Condition Monitoring for Steam Turbines I

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    Condition Monitoring for Steam Turbines

    and

    Sleeve Bearing Diagnostics and Failure Analysis

    Presented by:

    Timothy S. Irwin, P.E.

    Senior Mechanical Engineer

    M&B Engineered Solutions, Inc.

    13 Aberdeen Way

    Elgin, SC 29045

    Email: [email protected]

    17 February, 2006

    mailto:[email protected]:[email protected]
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    Condition Monitoring for Steam Turbines and

    Sleeve Bearing Diagnostics and Failure Analysis

    Part I - Condition Monitoring for Steam Turbines

    What is todays definition?

    We want an early warning so that when the operating condition of the turbine

    is changing, action can be taken to identify the failure mode. When the

    failure mode is properly identified, proper corrective action can be planned or

    taken to maintain or return the machine to reliable operation.

    Part IISleeve Bearing Diagnostics and Failure Analysis

    What is todays definition?

    Improve our understanding of sleeve bearings and their failure modes so thatwe can improve our monitoring techniques and failure analysis. Improvement

    in these areas will result in an improvement in the equipments performance

    and reliability.

    M&B ESI

    Timothy S IrwinJanuary 2006

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    Part I Condition Monitoring for Steam Turbines

    To develop effective condition monitoring we need tounderstand a little about the machine.

    What does a turbine actually do?

    Steam comes in and goes out right?

    The steam comes in under a certain set of

    pressure, temperature, and flow conditions;

    and goes out under another set of pressure

    temperature and flow conditions.

    The change in steam conditions occursbecause we are using some of the energy

    in the steam to rotate the turbine rotor.

    M&B ESI

    Timothy S IrwinJanuary 2006

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    Part I Condition Monitoring for Steam Turbines

    Just for a quick view, here is a decent description of a steam flow

    path in a multi-stage turbine:

    Courtesy of Power MagazineM&B ESI

    Timothy S IrwinJanuary 2006

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    Part I Condition Monitoring for Steam Turbines

    Here is one small mechanical drive turbine.

    This one was actually used to drive a positive displacement oil pump.

    M&B ESI

    Timothy S IrwinJanuary 2006

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    Part I Condition Monitoring for Steam Turbines

    Here is another small drive turbine

    This one is also used to drive a positive displacement oil pump. M&B ESI

    Timothy S IrwinJanuary 2006

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    Part I Condition Monitoring for Steam Turbines

    Here is a small industrial power generation turbine.

    Note the mechanical layout of this machine M&B ESITimothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Here is a big multi-casing utility class machine

    Note that a lot of the mechanical details from the

    smallest to the largest machines are very similar

    Courtesy of Power Magazine

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    What kind of monitoring can we do on a turbine?

    Steam conditions and flow rate.

    Vibration.

    Lubricant/bearing conditions.

    Rotor speed/load or power.

    Auxiliary system operation.

    Noise/Sound levels.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    What kind of failures typically occur to turbines?

    Bearing failures from:

    Loss of lubrication

    Lubrication contamination

    Excessive load

    Overspeed protection

    Blade failures:

    Foreign object damage

    Erosion

    Fatigue

    Valve failures:

    Solid particle damage

    Erosion

    Fatigue

    Steam seal failures:

    Wear

    Erosion

    Corrosion

    Governor/Regulation failure

    Insulation failure

    Coupling failures

    Hydraulic system failureM&B ESI

    Timothy S Irwin

    January 2006

    Alignment Changes

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    Part I Condition Monitoring for Steam Turbines

    Lets look a little closer at some of the failure

    modes. Bearing failures can occur from:

    Loss of lubrication

    Lubrication contamination

    Excessive load

    Electrolysis

    Fatigue

    Wear/wiping

    Corrosion

    Cavitation/erosion

    Faulty assembly

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Lets look a little closer at some of the failure

    modes. Blade failures:

    Foreign object damage

    Can cause damage to leading edge, trailing edge,

    shroud, etc.

    Can damage the stationary and/or rotating blades. Erosion

    Can be caused by moisture in the steam or solid

    particulates in the steam.

    Can affect the stationary and rotating blades. Fatigue

    Will more typically affect the rotating components and

    typically be a catastrophic event if the condition is not

    identified during an inspection. M&B ESITimothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Machine Condition Discussion:

    Called in to evaluate condition of machine. Site management knew that routine maintenance had

    been deferred for a significant amount of time.

    Could they defer further or were there indications of

    developing problems?

    What were the results of the condition assessment?

    Vibration levels were good (below 0.7 mils) using proximity

    probes.

    Power output was down.

    Steam discharge conditions were at saturated steamconditions.

    Steam leakage at shaft seals was excessive, causing constant

    moisture contamination in the lube oil system.

    My recommendation was not to defer the overhaul.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Blade failure/damage:

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Blade failure/damage:

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Blade failure/damage:

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Valve failures: What happens to valves?

    Erosion of the plug

    Erosion of the seat

    The steam admission valve or stop valve or emergencystop valve is part of the equipment protection!

    Corrosion of the spindle or stem

    Galling of the spindle or stem in the guide bushings or bearings.

    Wear of the guide bushings or bearings

    Wear of the linkage components

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Steam Seal failures: What happens to steam seals?

    Larger machines with actual seal strips (labyrinth seals)

    Wear of the seal tip height

    Corrosion of the mating surfaces

    Corrosion of the segments and housing.

    Corrosion and failure of segment springs

    Smaller machines with carbon seal rings

    Wear of the carbon rings

    Wear of the shaft surface

    Corrosion and wear of the housing faces.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Steam Seal failures: What happens to steam

    seals?

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Steam Seal failures: What happens to steam

    seals?

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Alignment

    M&B ESI

    Timothy S Irwin

    January 2006

    DefinitionWhat does alignment mean to coupled rotating machines?

    In short we are looking for the two (or more) shaft centerlines to be

    concentric to each other. If the shaft centerlines are not concentric

    to each other, then the shafts through the coupling try to force themselves

    together. Depending on the coupling type, this aligning force may show

    Itself as various vibration signature changes or indications, or if severe

    enough bearing temperatures or conditions may be affected.

    What can cause misalignment?

    Misalignment at installation or refurbishment

    Thermal growth changes

    Piping strain

    Sleeve bearing damage

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    Part I Condition Monitoring for Steam Turbines

    Alignment

    M&B ESI

    Timothy S Irwin

    January 2006

    Definition What does alignment internal to a single machine mean?

    In short We want to have the shaft/rotor within a certain position

    relative to the casing. Some machines behave better with the rotor not

    centered in the casing. Some machines behave better with the rotor

    centered. A very typical indication is a rub condition in the vibration data.

    What can cause misalignment?

    Misalignment at installation or refurbishment Thermal growth changes

    Piping strain

    Sleeve bearing damage

    Basically the same conditions apply to internal and external misalignment.

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    Part I Condition Monitoring for Steam Turbines

    Overspeed protection Sticking bolt

    Worn linkage

    Incorrect electronic settings

    Governor/Regulationfailure

    Worn parts

    Contaminated system

    Insulation failure Air gaps

    It has become wet

    Pieces are missing

    Incorrect installation Coupling failures

    Lubrication failure

    Wear

    Fatigue

    Hydraulic system failure

    Worn components

    Contaminated system

    Remaining failure modes:

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Failure modes and monitoring methods:

    Realistically determine the most appropriate uses of the available tools.

    We have to perform the following:

    Determine the realistic limits of the monitoring tools.

    Determine what we cannot measure or monitor.

    Determine what is appropriate per piece of equipment.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    What kind of monitoring can we do on a turbine?

    Steam conditions and flow rate.

    Vibration.

    Lubricant/lubrication conditions.

    Rotor speed/load or power.

    Auxiliary system operation.

    Noise/Sound levels.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Steam Conditions What kind of readings do we want to take?

    Depends on the machine, what kind of readings do we haveavailable or can we take?

    Is it a small machine with little instrumentation or is it a large

    machine with a considerable amount of instrumentation?

    Minimal measurements would be temperature and pressure

    upstream and downstream of the turbine.

    If you can include flow, power, inlet chamber pressure you will

    know a considerable amount about the power characteristics of the

    turbine.

    Look for: A change in downstream conditions from what is normal.

    It could be an increase in downstream pressure

    Also understand what the design conditions may mean

    (i.e. get a copy of some steam tables) M&B ESITimothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Steam Tables

    M&B ESI

    Timothy S Irwin

    January 2006

    Mechanical

    Engineering

    Reference

    Manual

    Michael R.

    Lindeburg

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    Part I Condition Monitoring for Steam Turbines

    Vibration What kind of readings do we want to take? Depends

    on the machine.If it is a small machine

    Is it a sleeve bearing, anti-friction bearing, or combination machine?

    Mag-based accelerometers are going to be severely limited with

    sleeve bearing machines. But smaller horsepower machines are not

    going to typically have proximity probes installed unless the machine

    is very critical to the process.

    What kind of data are we going to see on sleeve bearing machines

    using mag-based accelerometers?

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    PdM Routes

    What data do I want?For vibration:

    Horizontal and vertical on each bearing.

    Locate the thrust bearing and take an axial reading.

    Also include a speed reading if at all possible.

    What are we looking for?

    Vibration

    Changes

    Running speed multiples Increase in 1X

    Increase in noise floor

    Has the speed changed?

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    For larger machines with installed shaft vibration

    monitors:

    Compare the shaft data to casing data.

    How do those data sets compare?

    Are they at different amplitude levels, but similar characteristics?

    Are they different characteristics?

    Multiples on the casing, not on the shaft data? Different noise floor levels?

    Different phase indications?

    Does the orbit shape generally agree with where you see higher

    vibration levels on the casing?

    Remember, we are looking for changes. Having absolute limits foroperation and equipment protection is one thing, but all the monitoring

    instruments calculate vibration levels slightly differently. In the field, it

    is hard to have an absolute anything.

    M&B ESI

    Timothy S Irwin

    January 2006

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    Part I Condition Monitoring for Steam Turbines

    Lubrication /lubricant conditions

    Again, what kind of machine do we have? Large or small? If it is big enough to have a sump, then we can perform typical

    oil analysis testing.

    Viscosity, water, particulates, and spectrographic for routine

    Monitoring.

    M&B ESI

    Timothy S Irwin

    January 2006

    If it is not big enough for sump but uses oilers to ensure an oil supply

    for the bearing housing there are still things that need to be correct for

    a machine to achieve a reasonable time between repairs.

    Oil level in the oiler.

    Oil level in the bearing housing. Oil color in the oiler.

    Inspect the housing cavity for typical indications of

    contamination or condition during routine

    overhauls.

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Lubrication /lubricant conditions

    What are we looking for in an oil analysis?

    There are three major condition groups that oil analysis can monitor:

    Oil Condition

    Viscosity

    Additive packages

    Oil Contamination

    Moisture

    Particulates

    Equipment Condition Wear particles

    Material or source

    Ferrography

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Rotor speed/load or power.

    Is there any permanent monitoring available?

    Load

    Speed

    If no permanent monitoring is available, is there anythingelse you can use to verify operating load?

    Is a place on the shaft available for an optical or laser tachometer?

    Is the process controlled by inlet or discharge valves?

    Are there any flow indications?

    These items become even more critical for a variable load process!

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Auxiliary System Operation.

    On larger machines, there are considerable auxiliary systems

    that may also indicate development of a significant issue.

    Gland steam or Seal steam systems

    Shaft leakage increased

    More use of steam Changing pressure conditions

    Hydrogen seal oil systems

    Higher flow rates from increased shaft leakage

    Hydrogen purity issues

    Changing pressure conditions Cooling water conditions

    Conductivity

    Flow or pressure changes

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Auxiliary System Operation.

    On larger machines, there are considerable auxiliary systems

    that may also indicate development of a significant issue.

    Condenser conditions

    Vacuum pressure changes

    Condensate temperature changes Air in-leakage changes

    Feedwater Heater conditions

    Steam inlet/outlet condition changes

    Condensate inlet/outlet condition changes

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Noise/Sound levels.

    With modern ultrasound technologies, it should be possible to

    monitor and trend changing conditions within these machines.

    We should be able to monitor the following:

    Valve conditions at known positions, especially when closed

    Turbine noise levels at known conditions

    Bearing noise levels at known conditions

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    Summary

    There are considerable technologies that are available for use

    However, the tools we have discussed today are only several

    pieces of an overall reliability program.

    Preventive, Predictive, and Proactive or Reliability Centeredcomponents are all necessary to improve reliability and

    minimize overall operational cost.

    Basically, the more we know about the machine, the better we can

    diagnose a changing condition.

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    Part I Condition Monitoring for Steam Turbines

    M&B ESI

    Timothy S Irwin

    January 2006

    THE END

    ANY QUESTIONS?