CONDITION MONITORING

A K DarpeDepartment of Mechanical Engineering

Indian Institute of Technology Delhi

Sound Maintenance Program: Need of the day

Periodic Measurements: Not foolproof

Predictive Maintenance (online continuous monitoring):

# catches the fault early# cost effective

Narora Atomic Power Plant failure: could have been avoided

FDAS, OLES-OSBUDD for KAPS developed

Sound Maintenance Program: Need of the day

Periodic Measurements: Not foolproof

Predictive Maintenance (online continuous monitoring):

# catches the fault early# cost effective

Narora Atomic Power Plant failure: could have been avoided

FDAS, OLES-OSBUDD for KAPS developed

Definition of Expert System• A computing system capable of representing

and reasoning about some knowledge rich domain, which usually requires a human expert, with a view toward solving problems and/or giving advice.– The level of performance makes it “expert.”– Some also require it to be capable of

explaining its reasoning.– Does not have a psychological model of how

the expert thinks, but a model of the expert’s model of the domain.

Expert System Developed in IIT Delhi• OLES (online expert system)

• OSBUDD (operator support and backup data display).

• Uses knowledge base compiled by John S Sohre. • Continuous online vibration and process data

can be acquired from any machine.• The diagnosis of the fault is almost

instantaneous.• The important vibration data be trended over

any interval of time. • Orbit plot, waterfall plot, can be plotted.• An integrated signal analysis toolbox is

provided.

Schematic of the system

DEVELOPMENT OF AN ONLINE DIAGNOSTIC SYSTEM FOR KAKRAPAR ATOMIC POWER PLANT

Frequency Domain Signal

Transducer SignalConditioning FDAS

DiagnosticSystem(OLES)

TG Vibration Signals

Process Signals

Signal Flow for FDAS

Signals received by FDAS

• Vibration Signals– Bearing vibration signals - 12 Nos– Shaft vibration signals - 8 Nos

• Important Process Signals– Generator Power– Condenser vacuum

Schematic of the system

OSBUDD (Operator Support and Back Up Data

Display)Displays processed data in various format

Trend of important vibration parameters

Expert system diagnostic results

Provision of reviewing past data

Demo and Help for operator assistance

Plots: Time DomainFrequency DomainTrend OrbitWaterfall

Analysis: Expert System DiagnosisSignal Processing

Assistance: DemoHelp

Backup Data Loader

Expert System

Each fault produces a typical frequency pattern (signature)

Sohre’s Database as knowledge base

Direction and type (shaft/brg) of predominant vibration taken into account

Expert system estimates probability of each fault, lists five most probable ones.

Diagnostic tool from DSA International• Automated diagnostic system called Check-

mate• Uses frequency spectrum of vibration from

common data collection systems (either offline or online)

• User can select from the list of vibration spectra available at any particular point of the machine of interest.

• After selection the expert system compares the vibration levels of that particular point with alarm levels and suitable remedial action can be taken

• In the latest version of check-mate up to 700 spectra can be automatically analyzed in under 10 minutes.

COMMERCIAL CONDITION MONITORING SYSTEMS

Check-Mate identifies• Unbalance.• Off-set misalignment.• Angular misalignment.• Bent shaft.• Looseness.• Unequal foundation stiffness.• Coupling lock-up.• Bearing problems-preload, looseness, inner race,

outer race, ball train defects.• Gear defects-tooth wear, misalignment, eccentricity,

broken or worn tooth/teeth, hunting tooth faults.

Cont…

Check-Mate identifies• Sub-synchronous bearing instability.• Electrical faults-cracked rotor bars, eccentric rotor.• Rubs-rotor, axial.• Belt problems.• Cavitation.• Oil whirl.• Dry whirl.• Check-mate identifies faulty readings caused by a

loose or damaged sensor.

Unique Features of Check-Mate• Model based, object oriented and data driven .

• Machines are quickly modeled with in built parts such as gears, bearings, shafts and motors.

• Spectra are accessed simply by clicking on the measurement locations.

• Frequencies associated with the typical generic faults are easily displayed by clicking on that part's icon.

• Spectral peaks are quickly identified.• The user can go the the part and ask for 1X, 2X, 3X

rotation speed or the BPFO (outer race ball pass frequency) and multiples to be displayed on the current spectra.

Cont…

                                        

Unique Features of Check-Mate• Trends for specific fault frequencies are

extracted from waterfall diagrams.• Trends will also accurately track harmonics and

wide band frequencies.• Alert levels are set for individual fault

frequencies, harmonics and wide-band modulations.

• Actual frequencies for alerts are automatically recalculated for machine speed of each spectrum.

• Diagnostics include clear advice on appropriate operation or maintenance actions.

• DSA international can supply customized rules or machine parts to meet one’s special requirements.

DSA International Corporation4580 Marineview Crescent

North Vancouver, BC V7R 3P5Canada

phone:  604-986-0936fax:       604-986-0935

email:   alees@dsaint.com

A Fault Diagnosis and Maintenance Expert System for

Rotating Machinery• The FDMES for rotating machinery has its own distinguishing feature in both the rules and reasoning mode.

• Knowledge based rules of FDMES are compiled from diagnostic tables of mechanical faults.

• The FDMES can diagnose 58 kinds in 10 categories of mechanical faults give the second reasons: design and manufacture, installation and maintenance, operation and control, machine deterioration and give the methods of prevention and cure.

• FDMES is used in 18 large enterprises in China.

BENTLY NEVADA’ Data Manager • Bently Nevada’s data manager (DM2000) with

continuous, online data acquisition, archiving, and display capabilities.

• Static and dynamic data under steady-state and transient operating conditions can be collected.

• Data acquisition modes can be both automatically and manually initiated.

• Data display stations can be located where desired in LAN,WAN or RAS.

• MMS(Machinery Management Services) engineers are available for help. The MMS engineers may be able to determine the condition of machinery from the remotely transmitted data alone.

Display plots available• Current values, bar graph, machine train

diagram, trend, fast trend, high resolution trend , multivariable trend, acceptance region, time base, shaft average centerline, spectrum/full spectrum, alarm list, system list, waterfall, bode, polar, cascade, plus orbit and plus spectrums.

• Along with expert system, Bently Nevada provides hardware and software products primarily designed for online acquisition and presentation of data and information.

• Bently Nevada provides portable condition monitoring solutions.

BENTLY NEVADA’ System 1TM

• System 1™ is a patented modular and scalable software platform for managing plant asset data and information.

• Increases asset availability and reliability by providing a single, integrated tool for storing, accessing, and managing plant production assets with information, rather than simply data.

• System 1™ replaces previous Bently Nevada stand-alone online software programs such as Trendmaster® 2000, data manager® 2000, and machine condition manager™ 2000 by combining the functionality of these products into a single platform.

Cont…

• Accepts data from any data source, not just Bently Nevada condition monitoring hardware.

• Provides tools to capture and use condition data, historical data, baseline data, nameplate data, asset properties, lessons learned, and other relevant information.

• Provides tools to link documents and files, write reports, and to exchange data with other systems.

• High-end data analysis tools for diagnostics and root cause analysis are also part of System 1™

• SYSTEM 1TM is designed to be modular and scalable. Cont…

• Using this platform, a solution can be built to support a wide range of user scenarios in many industries such as

– Power generation– Pipelines– Refineries– Marine– Oil and gas– Waste water treatment– Food and pharmaceutical– Semiconductor manufacturing– Petrochemical – Pulp and paper– Metals and mining

MasCon/ ProCon•NAIDEN’S (an SKF group Company) MasCon/ ProCon online system monitors and diagnoses various process and machine component conditions, and provides automatic advice for correcting existing or impending conditions.

•MasCon’s in-built hardware auto-diagnosis system continuously checks all sensors, cabling and electronics for any faults, signal interruption, shortcuts, or power failure.

•Any malfunctions triggers an alarm, and in the case of system power failure the system will automatically restart when the power returns.

Cont…

MasCon/ ProCon•Data is transferred via TCP/IP. It can be sent to

company for quick help and action.•32 different sensors, signal and measurement

configuration can be accommodated. • Individual conditions for warning and alarm may

be set for each point.•By using expert guide, in-built software, One can

add the new machines using simple mouse clicks.

•The frequency bands, resolution, defect frequencies, machine diagnosis are generated automatically.

•Damaged machine components are identified independently of the measurement point position.

Cont…

• Warnings and alarms are indicated in machine picture by yellow or red color measurements.

• Measurements are made by mouse click over desired point with overdue measurement indicators.

• Remote access via modem or internet is available.

• Selected reference spectra may be fixed and automatically matched with new or earlier measurements.

• Early detection of bearing faults using DPE (digital peak enveloping).

• Triggering alarm levels may be set to adjust automatically to load level and rotational speed.

Cont…

• Advanced turbine fault diagnostics system:• Detection of eccentricity change in coupling, • Blade failure, • Bearing instability, • Steam whirl, • Rotor crack, • Rotor rubbing, • Temporary rotor bow, • Loose bearing pedestal, • Inclined position of bearing, • Electrical run-out, • Mechanical run-out, • Loose stator core in generator, • Change of imbalance at shutdown, • Radial bearing damage,• Inter turn short circuit in generator rotor, etc.

Korea Institute of Science and Technology .

• Development of integrated diagnostic system for rotating machinery.

• Development of a portable vibration monitoring system, which can transfer data on USB port.

• Diagnostic algorithm based on Sohre¡’s chart and a rule base.

• Monitoring test for various fault case by using integrated simulator.

• Tele-monitoring system by internet.• Pre-step of new technology commercialization

through a small-size and integration.• Integrated machine health monitoring system.

CONDITION MONITORING

Vibratory system

SENSORSSignal Acquisition

Signal Processing

Data AnalysisAnd Representation

Fault Identification

Damage Severity Identification

Knowledge base

Loading History

Residual Life

Gear Teeth Mesh Forces

First gear teeth mesh

Second gear teeth mesh

Time (sec)

Time for 1 revolution of gear

xcos(t)

Gear blank digs into pinion and withdraws once in one rotation xacos(at)

Time (sec)

Time for 1 revolution of gear

First gear teeth mesh

Time (sec)

Time for 1 revolution of gear

ttxxtx aa cos)]cos([)(

Amplitude Modulation in Gear Pair

ttxxtx aa cos)]cos([)(

txtxtxttxtxtx aa

aa

aa )cos(2

)cos(2

cos)]cos(coscos[)(

carrier frequencies i.e.,gear mesh frequency -

modulation frequency i.e., rotational speed of the gear - a

txtx cos][)( With perfect gearing condition

With imperfect gearing condition

Time domain information: mostly rich in content, little in information

Charge Amplifier

Lab view software loaded on PC

User defined software for further processing

Computer

AID card

Voltage

Accelerometer

Charge I/P

Vibration being sensed

VIBRATORY SYSTEM

ITEMS COST IN RUPEES(Rs)

a) Charge based accelerometer (piezoelectric)

20,000 to 50,000

b) ICP type Accelerometer 15,000 to 40,000

c) Charge Amplifier (required only for charge type accelerometer) 1,00,000 to 2,00,000

d) Analog to Digital Converter Card 25,000 to 1,20,000(depending upon number of channels & sampling rate)

e) Labview Software for acquisition & subsequent signal processing.

80,000 onwards(basic version could cost more for pvt industry.

f) MATLAB for making user defined program 1,00,000 approx

Charge Amplifier

Tacho

Channels

Portable data acquisition

system

Vibratory structure

Accelerometer

Laptop

ITEMS COST IN RUPEES(Rs)

Portable Data Acquisition system(OROS, PULSE (B&K), Pimento with Virtual Lab (LMS), etc.

18,00,000 roughlyfor 8 channel DataAcquisition System

Summary

• Knowledge about the system• Selection of transducers, acquisition

system• Features of signal processing and

problems/issues associated with it• Data representation techniques• Interpretation • Experience – knowledgebase – update