
Heater
The sample system enclosure is electrically heated using a 400 W heater
assembly. The heater assembly contains two RTDs for heater fin tempera-
ture feedback and over-temperature protection. One SIL 2 rated “Tem-
perature Signal Converter” is wired into the power loop for over-heating
protection.
Steam Blowback Valve (Optional)
Steam blowback is an optional feature. When selected, a three-way
valve (FV3) is used to direct steam back through the demister and pro-
cess probe. Steam blowback is used to reduce the build up of salts in the
demister. The valve is actuated using a high temperature, low pressure (50
psig) pneumatic operator. The valve and operator are located inside the
oven. The outlet of the demister is connected to the common port of the
three-way valve. During normal sampling, the valve position is such that
the sample gas is directed to the sample cell. During steam blowback, the
valve is switched and steam is directed through the demister, isolating the
sample cell at the same time.
Heat Exchangers
Two ¼” aluminum heat exchangers are used in the sample system. One of
the heat exchangers (HE2) is used to pre-heat zero gas. During zero flush,
SV2 opens allowing air or nitrogen to flow through a protective check
valve (CV2) and flow control orifice (O2). The zero gas supply is heated
before flushing out the sample cell and coming into contact with sample
system components that must remain at oven temperature. The second
heat exchanger (HE1) is used to pre-heat the aspirator drive. During
normal sampling, air or nitrogen flows through the heat exchanger and
protective check valve (CV1) using PV1 to control the flow. The aspirator
gas supply is heated before contacting the aluminum aspirator and pipe
flange that must remain at oven temperature.
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