Page 221 - Electrical Installation in Hazardous Area

General requirements for explosion protected apparatus 1 85

Table 8.1 Current european grouping system showing relationship
to historic German and UK systems and current USA
system

Test European Historic German us
gases grouping UK class groups and
groups and classes
classes
FLP IS
GRP CLS

Propane IIA I1 2c 1 Class I2
Group D
Ethylene IIB I11 2d 2 Class I*
Group C
Hydrogen IIC rv 2e 3a Class 1'
Group B
Acetylene IIC Iv' 2f 3c Class I*
Group A
Carbon IIC IV' 2f 3b Not
disulphide specifically
allocated
All gases 3n

~ ~ ~~ ~ ~~~~
Notes:
1 Although Group IV was allocated for these gases the Standard appropriate at
the time (BS 229) excluded construchon requirements for these gases and thus
no equipment exists.
2 Class I in the USA National Electrical Code was for gases, vapours and mists only.
Dusts were Class 11, and fibres and flyings Class 111.

T1

For T1 the maximum apparatus temperature must not exceed 440°C. (As
temperature classification is normally done at 40 "C ambient temperature,
this usually means an elevation due to self heating of 400°C.) Gases,
vapours and mists associated with this temperature class will have ignition
temperatures in excess of 450 "C.

T2

For T2 the maximum apparatus temperature must not exceed 290°C. (As
temperature classification is normally done at 40 "C ambient temperature,
this usually means an elevation due to self heating of 250°C.) Gases,
vapours and mists associated with this temperature class will have ignition
temperatures of between 300 "C and 450 "C.