Strategy For Implementation Of Condition Monitoring

Traditional Definition of Maintenance 

Keeping equipment in repair (Oxford)



The act of causing to continue (Websters)

Maintenance Strategies On Failure

Condition Based

Fix it when it fails

Maintain Based Upon known Condition

Maintenance Plan

Fixed Time Maintain Based upon Calendar

Design Out Identify & design Out root cause of failure

Run to Failure - Corrective Consciously allowing equipment to run to failure. No intervention is planned prior to failure. (this means there that every failure is planned - there are no unplanned failures. Every corrective task has a pre-planned action)

Breakdown - Reactive This is an unplanned, disruptive, interruption, which is the most costly ineffective response option. Allowing this to prevail as an existing response increases the overall cost and complexity of managing the system. (highly undesirable)

Advantages and Disadvantages Advantages • it requires no pre-care of the plant • it requires little management apart from organizing labor and stores • if applied correctly, it can be very cost effective Disadvantages • • • •

there is a need to provide standby plant if higher levels of availability are required - this can lead to higher build costs it requires a large standby maintenance team - as you have no indication of what will fail, you need a standby team ready to repair any of your equipment secondary or consequential damage may occur - a bearing failure may lead to the failure of the shaft, followed by the pump, etc, which will lead to higher costs of spares and longer repair times there is a requirement for a large spares stock to cater for any kind of failure that may occur

Preventative Maintenance Preventative maintenance is defined as regularly scheduled repair of components and equipment. It may consist of scheduled inspection, cleaning, lubrication, parts replacement, and repair of components. Preventative maintenance is time based intervention according to a prescribed schedule.

Advantages And Disadvatages Advantages • it reduces failures (compared to the on-failure strategy) • it uses the workforce cost-effectively with planned work schedules • it allows work to be planned well in advance • it can only be applied effectively on fixed time intervals where the deterioration is age related Disadvantages • the maintenance activity and associated costs will increase • the actual maintenance activity can sometimes cause failures itself • may be replacing a component that still has useful life

Predictive Maintenance A process which requires technologies and people skills which combines and uses all available diagnostic and performance data, maintenance histories, operations data and design data to make timely decisions about maintenance requirements of major / critical equipment.

Advantages •

• • • •

The advantages of utilizing the Predictive Maintenance strategy are many, some of which are not so tangible - such as increased motivation of the workforce through increased competency. The main advantage to Predictive Maintenance is that impending equipment failure can be detected, which in turn provides the following benefits: equipment can be shut-down before severe damage occurs alternatively, equipment can be run to failure if desired production can be modified to extend the unit life, for example, decrease the load on equipment so that it can continue to run until the next planned plant shutdown the required maintenance work can be planned, with labor organized, spares assembled, etc.

Disadvantages • following identification of the real root cause for failure, it is possible to plan in design modifications if required • Different organizations will present differing reasons for not implementing Predictive Maintenance, but the only disadvantage to the strategy is that: • it is costly if implemented incorrectly • That is, if condition monitoring is undertaken without an understanding of the equipment, and not as a part of an overall maintenance plan, then it is likely that it will fail, result in expenditure, and lose credibility within the organization. To succeed, Predictive Maintenance must be implemented correctly within the improvement context and against a complete understanding of the equipment, its failure modes, and root causes.

Proactive Maintenance Elimination of conditional failures through the identification of the root cause condition that initiates the failure cycle.

Advantages And Disadvantages Advantages • it is a one-off maintenance activity • it reduces failures • it will lead to increased production • it will remove or reduce the need for maintenance Disadvantages • large design changes can be costly • plant outages may be required to effect design changes • unless root causes of failure are fully understood, changes may be ineffectual, or potentially detrimental • there are sometimes unknown ‘knock-on’ effects of design changes that can cause further difficulties later on

Opportunity Maintenance Opportunity Maintenance is considered by many to be an additional maintenance strategy. This is where maintenance actions, whatever they may be, are performed on a piece of equipment only when the opportunity arises (i.e. when that piece of equipment is non-operational for one reason or another).

Relative Costs of Maintenance ($/HP)

60

50

40

US $ 30

20

10

0

Realtive Cost

Breakdown

Planned

Predictive

Proactive

51

30

12

7

ASME: Hudachek & Dodd

Survey Results:

Respondents Spending Over 50% Man-hours on Each Maintenance Type

Where Companies Focus Their Maintenance Efforts

All Industry Now 60

% 50 40 30 20 10 0

Reactive

Preventive

Predictive

Proactive

Survey Results:

Respondents Spending Over 50% Man-hours on Each Maintenance Type

Where Companies Focus Their Maintenance Efforts

All Industry Now All Industry in 5 years

60

% 50 40 30 20 10 0

Reactive

Source: Deloitte & Touche , CSI Survey

Preventive

Predictive

Proactive

Bathtub Curve

Failure Patterns

Maintenance Requirements Maintenance Requirements

First build the foundations

Determines the maintenance requirements of each physical asset in its operating context Reliability Centered Maintenance

19

Systems

Skills

Spares

Maintenance Requirements Maintenance Requirements

20

Tools

1930-1950

1st Generation • Fix it when Broke

1951-1990

1991-2000

2nd Generation

3rd Generation

• Schedule Overhauls • System for planning and controlling work • Low-tech computerization

• Condition monitoring • Design for reliability and maintainability • Hazard studies • High-tech computers • Failure modes and effects analysis • Expert systems • Multiskilling and team work

TECHNOLOGIES • Plant condition monitoring. • Asset optimization. • Non destructive Testing.

Why use vibration?

"Of all the parameters that can be measured non-intrusively in industry today, the one containing the most information is the vibration signature." Art Crawford

Why use vibration – Three Facts • All machines vibrate • Developing machinery problem, generate increase in vibration amplitude • Each fault generate vibration with unique characteristics • Vibration …a technique to diagnose the problems

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Condition monitoring is the study of conditions in machinery, which indicate functional problem or developing failure.

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Avoid the consequences of failure, before the failure occurs.

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It is a tool that helps effectively manage site plant assets, logistics and labor requirements.

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It is use of advanced technologies in order to determine equipment condition, and potentially predict failure.

 To predict equipment failures

 To reduce the cost of Maintenance  To improve equipment and component reliability  To optimize equipment performance  For a holistic view of equipment condition  For greater accuracy in failure prediction

Visual Inspection

Radiographic Inspection Mag./Elec. Inspection Ultrasonics Chemical Inspection

Thermal Inspection Vibration Analysis Corrective Measurements

 Dye Penetrant Testing  Videoscope Inspection

 X-Ray Inspection  Neutron Imaging  Magnetic Particle Inspection  Eddy Current Testing  Ultrasonic Testing  Acoustic Emission Testing  Chemical Spot Testing  Oil/Lube Analysis  Infrared Thermography

 Vibration Monitoring  Spectrum Analysis

 Dynamic Field Balancing  Laser Alignment

The use of noninvasive techniques to determine the integrity of a material, component or structure (Inspect/Measure without doing harm)

   

Test piece too precious to be destroyed Test piece to be re-use after inspection Test piece is in service For quality control purpose And many others….

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Flaw/Leak Detection and Evaluation

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Location & Dimensional Measurements

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Structure and Microstructure Characterization

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Estimation of Mechanical and Physical Properties

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Material Sorting and Chemical Composition Determination

What are Some Uses of NDE Methods? • • • • • • • •

Flaw Detection and Evaluation Leak Detection Location Determination Dimensional Measurements Fluorescent penetrant indication Structure and Microstructure Characterization Estimation of Mechanical and Physical Properties Stress (Strain) and Dynamic Response Measurements Material Sorting and Chemical Composition Determination

When are NDE Methods Used? There are NDE application at almost any stage in the production or life Cycle of a component.

– To assist in product development – To screen or sort incoming materials – To monitor, improve or control manufacturing processes – To verify proper processing such as heat treating – To verify proper assembly – To inspect for in-service damage

Common Application of NDT • Inspection of Raw Products • Inspection Following Secondary Processing • In-Services Damage Inspection

Visual Inspection Most basic and common inspection method. Tools include fiberscopes, borescopes, magnifying glasses and mirrors.

Portable video inspection unit with zoom allows inspection of large tanks and vessels, railroad tank cars, sewer lines. Robotic crawlers permit observation in hazardous or tight areas, such as air ducts, reactors, pipelines.

 DPT is one of the most widely used Non Destructive Testing (NDT) methods.  DPT can be used to inspect almost any material provided that its surface is not extremely rough or porous.

Materials that are commonly inspected using LPI include metals , glass, many ceramic materials, rubber, and plastics.

 Magnetic particle inspection can detect both production discontinuities and in-service damage in ferromagnetic materials.  It works on principal of electromagnetism.  A test specimen is magnetized with a strong magnetic field .

 If the specimen has a discontinuity, it will interrupt the magnetic field and a leakage field will occur.

X-Ray Source

 RT is based on the abruptness of change in ‘γ’ or X-rays while transferring from one medium to another.

Specimen X-Rays

 Radiation is directed through a part .  The resulting shadowgraph shows the internal features and soundness of the part.

X-ray film

 Material thickness and density changes are indicated as lighter or darker areas on the film. Top view

Radiographic Images

Eddy Current Testing Coil

Coil's magnetic field

Eddy current's magnetic field Eddy currents Conductive material

 In UT, very short ultrasonic pulse-waves having frequency range of 0.115 MHz are injected into the specimen.

IRT is based on the principle that:  Radiation can be detected in the infrared range of the electromagnetic spectrum (9–14 µm) through thermal imaging camera.  The amount of radiation emitted by an object increases with temperature.

 Oil analysis (OA) is the laboratory analysis of a lubricant's properties, suspended contaminants, and wear debris. 

OA is performed during routine preventive maintenance to provide meaningful and accurate information on lubricant and machine condition.

 By tracking oil analysis sample results over the life of a particular machine, trends can be established which can help eliminate costly repairs and early Oil Change

 Fact – All machines vibrate to greater or lesser extent.  Developing machinery problem, generate increase in vibration amplitude.  Each fault generate vibration with unique characteristics/pattern that distinguish it from others.  Examination of vibration spectrum indicates the type of fault. After Repair RMS (G’s)

Before Repair

Freq. (CPM)

 Fault – Unique vibration profile – Amplitude spikes after specific intervals in the spectrum.  For Example:  Imbalance  Misalignment  Looseness

– 1 x Ts (Turning Speed) – 2 x Ts – 3 x Ts

1X

2X

3X

•

Force created when the center of mass is not the center of rotation Center of Mass = Center of Shaft

Heavy Spot

Center of Shaft

Center of Mass Rotation

•

• •

Increase machine life by..... – Reduce cyclic fatigue on machine components – Reduce heat from preloading and friction – Lower vibration and noise levels Minimize shaft bending Life is extended dramatically with a slight alignment improvement!