There Are Many Good Reasons to Get Going and Apply Fieldbus in Your Process Plant
Potential Savings of Capital Expenditure?
Cost of ownership is key to answering the question of productivity and return on invest with fieldbus. Because calculated savings are based on assumptions and are subject to individual assessment, it is important for every decision maker to get a sample calculation and seriously question the assumptions, modifying them for relevancy to the actual plant.
While fieldbus can have significant savings on actual wiring, this saving is often offset through higher costs for instruments and DCS interface cards. Today this is still largely a question of economies of scale. Currently, the number of instruments sold with 4…20 mA interface is still significantly higher compared to fieldbus. In essence, the CapEx will be approximately the same.
Add to that the softer factors where fieldbus technology can help reduce CapEx:
1. Fieldbus instruments all have the same interface. This means that changing devices during commissioning requires zero hardware change in the DCS. To add an extra instrument, just find that open plug in a field junction box. Neither size nor function matter.
2. Multivariable instruments deliver more than one measurement. Pressure transmitters often deliver the temperature for free. Coriolis meters communicate volume and density measurements. It requires an extra look at the process design to reduce the number of instruments necessary.