Hochiki IFD-E(IS) - Manual (Page 2)

2 Hochiki Europe (UK) Ltd
2-3-0-809/ISS2/JUL07
General
Description
This Installation Guide gives information on the intrinsically safe (I.S.) version of the flame detectors that
have been approved by BASEEFA (British Approvals Service for Electrical Equipment in Flammable
Atmospheres). The requirements of the European Community Directive 94/9/EC, the ATmosphere
EXplosives ATEX Directive have been met. The approval have been accessed to European Standards
EN 50014, EN 50020 and EN 50284.
The detectors are certified II 1 G EEx ia IIC T4 and can be used with all listed gases.
The range comprises single infra-red (IR), dual infra-red (IR²) and triple infra-red (IR³) flame detectors.
The detector housings are available in zinc metal alloy or stainless steel and also stainless steel
(antistatic) glass filled polycarbonate.
The guide also provides information on intrinsic safety, the application, maintenance, installation and
adjustments of the detectors. Reference to other individual detector publications can be made for more
information on none intrinsically safety issues. These publications are available on request.
Introduction to Intrinsic Safety
There are many places where an explosive mixture of air and gas or vapour is or may be present
continuously, intermittently or as a result of an accident. These are defined as hazardous areas by BS
EN 50014:1998, Electrical apparatus for potentially explosive atmospheres – General requirements.
Hazardous areas are common in petroleum and chemical engineering plants and in factories processing
and storing gases, solvents, paints and other volatile substances.
Electrical equipment for use in these areas needs to be designed so that it cannot ignite an explosive
mixture, not only in normal operation but also in fault conditions. There are a number of methods
available to achieve this – oil immersion, pressurised apparatus and powder filling, for example, but the
two most common used are flameproof enclosures and intrinsic safety.
Flameproof equipment is contained in a box so strong that an internal explosion will neither damage the
box nor be transmitted outside the box. The surface must remain cool enough not to ignite the explosive
mixture.
When flameproof equipment is interconnected, flameproof wiring must be used. This method is most
valuable when high power levels are unavoidable but it is not acceptable for areas in which an explosive
gas/air mixture may be continuously present or present for long periods.
For this reason these flame detectors are made intrinsically safe rather than flameproof. Intrinsically safe
equipment operates at such low power and with such small amounts of stored energy that it is incapable
of causing ignition:
In normal conditions
With a single fault (for ib type of protection code)
With any combination of two faults (for ia type of protection code)
In any of these conditions every component must remain cool enough not to ignite gases for which it is
approved. See Table 2
Classification of Hazardous Areas
EN 50014 states that electrical apparatus for potentially explosive atmospheres is divided into:
Group I: Electrical apparatus for mines susceptible to fire damp;
Group II: Electrical apparatus for places with a potentially explosive atmosphere, other than
mines susceptible to fire damp.