SMAR FY302, Инструкция по установке, эксплуатации и обслуживанию

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Installation
1.17
( )
L R V V
C BN
*
− =
Where:
C
V
: Power supply output voltage;
R
: Loop resistance (Type A cable, R = 44
Ω
/km);
L
: H1 Bus total length;
: Voltage in the terminal block of the H1 devices most distant from the PSI.
BN
V
Being . This guarantees the powering of the last H1 device. Remember that the
communication signal should range from 750 to 1000 mV.
V V
BN
0 . 9
〉
Some junction boxes or short circuit protectors for segments, called spur guards, are active and can
be powered through the H1 bus; hence, it should be included in the calculation of the total current.
Besides, each spur guard output has an allowed current limit that should be respected.
In classified areas follow the established limits.
Foundation Fieldbus in Hazardous Areas
According to the standards, the Foundation Fieldbus technology can be applied in hazardous areas
with the following characteristics:
•
Ex d: In this case choose the power supply Ex and conduits with Ex d approval;
Ex i: There are three options. The first involves the Ex-i concepts and the second a combination of
Ex and Ex i. The third option is the FISCO.
Summary of Classified Areas
Zone/ Explosion Group Identification Observation
Zone 0 (Ex ia) IIx
Devices installed in Zone 0 should operate in a
segment with “Ex ia” protection.
Zone 1
(Ex ia) IIx
(Ex ib) IIx
Devices installed in Zone 1 should operate in a
segment with “Ex ia” or “Ex ib” protection.
All the circuits connected to this segment should be
certified for “Ex ia” or “Ex ib” protection.
Explosion Group IIC IIC (Ex ia) IIC
If the measures are taken in an IIC explosion group,
the devices and components should be certified for
the IIC.explosion group
Explosion Group IIB
(Ex ia) IIC
(Ex ib) IIB
For the IIB medium explosion group, both devices
and components can be certified for the IIC or IIB
groups.
Non -Ex Non-Ex
Devices that are operating in a no-Ex segment
should not be installed in explosion-risk areas.
Table 1.5 - Summary of Classified Areas
Intrinsic Safety Definition
Intrinsic safety limits the equipment circuit energy, so that they do not cause the ignition of
potentially explosive atmospheres even in the occurrence of failures that may produce sparks or
warm surfaces in contact.
As it deals with energy limitation, this is an adequate technique for electronic equipments, typically
used in control and process instrumentation.
Foundation Fieldbus Technology and Intrinsic Safety
According to standards, 1 to 4 devices may be connected together in the hazardous areas, after the
Intrinsic Safety Barrier, and two more devices in the safe areas in the same bus.
With the energy limitations for each device in the hazardous area, some instruments will need to be
run through other power supplies. Therefore, devices such as, process analyzers, of I/O
subsystems, magnetic or Coriolis effect meters can combine intrinsic safety with other installation or
contention techniques for protection against possible explosions.