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Bus diagnostics and troubleshooting Andreas Agostin MTL - - PowerPoint PPT Presentation

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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

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Foundation Fieldbus Seminar Malaysia November 2009

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Fieldbus FoundationTM Bus diagnostics and troubleshooting

Andreas Agostin MTL Instruments Pte Ltd Singapore

On behalf of

Fieldbus Foundation TM Marketing Committee (Malaysia)

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Bus diagnostics and troubleshooting

  • Plant life cycle
  • Costs of diagnosis
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Plant life cycle

Which tools for which purpose?

Calculation tools

Engineering

Wiring tools

Installation

Commissioning & troubleshooting tools

Commissioning & Troubleshooting

Predictive Maintenance tools

Operation & Maintenance

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Plant life cycle

Which tools for which purpose?

Calculation tools

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.

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Plant life cycle

Which tools for which purpose?

Wiring tools

Installation According to field experience,

  • approx. 95%1 of the problems
  • ccuring 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
  • …

1 Source:

http://forums.fieldbus.org/showthread.php?t=1298

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Plant life cycle

Which tools for which purpose?

Commissioning & troubleshooting tools

Commissioning & Troubleshooting Commissioning should be done

  • ne-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

  • ccurred at the device you

connected last.

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Plant life cycle

Which tools for which purpose?

Predictive Maintenance tools

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).

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Maintenance Strategies

  • Failure already occurred
  • Failure causes production

loss

  • Potentially very high

costs

Maintenance Repair Time based Condition based

On a schedule When required F a i l u r e

  • c

c u r r e d a l r e a d y …

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Maintenance Strategies

Maintenance Repair Preventive Time based Condition based

On a schedule When required F a i l u r e

  • c

c u r r e d a l r e a d y … No failure yet…

  • No failure yet
  • High and regular

maintenance costs

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Maintenance Strategies

Maintenance Repair Preventive Time based Condition based Predictive

On a schedule When required In time before failure occurs (Condition: “Warning”) F a i l u r e

  • c

c u r r e d a l r e a d y … No failure yet…

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Device Maintenance Effort

63% of time is spent investigating “problems” that do not exist. On Fieldbus, the fieldbus diagnostic module will alert you 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.

Routine check; 35% Failure suspect, but no problem found; 28% Re-ranging; 20% Zero Drift; 6% Process Interface; 6% Failure; 4%

Preventive Repair Predictive

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Why Predictive Intelligence?

Time to Fail 0% 100% Condition of Assets

Too Late

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Why Predictive Intelligence?

Time to Fail 0% 100% Condition of Assets Prediction gives you enough time to make proper decision and to prevent abnormal situations

Too Late

Conditions: (Alarms) OK Needs maintenance soon Needs maintenance now

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Why Predictive Intelligence?

Time to Fail 0% 100% Condition of Assets Prediction gives you enough time to make proper decision and to prevent abnormal situations

Conditions: (Alarms) OK Needs maintenance soon Needs maintenance now

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Typical Problems

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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
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Bend radius too tight, Upward facing gland risks water ingress Two cables into one gland prevents sealing of gland

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Corroded terminals:

  • Increasing number of retransmissions
  • Increase of FF noise
  • Can be a combination of both
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Case study: faults in operation

Short to shield on fieldbus trunk:

  • Indication of short to shield
  • Increasing number of retransmissions on all

devices

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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

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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

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Bad wiring technique

Welding, variable frequency drives (VFD), Motors, machinery:

  • Increase of HF noise
  • Increasing number of retransmissions
  • Can be a combination of both
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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

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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)

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Wires coming out of ferrules: Spur:

  • Device drops off (may or may not return)
  • Increasing number of retransmissions

Trunk:

  • Devices drop off (may or may not return)
  • Signal amplitude sometimes ok, sometimes high
  • Increasing number of retransmissions
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Problem indicated by Diagnostic Module

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Warning or alarm levels exceeded?

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On which segment?

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What’s the problem on the segment?

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… … Device Signal Level Low-Low Alarm If only one device low: check 1. alarm limits have not been wrongly set, 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

  • n the fieldbus barrier are set to “off”.

2. for water in devices, junction boxes and cabling. Device Signal Level Low Alarm Device Signal Level High Alarm If only one device high: check: 1. alarm limits have not been wrongly set, 2. device operation. If several/all devices on segment check: 1. for only one terminator on segment 2. for failed terminator. Device Signal Level High-High Alarm Corrective Action Name and Description And what does that mean, what is the cause of the alarm?

Alarm Identification

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In the device manager, you:

  • Compare actual vs historical data
  • See information about each device
  • See alarms of physical layer of device
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All data is communicated via FF, allowing full Integration into all host software packages. Example: Trending of noise and voltage levels in the historian.

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Example: Noise level trending

Noise Alarm level (critical) Warning level 2008 2009 2010 2012 2011 Warning and alarm levels are set so that there is sufficient time to fix the problem e.g. during a regular shutdown

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On-line monitoring

FFPS T FF Power Supply & Conditioner &Terminator 24VDC

Host Computer H1 Interface

Fieldbus barrier

Device 1 Device 3 Device 2

Fieldbus barrier & Terminator Intrinsically Safe Spurs T Fieldbus barrier

DM

F809F Fieldbus Diagnostic Module

Permanently installed at the fieldbus power supply in the control room.

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Portable diagnostic tools

PDI

Portable Diagnostic Instrument FFPS T FF Power Supply & Conditioner &Terminator 24VDC

Host Computer H1 Interface

Fieldbus barrier

Device 1 Device 3 Device 2

Fieldbus barrier & Terminator Intrinsically Safe Spurs T Fieldbus barrier

To measure at fieldbus barrier, PDI needs to be Ex i approved. Important since the galvanic isolation of fieldbus barrier impacts on measurement.

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Typical measured parameters

  • DC voltage

– Indicates correct function of power supply/conditioner – Instrument supposed to operate from 9V onwards

  • Shield short (+ or – connected to shield/ground/screen)

– Easy to measure and understand – Further measurements can identify location

  • Signal level

– Minimum level is specified by Fieldbus specification – Low or high levels on all devices suggests incorrect bus termination – If only one device, suggests problem on single spur

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Typical measured parameters

  • Noise

– Maximum level is specified by Fieldbus specification – Tri-band measurement helps to identify source

  • LF: bulk supply
  • IF: fieldbus device
  • HF: induction from outside the network
  • Retransmissions / Retransmission rate

– Good measurement of physical layer health – Measured in absolute retransmissions and in % of total transmissions (rate) – Re-tries can obscure faulty device or network

http://forums.fieldbus.org/showthread.php?t=1298 Follow link to access Fieldbus Forum posting on physical layer problem (see summary on next page)

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http://forums.fieldbus.org/showthread.php?t=1298

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Amount of diagnostic information

  • Fieldbus Diagnostic Modules can provide a

multitude of data and information

  • Not every maintenance technician is a fieldbus

expert

  • Tools must match the employee skills
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The various solutions

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The various solutions

Differentiators:

  • Physical Interface

(FF H1 / FF HSE / RS485 / Contact)

  • Measurements
  • Level of detail
  • User Interface

(H1 Host integration / DTM / OPC)

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Conclusion

“Key Three”:

  • Foundation Fieldbus communication is very

robust

  • If you do your installation right, you avoid many

problems down the road

  • Online-diagnostic of the physical layer is an add-
  • n that can help you to identify problems before

they cause a failure

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Any Questions?

Andreas Agostin contact: +65 9758 5161 aagostin@mtlsing.com.sg

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www.fieldbus.org