STM Power Transmission Ltd
Unit 1
Oasis Business Park
Road One
Winsford Ind Est
Winsford, CW7 3RY
Tel: +44 (0)1606 557200
Fax: +44 (0)1606 557396
Email: sales@stmuk.co.uk
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“ATmosphéres EXplosible” – 94/9/EC/ATEX Directive
The new Atex directive covers equipment (with its own source of ignition) and protective systems intended for use in a potentially Explosives Atmosphere.
The directive which became mandatory on 1st July 2003 covers all flameproof electric motors purchased and commissioned within the EU.
The directive also covers Gearboxes and we are pleased to announce that the following STM Gearboxes are available with Atex certification -
- RM - Worm Gearbox
- AM - Helical In-line
- OM - Bevel Helical
- PM/PL - Parallel Shaft
- RX700 Series - Bevel Helical + Parallel Shaft
- SM Skew - STM Patented Bevel Helical
- EX - Planetary Gearboxes
The directive classifies equipment into different categories, levels of protection, and areas/zones of use, according to the frequency and length of time in which an explosive atmosphere could occur.
Flameproof motors are divided into two groups:
GROUP I - For mines susceptible to firedamp (Methane)
GROUP II – For other explosive atmospheres (i.e. above ground)
Apparatus Groups and Categories
|
Level Of Protection |
MINE
GROUP I |
SURFACE
GROUP II |
|
|
Category
|
GAS
|
DUST
|
|
|
Category
|
Category
|
||
|
Very High
|
M1
|
1G
|
1D
|
|
High
|
M2
|
2G
|
2D
|
|
Normal
|
N/A
|
3G
|
3D
|
Source : Cemp SpA
GROUP II – is divided into three further categories for EEx-d, namely GAS GROUPS IIA, IIB & IIC, with IIC having the highest protection.
Motors in a gas environment are further divided into 6 temperature classes categorised by the maximum surface temperature under normal running conditions.
Temperature Classes for Gas
|
Group
|
T1
|
T2
|
T3
|
T4
|
T5
|
T6
|
|
(oC) 450
|
300
|
200
|
135
|
100
|
85
|
|
|
I
|
Methane (firedamp)
|
|
|
|
|
|
|
IIA
|
Acetone, Acetic acid, ammonia, Methane, Methanol, Propane, Toluene
|
Butane, ethyl, alcohol
|
Cyclo-hexane, kerosene, THF
|
Acetal-dehyde
|
|
|
|
IIB
|
Coke-oven gas, water gas
|
Ethylene
|
Hydrogen sulphide
|
Ethyl ether
|
|
|
|
IIC
|
Hydrogen
|
Acetylene
|
|
|
|
Ethyl nitrate
|
Source : Cemp SpA
Temperature Classes for Dust
For protection against conductive dust the ignition temperature of the dust involved, both as air borne and surface dust, must be calculated, to work out a lower value surface temperature required from the motor.
Choice of Safety Motors
|
Hazardous area's class |
Explosive atmosphere
|
Zone
|
Motor category
|
Protection type
|
|||
|
Presence of flammable gas atmosphere
|
Always present
|
0
|
1G
|
Electric motors are not permitted
|
|||
|
Likely to occur
|
1
|
2G
|
EEx-d
|
EEx-de
|
EEx-e
|
||
|
NOT likely to occur
|
3
|
3G
|
EEx-d
|
EEx-de
|
EEx-e |
EE-n
|
|
|
Presence of flammable dust
|
Always present
|
20
|
1D
|
Electric motors are not permitted
|
|||
| Likely to occur | 21 | 2D | IP 6X | ||||
| NOT likely to occu | 22 | 3D | IP 6X | Conductive dust | |||
| IP 5X | Non conductive dust | ||||||
Source : Cemp SpA
In compliance with the directive all apparatus must be labelled with the CE mark, and supplied with a CE declaration of Conformity and Safety Manual.
