Feb 6, 2014 - Viewing and monitoring of internal variables can also be helpful for troubleshooting. .... A valve positio
wp_EDDL device diagnostics rD 02/06/2014 00:44:00
Intelligent Device Management Tutorial: Device Diagnostics Device diagnostics can be carried out using a handheld communicator in the field, a laptop in the workshop, or from intelligent device management software as part of asset management system, either from a dedicated maintenance console or integrated in the operator console (see separate white papers on integrated operation and NAMUR NE107). Electronic Device Description Language (EDDL) is the technology used by device manufacturers to control how the device diagnostics is displayed to the technician. EDDL makes diagnostics of smart transmitters and other intelligent devices easier thanks to user guidance such as wizards and help, and provides unparalleled consistency of use. With the “device level access” and these wizards the user interface for fieldbus devices and for 4-20 mA/HART devices have become equally easy to use and look almost identical, but the device diagnostics is not the same. Viewing and monitoring of internal variables can also be helpful for troubleshooting. See separate white paper on internal variables.
Device Diagnostics Device diagnostics is performed by the device itself, that is, self-diagnostics or self-tests. 4-20 mA/HART, FOUNDATION fieldbus, PROFIBUS, or WirelessHART protocols are used to communicate the result of the self-diagnostics to the handheld communicator or intelligent device management software. Each protocol has a different mechanism for reporting diagnostics and therefore performs differently. That is, the computer software or handheld is used for display. In a vast majority of cases diagnostics is embedded in the device itself as firmware so that the device is monitored continuously. In some rare cases when the device is unable to perform the test, the test must be conducted from computer software, with the drawback it is not continuous, it is active only when the computer software is running. Different communication technology is associated with different power availability for the device, and thus different levels of sophistication are possible for the diagnostics. FOUNDATION fieldbus Information in FOUNDATION fieldbus devices is organized in different kinds of blocks: • Resource block • Transducer blocks • Function blocks The function blocks are referred to as the "Control Application" and the resource block and transducer blocks are referred to as the "Device Application". Each device has one resource block and one or more transducer and function blocks. Function blocks are the control strategy. There is one transducer block associated with each sensor or transducer. Each block has some device diagnostics (and some setup parameters). However, in the past, the compartmentalization of information by blocks made troubleshooting of fieldbus devices cumbersome as diagnostics in different blocks did not appear on the same page in the device management software (the technician had to know which block to look at for each potential problem to be checked). However, now EDDL "device level access" (aka "cross-block") makes FOUNDATION fieldbus devices easier to use by displaying all diagnostics on one page. Technicians will not have to worry about different kinds of blocks. www.eddl.org
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Function blocks
Troubleshooting of the function blocks (the control strategy problems) is normally done from the DCS engineering station, by system engineers, not instrument technicians. Transducer and Resource blocks
Transducer blocks and the resource blocks are for troubleshooting of the device itself, normally handled from the intelligent device management software. A device may have several transducer blocks including for example: sensor transducer block, actuator transducer block, display transducer block, and other transducer blocks for special features such as advanced diagnostics, flow computer etc. PROFIBUS PROFIBUS groups diagnostics in blocks (slots) somewhat similar to FOUNDATION fieldbus. This will not be explained again. In PROFIBUS the resource block is instead called physical block.
Device Integration Plants have a mix of simple and sophisticated (complex) devices from different manufacturers using different communication protocols. The diagnostics available depends on the type of device: • Pressure transmitter: sensor failure, plugged impulse line, sensor temperature limits exceeded • Temperature transmitter: sensor failure, thermocouple degradation • Control valve positioner: 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. • Shutdown valve monitor: Partial Stroke Testing (PST) • Coriolis flowmeter: flow tube stiffness, drive gain • Magnetic flowmeter: magnetic field strength, coil resistance, electrode resistance, grounding, noise, and empty pipe • Ultrasonic flowmeter: flow profile, turbulence, Speed of Sound • Vortex flowmeter: pickup failure • pH analyzer: glass electrode impedance, reference electrode impedance • Gas chromatograph: power failure, user calculation failure, warm start failed, heater out of range, flameout, flame over-temperature, no sample flow, low carrier pressure, and stream validation failure • Electric actuator / Motor Operated Valve (MOV): over torque, actuator fail, lost control voltage, lost phase, motor overload, and valve stall • Uninterruptible Power Supply (UPS): fuse blown • Variable Speed Drive (VSD) / Variable Frequency Drive (VFD): motor decelerating too quickly, overload, overheating, and mains loss • Bus diagnostics: supply voltage, noise level, signal level, and retransmission statistics The diagnostics available vary greatly from one manufacturer to the next
Poor Hosts The original DD technology from 1992 made it possible to troubleshoot all devices using the same handheld field communicator or laptop software. Before DD only proprietary solutions existed. The most basic content of a DD file is the Device Definition describing the blocks and the parameters in the device, including limits, options, and help etc. The original DD technology from 1992 also included Business Logic such as "wizards" (aka "methods") which is a kind of script created by the device manufacturer to guide the technician through more sophisticated test procedures, for instance valve step response test requiring the steps to be predefined and lastly a www.eddl.org
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prompt validation sequence before the self-test actually starts. Wizards thus make diagnostics and troubleshooting easy. Wizards, conditionals, and help are explained further in the section on EDDL. However, not all devices provided wizards in their DD file and not all intelligent device management software supported wizards. Lack of wizards was not a problem with the DD technology itself; it was poor implementation in many early products. However, for some devices, the manufacturer may chose to display test results graphically, such as a valve signature, vibration spectrum, or signal waveform. This was not supported by original DD technology. Thus diagnostics of some devices was not supported using DD. EDDL Device Definition
Business Logic
•Blocks •Parameters
•Wizards •Conditionals
User Interface Description •Menus •Graphics
Figure 1 Not all systems supported Business Logic, and the User Interface Description was not introduced until 2006. The EDDL enhancement done in 2006 is a User Interface Description which includes graphics such as trend charts, waveform graphs, dial gages, bargraphs, bar charts, and tables etc. Graphics, menu system, wizards, and conditionals are now mandatory for all FOUNDATION fieldbus and 4-20 mA/HART compliant host systems. Therefore, make sure to use a control system which supports enhanced EDDL.
Device Troubleshooting Made Easy EDDL technology provides a vast array of possibilities for the device manufacturer to organize the diagnostics display and make the device user-friendly, and also to add graphics such as waveforms for valve signatures and vibration spectrum etc. Depending on the type of device, the manufacturer uses different EDDL elements. No device uses all EDDL capabilities. EDDL supports both basic and advanced diagnostics for simple as well as sophisticated (complex) devices. Below are a few examples of devices to give an idea of what device manufacturers have done to make their devices easy and fast to troubleshoot and repair. Thanks to EDDL wizards, device diagnostics for FOUNDATION fieldbus is now just as easy as 4-20 mA/HART. Temperature Transmitter Diagnostics A temperature transmitter is a relatively simple device, but high-end models have some interesting diagnostics. When a sensor fails, the diagnostics display pin-points which sensor it is and what the problem is. Device manufacturer experts often include conditional images to clearly illustrate the problem.
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Figure 2 Temperature transmitter diagnostics indicates sensor failure Details of the problem are revealed at the click of a button permitting the technician to determine that the problem is not with the transmitter but with the sensor. Because problem areas are highlighted, lots of time is saved.
Figure 3 Detail diagnostics display In the past, temperature transmitters where primitive devices with rudimentary diagnostics only able to diagnose if the sensor was dead or alive. Today, temperature transmitters have sophisticated diagnostic able to detect if the temperature sensor is slowly degrading, and alerts before the sensor fails completely.
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Figure 4 Diagnostics setup and result from the same screen using EDDL Pressure Transmitter Diagnostics In the past, pressure transmitters where primitive devices with rudimentary diagnostics only able to diagnose if the sensor was dead or alive. Today, pressure transmitters have sophisticated diagnostic able to detect if the impulse line is plugging and other abnormal conditions such as detecting unexpected liquids in gas flow, or unexpected aeration in liquids, loss of agitation, and leaks. In the past, pressure transmitters were not as intelligent as they are now, and original DD did not have the graphics display capability. Back then, intelligence and display for diagnostics had to be in dedicated programs or plug-in software that ran in a computer, for instance plug-in software for plugged impulse line detection. Devices are getting ever more intelligent, and as devices get more intelligent, they are able to perform all functions internally round-the-clock. The result is graphically presented using EDDL, without the need for external software.
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Figure 5 strip charts for standard deviation and mean for visualization of process noise Valve Positioner Diagnostics A valve positioner is a sophisticated device with advanced diagnostics to monitor the health of the complete assembly including valve body, actuator, and the positioner itself. The positioner manufacturer organizes the diagnostics information logically using a hierarchical tree, tabbed cards, and frames thereby structuring the information to make the valve assembly easy to troubleshoot, on any control system.
Figure 6 a wealth of diagnostics is available organized in tree, tabs, and frames Visual dial gauges are one way device manufacturers chose to present the information. Numeric values are very accurate, but numerical values running up and down make it hard to see if the value is increasing or decreasing, or changing faster or slower. For a valve positioner, dial gage graphics makes it easy to visualize the actuator chambers vent or fill with air, just like the mechanical gauges for on the positioner itself. Thus EDDL graphics helps resolve problems with the pneumatics. www.eddl.org 6
Figure 7 EDDL dial gauge graphics visually show actuator pressure change A valve positioner also tracks operational statistics such as total travel and the number of reversals (cycles). This is used as a more accurate estimate of actual wear and tear for more precise prediction of remaining life and scheduling of maintenance such as replacement or stem packing or seat etc.
Figure 8 operational statistics are used as a basis for predictive maintenance scheduling Strip chart for trending is helpful for certain adjustments and therefore provided by the device manufacturer. Multiple values are often displayed in the same graphics.
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Figure 9 valve assembly behavior is easily visualized in a strip chart The position histogram illustrates in which position the valve stem spends most of its time. This helps identify wrong valve sizing.
Figure 10 Valve positioner position histogram Side-by-side bar-charts helps in comparing related performance indexes
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Figure 11 Valve positioner response history bar-chart Some valve diagnostics such as step-response test and valve signature etc. are rendered graphically using EDDL
Figure 12 Positioner valve analysis Since EDDL is an international standard (IEC 61804-3) diagnostics results from the devices can be visualized in device management software from different manufacturers.
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Figure 13 Valve positioner test results displayed graphically Some valve tests must be configured before the test is run.
Figure 14 Valve positioner step response test setup Valve positioners may also maintain an audit trail internally logging events such as failures in case the plant does not have device management software to provide this functionality.
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Figure 15 valve positioner event log Drive signal graph is another diagnostic used to for troubleshooting of the positioner.
Figure 16 Valve positioner drive signal diagram Shutdown Valve Monitor Diagnostics Special device are used to monitor emergency shutdown valves for which they periodically perform Partial Stroke Testing (PST). The results from the test are rendered graphically as a signature using EDDL.
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Figure 17 EDDL rendering of valve Partial Stroke Test (PST) results On/Off Valve Coupler Diagnostics Diagnostics such as travel time, cycle counts, stuck valve, and possibly partial stroking for on/off valves is possible with fieldbus valve couplers, as well as the ability to tell if the solenoid is working or not.
Figure 18 Intelligent two-wire on/off valve integrated in the same software as transmitters and control valves thanks to EDDL Vibration Transmitter Diagnostics Vibration transmitters are slightly different in that they essentially are dedicated diagnostics devices. That is, the diagnostics is not so much for the transmitter itself, as it is for the machinery it is monitoring. They monitor equipment like motors, pumps, fans, agitators, conveyor belts, and gears etc. to detect developing fault conditions like imbalance, misalignment, looseness, and latestage bearing problems.
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Figure 19 EDDL graphics visualizes complex diagnostics results Graphs defined by the vibration transmitter manufacturer are displayed in the system the way the device manufacturer intended.
Figure 20 The number of pens in the EDDL waveform graph is decided by the device manufacturer Magnetic Flowmeter Diagnostics In-situ meter verification tests the complete performance of a magnetic flowmeter to detect change in magnetic field strength, coil resistance, or electrode resistance to determine if calibration is needed. EDDL makes it possible to initiate the meter verification from any control system supporting EDDL. Wizards created by the flowmeter manufacturer guide the technician step-bystep; no specialized training is required. Wizards may display percent completion for lengthy procedures so technicians know how much longer they need to wait.
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Figure 21 EDDL wizard guides the user step-by-step through flowmeter verification Advanced diagnostics does not necessarily mean the presenting incomprehensible numerical values or charts that need interpretation. On the contrary, truly advanced diagnostics offers clear, actionable information. For instance, a clear pass or fail result. Test results may automatically be presented in a report, ready for print out from any EDDL-based system.
Figure 22 The meter verification report can be printed documenting the results Some devices may combine illustrating graphics and explaining text on the same page
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Figure 23 Magnetic flowmeter diagnostics page with actionable help provided by manufacturer's expert pH analyzer Diagnostics Apart from measuring the pH, the analyzer continuously measures the impedance of the pH glass electrode and the reference electrode to detect sensor failure or degradation. High reference electrode impedance indicates the junction is plugged or that the filling solution or gel is depleted (dry).
Figure 24 pH analyzer 'dashboard' A low glass electrode impedance indicates the glass is cracked, while a high impedance suggests it's aging and nearing the end of its life.
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Ultrasonic Flowmeter Diagnostics Ultrasonic flowmeter diagnostics requires some baseline values to be set. A setup wizard created by the flowmeter manufacturer's expert, using EDDL, guides the technician step-by-step, capturing the baseline values.
Figure 25 Baseline capture is part of the setup wizard, guided step-by-step by EDDL wizards created by the flowmeter manufacturer The flow profile and measured Speed of Sound are easily visualized and compared in bar graphs to identify build-up on transducers.
Figure 26 diagnostics depicted as EDDL bargraphs to visualize flow profile Gas Chromatograph (GC) Diagnostics In the past, Gas Chromatograph (GC) diagnostics required proprietary software only a GC expert is qualified to use. Today fieldbus integrates the GC in the same software as other field instruments. Using EDDL, the GC manufacturer explains what is causing the problem and how to fix it. GC diagnostics may include: power failure, user calculation failure, warm start failed, heater out of range, flameout, flame over-temperature, no sample flow, low carrier pressure, and stream validation failure etc.
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Figure 27 EDDL images and help text from GC manufacturer's expert guide technician in troubleshooting Electric Actuators / Motor Operated Valves (MOV) Diagnostics Diagnostics from electric actuators such as overheating, over torque, actuator fail, lost control voltage, lost phase, motor overload, and valve stall etc. are communicated using fieldbus. Many internal variables are also available (see separate tutorial on internal variables).
Figure 28 Electric actuator integrated in the same software as transmitters and control valves thanks to EDDL Uninterruptible Power Supply (UPS) Diagnostics Diagnostics in Uninterruptible Power Supply (UPS) units digitally integrated using PROFIBUS-DP can also be accessed from the same Intelligent Device Management (IDM) software as valves and instrumentation.
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Figure 29 UPS diagnostics displayed using EDDL Variable Speed Drive (VSD) / Variable Frequency Drive (VFD) Diagnostics Variable Speed Drive (VSD) / Variable Frequency Drive (VFD) can be digitally integrated using PROFIBUS-DP. Diagnostics include motor decelerating too quickly, overload, overheating, and mains loss etc. as well as many internal device variables (see separate tutorial on internal variables).
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Figure 30 VSD/VFD integrated in IDM thanks to EDDL Bus Diagnostics Advanced diagnostics modules for fieldbus diagnostics can also be integrated into IDM software. Diagnostics includes supply voltage, noise level, signal level, and retransmission statistics etc.
Illustrations and Context Sensitive Help Running a lean maintenance team with traditional maintenance practices will not be successful. Institutional knowledge is often kept by experienced technicians and engineers and is lost with then when teams change. However, with EDDL the device manufacturer's experts build their know-how about their device into help text associated with all diagnostic indicators, parameters, and wizards www.eddl.org 19
etc. to help in testing and the interpretation of diagnostics and deciding on the most appropriate action. The technician can easily access this expert help simply by clicking on the diagnostic indicator in question, and the help text will appear. This saves the technician the trouble of having to search through large manuals. Even if the information is buried deep in the manual, it's easily accessed from the device management software thanks to EDDL. The easily available help makes troubleshooting and resolution faster.
Figure 31 manufacturer expert know-how built into EDDL Illustrations such as exploded views helps by guiding troubleshooting
Figure 32 Valve positioner illustration of option boards
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Figure 33 Uninterruptible Power Supply (UPS) illustration of fuse replacement
Beyond Diagnostics Software and communicators based on EDDL assist the technician in diagnosing and troubleshooting devices correctly and as quickly as possible. Notes Annotations can be entered by the plant's experienced technicians over the years, and later retrieved by less experienced technicians any time. This mechanism channels knowledge from one technician to another. Manual A softcopy of the manual including exploded view, spare parts list, and troubleshooting tips, as well as other documents related to the device type or plant location, for the device can easily be called up at a click of a button.
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Figure 34 softcopy manual accessed at the click of a button Once the softcopy manual is opened it is possible to navigate from the table of contents or search for specific words and using all the features in Adobe Acrobat to quickly find the answer.
Figure 35 softcopy manual can be navigated or searched www.eddl.org 22
Audit Trail EDDL-based device management software supports audit trail functionality. This includes tracking of configuration changes, calibration records as well as failures. A unique characteristic of the EDDL technology is that device manufacturers do not need to create special functionality in the EDDL files to enable audit trail and export. Therefore these functions work for all devices regardless of manufacturer, type, or protocol – not just for some. No other device integration technology has this capability. As long as the intelligent device management (IDM) software supports such capability, it works for any device.
Figure 36 Audit trail for calibration, configuration/setup, and diagnostics etc. Device Diagnostic Alarm Summary EDDL-based device management software supports device diagnostic alarm management. This includes a summary of instrument diagnostic alarms. A unique characteristic of the EDDL technology is that device manufacturers do not need to create special functionality in the EDDL files to enable device diagnostic alarm management. Therefore these functions work for all devices regardless of manufacturer, type, or protocol – not just for some. The instrument diagnostic alarm summary makes planning of daily maintenance and turnarounds by helping to prioritize troubleshooting. This is key to condition-based desktop maintenance planning.
Figure 37 Instrument diagnostic alarm summary Maintenance Schedule EDDL-based device management software is also able to schedule maintenance tasks such as inspection and calibration. www.eddl.org
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NAMUR NE107 The operator immediately needs to be shown a status signal if a critical device in the plant malfunctions so they can take appropriate action. This may include taking safe action such as putting the loop in manual or shutting the unit down. An advisory device alarm is instead shown to the operator in the case of a less critical device or less severe problem. The operator can then decide to safely continue until maintenance replaces the device, or even wait for the next turnaround. Device problems not requiring operator action are not annunciated to operators at all, only to maintenance. In critical situations operators need information to make decisions. The primary pieces of information associated with transmitters and valves are the process variables and manipulated variables. The NAMUR working group 3 together with VDI/VDE and WIB have identified that to help the plant operators run the plant better the status of the devices themselves is also important. Simple consistent indication of device status for operators is defined in the NAMUR NE107 recommendation. More detailed device diagnostics is used by the maintenance organization in the plant for troubleshooting and to plan daily maintenance and turnarounds. The Electronic Device Description Language (EDDL) plays an important role in the configuration of instrument diagnostic alarm management such as categorization and prioritization to enable filtering and routing based on NAMUR NE107 status signals, as well as in the display of NAMUR NE107 status signals in device faceplates. See separate white paper on NAMUR NE107.
Consistency of Use Because EDDL is a text file from which the device page graphics is rendered by the device management software, the status indicators and help are rendered the same way for all devices regardless of protocol, manufacturer, or type. This consistency achieved thanks to EDDL makes use of device diagnostics easier and intuitive (see separate technical white paper on consistency of use). No other technologies can provide a comparable result.
Conclusion For plants that are looking for an easy solution to troubleshooting multiple types and versions of devices, EDDL technology is a perfect match. EDDL meets the need of plants to diagnose faults in all types of devices from a single software application using a single technology while at the same time making it fast and easy to keep the system up to date with new device versions. Plants should upgrade existing DD systems to EDDL with enhancements to enjoy the greater ease of use afforded by the standard graphical display. Device diagnostics for troubleshooting is just one of the ways in which intelligent device management software based on EDDL reduces maintenance & operational cost. Please refer to other technical white papers on advanced diagnostics, configuration/setup, and system administration etc.
Questions Post your questions on device diagnostics and intelligent device management with the EDDL group on Linkedin: http://www.linkedin.com/groups?gid=3736433
References EDDL Brochure and Technical Description on www.eddl.org site Jonas Berge, "Fieldbuses for Process Control: Engineering, Operation, and Maintenance", ISA, 2002, ISBN 1-55617-760-7 www.eddl.org
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