Busting Myths About Foundation Fieldbus

Mythperceptions About Fieldbus Can Be Changed

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Wasted Effort
Figure 1. End users estimate that more than half of maintenance activities result in no action. Predictive diagnostics can help users develop a proactive maintenance strategy that avoids unnecessary trips to the field for routine scheduled maintenance.

Myth: There Aren't Enough Systems Integrators with Good Project Implementation Experience

With thousands of systems installed, there is a substantial body of knowledge that has been established around successful implementation of Foundation fieldbus projects. The list of both suppliers and systems integrators with experience in implementation is substantial. Representatives from leading engineering firms are on the Fieldbus Foundation End User Advisory Council, and were instrumental in the creation of the System Engineering Guide.

Myth: Control in the Field Poses Risks and Compromises System Availability

Control in the field is a chief enabler for achieving high-availability control and single-loop integrity. If there's a malfunction in the HMI that produces a loss of visibility into the process and stops communication with the controllers or any other component in the system, the control loops, including intelligent field devices, actuators, positioners and the network remain unaffected. In cases where control resides in the DCS, field-level control can add another level of redundancy. Many end users have already managed to avoid unplanned downtime when field level control took over after a failure in the system. Field-level control means not only increased availability and reliability, but also increased flexibility. In addition, controllers are free to handle higher-level control functions, such as advanced control and optimization.

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
Benefits include
  • Improved control loop performance
  • Increased reliability & availability
  • Improved loop integrity
  • Reduced loading on DCS/PLC and network
  • Lower capital and installation costs
  • Reduced operating costs
 

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.

Myth: I Can Get Most of the Field Diagnostics I Need from Other Technologies

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.

Myth: There Are Interoperability Issues with Devices

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
  • Statistical process monitoring: Uses process "noise" to detect process problems such as hydrate formation, scaling formation, thermowell coating, etc.
  • Predictive thermocouple degradation diagnostics: Process/cold-junction sensor failures, sensor drift, configuration error.
  • Extreme temperature tracking: Heat conducted from integral sensor to transmitter housing, transients.
 

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.

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