Yokogawa YVP110 - Manual (Page 15)

<1. Notes on Handling>
1-4
IM 21B04C01-01E
l Installation Diagram (Intrinsically safe,
Division 1 Installation)
F0102.ai
Terminator
Valve Positioner
Safety Barrier
Terminator
+
−
Transmitter +
−
Transmitter +
−
− +
Hazardous Location
Non-hazardous Location
− +
Note 4. FISCO rules
The FISCO concept allows the interconnection
of intrinsically safe apparatus to associated
apparatus not specifically examined in
such combination. The criterion for such
interconnection is that the voltage (Ui), the
current (Ii) and the power (Pi) which intrinsically
safe apparatus can receive and remain
intrinsically safe, considering faults, must be
equal or greater than the voltage (Uo, Voc,
Vt), the current (Io) and the power (Po) which
can be provided by the associated apparatus
(supply unit). In addition, the maximum
unprotected residual capacitance (Ci) and
inductance (Li) of each apparatus (other than
the terminators) connected to the fieldbus
must be less than or equal to 5 nF and 10 µH
respectively.
In each I.S. fieldbus segment only one active
source, normally the associated apparatus, is
allowed to provide the necessary power for the
fieldbus system. The allowed voltage Uo of the
associated apparatus used to supply the bus is
limited to the range of 14 V d.c. to 24 V d.c. All
other equipment connected to the bus cable
has to be passive, meaning that the apparatus
is not allowed to provide energy to the system,
except to a leakage current of 50 µA for each
connected device.
Supply unit
trapezoidal or rectangular output characteristic
only
Uo = 14 to 24 V (I.S. maximum value)
Io according to spark test result or other
assessment,
e.g. 133 mA for Uo = 15 V (Group IIC, rectangular
characteristic)
No specification of Lo and Co in the
certificate and on the label.
Cable
The cable used to interconnect the devices
needs to comply with the following parameters:
loop resistance R’: 15 to 150 Ω/km
inductance per unit length L’: 0.4 to 1 mH/km
capacitance per unit length C’: 80 to 200
nF/km
C’ = C’ line/line + 0.5 C’ line/screen, if both
lines are floating
or
C’ = C’ line/line + C’ line/screen, if the screen
is connected to one line
length of spur cable: max. 30 m (Group IIC)
or 120 m (Group IIB)
length of trunk cable: max. 1 km (Group IIC)
or 1.9 km (Group IIB)
Terminators
At each end of the trunk cable an approved
line terminator with the following parameters is
suitable:
R = 90 to 100 Ω
C = 0 to 2.2 µF
The resistor must be infallible according to IEC
60079-11. One of the two allowed terminators
might already be integrated in the associated
apparatus (bus supply unit).
System evaluation
The number of passive devices like
transmitters, actuators, hand held terminals
connected to a single bus segment is not
limited due to I.S. reasons. Furthermore, if the
above rules are respected, the inductance
and capacitance of the cable need not to be
considered and will not impair the intrinsic
safety of the installation.