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Recently, U.K.-based Industrial Systems and Control Ltd. (ISC, www.isc-ltd.com) released a study called "Control in the Field: Analysis of Performance Benefits." In a series of illustrative simulation studies, ISC determined that control in the field has the potential to offer improved control-loop performance due to its ability to offer faster sample rates and shorter latencies in the read-execute-write cycle of a control loop.
Benefits of Control in the Field
Many end users have taken advantage of control in the field for years, and have had no problems with system availability or fault tolerance. Applications where control in the field are especially effective include compressor anti-surge control, many flow and pressure loops, and some fast temperature, pH, position and speed loops.
Power generation has long been one of the major users of Foundation fieldbus, even in nuclear applications. There are many important pressure and flow loops in a typical power generation facility that have an impact on overall plant performance, and can determine how fast a power generation facility can handle load changes or increase process efficiency.
Some network technologies offer diagnostic information, either digitally or through 4-20mA technology. Digital networks can handle more diagnostic data than their analog counterparts can, but their real value goes beyond diagnostic data. It's what you do with all that data to turn it into useful information to help you run your business. Foundation fieldbus technology has the ability to take large amounts of data from field devices, digital valve positioners and other instruments, and turn it into useful information.
Problem resolution hinges on the ability of systems to put data into the appropriate context. The data from Foundation fieldbus devices is constantly being updated. Instead of having to poll devices for data, the data is pushed to the applications and the people that need it when they need it. Data is prioritized to avoid alarm flooding. The data is time-stamped, and you can archive and retrieve it. Foundation fieldbus technology also has peer-to-peer communication capability, allowing devices to communicate with each other, which significantly expands the diagnostic capability of the overall system.
One of the founding principles of the Foundation is the support of interoperability—the ability to operate multiple devices from multiple manufacturers in the same system without loss of functionality. The H1 Interoperability Test Kit (H1 ITK) tests the functionality of a device and its conformity with Foundation fieldbus function block and transducer block specifications.
Diagnostic Data Provided by Registered Foundation Temperature Transmitter
An excellent tool for troubleshooting and debugging devices, the test kit includes all hardware and software required to ensure a manufacturer's complete device interoperability as specified by the Foundation's official registration testing procedure. The H1 ITK has now been updated to support field diagnostics capabilities, which standardize how all devices communicate their diagnostic data to the host system and asset management system, regardless of the vendor.
The Fieldbus Foundation also offers an extensive Host Registration Program. The foundation's Host Profile Registration Process requires that the host profile under test must support a clear set of required features. Under the registration process, hosts successfully completing the test requirements are authorized to bear the official Foundation fieldbus product registration symbol. Hosts may include configuration tools, recording devices, alarm display panels, HMIs or systems with a combination of functionality.
Foundation fieldbus technology is well-suited for modernization and migration projects, not just for large grassroots applications. According to ARC Advisory Group (www.arcweb.com), control system migration is the biggest issue facing end users today, and the installed base of process automation systems reaching the end of their useful life is worth around $65 billion. Over the years, many systems have been upgraded in a phased manner, usually at the application level. Today, we see more and more of the I/O, wiring and control infrastructure that needs to be replaced.
More than anything, users are looking to avoid a functional replacement in their migration strategy—replacing their old system with a new system that has exactly the same functionality and architecture. As more end users replace their legacy hardware and applications, they are realizing the value of Foundation fieldbus technology for getting more diagnostic data from their devices, reducing unplanned downtime and cutting down on the amount of wiring, I/O and associated labor and infrastructure required in a conventional 4-20mA system.