Gonnheimer Elektronic F870S, User Manual

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F870S 2 Pressurized enclosure system F870S Page 5
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2 Introduction: Pressurized enclosure system F870S
2.1 Explosion protection: pressurized enclosure
The use of pressurized enclosures allows the operation of ‘non explosion protected’ devices
in hazardous areas inside zone 1 and zone 2. The protection type ‘pressurization’ is based
on the principle of maintaining a constant pressure using air or a protective gas to prevent
an explosive mixture forming near the device inside the pressurized enclosure.
Before start-up, the pressurized enclosure must be purged with air or protective gas to re-
move any explosive mixture that may be inside the enclosure.
2.2 Pressurized enclosure according to EN 60079
Since the second issue of the standard EN 50016 (May, 1996) control devices for the pro-
tection type "pressurized enclosure" are classified as security related devices.
At that time, the notified bodies, (PTB, EXAM, TUEV NORD, etc.) declared that an ex p-
control device must fulfill the category 3 of EN 954-1. This concept was taken over also in
the standards EN 60079 ff.
After the replacement of EN 954-1 by the standards IEC / EN 61508-1 and -2, respectively
EN ISO DIN 13849-1 and -2 and DIN EN 50495 a security level of at least SIL 2 is required
for a pressurized enclosure control unit according to EN 60079-2. This is a valid arrange-
ment between the German notified bodies.
Figure 1: Performance levels
The pressurized enclosure system F870S reaches
performance level „d“ according to
EN 13849 and therefore
it reaches
SIL Level 2
according to IEC / EN 61508.