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The MTL open-frame redundant fieldbus barrier provides intrinsically safe spur connections from a high-energy trunk, for connection to suitably certified Foundation fieldbus H1 instruments. The unit comprises pre-wired and assembled system components on a stainless steel baseplate, for installation into a suitably certified field enclosure. Connection facilities are provided for the trunk and spur wiring, as well as all electronic modules needed to support a fully working Fieldbus barrier. In a typical application, an Ex e (increased safety) certified field enclosure will be selected to allow installation in a Zone 1 hazardous area. Third-party approval of the enclosure and contents is normally required.

The assembly uses duplicated fieldbus barrier modules in a redundant configuration to achieve significantly higher system availability than equivalent ‘simplex' units. The 9387-FB-R may therefore be selected for critical process applications where failure of the Fieldbus barrier would otherwise result in unacceptable downtime or lost production. It is also ideal for use in Fieldbus Safety Instrumented Function (SIF) networks in which nuisance trips cannot be tolerated. Failure notification to the host control system is provided by means of an integrated Foundation fieldbus device with Digital Input Function Block capability.

In common with conventional fieldbus barriers, each intrinsically safe spur can support a FISCO or ‘Entity' certified fieldbus device located in a Zone 0 or 1 hazardous area. The short-circuit protected spurs are galvanically isolated from the trunk and require no protective ground connection in the field.

The 9387-FB-R redundant fieldbus barrier assembly is based on the 9370-FB range of products, which are supplied as complete, factory-assembled systems that do not require additional wiring or complex ancillary components. The electrical and mechanical aspects of this design have been integrated to provide a complete, ergonomic solution for ‘High Energy Trunk' applications in hazardous areas.

The key modular components of the system (Fieldbus barrier, terminator and surge protectors) may be ‘hot-plugged' by design and without gas-clearance procedures or separate isolating switches. This virtually eliminates the risk associated with hazardous area maintenance activities, speeds module replacement and avoids the need for specialist operator training.

The 9387-FB-R Fieldbus barrier assembly is bus powered and requires no additional power supply in the field. When used with a fieldbus host control system, power for the trunk may be provided by redundant MTL power supplies.