Yokogawa GC1000 Mark II Process Gas Chromatograph - Manual (Page 23)

3-2
<Toc> <Ind> <3. Overview >
IM 11B03A03-01E 3rd Edition : Aug. 23. 2006-00
3.2 Components and Their Functions
3.2.1. Protection System
The protection system has a explosion-proof construction and is equipped with a built-in
protection circuit. The power relay, pressure switch, timer, relays, override switch, etc. are
internal to the instrument. The override function is particularly important for maintenance,
since it allows the power to be turned on even if there is an internal pressure loss. The
system monitors the internal pressures of the electronic section, isothermal oven and the
programmed-temperature oven (GC1000D / GC1000T / GC1000W), and if any of them
indicates an internal pressure lower than 392 Pa, it shuts down the power supply to those
components. After a power shut-down, when the internal pressure is restored, the system
automatically purges over the 12 minutes, then turns on the power again. Analyzers of non-
explosion-proof type and with FM/CSA Type Y purging do not have this protection system.
3.2.2 Electronic Section
The electronic section has a pressurized protection/Type X purged structure and is de-
signed for control of a detector, an isothermal oven, various valves and others, for process-
ing and computation, and for output of the results. The LCD and operation keys on the
front of the electronic section allow manual operation of the GC1000 Mark II.
3.2.3 Pressure and Flow Control Section
The pressure and flow control sections control and indicate the pressures of sample gases,
standard gases, carrier gases, FID or FPD hydrogen (or nitrogen) for combustion, or FID or
FPD air for combustion. Regulator values or EPC is installed. It also contains pressure-
reducing valves for controlling purge gases, the air for actuating valves or the vortex tube,
an air-actuated valve for balancing atmospheric pressure, a vortex tube and a hydrogen
restriction system.
3.2.4 Isothermal Oven
The isothermal oven has an pressurized protection / Type X purged structure. The tem-
perature is set at a fixed level from 55 to 225
°
C (setting by 1
°
C unit). The isothermal oven
contains valves such as the sample valve which is air-activated, the back flush valve, the
column for separating a multi-component gas mixture into its individual components and
leading the components to the detector in sequence, the detector for detecting the compo-
nents, and the restrictor for controlling the gas flow rate, etc.
There are three types of detector, the thermal conductivity detector (TCD), the flame
ionization detector (FID) and the flame photometric detector (FPD); either one or two of
these detectors can be used simultaneously (however, the FPD can only be installed in the
combustion chamber).
The component signals picked up by the detector are led to the electronic section for signal
processing.