Critical loops have dual redundancy

The Nynas bitumen refinery in Gothenburg, Sweden has chosen PlantWeb field-based architecture from Emerson Process Management, and Foundation Fieldbus digital communications, to update some critical control loops

Nynas relies on steam jacket heating of its main bitumen storage and delivery tanks to keep the product liquid - and therefore able to flow throughout the Scandinavian winter. Fisher Control valves, fitted with Fieldvue digital valve controllers, are used to control the steam flow used to maintain the tanks and process lines at the right temperature. These valves are installed on the same Foundation Fieldbus segment as the relevant temperature transmitters, which are the dual sensor Rosemount Model 3244MV.

The Hot Backup feature in this unit allows connection of two independent temperature monitoring elements to provide dual redundancy. If the first primary temperature sensor element should be detected as having failed, there is a seamless transfer of the 3244MV transmitter output to follow the second element. Measurement is maintained and the bitumen continues to flow. An alarm message would be transmitted to the operator over the fieldbus link, informing that one of the sensors is faulty.

The Hawke Route-Master dual redundant intrinsically safe fieldbus network power supply and isolated segment couplers were chosen for installation on the field outputs from the Emerson Process Management DeltaV automation system. This provides intrinsically safe power for the Foundation Fieldbus segment used on the heating control system, in the Gas Group IIB hazardous area around the tanks. It again provides the same dual redundancy approach of having primary and secondary supplies, with a seamless transfer between them in the event of a problem.

Foundation Fieldbus uses simple cabling and can use pre-existing plant cabling where available. Following installation of the heating control system, further Foundation Fieldbus segments have now been completed. These involve five Micro Motion T-Series straight tube Coriolis meters, monitoring heavy oil flows along 50mm lines in the distillation area, and providing signals to five Masoneilan control valves, fitted with Fisher Fieldvue digital valve controllers.

• Emerson Process Management
  e103@industrialnetworking.co.uk