wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

35-8 Industrial Communication Systems
FISCO intrinsically safe barriers on field
EEx e wiring
Classified zone 1
Power supply
default with
28 V @ 500 mA
Field
barrier
EEx ia IIC Outputs in accordance with
FISCO and Entity models
FIGURE 35.5
Intrinsically safe barriers.
noted, however, that because FISCO power conditioners are also repeaters, if desired it is possible to install
up to four FISCO power conditioners in a single fieldbus network. Because FISCO uses IS-equivalent
circuitry throughout, the resulting segment is similar to that shown in Section 35.6 with simple field
device couplers in the field junction boxes.
35.9.2 High-Energy Trunk–Fieldbus Barrier Solution
For those cases in which longer trunk length is required without the need for live working of the
trunk cable, the high-energy trunk–fieldbus barrier solution is often used. As mentioned earlier, in
this configuration, the individual spurs from the fieldbus barrier are IS or IS equivalent as the energylimiting
circuitry is contained in the fieldbus barrier devices. As shown in Figure 35.5, this technology
has a high-voltage “conventional” FF power conditioner at one end of the trunk, and then a
number of spurs from each fieldbus barrier. Each of these spurs can be the full 120.m specified by the
Foundation documents.
35.10 Project Documentation
Because FF technology is based on segments rather than individual loops; the traditional “loop diagram”
should be replaced with a segment diagram, as shown in Figure 35.6.
The reason to use network or segment diagrams rather than single-loop diagrams is so that you can
see on one drawing all the equipment that is interconnected. This is important especially when doing
maintenance, so that in the event of some unexpected happening, you are aware of what other devices
and control loops will be affected.
35.11 Installations and Commissioning
By now, readers should have realized that FF is different from traditional analog systems. The same is
true for the installation and commissioning procedures. Unfortunately, for those projects that do experience
troubles with their fieldbus system during start-up, the majority of the time this occurs is because
of the fieldbus network. Fortunately, these errors are easily fixed through the use of good practices
© 2011 by Taylor and Francis Group, LLC