GLA531 Series LGR-ICOS™ Gas Analyzer
Operating Manual
3KXG165002R4201_2021_04
ABB PROPRIETARY INFORMATION 43
Table 11 Typical N
2
Purging Design for GLA531 Series Protection System
Process Gas All gases as long as O
2
< 2%, UFL < 80%
Maximum intake to enclosure, sccm 824
Enclosure Overpressure, mBar 0.5 – 8.78
Startup Purge N
2
flow rate SCFM (slpm) 0.7 (20)
Normal Purge N
2
flow rate SCFM (slpm) 0.071 (2.01)
Purge N
2
regulated pressure, PSIG (kPa) 20 (137.9)
Purge N
2
supply pressure, PSIG (kPa) 30- 100 (206 - 690)
Protection System Types for Analyzers
The purged-and-pressurized protection system of ABB GLA531 Series LGR-ICOS™ Gas Analyzer uses fixed
orifices as restrictors for regulating air flow. As long as the air pressure is regulated and controlled, a steady
stream of air can be guaranteed within a certain range. Redundant design of pressure sensors and differential
pressure switches monitor air pressure and overpressure inside the enclosure (see Figure 36, Figure 38, Figure
40, and Figure 42).
The typical requirements of air pressures and enclosure overpressure settings for the analyzers are listed in Table
10. If there is a large leak of flammable gas inside an enclosure, the purge air-flow rate must be sufficient to dilute
the maximum intake of the flammable gas below 25% of its lower flammability limit (LFL).
The ABB GLA531 Series LGR-ICOS™ Gas Analyzer offers two types of protection systems. Both are certified
designs for installations in hazardous locations for flammable-gases:
• X-Purge configured unit with Power Interlock system. When loss of pressurization occurs, the X-Purge
controller shuts down the power and prevents any analyzer operation. The protection system includes a
single-pole normally-open alarm contact for triggering a safety fault-signal. The X-Purge type is the
safest protection system to prevent possible fire and explosion hazards. The X-Purge type is normally
recommended for CID1 or Zone 1 installations.
• Z-Purge configured unit. When loss of pressurization occurs, the Z-Purged controller activates an alarm
contact for triggering a safety fault-signal. A Z-Purge system does not shut down the power source
when a fault alarm is activated. The Z-Purge type is only recommended for CID2 or Zone 2 installations.
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