Yokogawa In-Situ Gas Analyzer TDLS200 - Manual (Page 35)

<3 INSTALLATION AND WIRING> 3-22
3.12 Cyclops Division 2/Zone 2 Purge Indictor, with switch
Type Z purging reduces the classifi cation within a protected electronics enclosures from Division 2 or Zone 2
to nonhazardous. Failure to maintain pressure within the protected enclosure shall be detected by an alarm
or indicator at the electronics enclosure. The dilution purge time shall be a manual operation and once the
electronics enclosure has been purged of ignitable or fl ammable concentrations, only positive pressure of at least
0.20 inches H
2
O (0.50 mbar) is required to be maintained within the electronics enclosure and it is not necessary
to remove power from the protected equipment upon the loss of purge pressure. The CYCLOPS
Z – Purge Indicator is used to provide safe monitoring of electrical equipment in Division 2 and Zone 2 hazardous
areas, which can be used to prevent the possibility of fi re or explosion inside the enclosure of energized electrical
equipment, a protective gas supply is used to dilute potentially fl ammable materials to an acceptable level,
creating a safe area for the electrical equipment within the enclosure. Positive pressure prevents the ingress
of fl ammable materials in the surrounding atmosphere from entering into the enclosure, as long as positive
pressure is maintained. After the enclosure is purged, power may be manually applied to the protected electrical
equipment.
The CYCLOPS Z – Purge Indicator provides an objective evidence of the presence of adequate positive purge
pressure within the electrical equipment enclosure. A normally open differential pressure switch continuously
compares the pressure inside the monitored electronics enclosure with respect to the atmospheric pressure
surrounding the electronics enclosure. When the monitored electronics enclosure register’s a pressure of at
least 0.20 inches H
2
O (0.50 mbar) above the reference atmospheric pressure a manually controlled dilution
time cycle may then begin. Typically, a minimum dilution time cycle is specifi ed to ensure that at least fi ve
times the volume of free space in the electronics enclosure is exchanged before power is manually applied to
the electrical equipment. (The number of exchanged volumes may be higher in some situations). After the
manual dilution time cycle has elapsed and the monitored electronics enclosure pressure is being maintained
above 0.20 inches H
2
O (0.50 mbar), power may be manually applied to the electrical equipment within the
purged electronics enclosure. The CYCLOPS Z – Purge Indicator is designed to indicate the presence of purge
pressure from one pressure reference point. Several electronics enclosures can be installed in series with purge
gas being introduced into the fi rst electronics enclosure and the CYCLOPS Z – Purge Indicator monitoring the
last electronics enclosure in the series; multiple electronics enclosures can now be monitored using only one
CYCLOPS Z – Purge Indicator. The pressure inside the monitored electronics enclosures must maintain at least
0.20 inches H
2
O (0.50 mbar) higher than the atmospheric pressure surrounding the electronics enclosure. This
ensures that hazardous materials are not going to ingress into the pressurized and now protected electronics
enclosures. If any of the electronics enclosures installed in the series door is opened, pressure will show to be
below the required 0.20 inches H
2
O (0.50 mbar) in all electronics enclosures. The exhaust vent which comes as
part of the CYCLOPS Z – Purge Indicator casing, can exhaust purge gas from enclosures with volumes up to 15
cubic feet (425 liters).
Cyclops Features
Certifi ed for installation and use in ATEX and IECEx for
Type Z – Purge, II 3 G Ex nA nL [pz] IIC T6
For Zone 2 gas hazardous areas
Certifi ed for installation and use in ATEX and IECEx for
Type Z – Purge, II 3 G Ex nA nL [pz] IIC T6
For Zone 2 gas hazardous areas
IM 11Y01B02-11E-A 5th Edition :June 5, 2012-00