09-2018
file: ISAFE3-OperationManual_EN_DE.R4.VEXH.docx
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Vallen ISAFE3 Operation Manual - Operation Manual
9.4
Sensor installation -
safety relevant requirements for EPL “Gb”
and “Gc” (Earth connection)
EN 60079-14:2008 / 12.2 defines the safety relevant requirements for the erection of intrinsically
safe electrical installations of Equipment Protection Level (EPL) “Gb” (for hazardous areas of
zone 1) and “Gc” (for hazardous areas of zone 2.)
The metallic case of sensor ISAS3 is in electric contact to the intrinsically safe circuit (shield &
minus pole). It must be safely and reliably connected to potential equalization of the test object
(EN 60079-14:2008 / 12.2.4). Most metallic test objects provide potential equalization at the
point of sensor location due to their full metallic construction.
Pressing the contact face of an AE sensor to a test object, even if painting is removed, is not a
safe electrical contact. Welded bolts used for holding the ISAS3 mounting plate are well suited
contact points for potential equalization. Where ISAS3 cannot be directly screwed onto a
metallic surface carrying potential equalization, ISAS3 provides two threads M4, one with a pre-
mounted screw, earth symbol, nut, and a ring cable lug, chopper disk and another nut (see
Figure 8-2). A wire of at least 4 mm
2
copper (or two wires of at least 1.5 mm
2
copper each) is to
be used to connect the ISAS3 to the potential equalization. Sufficient torque to ensure the
connection is not twistable at ISAS3 as well as at the welded bolts must be used.
For temporary installations, where magnet holders are used instead of welded bolts, safe
access points for connecting ISAS3 case with the potential equalization must be found and
used nearby.
Block diagram in Figure 9-1 applies.
9.5
Sensor installation - safety relevant requirements
for EPL “Ga”
(Earth connection)
EPL “Ga” is required for zone 0, the most hazardous environment.
The requirements for EPL “Ga” installations are summarized in EN 60079-14:2008 / 12.3. There
it is urgently recommended to use isolating barriers, as given with SISO3. This eliminates
additional requirements for safety transformers and allows that earth connection of the
intrinsically safe sensor is only required at the sensor side and not at the side of the isolating
barrier.
In addition, EN 60079-14:2008 / 12.3 requires a risk analysis that the installation is protected
against atmospheric electricity (in worst case a lightning strike). If a risk of atmospheric
electricity cannot be excluded, an appropriate overvoltage protection (10 kA 8/20µs) is required.
ISAFE3 does not provide overvoltage protection against atmospheric electricity.
