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Advanced instrumentation network control system (USA)
United States
PROFIBUS,PROFIBUS PA

Project
The Joint Abbotsford Mission Environmental System (J.A.M.E.S.) water pollution control center implemented an expansion program that incorporates an emerging communications network technology based on PROFIBUS PA. The project requires the addition of new instrumentation that included temperature, level transmitters and flow transmitters to be installed at the new grit tank, pasteurization tank, and digester areas.

Solution
PROFIBUS PA has been chosen as the communication network of choice because it provides:

  • Savings in cabling cost
  • Reduction in the number of PLC analog input modules
  • Redundant cabling support
  • Operation within Intrinsic safe environment without the added cost required to install intrinsically safe barriers 
  • Enhanced instrument diagnostic and maintenance
  • Ease of upgrading existing instruments based on the conventional 4 to 20mA signal.

The new instrumentation data are networked into four PLCs through a redundant cabling architecture. PROFIBUS is designed to allow configurations where redundant cabling is possible and this takes account of wire breakage. Instrument failures can also be configured to ignore or to trigger a stop in the PLC while unaffecting instruments can continue operation.

Conclusion
With PROFIBUS PA, operators can now access more information from each instrument in addition to the process variable. Instruments with self-checking diagnostic functions can now report failures to the plant's alarm system. PROFIBUS will also allow operators to quickly locate instrument problems by conducting a status check from the control room SCADA console and can access information of the fault using software and diagnosis wizards.
One of the most important features of PROFIBUS is its ability to allow both the existing (4 to 20mA) instruments and the PROFIBUS PA system to utilize the same twisted pair cable system used throughout the plant. Existing instruments can now be easily upgraded to a PROFIBUS PA system in the future without the expense of laying new cable.