Foundation fieldbus
- 2. What is fieldbus? Family of industrial computer network protocols IEC 61158 Standard Multiple instruments- Single cable Used for real-time distributed control
- 3. Traditional 4-20mA field wiring Rat’s nest of wires, cables and terminators
- 4. Fieldbus configuration Trunk Power conditioner Terminators Device couplers
- 5. Trunk Carries both digital signal and DC power Connects up to 32 field devices to DCS Interface at DCS is called H1 card for FF Wiring and power requirement ◦ Minimum device operating voltage : 9V ◦ Maximum bus voltage : 32V ◦ Maximum cable length (trunk + spur) : 1900m Maximum distance ◦ 9500m with 4 repeaters
- 6. Fieldbus power supply 24VDC 350 mA Components of Fieldbus power supply. ◦ Isolation ◦ Power conditioning ◦ Current limiting
- 7. Terminator Two terminators are required on each segment One at the control room end of cable Other is in the junction box in the field An extra terminator cause 300 mV drop in signal level
- 8. Device couplers One or more fieldbus devices can connect to the segment at one location Short-circuit protection
- 9. Redundant fieldbuses All communications and power depend on single twisted pair wire If the trunk cable fails it can “take down” all the segments at one time MooreHawke’s FaultTolerant fieldbus system
- 12. System architecture Each layer adds a portion of the message that is transmitted on the fieldbus.
- 13. Physical layer Converts received messages into physical signals and vice-versa. Add, remove preamble, and delimiters Signals are encoded using Manchester code
- 14. Physical layer 31.25 kbps fieldbus signaling ◦ Device delivers ±10 mA at 31.25 kbps ◦ 1.0 volt peak-to-peak voltage modulated on top of the DC supply voltage
- 15. Data link layer DLL ◦ Controls transmission of messages ◦ Manages access to the fieldbus through LAS ◦ LAS is a deterministic centralized bus scheduler ◦ Basic device and Link master
- 16. Data link layer Scheduled communication ◦ LAS schedules publisher/subscriber communication ◦ Scheduled data transfers are done deterministically.
- 17. Data link layer LAS Algorithm
- 18. Fieldbus access sublayer Communication Relationships
- 19. Fieldbus Message Spec. FMS services allows user applications to send messages to each other across the fieldbus FMS describes ◦ Communication services ◦ Message formats ◦ Protocol behavior
- 20. User layer Types of blocks used in user application ◦ Resource block ◦ Transducer block ◦ Function block
- 21. User layer Resource block ◦ It describes characteristics of device. ◦ Used to configure devices Function block ◦ Control system behavior ◦ FF has sets of standard function blocks. Transducer blocks ◦ Calibration date, sensor type
- 24. Justifying fieldbus Wiring ◦ 98 % reduction in homerun Control room ◦ 84% reduction in terminations freed up two third of cabinet space Cost saving ◦ Lowers CAPEX and OPEX Commissioning ◦ Easy to diagnose equipment problems ◦ Cut maintenance cost
- 25. Questions?
- 26. Nested messages in HSE
Editor's Notes
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