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F3200 Installation & Programming Manual Document No: LT0122
Applications
Page 9-22 5 July 2001 Issue 2.7
9.4 FIRE DETECTION IN HAZARDOUS AREAS
(EXPLOSIVE ATMOSPHERES)
9.4.1 REFERENCES
AS 2380 Electrical Equipment for Explosive Atmospheres - Explosion-Protection
Techniques.
AS 2381 Electrical Equipment for Explosive Atmospheres - Selection, Installation &
Maintenance.
AS 2430 Classification of Hazardous Areas.
IEC79 Electrical Apparatus for Explosive Atmospheres.
SAA HB13 Electrical Equipment for Hazardous Areas (handbook).
9.4.2 GENERAL
A hazardous area is one which has a potentially explosive atmosphere due to combustible
gases, liquids or dusts. In such an area there has to be a constraint to prevent an electrical
fault from causing an explosion.
For fire detection in hazardous areas there are two main options:
1) Use approved IS (Intrinsically Safe) detectors and bases with IS isolators or Zener
barriers and approved cabling.
2) Use approved detectors with explosion proof housings and compatible cabling. (E.g.
Olsen V41B, (V42B), V44B, T54B). These are not discussed further in this section
as the constraints are primarily mechanical.
Note that in addition to equipment selection and inter-connection, there are other
requirements for wiring in hazardous areas that must be satisfied.
These include (but are not limited to):
• Matching “Ex” rating of equipment chosen with hazardous area classification.
• Ensuring cable capacitance and inductance is within the limits of the repeaters used
(see Tables 9.4.3, 9.4.4, 9.4.5 for more details).
• Providing adequate physical protection for equipment according to local hazardous
area wiring regulations.
• Using cable of the correct insulation and physical strength according to local
hazardous area wiring regulations.
• Complying with manufacturer’s instructions for mounting of “Ex” rated devices.
• Inspection and certification of the finished installation.