Networking hardware: Avoid process shutdowns from FOUNDATION fieldbus segment faults
A failure in a fieldbus can shut down a major process causing loss of product and production time. However, with the right switching equipment, the system can reroute itself in the event of a segment fault and avoid shutdowns. Trunksafe from MooreHawke reportedly provides a cost-effective and reliable method for maintaining continuous communications on a FOUNDATION fieldbus H1 segment.
In the event of a failure on a fieldbus segment, Trunksafe makes it possible for the control system to switch immediately and automatically to a redundant path. This action helps prevent losing the complete segment and avoids resulting shutdowns. Normally, a control system cannot easily detect a segment failure beyond an H1 card, but Trunksafe is said to provide the means to support and fully utilize true redundancy.
A Trunksafe segment consists of two TPS200 advanced power conditioners, a fieldbus cable from each power conditioner, and a TS200 fault tolerant device coupler, currently available for a maximum of either six or ten field devices. The power conditioners each feed the parallel, redundant legs of fieldbus cable, which meet at the device coupler. When a cable failure in either leg occurs, the system shuts off power to the failed leg, letting the redundant power conditioner keep power to the remaining healthy leg. The control system detects loss of power at the H1 card on the failed leg and automatically switches to its backup H1 card.
If desired, Trunksafe can provide a hard-wired alarm to alert operators to the cable fault. When the failed segment has been repaired and normal cable integrity restored, the H1 card is automatically allowed access to the segment once more. MooreHawke reports that installing Trunksafe protection requires no hardware or software modifications to an existing control system and follows conventional FOUNDATION Fieldbus practices except that it has two cables. Switchover during a fault and reset after are automatic, requiring no action by maintenance or operations personnel.
Although such technology could be useful for other fieldbus platforms, Moore said it has no current plans to create similar solutions beyond FOUNDATION fieldbus.
-- Daily News Desk, Peter Welander ,
process industries editor , Control Engineering
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