Think of the usefulness of the diagnostics in your automobile: Few of us know or even care about the hundreds of functions being carried out by a car’s “brain” under the hood. On-board diagnostic (OBD) systems give the vehicle owner or repair technician access to the status of the various vehicle subsystems.
Modern OBD implementations use a standardized digital communications port to provide real-time data in addition to a standardized series of diagnostic trouble codes that allow a technician to rapidly identify and remedy malfunctions or potential problems within the vehicle. Your car’s “Check Engine” warning indicator, however, is only helpful if the owner recognizes the benefit of being alerted to a pending problem and then takes action to have it investigated. In an industrial setting, the equivalent of the “Check Engine” light in smart measurement devices is the diagnostic information.
Of course, if you don’t know if the warning light is on, you won’t recognize potential problems or communicate them to the people who could use that information to rectify the problem and avoid unplanned situations.
Intelligent Device Diagnostic Information
The type and amount of diagnostic information in your intelligent devices varies by product type and supplier. Diagnostic information − the “hidden asset” − can be grouped into two categories: 1) common/universal attributes; and 2) device specific attributes. Following is a partial list of examples in each category, so be sure to speak with your device supplier to get the complete list of information and capabilities in each of your intelligent measurement devices: Common and Universal Attributes – Alerts and Device Status Information
- Analog and digital process measurement values (PV) do not match: This might indicate condensation (water) in the device housing.
- Device status alerts: This may indicate a device malfunction, loop current fixed, PV out of limits, maintenance required, etc.
- Cold start or reset: Potential power failure or loop power supply problems.
- 30-40 data items: Standard in most devices including four to eight process variables and range values.
- Remote access: Check all diagnostics from the safety of the control room or instrument shop.
Device Specific Attributes – Device Performance of Process Information
- Magnetic Flowmeter: Empty pipe detection or coated electrodes, conductivity variations, etc.
- Pressure Transmitter: Plugged impulse lines, flow rate, internal temperature, etc.
- pH Analyzer: Electrode performance problems (reference or measurement electrodes).
- Valve Positioner: Stem position, supply or actuator pressure, total strokes, deviation from SP, etc.
- Vortex Flowmeter: Shedder bar frequency, flow rate too low.
- Coriolis Mass Flowmeters: Presence of trapped air, build up, etc.
NAMUR, Europe’s preeminent process automation user association, has published recommendations in a document titled “NE 107, Self-Monitoring and Diagnosis of Field Devices,” which provides guidelines on displays and alerts to help plant operators monitor the status of field devices. By standardizing on the symbols defined in NE 107, operators can get a quick indication of the “Check Engine” status for each of their devices. One of the greatest benefits of these new NE 107 status functions is the customization available based on the specific application. In general, the manufacturer defines a default mapping but the user can customize the mapping based on plant experience or the specific application.
Once the configuration is complete, the status can be simulated so you can verify that the configuration matches your expectations. The key point is that these intelligent devices can provide the hidden asset in the form of a “Check Engine” light displaying the condition of your critical devices − the ones that can shut your plant down. A technician can then look at the diagnostic information available in the device to mitigate the situation. Using your DCS or asset management software you can quickly assess the status of your devices saving time and money; and likewise improve your plant’s safety and energy efficiency.
Move From Reactive To Proactive
In many updated control and asset management systems, intelligent device diagnostic information is accessible and available for immediate use. With all this data, a change in work processes is increasingly important to make the right decisions. Changing your maintenance activities from reactive (work on what is broken) to more proactive or even predictive (fix small problems before they turn into bigger problems) improves production and saves money. Imagine the benefits of using real-time device diagnostics to reduce the number of trips to the field, prevent an unscheduled shutdown or reduce the length of a scheduled shutdown. W
Whether you’re part of the reliability, maintenance, process improvement, management or other plant function, putting this valuable information to work can produce big results with relatively small investments and with very low risk. ISA is in support of open standards such as ISA108 to help with standardized work flow processes to manage field data and ISA103 for easier integration of field and network information.
By using smart device data, and integrating intelligent device diagnostics into an asset management or automation system, you begin the process of monitoring the “Check Engine” status allowing the opportunity to improve your bottom-line profitability. Take the first step to discover the hidden asset in your own intelligent measurement devices. Speak with your automation suppliers and learn about new solutions that enhance your facility to take full advantage of the diagnostics in intelligent devices that identify minor problems before they become critical − lowering maintenance and operating costs.
About the Author
Ian Verhappen, P.Eng., CAP, is a senior project manager at CIMA+ where he specializes in industrial communications networks, including Foundation Fieldbus technology; control system migrations/upgrades; process analyzers; sample systems; and oil sands automation. Ian, an ISA Fellow, has been involved in digital communications since 1994. He helped to install the first multi-vendor Foundation Fieldbus project in 1996. Since then, he has served as both a project engineer/designer and an external review consultant for a number of companies in pulp and paper, mining, food processing, water and wastewater, oil sands processing, petrochemical and refining industries. Ian is an active ISA volunteer leader, serving as Vice-President of ISA Standards and Practices and a former ISA District 10 Vice President. As a leader in automation practices, he has worked closely with the Standards Council of Canada and the International Electrotechnical Commission (IEC). He currently serves as Canadian Chair of IEC TC65, SC65B and SC65E. He is co-author of several ISA books, including A Guide to the Automation Body of Knowledge and Foundation Fieldbus. An inductee into the Process Automation Hall of Fame, Ian earned a bachelor of science degree in environmental science and a bachelor of chemical engineering degree, both from the University of Alberta.