Detectors; Detector Functional Descriptions - Siemens Maxum II Manual

Note that the wiring from the valve temperature sensors to the electronics enclosure must be
installed in conduit or connected to intrinsic safety barriers inside the electronics enclosure. In
either case, be careful not to damage or alter the wiring. If conduit is in use, a vent coil may
be installed near the valve. If this is present it must not be shortened, cut, bent or plugged in
any way.
It is important that the temperature of the SLIV heater does not exceed the temperature limit.
If a vaporization temperature is necessary that is higher than the T-rating, then it may be
necessary to locate the analyzer in a location with an appropriate T-rating.
Note that the wiring from the SLIV heater to the electronics enclosure must be installed in
conduit while inside the oven (refer to figure 4-3). A vent coil will be installed on the SLIV heater
near the wiring (refer to figure 4-3). This vent allows the heater to purge. The coil is a flame
arrestor and as such it must not be shortened, cut, bent or plugged in any way.
To prevent temperatures that exceed the maximum temperatures specified by the T-rating,
the set point resistors for over-temperature and temperature limit must NOT be changed. If
the set point resistors must be replaced, it must be verified that the resistor values for the
replacement parts are correct.
4.2

Detectors

4.2.1

Detector Functional Descriptions

In order to analyze the chemical compositions of different samples, four major types of
detectors are used in the Maxum II Gas Chromatograph (refer to figures 4-4 through 4-6). The
types of detectors are:
● Explosion Proof/Flameproof Thermal Conductivity Detector (TCD)
● Intrinsically Safe Thermal Conductivity Detector (ISTCD)
● Flame Ionization Detector (FID)
● Flame Photometric Detector (FPD)
● Valco Pulsed Discharge Detector (PDD)
The PDD is manufactured by Valco Instruments and at this time it is not rated for use in
hazardous areas. The PDD is currently suitable only for general purpose use (in non-
hazardous areas) and for this reason is not applicable to the rest of this section.
The Explosion Proof/Flameproof TCD has two variants, one with thermistor bead sensors and
one with filament sensors. However, there are no safety related differences between the two
variants. Detectors within the Maxum II are housed either in the oven or in the detector
enclosure (refer to figures 1-1 and 1-2).
Explosion Protection Safety Standards
Manual, August 2017, A5E02220442001 Rev 8
WARNING
Valves, Detectors, and External Systems
4.2 Detectors
47