Fieldbus Segment Design
The buses selected for our facility also fall into two distinct categories—a powered bus and an unpowered bus. The powered buses include Foundation fieldbus and AS-i bus. The unpowered buses include Profibus-DP and DeviceNet. The powered bus includes the communications and device power on the same wires.
|FIGURE 4: FIELDBUS VERSION|
| Fieldbus reduces the amount of space needed. |
The FTBs would house this short-circuit protection equipment for field devices of both powered buses, and we hoped to identify a common short-circuit device type that could be used for both Foundation fieldbus and AS-i. At the time of our detail design effort, Relcom offered its Spurguard for Foundation fieldbus. We’d also hoped to find something in a similar form factor for AS-i. At our request, Relcom designed and manufacturing a Spurguard for AS-i, which enabled our powered buses to have the same look and feel. Figure 6 below illustrates where he Relcom’s Spurguard devices are located.
Our project’s ultimate goal was to have the stick-built process equipment, which included vessels, transfer panels, and skid equipment using an identical segment design approach. This allowed us to develop segment design standards that were followed by our engineering design contractor for the stick-built process equipment and by the various skid vendors.
Are Fieldbuses Right for Biopharma and You?
CRITERIA used for assessing the viability of fieldbuses include the following:
- Instrumentation availability: are instruments typically found in a biopharm facility available with fieldbus?
- Bus selection and bus quantity: would it require two, three, or four fieldbuses to address the various I/O types?
- Electrical classification: could bus instrumentation be deployed in electrically hazardous environments?
- Cost: is bus implementation more expensive? If so, is there payback over time based on a predictive maintenance model (inherent in bus systems) compared to our present run-to-failure?
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