Fieldbus Foundation TM Bus diagnostics and troubleshooting Andreas Agostin MTL Instruments Pte Ltd Singapore On behalf of Fieldbus Foundation TM Marketing Committee (Malaysia) Foundation Fieldbus Seminar Malaysia 1 November 2009
Bus diagnostics and troubleshooting • Plant life cycle • Costs of diagnosis Foundation Fieldbus Seminar Malaysia 2 November 2009
Which tools for which purpose? Plant life cycle Commissioning & Operation & Engineering Installation Troubleshooting Maintenance Predictive Calculation tools Wiring tools Commissioning & Maintenance troubleshooting tools tools Foundation Fieldbus Seminar Malaysia 3 November 2009
Which tools for which purpose? Plant life cycle Engineering Proper engineering ensures that the plant works as designed. Flaws in engineering will cause the actual plant not to work, and will trigger expensive redesign and re-work. Calculation tools Foundation Fieldbus Seminar Malaysia 4 November 2009
Which tools for which purpose? Plant life cycle Installation 1 Source: According to field experience, http://forums.fieldbus.org/showthread.php?t=1298 approx. 95% 1 of the problems occuring in a plant’s lifetime are related to installation. Cause can be: - Wrong ferrule diameter - Wrong crimping tool - Wrong crimping method - Wrong wire cutter - Wrong screw driver - Wrong torque Wiring tools - … Foundation Fieldbus Seminar Malaysia 5 November 2009
Which tools for which purpose? Plant life cycle Commissioning & Troubleshooting Commissioning should be done one-by-one. There are voices suggesting to connect all instruments and then switch on. However, a fault such as the frequently seen short-to-shield, will be impossible to locate. Connecting devices one-by-one will tell you that the problem occurred at the device you connected last. Commissioning & troubleshooting tools Foundation Fieldbus Seminar Malaysia 6 November 2009
Which tools for which purpose? Plant life cycle Operation & Maintenance In large installations with hundreds of bus segments, it can be of help to use physical layer online monitoring (“advanced diagnostics for the physical layer”). Using such tool you can detect degradation in the installation. There are voices suggesting to use such tool for troubleshooting. However, due to the location of the tool in the control room, accurate measurements are not possible, and some faults are even not detectable (e.g. short to shield on a spur of a fieldbus barrier). Predictive Maintenance tools Foundation Fieldbus Seminar Malaysia 7 November 2009
Maintenance Strategies Maintenance … y d a e r l a d e r r u c c o e r u l i a F Failure already occurred • Repair Failure causes production • loss Potentially very high • costs Time based Condition based On a schedule When required Foundation Fieldbus Seminar Malaysia 8 November 2009
Maintenance Strategies Maintenance … y d a e r l a d e r r u c No failure yet… c o e r u l i a F No failure yet • Repair Preventive High and regular • maintenance costs Time based Condition based On a schedule When required Foundation Fieldbus Seminar Malaysia 9 November 2009
Maintenance Strategies Maintenance … y d a e r l a d e r r u c No failure yet… c o e r u l i a F Repair Preventive Predictive In time before failure occurs (Condition: “Warning”) Time based Condition based On a schedule When required Foundation Fieldbus Seminar Malaysia 10 November 2009
Device Maintenance Effort Process Interface; 6% Failure; Preventive 4% Zero Drift; 6% Routine check; 35% Re-ranging; 20% Failure suspect, but no problem found; 28% Repair 63% of time is spent investigating “problems” that do not exist. On Fieldbus, the fieldbus diagnostic module will alert you Predictive when maintenance is needed, and will keep quiet if not. Source: ARC Advisory Group, Intelligent Devices Provide Foundation for Operational Excellence – ARC Strategies, January 2003. Foundation Fieldbus Seminar Malaysia 11 November 2009
Why Predictive Intelligence? 100% Condition of Assets Too Late 0% Time to Fail Foundation Fieldbus Seminar Malaysia 12 November 2009
Why Predictive Intelligence? 100% Condition of Assets Prediction gives you enough time to make Too Late proper decision and to prevent abnormal situations 0% Time to Fail Conditions: OK (Alarms) Needs maintenance soon Needs maintenance now Foundation Fieldbus Seminar Malaysia 13 November 2009
Why Predictive Intelligence? 100% Condition of Assets Prediction gives you enough time to make proper decision and to prevent abnormal situations 0% Time to Fail Conditions: OK (Alarms) Needs maintenance soon Needs maintenance now Foundation Fieldbus Seminar Malaysia 14 November 2009
Typical Problems Foundation Fieldbus Seminar Malaysia 15 November 2009
Case study: faults in operation Water in junction box, cable or device: • Increasing number of retransmissions • Indication of shorts to shield • Can be a combination of both Foundation Fieldbus Seminar Malaysia 16 November 2009
Bend radius too tight, Upward facing gland risks water ingress Two cables into one gland prevents sealing of gland Foundation Fieldbus Seminar Malaysia 17 November 2009
Corroded terminals: Increasing number of retransmissions • Increase of FF noise • Can be a combination of both • Foundation Fieldbus Seminar Malaysia 18 November 2009
Case study: faults in operation Short to shield on fieldbus trunk: • Indication of short to shield • Increasing number of retransmissions on all devices Foundation Fieldbus Seminar Malaysia 19 November 2009
Case study: faults in operation Short to shield on fieldbus spur (wiring block): • Indication of short to shield • Increasing number of retransmissions on this specific device or on the devices of this wiring block Foundation Fieldbus Seminar Malaysia 20 November 2009
Case study: faults in operation Short to shield on fieldbus barrier spur: • Indication of short to shield only on Handheld tester (due to galvanic isolation of fieldbus barrier) • Increasing number of retransmissions on this specific device or on the devices of this fieldbus barrier Foundation Fieldbus Seminar Malaysia 21 November 2009
Bad wiring technique Welding, variable frequency drives (VFD), Motors, machinery: Increase of HF noise • Increasing number of retransmissions • Can be a combination of both • Foundation Fieldbus Seminar Malaysia 22 November 2009
Case study: faults in operation Cable jacket stripped back too far can cause instrument malfunction: – Water ingress – Wires shorted to housing – Corrosion – Tearing wires (increasing resistance) Increasing number of • retransmissions Signal amplitude rises • Increase of FF noise • Can be a combination of • above Foundation Fieldbus Seminar Malaysia 23 November 2009
Case study: faults in operation Fieldbus terminator missing: • All signal amplitudes rise (best indicator) • Increased noise in all frequency bands • Increasing number of retransmissions (usually on all devices) • One or more devices drop off the bus (may or may not come back) Note: likely to be the terminator in the field, not on the baseplate (soldered, controlled environment) Foundation Fieldbus Seminar Malaysia 24 November 2009
Wires coming out of ferrules: Trunk: Spur: Devices drop off (may or may not return) • Device drops off (may or may not return) Signal amplitude sometimes ok, sometimes high • • Increasing number of retransmissions Increasing number of retransmissions • • Foundation Fieldbus Seminar Malaysia 25 November 2009
Foundation Fieldbus Seminar Malaysia November 2009 Problem indicated by Diagnostic Module 26
Foundation Fieldbus Seminar Malaysia November 2009 Warning or alarm levels exceeded? 27
On which segment? Foundation Fieldbus Seminar Malaysia November 2009 28
Foundation Fieldbus Seminar Malaysia November 2009 What’s the problem on the segment? 29
Alarm Identification Name and Description Corrective Action Device Signal Level High-High Alarm If only one device high: check: 1. alarm limits have not been wrongly set, Device Signal Level High Alarm 2. device operation. If several/all devices on segment check: 1. for only one terminator on segment 2. for failed terminator. Device Signal Level Low Alarm If only one device low: check 1. alarm limits have not been wrongly set, Device Signal Level Low-Low Alarm 2. spur cabling, spur and device connections are tight 3. for water in spur cable or device 4. device operation. If several/all devices on segment low check: 1. for more than two terminators on segment, check that terminator switches on the fieldbus barrier are set to “off”. 2. for water in devices, junction boxes and cabling. … … And what does that mean, what is the cause of the alarm? Foundation Fieldbus Seminar Malaysia 30 November 2009
In the device manager, you: • Compare actual vs historical data • See information about each device • See alarms of physical layer of device Foundation Fieldbus Seminar Malaysia 31 November 2009
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