The Fieldbus Diagnostics Difference


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What's different about FOUNDATION fieldbus diagnostics. How we can manage diagnostic information better.

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  • For FF the device "pushes" the alert to the intelligent device management software almost instantly. This quick delivery mechanism in the FF protocol enables operators to respond faster to a critical device failure. There is time to take action before the process is affected, for instance operating the loop in manual.   Because Foundation devices have an internal real-time clock kept synchronized with the system, the alerts are time-stamped in the device as they are detected, and thus more accurate as compared to traditional time-stamping in the controller after status was polled. This makes it easier to correlate to external events to determine the root cause and eliminate the source. Knowing exactly when abnormal situations occur can help technicians troubleshoot.
  • Understandable = Provide a clear message that is easily understood, not a cryptic code Diagnostic = Helps with the identification of the problem Advisory = Provides guidance towards the correct action Focusing = Directs attention to the important aspects
  • Self-diagnostics in transmitters with 4-20 mA output flag sensor failure etc. by driving the signal to a failsafe state: either high > 20 mA or low < 4 mA. This in turn drives the PID controller action to one extreme, fully opening or fully closing the control valve (depending on the transmitter high/low configuration) as if there was a process problem. Similarly, high alarms would trip on the high signal and vice-versa, as if there was a process problem. That is, most control systems can't tell this 20 mA or 4 mA current indicate a sensor failure. The operator cannot tell the difference between a sensor failure and a process problem, because they look the same.   However, for FOUNDATION fieldbus, device diagnostics is also reflected in the status communicated together with real-time values between devices. Among other things, this status indicates the quality of the value as a simple Good, Bad, or Uncertain. If there is a sensor failure, the status flags this as Bad. Therefore, both the operators and the control strategy can clearly tell the difference between a device problem and a genuine process problem. If the sensor fails, the status turns Bad. The operator knows that the process itself is most likely OK and in many cases need not be shut down. The control strategy sheds to manual mode. The operator can take action to handle the process, minimizing downtime. However, if the process is critical the loop is configured to initiate its fault state on Bad status. That is, an FF system is able to make use of diagnostics to distinguish between a process problem and a device problem, thus avoiding unnecessary shutdowns increasing plant availability.
  • This slide merely points out that after the fix, you might be able to get additional information about what led to the problem or what was done to the device at an earlier time. Audit windows can be very helpful in locating exactly when something might have been impacted by an “external” action. For example, one can locate when a range might have been changed in an AI block and from what computer, etc.
  • More versatile statistical process monitoring statistical process monitoring is available for both the FF and 4-20 mA (HART) versions of pressure transmitters to detect process anomalies. However, the FF version is more versatile since it has a more powerful function block which can extend ASP applications.
  • Statistical process monitoring The FF version has statistical process monitoring for abnormal situation prevention. statistical process monitoring is able to detect abnormal process behavior before operation constraints are reached, providing an early warning. statistical process monitoring alerts provide process engineers with a better view of what is going on in the process. It may be used to detect hydrate formation in natural gas lines, scaling formation, and thermowells coating etc. Predictive Thermocouple Degradation Diagnostics Both the 4-20 mA (HART) and FF versions detect if sensor wiring is open or shorted or if a sensor breaks and fails completely, but the FF version has predictive thermocouple degradation diagnostics that alerts before the thermocouple fails. Such failure prediction helps reduce process downtime and decrease energy costs   Thermocouple Degradation Diagnostic can help detect a failing thermocouple and allow preventive maintenance to be scheduled. Scheduled maintenance avoids the removal of a thermocouple from a process while in operation, which is not always possible. The automatic testing provided by the Thermocouple Degradation Diagnostic feature also eliminates the need for periodic manual resistance testing, which may lower maintenance costs and cause less process disruption.
  • Continuous Performance Diagnostics The performance diagnostics run continuously inside the positioner known as the "PD inside" feature, and any abnormalities are reported through alerts (in the 4-20 mA HART positioners the diagnostics is done on-demand from software using. Common Diagnostics Partial Stroke Testing (PST), travel histogram, step-response, valve signature, pressure sensor failure, abnormal drive current, travel deviation, reversal count alert, accumulated travel alert, low supply pressure, high supply pressure, position feedback sensor failure, etc.
  • Similarly, diagnostics such as travel time, stuck valve, and possibly partial stroking for on/off valves is possible with FF valve couplers.
  • Mount the gas chromatograph near the process to eliminate long sampling lines to the analyzer shelter. Analyser shelter is not required. Use fieldbus to bring the data and diagnostics back. Tank gauging has always used digital communication for accuracy – never 4-20 mA. The difference is how and when Fieldbus makes the digital data available. Convenient and timely.
  • Examples of a few testers on the market today. More are in the works, so check with the vendors beforehand to see if there is a new one that needs to be mentioned. Note that these are hand-held units. On-board software-based diagnostics will be covered in a later slide. Each tester has features (and limits) to what is does.
  • Specialized windows place the data in locations where the user can more easily absorb the information and visualize what is occurring. Also, even when specialized windows are not available, some devices contain tattle-tale lights which at least focus the user to a particular reason a diagnostic alert may be occurring.
  • Note the quantity of available parameters Note the difference among different manufacturer offerings. One make/model only has 29 parameters, while another has 230! Ask what does this mean to the user? The problem this brings to the new user is the amount of data one may have to deal with. Which data points are critical? Which do not make much difference? Which are there only for the manufacture's use
  • The Fieldbus Diagnostics Difference

    1. 1. ©2013 Fieldbus Foundation FOUNDATION Fieldbus: the Diagnostics Difference
    2. 2. ©2013 Fieldbus Foundation • There’s Diagnostics and There’s Diagnostics. • The Value of Fieldbus Diagnostics • Physical Layer Diagnostics • Managing the Diagnostics Storm • PAM and IDM Software, Work Processes and Training
    3. 3. ©2013 Fieldbus Foundation
    4. 4. ©2013 Fieldbus Foundation Why do we Use Diagnostics? • Diagnostics can be a valuable tool that can help save you time and money and avoid unplanned shutdowns. • Diagnostic data can be vague and require a lot of digging to get to the root cause. • Diagnostic data can also provide you with avalanche of useless information that can grind your process to a halt. • Not all technologies handle diagnostic information the same way. • Trick is to get only the right information, at the right time, to the right people.
    5. 5. ©2013 Fieldbus Foundation The Current State of Non Digital Diagnostics: Or the Idiot Light • Doesn’t tell you what’s wrong • No predictive guidance • Is it a process problem or device problem? • Sensor problem? Electronics problem? Who knows.
    6. 6. ©2013 Fieldbus Foundation The FOUNDATION Fieldbus Diagnostics Difference • FOUNDATION fieldbus has a unique approach to management of device diagnostics. • The publish/subscribe structure of FOUNDATION fieldbus means that diagnostic information is available immediately to a wide range of workers in the plant. • Data is available at all times and is constantly being updated. • Allows you to organize and prioritize data in a way that turns it into useful information for the right people at the right time.
    7. 7. ©2013 Fieldbus Foundation Fieldbus Device Alerts Bring the Data to the Front Early warning system Gives operators more time to take action before device problem affects the process Time-stamped Sequence of event recording Relate problem time to true causative factors
    8. 8. ©2013 Fieldbus Foundation Actionable Information In the past, device alarms were not displayed with actionable information  Just error messages or cryptic codes – “Error 13”  The technician didn’t know what to do Device alarms must be displayed with advice that maintenance technicians can act upon Use devices which provide guidance for the device diagnostic alarms... Understandable Provide a clear message that is easily understood, not a cryptic code Diagnostic Helps with the identification of the problem Advisory Provides guidance towards the correct action Focusing Directs attention to the important aspects
    9. 9. ©2013 Fieldbus Foundation Distinctions should be made between Instrument and Process Diagnostics Sensor includingprocessconnectionandsensor electronic Instrument Electronic Configuration e.g.Linearization Process Process/ Environment Information Root Group InformationInformation RootRoot GroupGroup InstrumentInstrument Process/ Environment Process/ Environment SensorSensor ElectronicsElectronics ConfigurationConfiguration ProcessProcess
    10. 10. ©2013 Fieldbus Foundation Data Quality Indication in Action
    11. 11. ©2013 Fieldbus Foundation Device Problem or Process Problem – Do you have sufficient data to guide you? Hardwired Device drives current <4 mA or >20 mA on device failure Masquerades as a process problem PID counteracts thus tripping the loop Operator cannot tell the difference between a process alarm and a device alarm Fieldbus Device health indicated by associated status Clear distinction between device problem and process problem Controller holds last position and alarms on device failure Shutdown is optional Operator can easily distinguish process problem from a device problem
    12. 12. ©2013 Fieldbus Foundation After the Fix – Embedded Causes? When was device configuration changed? Who did it? What was changed?
    13. 13. ©2013 Fieldbus Foundation Fieldbus Pressure Transmitter Data Provides: More versatile statistical process monitoring Uses process “noise” to detect process problems: Pulsation indicative of pump or compressor damage Entrained air = flow measurement errors Leaks in impulse lines and manifolds Plugged impulse line
    14. 14. ©2013 Fieldbus Foundation Fieldbus Temperature Transmitter Data Provides: Statistical process monitoring: Hydrate formation, scaling formation, thermowell coating, etc. Predictive thermocouple degradation diagnostics - before a T/C or RTD fails, Extreme Temperature Tracking Heat conducted from integral sensor to transmitter housing
    15. 15. ©2013 Fieldbus Foundation Fieldbus Control Valve Positioner Data Provides: Continuous (not on-demand) Performance Diagnostics: Actuator/tubing leakage, air supply availability, calibration shift, etc. Common Diagnostics Partial Stroke Testing (PST), travel histogram, step-response, valve signature, pressure sensor failure, travel deviation, reversal count alert, accumulated travel alert, supply pressure, position feedback…
    16. 16. ©2013 Fieldbus Foundation Fieldbus On/Off Valve Data Provides: Open/close travel time On/Off Valve Cycle counts Stuck valve
    17. 17. ©2013 Fieldbus Foundation Fieldbus Data Goes Beyond “Common” Transmitters and Valves Gas Chromatographs Tank Gauging Systems
    18. 18. ©2013 Fieldbus Foundation Segment data can provide a good analysis of the system’s health and may include: Communications Data - Testers/Communicators  Monitoring and diagnostics  Online and in real-time with remote access  Simple-to-interpret data reports  Built-in oscilloscope for visual detail
    19. 19. ©2013 Fieldbus Foundation Data can Appear in a Variety of Forms Diagnostic WindowsDiagnostic Lamps
    20. 20. ©2013 Fieldbus Foundation OK, so FOUNDATION Fieldbus clearly can provide the data I have always wanted… So what can possibly stop me from getting the most value from the data?...
    21. 21. ©2013 Fieldbus Foundation The Power is in the Data, and there can be a lot of data! Manufacturer (Coded) A B C D E F G H I J K L Block Type Number of Parameters in each block XD 1 (generally the measurement transducer) 44 106 85 34 37 91 45 29 45 61 45 42 XD 2 38 42 36 50 34 27 XD 3 93 20 XD 4 55 17 XD 5 33 # of parameters 230 148 121 34 37 211 45 29 79 88 45 42 # of Transducer Block Parameters in d/p transmitters. Extracted from Differential Pressure Transmitters with similar capsule ranges At least one device contained~75 parameters specifically for specialized diagnostics Different Manufactures = different levels of granularity (data)
    22. 22. ©2013 Fieldbus Foundation The Diagnostics Storm Sample Diagnostic Parameters of a FOUNDATION Fieldbus Flowmeter
    23. 23. ©2013 Fieldbus Foundation NAMUR NE 107 Definition of NE 107 Status Signals
    24. 24. ©2013 Fieldbus Foundation Definition of NE 107 Status Signals
    25. 25. ©2013 Fieldbus Foundation 32 Bit Bitstring for Prioritizing Diagnostic Data
    26. 26. ©2013 Fieldbus Foundation Grouping Diagnostic Conditions
    27. 27. ©2013 Fieldbus Foundation Diagnostic Mapping Workflow
    28. 28. ©2013 Fieldbus Foundation Embedded in Supplier Solution
    29. 29. ©2013 Fieldbus Foundation Utilizing Diagnostic Data from Multiple Devices Together Utilizing Diagnostic Data from Multiple Devices • Certain diagnostic anomalies expressed in multiple field devices can indicate an anomaly or impending abnormal situation in the process. • Placing a structure around which these diagnostics can be consistently managed makes these more advanced diagnostics possible. • Being able to diagnose the overall health of a unit, area, or even the entire plant is predicated on this good diagnostic data at the most basic level of the measurement devices and actuators.
    30. 30. ©2013 Fieldbus Foundation Plans for Using a Plant Asset Management System
    31. 31. ©2013 Fieldbus Foundation Location of Intelligent Device Management Software In the past, intelligent device management software fell into disuse because it was not easily accessible  Hidden away in the workshop  Local equipment room (LER) / field auxiliary room (FAR)  Stand-alone workstation in the corner of the control room • Separate login • Must type the tag to search Must be accessible to become a natural part of the daily work process  Client integrated on the operator console • A mindset change • The idea is not for operators to take over maintenance  Dedicated maintenance workstation for instrument technicians
    32. 32. ©2013 Fieldbus Foundation Engineering Operator Operator Operator Maintenance Traditional Architecture Operators Using Device Diagnostics as Early Warning for Process • Intelligent device management client integrated in DCS operator console • Device diagnostics becomes a natural part of daily operations • Operators tend to the process, not the devices Plus: Process visibility Plus: Device Diagnostics Plus: Device Configuration
    33. 33. ©2013 Fieldbus Foundation Training for New Competency In the past the operators got training on the operator station software  But not the device management software The technicians got training on the handheld field communicator  But not the device management software Make sure operators and technicians are trained on the device management software  Understand the NE107 status signals  Navigate the device menu  How to search for tags, plant unit, device classes  How to search for specific device types
    34. 34. ©2013 Fieldbus Foundation Work Processes Have to Be Rewritten Around Device Management Software Standard company work processes for 4-20 mA and on/off signals are not optimized for intelligent devices  Technicians start by going to the field to inspect Rewrite work processes around the device management software  Urgent maintenance: • Troubleshoot and verify from the device management software first, before going to the field, to determine if there is a problem  Daily maintenance: • Extract device diagnostic alarm report from intelligent device management software, and prioritize before morning meeting  Turnaround maintenance: • Screen which devices need calibration and adjustment to better plan the turnaround activities
    35. 35. ©2013 Fieldbus Foundation Let’s Now See Device Diagnostics in Action!
    36. 36. ©2013 Fieldbus Foundation