Supplementary installation, operating and maintenance instructions English
Explosion-proof three-phase asynchronous motors with squirrel-cage rotor for high voltage
815001 Edition 09.2020
13
Risk of ignition at the stator
The same criteria apply as for ignition protection type “eb”. We advise the plant operator to carry out the risk
assessment (according to IEC/EN60079-7, Annex G) before commissioning, as changes to operating condi-
tions compared to the design or order cannot be excluded.
Ignition risk in the air gap with squirrel cage rotors
Machines with an operating mode other than S1 or S2 and with a rated power in excess of 100 kW
must undergo a risk assessment in accordance with EN 60079-15 with regard to possible sparking
in the air gap This risk assessment has already been carried out by the manufacturer.
If the sum of the factors is greater than 6 for the risk assessment for squirrel-cage rotors according to EN
60079
–7:2015, Table 5, the machine must be pre-purged before starting. The electrical machine is prepared
accordingly and is provided with an additional sign.
Additional sign: Pre-purge required before start-up
.
See annex “Pre-purge before start-up”
In order to draw the attention of the operator to the special measures required to avoid sparking based on
the risk assessment,
the machine label ends in an “X” as per IEC/EN 60079-0.
4.
Information about ignition protection type protection by enclosure “t”
Protective principle/labelling
The temperatures of surfaces on which dust may be deposited or which may come into contact with a
cloud of dust are kept below the temperatures specified in this standard. All parts with electrical sparks or
temperatures above the limits specified in IEC/EN 60079-31
are encased in an enclosure that adequately
prevents ingress of dust.
Procedure A: Compliance with specified protection types
Procedure B: Minimum gap lengths and maximum gap widths
Prevention of sparks and other ignition sources
Enclosure minimum protection types for procedure A:
Use in zone 21 and zone 22 with conductive dust: IP65
Use in zone 22 with non-conductive dust: IP55
Observance of creepage and clearance distances
Special attention to insulation materials and seals
Temperatures of the outer surfaces must be lower than the limit values during normal operation
Areas of application:
Equipment zone 21 and 22, category 2D and 3D (Db, Dc)
Ignition protection type protection by enclosure “tx IIIY Dx”
Labelling of the motors according to Directive 2014/34/EU:
Use in zone 22
II 3D Ex tc IIIB T125°C Dc
or for conductive dust
II 3D Ex tc IIIC T125°C Dc
Use in zone 21
II 2D Ex tb IIIC T125°C Db
Protective principle:
Dangerous enclosures are encased in an enclosure that is not susceptible to faults.
Proof of the max. surface temperature according to category.
Minimum protection type IP 5X/6X (IEC/EN 60529)
Pressure test before the dust test with an overpressure of
-
2 kPa for devices with protection level “tb” or “tc”
Limitation of the assumed short circuit current 10kA for EPL Da
Temperature limitation depending on EPL
Group classification
IIIA, combustible fluff
IIIB, non-conductive dust
IIIC, conductive dust
