Posted to News on 7th Feb 2007, 19:54
Second-generation fieldbus barrier has better performance
MTL is releasing a 'second generation' design of its Fieldbus Barrier wiring hub. The 9311-FB is a field-mounted unit that provides intrinsically safe spur connections from a non-intrinsically safe trunk, for connection to Foundation fieldbus H1 or Profibus-PA field devices. When used with a suitable enclosure, the 9311-FB can be installed in Zone 1 (gas) or Zone 2 (dust) hazardous areas, with the trunk wiring implemented using suitably protected cable and increased safety (Ex e) connection facilities. Each unit supports four intrinsically safe spurs that may be connected to FISCO or 'Entity' certified fieldbus devices in a Zone 1 or Zone 0 hazardous area. The spurs are short-circuit protected and each unit includes an optional fieldbus terminator by means of a linking plug.
Key benefits of the new unit include intelligent power management, flexible grounding options and a wide ambient temperature range of -40 to +75degC. The 9311-FB Fieldbus Barrier is bus-powered and requires no additional power supply in the field. Typically up to four 9311-FB units may be connected to one hazardous area trunk, allowing up to 16 intrinsically safe fieldbus devices to be supported on the fieldbus segment. When used with a fieldbus host control system, power for the trunk can be provided by the MTL-Relcom F800 or FPS Series power supplies in redundant or non-redundant format. The 9311-FB module may be housed in a variety of field enclosures to suit end-user requirements. A range of standard, single-unit glass reinforced polyester (GRP) and stainless steel (SS) enclosures is available, as well as custom enclosures that can accommodate multiple Fieldbus Barriers together with field wiring terminals, surge protectors and live-disconnect switches.
A software calculator tool is available free of charge from MTL for the design of fieldbus segments using 9311-FB Fieldbus Barriers. The tool calculates the voltage and current levels in the segment according to input parameters, including the number of Fieldbus Barriers connected, field device currents, cable length, cable cross-section and power supply rating. Error conditions such as trunk overload are displayed.
