Gas Data GFM600, Руководство пользователя

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G F M 6 0 0 U S E R M A N U A L
THE GFM600
SERIES
IS SUITABLE FOR USE IN FLAMMABLE
ATMOSPHERES CAUSED BY THE PRESENCE OF GASES IN
GROUP I, GROUP IIA AND GROUP IIB.
Design and construction of intrinsically safe instruments for use in
flammable atmospheres.
The technique of intrinsically safe design and construction is defined in the
European Standard EN50020:1995. The technique identifies potential sources of
ignition (by spark or by heat) and specifies the design of safety circuits that limit the
energy of the spark and/or the component temperatures such that they cannot
ignite the gases expected within the hazardous area. There are two categories if
intrinsically safe instruments;
1. ‘ia’ The safety circuits used will prevent the generation of a spark or
temperature capable of igniting the gas even if the instrument develops TWO
faults.
2. ‘ib’ The safety circuits used will prevent the generation of a spark or
temperature cable of igniting the gas even if the instrument develops ONE fault.
THE GFM600 SERIES IS DESIGNED TO MEET THE
REQUIREMENTS OF CATEGORY ‘ib’.
By testing components in fault conditions (as required by ‘ib’) the worst case
temperature within the instrument is determined. This is used to give the
instrument a temperature classification. A guide to temperature classifications is
given below.
The higher the T class the lower the temperature.
Different gases will be ignited at different temperatures. Some examples are given
below.
GFM600 - 14 - GFM600 Velocity Monitor User Manual
Petrol vapour IIA
Methane Least easily ignited I
Temperature Class Maximum Temperature (C)
T1 450
T2 300
T3 200
T4 135
T5 100
T6 85