Control In The Field Enhances Process Integrity
New white paper examines business value proposition of FOUNDATION™ technology
Papers maybe downloaded from the Fieldbus Foundation Site here.
The Fieldbus Foundation, conducting a press briefing at SPS/IPC/DRIVES 2009 in Nuremberg (D) announced that a new ARC Advisory Group white paper describes the benefits of control in the field (CIF) with FOUNDATION™ fieldbus. According to ARC CIF strategies supported by FOUNDATION technology improve process control performance by allowing for superior reaction to deterministic disturbances in industrial plant operations.
In the white paper, titled “The Business Value Proposition of Control in the Field,” ARC describes the incorporation of a function block structure and other supporting functions in FOUNDATION fieldbus providing a complete automation infrastructure for operational excellence. Embedded control functionality in FOUNDATION devices is one of the key enablers for achieving high availability control and a stepping-stone towards single-loop integrity.
Results from testing and real-world applications demonstrate that control in the field with FOUNDATION technology has the potential to deliver a 30 percent improvement in control performance with very fast, fast and medium-speed process dynamics. CIF can also provide up to three-times higher control loop availability than conventional analogue control.
Fieldbus Foundation President and CEO Rich Timoney indicated that the new white paper provides valuable insights for automation end users seeking to maximise the benefits of FOUNDATION technology. “As reported by ARC, FOUNDATION fieldbus provides business value in three key areas—process integrity, business intelligence, and open and scalable integration of information across process manufacturing plants. FOUNDATION fieldbus control in the field ensures tighter control and higher availability. It is a critical element in providing significantly enhanced process integrity for many applications and control loops. This enables process industry end users to increase revenue and profits, which are the drivers for investing in new technologies.”
Timoney added, “Thanks to recent, comprehensive studies of control in the field, end users now have the first definitive proof that FOUNDATION-based CIF strategies yield significant operational improvements, which result in bottom-line business benefits.”
Shell Global Solutions International (SGSI) has performed extensive evaluation of control in the field. A statement by the company indicated, “Control in the field using FOUNDATION fieldbus technology is recommended by SGSI for simple and cascading loops, not for complex loops. Major benefits identified by SGSI are reduced process controller loading, reduced network traffic enabling more loops per segment, as well as very fast loop response.”
With control at the device level, process automation functions are truly distributed and there is no single point of failure in the control system above the H1 (field device) level. If there is a malfunction in the Human-Machine Interface (HMI) and a loss of visibility into the process, controllers, or any other component in the system and the control loop, including intelligent field devices, actuators and positioners, and the network, remain unaffected.
Field-level control also enables greater flexibility in plant automation strategies. For example, controllers are free to handle higher-level control functions such as advanced control and optimisation. FOUNDATION fieldbus allows for "dynamically instantiable function blocks,” meaning that function blocks can be activated in different components of the system as they are required. In addition, there is a large library of different block types that can be used aside from basic PID, such as switches, alarms, etc.
According to ARC Analyst Larry O’Brien, principal author of the white paper, control in the field improves control loop performance due to its ability to offer faster sample rates and shorter latencies in the read-execute-write cycle of control loops. While the advantages of increased integrity, flexibility and reliability can be attributed to all control in the field loops, control loop performance benefits can be most significant in fast process loops, including many flow and pressure loops and some temperature, pH, position and speed loops. The improved flow and pressure control provided by control in the field means that the performance of slower loops could also be improved because of the complex interactions of control loops in process plants.
Industrial Systems and Control Ltd. (ISC), a specialised control engineering consultancy with close links to the Industrial Control Centre at the University of Strathclyde, Scotland, recently issued a study titled “Control in the Field: Analysis of Performance Benefits.” In the first of a series of simulation studies, ISC examined the differences in timing and sequencing associated with control in the field with a fieldbus system versus a fieldbus system employing control in the host (DCS) to establish typical latencies and sample rates that limit control performance. Many different scenarios and process dynamics were tested.
As described in the ARC white paper, ISC found that in typical fast process applications, control in the field can provide improved performance over conventional analogue control. Improvements in response time of between 10 and 30 percent were recorded, in addition to improvements in disturbance rejection of up to 20 percent.
The white paper concludes that the performance improvements of control in the field must ultimately be linked to a business value proposition, which is the measure of value for the implementation of any new technology in the plant. Additional benefits above and beyond control performance include reducing product variability, speed of grade changes, reduced time to startup, increased availability, and energy savings.
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