KROHNE VFM 1091 - Manual (Page 28)

Part D VFM 1091 (I) Ex
VFM 1091 (I) Ex is a two wire loop powered flow transmitter
designed with electronic circuits incorporating Intrinsic safety
features.
EEx [ib] IIC T2.... T6
Applicable standards: EN 50014 & EN 50020
The temperature class of the equipment operated in hazardous
area is determined by the process or medium temperature.
The relationship between the maximum process temperature
and the temperature class is approved by PTB and stated as
shown the following table.
9.2 Electrical connection 9. Description of the system
VFM 1091 (I) Ex has two isolated Intrinsically safe circuits
1. Loop power / Current output circuit
2. Pulse output circuit
The entity parameters for both these circuits are approved by
PTB and stated as: -
Ui= 30 V
Ii = 100 mA
9.1 Temperature class
Pi = 0.8 W
Li Ci <20 nF
The loop power supply connections from safe area to the flow
meter in hazardous area must be routed through a suitable
Zener Barrier placed in safe area or the instrument should be
powered through an Intrinsically safe power supply.
Note: On the current output lines, HART
® signal is
superimposed as an option. In such case compatible Barrier
needs to be chosen which will pass the HART
® signal for
detection and processing in safe area.
200 °C
100 °C
135 °C
220 °C
85 °C T6
T5
T4
T3
T2
The Hazardous and safe area connections are illustrated in
diagram
The meter is provided with two cable entries in the terminal
compartment of enclosure. Each cable entry must be used to
insert cable to route loop power and pulse output circuit.
Refer the schematic where the positions of the cable entries
and cable routing is indicated.
28