Chapter 6 Predictive Maintenance Technologie

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O&M Best Practices Guide, Release 3.0 6.1

Chapter 6 Predictive Maintenance Technologies

6.1 Introduction

Predictive maintenance attempts to detect the onset o a degradation mechanism with the goalo correcting that degradation prior to signifcant deterioration in the component or equipment. Thediagnostic capabilities o predictive maintenance technologies have increased in recent years withadvances made in sensor technologies. These advances, breakthroughs in component sensitivities,size reductions, and most importantly, cost, have opened up an entirely new area o diagnostics to theO&M practitioner.

As with the introduction o any new technology, proper application and TRAINING is ocritical importance. This need is particularly true in the feld o predictive maintenance technologythat has become increasingly sophisticated and technology-driven. Most industry experts wouldagree (as well as most reputable equipment vendors) that this equipment should not be purchasedor in-house use i there is not a serious commitment to proper implementation, operator training,

and equipment monitoring and repair. I such a commitment cannot be made, a site is well advisedto seek other methods o program implementationa preerable option may be to contract or theseservices with an outside vendor and rely on their equipment and expertise.

Table 6.1.1 below highlights typical applications or some o the more common predictivemaintenance technologies. O course, proper application begins with system knowledge andpredictive technology capability beore any o these technologies are applied to live systems.

Table 6.1.1. Common predictive technology applications (NASA 2000)

Technologies Applications

Pumps

ElectricMotor

s

DieselGenerators

Condensers

HeavyEquipm

ent/

Cranes

CircuitBreakers

Valves

HeatExchangers

ElectricalSyst

ems

Transformers

Tanks,Piping

Vibration Monitoring/Analysis X X X X

Lubricant, Fuel Analysis X X X X X

Wear Particle Analysis X X X X

Bearing, Temperature/Analysis X X X X

Perormance Monitoring X X X X X X

Ultrasonic Noise Detection X X X X X X X

Ultrasonic Flow X X X X

Inrared Thermography X X X X X X X X X X

Non-destructive Testing (Thickness) X X X

Visual Inspection X X X X X X X X X X X

Insulation Resistance X X X X X

Motor Current Signature Analysis X

Motor Circuit Analysis X X X

Polarization Index X X X

Electrical Monitoring X X


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Predictive Maintenance Technologies

6.2 Thermography

6.2.1 Introduction

Inrared (IR) thermography can be defned as the process o generating visual images that repre-

sent variations in IR radiance o suraces o objects. Similar to the way objects o dierent materialsand colors absorb and reect electromagnetic radiation in the visible light spectrum (0.4 to 0.7 microns),any object at temperatures greater than absolute zero emits IR energy (radiation) proportional toits existing temperature. The IR radiation spectrum is generally agreed to exist between 2.0 and15 microns. By using an instrument that contains detectors sensitive to IR electromagnetic radiation,a two-dimensional visual image reective o the IR radiance rom the surace o an object can begenerated. Even though the detectors and electronics are dierent, the process itsel is similar to thata video camera uses to detect a scene reecting electromagnetic energy in the visible light spectrum,interpreting that inormation, and displaying what it detects on a liquid crystal display (LCD) screenthat can then be viewed by the device operator.

Because IR radiation alls outside that o visible light (the radiation spectrum to which our eyes

are sensitive), it is invisible to the naked eye. An IR camera or similar device allows us to escape thevisible light spectrum and view an object based on its temperature and its proportional emittanceo IR radiation. How and why is this ability to detect and visualize an objects temperature profleimportant in maintaining systems or components? Like all predictive maintenance technologies,IR tries to detect the presence o conditions or stressors that act to decrease a components useul ordesign lie. Many o these conditions result in changes to a components temperature. For example,a loose or corroded electrical connection results in abnormally elevated connection temperaturesdue to increased electrical resistance. Beore the connection is hot enough to result in equipmentailure or possible fre, the patterns are easily seen through an IR imaging camera, the conditionidentifed and corrected. Rotating equipment problems will normally result in some orm o rictionalchange that will be seen as an increase in the components temperature. Faulty or complete loss oreractory material will be readily seen as a change in the components thermal profle. Loss o a roos

membrane integrity will result in moisture that can be readily detected as dierences in the roothermal profle. These are just a ew general examples o the hundreds o possible applications o thistechnology and how it might be used to detect problems that would otherwise go unnoticed until acomponent ailed and resulted in excessive repair or downtime cost.

6.2.2 Types of Equipment

Many types o IR detection devices exist, varying incapability, design, and cost. In addition, simple temperaturemeasurement devices that detect IR emissions but do notproduce a visual image or IR profle are also manuactured.The ollowing text and pictures provide an overview o eachgeneral instrument type.

Spot Radiometer (Inrared Thermometer) Althoughnot generally thought o in the world o thermography,IR thermometers use the same basic principles as higherend equipment to defne an objects temperature based onIR emissions. These devices do not provide any image Figure 6.2.1. Typical IR spot thermometer

representative o an objects thermal profle, but rather a valuerepresentative o the temperature o the object or area o interest.

O&M Best Practices Guide, Release 3.06.2


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6.2.3 System Applications

6.2.3.1 Electrical System Applications

The primary value o thermographic inspections o electrical systems is locating problems so

that they can be diagnosed and repaired. How hot is it? is usually o ar less importance. Once theproblem is located, thermography and other test methods, as well as experience and common sense,are used to diagnose the nature o the problem. The ollowing list contains just a ew o the possibleelectrical system-related survey applications:

Transmission lines- Splices- Shoes/end bells

Inductive heating problems- Insulators

Cracked or damaged/tracking

Distribution lines/systems- Splices- Line clamps- Disconnects- Oil switches/breakers- Capacitors- Pole-mounted transormers- Lightning arrestors- Imbalances

Substations- Disconnects, cutouts, air switches- Oil-flled switches/breakers (external and

internal aults)- Capacitors- Transormers

Internal problems Bushings Oil levels Cooling tubes Lightning arrestors

- Bus connections Generator Facilities

- Generator Bearings Brushes Windings Coolant/oil lines: blockage

- Motors Connections Bearings Winding/cooling patterns Motor Control Center Imbalances

In-Plant Electrical Systems- Switchgear- Motor Control Center- Bus- Cable trays- Batteries and charging circuits

- Power/Lighting distribution panels

Software analysis tools can quantify and graphicallydisplay temperature data. As shown above, the middleconductor/connection is a much higher temperatureindicating a loose connection.



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Figure 6.2.4. Air breaker problem. Highlighted by temperature differencebetween two different breakers. Likely caused by poor connection.

Figure 6.2.5. Overloaded contacts show different temperature proles indicatingone contact seeing much greater load, a potentially unsafe situation.

6.2.3.2 Mechanical System Applications

Rotating equipment applications are only a small subset o the possible areas where thermographycan be used in a mechanical predictive maintenance program. In addition to the ability to detect

problems associated with bearing ailure, alignment, balance, and looseness, thermography can beused to defne many temperature profles indicative o equipment operational aults or ailure. Theollowing list provides a ew application examples and is not all inclusive:

Steam Systems Environmental- Boilers - Water discharge patterns

Reractory - Air discharge patterns Tubes Motors and rotating equipment

- Traps - Bearings- Valves Mechanical ailure- Lines Improper lubrication

Heaters and urnaces - Coupling and alignment problems

- Reractory inspections - Electrical connections on motors- Tube restrictions - Air cooling o motors

Fluids- Vessel levels- Pipeline blockages



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Figure 6.2.6. IR scans of multiple electric motors can highlight those with hotbearings indicting an imbalance or wear problem.

Figure 6.2.7. Possible gearbox problem indicated by white area dened byarrow. Design drawings of gearbox should be examined to dene possible causeof elevated temperatures.

Figure 6.2.8. Seized conveyer belt roller as indicated by elevated temperatures inbelt/roller contact area.

Figure 6.2.9. Inoperable steam heaters seen by cooler blue areas when comparedto the operating heaters warmer red or orange colors.



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Figure 6.2.10. IR scans of boiler can highlight those areas where the refractoryhas broken down leading to costly heat loss.

Figure 6.2.11. When trended, IR scans of single bearings provide a useful indicator ofwear and eventual need for replacement.

Figure 6.2.12. Steam or hot water distribution systemleaks and/or underground line location can bedened with IR.



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Computer hardware, personnel training, manpower, etc., needs to be accounted or in the budget.Below is a listing o equipment and program needs recommended by a company recognized as a leaderin the world o IR program development:

Level I thermographic training

Level II thermographic training

Ongoing proessional development

IR camera and accessories

Report sotware

Laptop computer

Color printer

Digital visual camera

Personal Protective Equipment (PPE) or arc ash protection

Payback can vary widely depending on the type o acility and use o the equipment. A produc-tion acility whose downtime equates to several thousands o dollars per hour can realize savings muchaster than a small acility with minimal roo area, electrical distribution network, etc. On average, aacility can expect a payback in 12 months or less. A small acility may consider using the services oan IR survey contractor. Such services are widely available and costs range rom $600 to $1,200 perday. Contracted services are generally the most cost-eective approach or smaller, less maintenance-intensive acilities.

6.2.5 Training Availability

Training or inrared thermography is available through a variety o system manuacturers and

vendors. In addition, the American Society o Non-destructive Testing (ASNT) has establishedguidelines or non-destructive testing (NDT) (Level I, II, or III) certifcation (NASA 2000). Thesethree levels are designed to take the student rom Level I - where the student is competent withequipment unction and use, to Level II where the student is ully capable and experienced and cancomplete diagnostics and recommendations, to Level III where the student is ully experienced tosupervise and teach Level I and II students.

6.2.6 Case Studies

IR Diagnostics o Pump

A acility was having continual problems with some to its motor and pump combinations. Pumpbearings repeatedly ailed. An IR inspection confrmed that the lower thrust bearing was warmerthan the other bearing in the pump. Further investigation revealed that the motor-pump combina-tion was designed to operate in the horizontal position. In order to save oor space, the pump wasmounted vertically below the motor. As a result, the lower thrust bearing was overloaded leading topremature ailure. The ailures resulted in a $15,000 repair cost, not including lost production time($30,000 per minute production loss and in excess o $600 per minute labor).



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IR Diagnostics o Steam Traps

Steam trap ailure detection can be difcult by other orms o detection in many hard to reachand inconvenient places. Without a good trap maintenance program, it can be expected that 15%to 60% o a acilitys traps will be ailed open. At $3/1,000 lb (very conservative), a -in. orifce

trap ailed open will cost approximately $7,800 per year. I the system had 100 traps and 20% wereailed, the loss would be in excess o $156,000. An oil refnery identifed 14% o its traps weremalunctioning and realized a savings o $600,000 a year ater repair.

IR Diagnostics o Roo

A state agency in the northeast operated a acility with a 360,000 square oot roo area. Theroo was over 22 years old and experiencing several leaks. Cost estimates to replace the roo rangedbetween $2.5 and $3 million. An initial IR inspection identifed 1,208 square eet o roo requiringreplacement at a total cost o $20,705. The ollowing year another IR inspection was perormedthat ound 1,399 square eet o roo requiring replacement at a cost o $18,217. A roo IR inspectionprogram was started and the roo surveyed each year. The survey resulted in less than 200 square

eet o roo identifed needing replacement in any one o the ollowing 4 years (one year resultswere as low as 30 square eet). The total cost or roo repair and upkeep or the 6 years was less than$60,000. I the acility would have been privately owned, interest on the initial $3 million at 10%would have amounted to $300,000 or the frst year alone. Discounting interest on $3 million overthe 5-year period, simple savings resulting rom survey and repair versus initial replacement cost($3 million to $60,000) amount to $2,940,000. This fgure does not take into account interest onthe $3 million, which would result in savings in excess o another $500,000 to $800,000, dependingon loan interest paid.

6.2.7 Resources

The resources provided below are by no means all-inclusive. The listed organizations are not

endorsed by the authors o this guide and are provided or your inormation only. To locate additionalresources, the authors o this guide recommend contacting relevant trade groups, databases, and theworld-wide web.

FLIR Systems RaytekBoston, MA Santa Cruz, CATelephone: 1-800-464-6372 Telephone: 1-800-227-8074Web address: www.irthermography.com Web address: www.raytek-northamerica.com

Mikron Instrument Company, Inc. ElectrophysicsOakland, NJ Fairfeld, NJTelephone: (201) 405-0900 Telephone: (973) 882-0211Web address: www.irimaging.com Web address: www.electrophysics.com

http://www.flirthermography.com/http://www.raytek-northamerica.com/http://www.irimaging.com/http://www.electrophysics.com/http://www.electrophysics.com/http://www.raytek-northamerica.com/http://www.irimaging.com/http://www.flirthermography.com/


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6.2.7.1 Infrared Service Companies

Hartord Steam BoilerEngineering ServicesTelephone: (703) 739-0350

Web address: www.hsb.com/infrared/

American Thermal Imaging

Red Wing, MNTelephone: (877) 385-0051Web address: www.americanthermalimaging.com

Inrared Services, Inc.

5899 S. Broadway Blvd.Littleton, CO 80121Voice: (303) 734-1746Web address: www.infrared-thermography.com

Snell Thermal Inspections

U.S. wideTelephone: 1-800-636-9820Web address: www.snellinspections.com

6.2.7.2 Infrared Internet Resource Sites

Academy o Inrared Thermography(www.infraredtraining.net)

Level I, II, and III certifcation inormation and training schedule

Online store (books, sotware, videos)

Online resources (links, image gallery, message board)

Communication (classifeds, news, industry-related inormation

Company profle and contact inormation

Snell Inrared (Snellinfrared.com)

Training and course inormation

Industry links IR library

Newsletter

Classifeds

IR application inormation

http://www.hsb.com/infrared/http://www.americanthermalimaging.com/http://www.infrared-thermography.com/http://www.snellinspections.com/http://www.infraredtraining.net/http://snellinfrared.com/http://snellinfrared.com/http://www.infraredtraining.net/http://www.snellinspections.com/http://www.infrared-thermography.com/http://www.americanthermalimaging.com/http://www.hsb.com/infrared/


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6.3.1 Introduction

One o the oldest predictive maintenance technologies still in use today is that o oil analysis.

Oil analysis is used to defne three basic machine conditions related to the machines lubricationor lubrication system. First is the condition o the oil, that is, will its current condition lubricateper design? Testing is perormed to determine lubricant viscosity, acidity, etc., as well as otherchemical analysis to quantiy the condition o oil additives like corrosion inhibitors. Second is thelubrication system condition, that is, have any physical boundaries been violated causing lubricantcontamination? By testing or water content, silicon, or other contaminants (depending on thesystem design), lubrication system integrity can be evaluated. Third is the machine condition itsel.By analyzing wear particles existing in the lubricant, machine wear can be evaluated and quantifed.

In addition to system degradation, oil analysis perormed and trended over time can provideindication o improperly perormed maintenance or operational practices. Introduction ocontamination during lubricant change-out, improper system ush-out ater repairs, addition o

improper lubricant, and improper equipment operation are all conditions that have been ound bythe trending and evaluation o oil analysis data.

Several companies provide oil analysis services. These services are relatively inexpensive andsome analysis laboratories can provide analysis results within 24 hours. Some services are currentlyusing the Internet to provide quick and easy access to the analysis reports. Analysis equipmentis also available should a acility wish to establish its own oil analysis laboratory. Regardless owhether the analysis is perormed by an independent laboratory or by in-house orces, accurateresults require proper sampling techniques. Samples should be taken rom an active, low-pressureline, ahead o any fltration devices. For consistent results and accurate trending, samples should betaken rom the same place in the system each time (using a permanently installed sample valve ishighly recommended). Most independent laboratories supply sample containers, labels, and mailingcartons. I the oil analysis is to be done by a laboratory, all that is required is to take the sample,fll in inormation such as the machine number, machine type, and sample date, and send it to thelaboratory. I the analysis is to be done on-site, analytical equipment must be purchased, installed,and standardized. Sample containers must be purchased, and a sample inormation orm created andprinted.

The most common oil analysis tests are used to determine the condition o the lubricant,excessive wearing o oil-wetted parts, and the presence o contamination. Oil condition ismost easily determined by measuring viscosity, acid number, and base number. Additional testscan determine the presence and/or eectiveness o oil additives such as anti-wear additives,antioxidants, corrosion inhibitors, and anti-oam agents. Component wear can be determined by

measuring the amount o wear metals such as iron, copper, chromium, aluminum, lead, tin, andnickel. Increases in specifc wear metals can mean a particular part is wearing, or wear is takingplace in a particular part o the machine. Contamination is determined by measuring watercontent, specifc gravity, and the level o silicon. Oten, changes in specifc gravity mean that theuid or lubricant has been contaminated with another type o oil or uel. The presence o silicon(usually rom sand) is an indication o contamination rom dirt.



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6.3.2 Test Types

Karl Fischer Water Test The Karl Fischer Test quantifes the amount o water in the lubricant.

Signifcance: Water seriously damages the lubricating properties o oil and promotes componentcorrosion. Increased water concentrations indicate possible condensation, coolant leaks, orprocess leaks around the seals.

ICP Spectroscopy Measures the concentration o wear metals, contaminant metals, and additive metals in a lubricant.Signifcance: Measures and quantifes the elements associated with wear, contamination, andadditives. This inormation assists in determining the oil and machine condition.

The ollowing guide highlights the elements that may be identifed by this test procedure. Alsoprovided are brie descriptions explaining where the particles came rom or engines, transmissions,gears, and hydraulic systems.

Spectrometer Metals Guide

Metal Engines Transmissions Gears Hydraulics

Iron Cylinder liners, rings, gears,crankshat, camshat, valvetrain, oil pump gear, wristpins

Gears, disks, housing,bearings, brake bands,shat

Gears, bearings, shat,housing

Rods, cylinders, gears

Chrome Rings, liners, exhaustvalves, shat plating,stainless steel alloy

Roller bearings Roller bearings Shat

Aluminum Pistons, thrust bearings,turbo bearings, mainbearings (cat)

Pumps, thrust washers Pumps, thrust washers Bearings, thrust plates

Nickel Valve plating, steel alloy

rom crankshat, camshat,gears rom heavy bunker-type diesel uels

Steel alloy rom roller

bearings and shat

Steel alloy rom roller

bearings and shat

Copper Lube coolers, main and rodbearings, bushings, turbobearings, lube additive

Bushings, clutch plates(auto/ powershit),lube coolers

Bushings, thrust plates Bushings, thrust plates,lube coolers

Lead Main and rod bearings,bushings, lead solder

Bushings (bronzealloy), lube additivesupplement

Bushings (bronzealloy), greasecontamination

Bushing (bronze alloy)

Tin Piston ashing, bearingover-lay, bronze alloy,babbit metal along withcopper and lead

Bearing cage metal Bearing cage metal,lube additive

Cadmium N/A N/A N/A N/A

Silver Wrist pin bushings(EMDs), silver solder (romlube coolers)

Torrington needlebearings (Allisontransmission)

N/A Silver solder (rom lubecoolers)

Titanium Gas turbine bearings/hub/blades, paint (white lead)

N/A N/A N/A

Vanadium From heavy bunker-typediesel uels

N/A N/A N/A



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Spectrometer Metals Guide (contd)

Contaminant Metals

Silicon Dirt, seals and sealants,coolant inhibitor, lubeadditive

(15 ppm or less)

Dirt, seals andsealants, coolantinhibitor, lube additive

(15 ppm or less)

Dirt, seals andsealants, coolantadditive, lube additive

(15 ppm or less)

Dirt, seals and sealant,coolant additive, lubeadditive

(15 ppm or less)

Sodium Lube additive, coolantinhibitor, salt watercontamination, washdetergents

Lube additive, coolantinhibitor, salt watercontamination, washdetergents

Lube additive,saltwatercontamination,airborne contaminate

Lube additive, coolantinhibitor, saltwatercontamination,airborne contaminate

Multi-Source Metals

Molybdexznum Ring plating, lube additive,coolant inhibitor

Lube additive, coolantinhibitor

Lube additive, coolantinhibitor, coolantinhibitor, greaseadditive


Antimony Lube additive Lube additive Lube additive Lube additive

Manganese Steel alloy Steel alloy Steel alloy Steel alloy

Lithium N/A Lithium complexgrease

Lithium complexgrease

Lithium complex grease

Boron Lube additive, coolantinhibitor




Additive Metals

Magnesium Detergent dispersantadditive, airbornecontaminant at some sites

Detergent dispersantadditive, airbornecontaminant at somesites



Calcium Detergent dispersantadditive, airbornecontaminant at some sites,contaminant rom water

Detergent dispersantadditive, airbornecontaminant at somesites, contaminantrom water

Detergent dispersantadditive, airbornecontaminant at somesites, contaminantrom water

Detergent dispersantadditive, airbornecontaminant at somesites, contaminant romwater

Barium Usually an additive romsynthetic lubricants

Usually an additiverom syntheticlubricants



Phosphorus Anti-wear additive (ZDP) Anti-wear additive(ZDP)

Anti-wear additive(ZPD), EP additive(extreme pressure)

Anti-wear additive(ZDP)

Zinc Anti-wear additive (ZDP) Anti-wear additive(ZDP)

Anti-wear additive(ZPD)

Anti-wear additive(ZDP)

Test Types (contd)

Particle Count Measures the size and quantity o particles in a lubricant.

Signifcance: Oil cleanliness and perormance. An increase in particle size and gravity is anindication o a need or oil service.

Viscosity Test Measure o a lubricants resistance to ow at a specifc temperature.

Signifcance: Viscosity is the most important physical property o oil. Viscosity determinationprovides a specifc number to compare to the recommended oil in service. An abnormal viscosity(15%) is usually indicative that lubricant replacement is required.



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Fourier transorm (FT)-IR Spectroscopy Measures the chemical composition o a lubricant.

Signifcance: Molecular analysis o lubricants and hydraulic uids by FT-IR spectroscopyproduces direct inormation on molecular species o interest, including additives, uid breakdownproducts, and external contamination.

Direct Read Ferrography Measures the relative amount o errous wear in a lubricant.

Signifcance: The direct read gives a direct measure o the amount o errous wear metals odierent size present in a sample. I trending o this inormation reveals changes in the wearmode o the system, then action is required.

Analytical Ferrography Allows analyst to visually examine wear particles present in a sample.

Signifcance: A trained analyst visually determines the type and severity o wear deposited ontothe substrate by using a high magnifcation microscope. The particles are readily identifed andclassifed according to size, shape, and metallurgy.

Total Acid Number Measures the acidity o a lubricant.

Description: Organic acids, a by-product o oil oxidation, degrade oil properties and lead tocorrosion o the internal components. High acid levels are typically caused by oil oxidation.


Although independent laboratories generally perorm oil analysis, some vendors do provideanalysis equipment that can be used on-site to characterize oil condition, wear particles, and con-tamination. These devices are generally composed o several dierent types o test equipment andstandards including viscometers, spectrometers, oil analyzers, particle counters, and microscopes.On-site testing can provide quick verifcation o a suspected oil problem associated with criticalcomponents such as water contamination. It can also provide a means to quickly defne lubricantcondition to determine when to change the lubricant medium. For the most part, detailed analysis

will still require the services o an independent laboratory.


All machines with motors 7.5 hp or larger, and critical or high-cost machines should be evaluatedor routine lubricating oil analysis (NASA 2000) rom monthly to quarterly. All hydraulic systems,except mobile systems, should be analyzed on a quarterly basis. Mobile systems should be consideredor analysis based upon the machine size and the cost eectiveness o perorming the analysis.Generally speaking, it is more cost eective in mobile equipment to maintain the hydraulic uidbased on the uid condition. However, or small systems, the cost to ush and replace the hydraulicuid on a time basis may be lower than the cost to analyze the uid on a routine basis. Typicalequipment applications include:

Typical oil analysis equipment availablefrom several different vendors.


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Turbines

Boiler eed pumps

Electrohydraulic control (EHC) systems

Hydraulics

Servo valves

Gearboxes

Roller bearings

Anti-riction bearings

Any system where oil cleanliness is directly related to longer lubricant lie, decreased equipmentwear, or improved equipment perormance

6.3.5 Equipment Cost/Payback

For acilities utilizing a large number o rotating machines that employ circulating lubricant,or or acilities with high dollar equipment using circulating lubricant, ew predictive maintenancetechnologies can oer the opportunity o such a high return or dollars spent. Analysis or a singlesample can run rom $15 to $100 depending on the level o analysis requested samples are typicallysent through the mail to the testing center. Given the high equipment replacement cost, laborcost, and downtime cost involved with a bearing or gearbox ailure, a single ailure prevented by theperormance o oil analysis can easily pay or a program or several years.


Training or lubricant and wear particle analysis typically takes place via vendors. Because theanalysis is usually conducted by outside vendors at their location, training consists o proper samplingtechniques (location and requency) as well as requisite sample handling guidance.

6.3.7 Case Studies

Reduced Gear Box Failure

Through oil analysis, a company determined that each time oil was added to a gear reducer, con-tamination levels increased and this was accompanied by an increase in bearing and gear ailures.Further examination determined that removing the cover plate to add oil allowed contaminationfrom the process to fall into the sump. Based on this, the system was redesigned to prevent the intro-duction of contamination during oil addition. The result was a reduction in bearing/gearbox failure rates.

Oil Changes When Needed

A major northeast manuacturer switched rom a preventive maintenance approach o changingoil in 400 machines using a time-based methodology to a condition-based method using in-house oilanalysis. The oil is now being changed based on its actual condition and has resulted in a savings inexcess o $54,000 per year.



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Oil Changes and Equipment Scheduling

A northeast industrial acility gained an average o 0.5 years between oil changes when it changedoil change requirements rom a preventive maintenance time-based approach to changing oil basedon actual conditions. This resulted in greater than a $20,000 consumable cost in less than 9 months.

A large chemical manuacturing frm saved more than $55,000 in maintenance and lost produc-tion cost avoidance by scheduling repair o a centriugal compressor when oil analysis indicated watercontamination and the presence o high errous and non-errous particle counts.

6.3.8 References/Resources

The reerences and resources provided below are by no means all-inclusive. The listed organiza-tions are not endorsed by the authors o this guide and are provided or your inormation only. Tolocate additional resources, the authors o this guide recommend contacting relevant trade groups,databases, and the world-wide web.

6.3.8.1 Analysis Equipment 6.3.8.2 Oil AnalysisResources Laboratories

Computational Systems, Inc./ Computational Systems, Inc./Emerson Process Management Emerson Process ManagementKnoxville, TN Knoxville, TNTelephone: (865) 675-2400 Telephone: (865) 675-2400Fax: (865) 218-1401 Fax: (865) 218-1401Web address: www.compsys.com Web address: www.comsys.com

Reliability Direct, Inc. Polaris LaboratoriesLeague City, TX Indianapolis, IN

Telephone: 1-888-710-6786 Telephone: (877) 808-3750Fax: (281) 334-4255 Fax: (317) 808-3751Web address: www.reliabilitydirect.com Web address: www.polarislabs1.com

Spectro, Inc. Analysts, Inc.Industrial Tribology Systems Locations throughout the U.S.Littleton, MA Telephone: (800) 336-3637Telephone: (978) 486-0123 Fax: (310) 370-6637Fax: (978) 486-0030 Web address: www.analystsinc.comE-Mail: [email protected] address: www.spectroinc.com LubeTrak

Sandy, UTTelephone: 1-866-582-3872 (Toll Free)Web address: www.lubetrak.com

http://www.compsys.com/http://www.comsys.com/http://www.reliabilitydirect.com/http://www.polarislabs1.com/http://www.analystsinc.com/http://www.spectroinc.com/http://www.lubetrak.com/http://www.lubetrak.com/http://www.analystsinc.com/http://www.polarislabs1.com/http://www.comsys.com/http://www.spectroinc.com/http://www.reliabilitydirect.com/http://www.compsys.com/


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6.3.8.3 Internet Resource Sites

www.testoil.com

Sample report Free oil analysis

Industry-related articles Test overview Laboratory services Training services

www.compsys.com

Laboratory service Technical articles Application papers Sample report Training services Technical notes

www.natrib.com

Technical articles Case studies

Newsletters Application notes

http://www.testoil.com/http://www.compsys.com/http://www.natrib.com/http://www.natrib.com/http://www.compsys.com/http://www.testoil.com/


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6.4 Ultrasonic Analysis

6.4.1 Introduction

Ultrasonic, or ultrasounds, are defned as sound waves that have a requency level above 20 kHz.

Sound waves in this requency spectrum are higher than what can normally be heard by humans.Non-contact ultrasonic detectors used in predictive maintenance detect airborne ultrasound. Therequency spectrums o these ultrasounds all within a range o 20 to 100 kHz. In contrast to IR emis-sions, ultrasounds travel a relatively short distance rom their source. Like IR emissions, ultrasoundstravel in a straight line and will not penetrate solid suraces. Most rotating equipment and manyuid system conditions will emit sound patterns in the ultrasonic requency spectrum. Changes inthese ultrasonic wave emissions are reective o equipment condition. Ultrasonic detectors can beused to identiy problems related to component wear as well as uid leaks, vacuum leaks, and steamtrap ailures. A compressed gas or uid orced through a small opening creates turbulence with strongultrasonic components on the downstream side o the opening. Even though such a leak may not beaudible to the human ear, the ultrasound will still be detectable with a scanning ultrasound device.

Ultrasounds generated in vacuum systems are generated within the system. A small percentageo these ultrasonic waves escape rom the vacuum leak and are detectable, provided the monitoring isperormed close to the source or the detector gain is properly adjusted to increase detection perorm-ance. In addition to system vacuum or uid leaks, ultrasonic wave detection is also useul in defningabnormal conditions generated within a system or component. Poorly seated valves (as in the caseo a ailed steam trap) emit ultrasounds within the system boundaries as the uid leaks past the valveseat (similar to the sonic signature generated i the uid was leaking through the pipe or ftting walls).These ultrasounds can be detected using a contact-type ultrasonic probe.

Ultrasonic detection devices can also be used or bearing condition monitoring. According toNational Aeronautics and Space Administration (NASA) research, a 12-50x increase in the ampli-tude o a monitored ultrasonic requency (28 to 32 kHz) can provide an early indication o bearingdeterioration.

Ultrasonic detection devices are becoming more widely used in detection o certain electricalsystem anomalies. Arcing/tracking or corona all produce some orm o ionization that disturbs theair molecules around the equipment being diagnosed and produces some level o ultrasonic signature.An ultrasonic device can detect the high-requency noise produced by this eect and translate it, viaheterodyning, down into the audible ranges. The specifc sound quality o each type o emission isheard in headphones while the intensity o the signal can be observed on a meter to allow quantif-cation o the signal.

In addition to translating ultrasonic sound waves into requencies heard by the human ear orseen on a meter ace, many ultrasonic sound wave detectors provide the capability to capture andstore the detectors output. Utilizing display and analysis sotware, a time waveorm o the ultrasonicsignature can then be visually displayed. This unctionality increases the technologys capability tocapture and store quantifable data related to a components operating condition. Ultrasonic signatureinormation can then be used to baseline, analyze, and trend a components condition. In contrast toa technicians subjective analysis o a components condition using an audio signal, many ultrasonicanomalies indicative o component problems are more easily defned using a signature profle. Theollowing images o ultrasonic time waveorms rom two identical gearboxes illustrate how ultrasonic



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signature data storage and analysis can be used to quantiy machine condition. Gearbox 1waveorm shows an ultrasonic signature anomaly that may be attributable to missing or worn gearteeth, while Gearbox 2 signature shows a at profle.

Gearbox 1

Gearbox 2

Generally, this type o diagnosis can be perormed on a standard personal computer (PC). Theprograms not only provide the spectral and time series views o the ultrasonic signature but enableusers to hear the translated sound samples simultaneously as they are viewing them on the PCmonitor.


Ultrasonic analysis is one o the less complex and less

expensive predictive maintenance technologies. The equipmentis relatively small, light, and easy to use. Measurement data arepresented in a straightorward manner using meters or digitalreadouts. The cost o the equipment is moderate and the amounto training is minimal when compared to other predictivemaintenance technologies. The picture to the right shows atypical ultrasonic detection device. Typical hand-held ultrasonic detector



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Since ultrasounds travel only a short distance, some scanningapplications could present a saety hazard to the technician or thearea o interest may not be easily accessible. In these applications,the scanning device is generally designed with a gain adjust toincrease its sensitivity, thereby allowing scanning rom a greater

distance than normal. Some ultrasonic detectors are designed toallow connection o a special parabolic dish-type sensing device(shown at right) that greatly extends the normal scanning distance.


6.4.3.1 Pressure/Vacuum Leaks

Compressed air

Oxygen

Hydrogen

Heat exchangers

Boilers

Condensers

Tanks

PipesUltrasonic detection can be used to locate underground system leaks

Valves and detect heat exchanger tube leakage.

Steam traps.

6.4.3.2 Mechanical Applications

Mechanical inspection

Bearings

Lack o lubrication

Pumps

Motors

Gears/Gearboxes Fans

Compressors

Conveyers.

Parabolic dish used with ultrasonicdetector greatly extends detectionrange abilities.

From steam trap faultsand valve leakage tocompressor problems,

ultrasonic detection canbe used to nd a varietyof problems that generateultrasonic signatures.



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6.4.3.3 Electrical Applications

Arcing/tracking/corona

Switchgear

Transormers Insulators

Mechanical devices are not the only sources of ultrasonic Seals/Potheadsemission. Electrical equipment will also generate ultrasonic

waves if arcing/tracking or corona are present. Junction boxes

Circuit breakers.


As indicated earlier, ultrasonic analysis

equipment cost is minimal when compared toother predictive maintenance technologies.A typical handheld scanner, sotware, probes,will cost rom $750 to $10,000 depending onthe type, accuracy and eatures. The minimalexpense combined with the large savingsopportunities will most oten result in anequipment payback period o 6 months or less.


Training or ultrasonic analysis is availablethrough a variety o system manuacturers andvendors. Depending on your needs, considertraining that will qualiy you or the AmericanSociety o Non-destructive Testing (ASNT)various levels o certifcation. Generically, theselevels take the ollowing orm:Level I the student is competent withequipment unction and use; Level II thestudent is ully capable and experienced and cancomplete diagnostics and recommendations;Level III the student is ully experienced to

supervise and teach Level I and II student.

Steam Trap Applications(NASA 2000):

Steam traps should be monitored on the down-stream side of the trap using the test equipmentscontact mode. Each type of steam trap producesa distinct sound as briey described below. It isrecommended that users receive training and thengain experience in a controlled environment beforediagnosing operating systems.

Typical ultrasonic signatures will include andopening and closing sound characterized by steamrushing sound followed by a period of relativequiet. Many types of traps fail in the open position,producing a continuous, rushing sound. Commontrap types and their diagnostic signatures include:

Inverted Bucket: A normal trap sounds as if it isoating; a failed trap sinks, producing a continuousow noise.

Float and Thermostatic (Continuous Load): Flowand noise associated with these traps are usuallymodulated as the trap opens and closes. Failedtraps are normally cold and silent.

Thermostatic: Ultrasonic testing results of this type oftrap vary. The signatures produced by these trapscan be continuous or intermittent depending on thetype. It is best to reference a properly functioningtrap for a baseline signature for comparison.



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6.4.6 Case Studies

Ultrasound Detects Compressed Air Leaks

A northeast industrial plant was experiencing some air problems. The acilitys two compressorswere in the on mode or an inordinate amount o time, and plant management assumed a third com-

pressor was needed, at a cost o $50,000. Instead, the oundry invested less than $1,000 in contract-ing an outside frm to perorm an ultrasound inspection o its air system. In a single day, theultrasound technician detected 64 air leaks accounting or an estimated total air loss o 295.8 cm(26% o total system capacity). Considering it cost approximately $50,014 per year (calculated at$.04/kilowatt/hour) to operate the two air compressors, at a total o 1,120 cm, correcting this air losssaved the plant $13,000 per year. In addition, the plant avoided having to spend another $50,000 onanother air compressor, because ater the leaks were ound and repaired, the existing compressors wereadequate to supply demand.

A Midwest manuacturer saved an estimated $75,900 in annual energy costs as a result o anultrasound survey o its air system. A total o 107 air leaks were detected and tagged or repair. Theseleaks accounted or an air loss o 1,031 cm, equal to 16% o the total 6,400 cm produced by the aircompressors that supply the acility.

Steam Trap Monitoring (NASA 2000)

Implementation o a steam trap monitoring program oten has signifcant fnancial beneft. Initialsteam trap surveys in the petrochemical industry revealed that 34% o the steam traps inspected hadailed, mostly in the open position. For acilities with a periodic steam trap monitoring program, theollowing distribution o degradations were discovered during each survey:

Five steam leaks (other than traps) per 150 traps

Two leaking valves per 150 traps

Twenty o the 150 traps leakBuilding o these fndings one trap (ailed open) with a inch orifce will lose roughly

500 MBtu/year (at 25 psi) i undiscovered. With a cost o steam at $7.50 per MBtu, a boiler efciencyo 75% and a system energized or 50% o the year, the annual cost savings o detecting this leak is$2,500. This one leak could justiy the purchase o an ultrasonic detector and this is likely one omany leaks to be ound.

6.4.7 References/Resources 6.4.7.1 Equipment Resources

The reerences and resources provided UE Systemsbelow are by no means all-inclusive. The Elmsord, NY

listed organizations are not endorsed by Telephone: (914) 592-1220 orthe authors o this guide and are provided 1-800-223-1325or your inormation only. To locate Fax: (914) 347-2181additional resources, the authors o this guide Web address: www.uesystems.comrecommend contacting relevant trade groups,databases, and the world-wide web. CTRL Systems, Inc.

Westminster, MDTelephone: (877) 287-5797Web address: www.ctrlsys.com

http://%20www.uesystems.com/http://www.ctrlsys.com/http://www.ctrlsys.com/http://%20www.uesystems.com/


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Specialized Diagnostic Technologies, Inc.

SDT North AmericaCobourg, OntarioCanadaTelephone: 1-800-667-5325

Web address: www.sdtnorthamerica.com

Superior Signal CompanySpotswood, NJTelephone: 1-800-945-TEST(8378) or(732) 251-0800Fax: (732) 251-9442Web address: www.superiorsignal.com

6.4.7.2 Service Companies

Mid-Atlantic Inrared Services, Inc.

Bethesda, MDTelephone: (301) 320-2870Web address: www.midatlanticinfrared.com

UE Systems, Inc.Telephone: (914) 592-1220 or1-800-223-1325 (Toll Free)Fax: (914) 347-2181Web address: www.uesystems.com

Leek Seek

Telephone:TX: (512) 246-2071CA: (909) 786-0795FL: (727) 866-8118

Web address: www.leekseek.com

6.4.7.3 Internet Resource Sites

www.uesystems.com

Technology overview Training

Links Sound demos

www.superiorsignal.com

Technology overview Ultrasonic sound bites (examples) Ultrasonic spectral graphs

http://www.sdtnorthamerica.com/http://www.superiorsignal.com/http://www.midatlanticinfrared.com/http://www.uesystems.com/http://www.leekseek.com/http:///reader/full/www.uesystems.comhttp://www.superiorsignal.com/http:///reader/full/www.uesystems.comhttp://www.leekseek.com/http://www.uesystems.com/http://www.midatlanticinfrared.com/http://www.superiorsignal.com/http://www.sdtnorthamerica.com/http://www.superiorsignal.com/


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6.5 Vibration Analysis

6.5.1 Introduction

As all o us who ride or drive an automobile with some regularity know, certain mechanical aults

or problems produce symptoms that can be detected by our sense o eel. Vibrations elt in the steer-ing wheel can be an indicator o an out-o-balance wheel or looseness in the steering linkage. Trans-mission gear problems can be elt on the shit linkage. Looseness in exhaust system components cansometimes be elt as vibrations in the oorboard. The common thread with all these problems is thatdegeneration o some mechanical device beyond permissible operational design limitations has mani-ested itsel by the generation o abnormal levels o vibration. What is vibration and what do wemean by levels o vibration? The dictionary defnes vibration as a periodic motion o the particleso an elastic body or medium in alternately opposite directions rom the position o equilibriumwhen that equilibrium has been disturbed or the state o being vibrated or in vibratory motion as in(1) oscillation or (2) a quivering or trembling motion.

The key elements to take away rom this defnition are vibration is motion, and this motion is

cyclic around a position o equilibrium. How many times have you touched a machine to see i itwas running? You are able to tell by touch i the motor is running because o vibration generated bymotion o rotational machine components and the transmittal o these orces to the machine housing.Many parts o the machine are rotating and each one o these parts is generating its own distinctivepattern and level o vibration. The level and requency o these vibrations are dierent and thehuman touch is not sensitive enough to discern these dierences. This is where vibration detectioninstrumentation and signature analysis sotware can provide us the necessary sensitivity. Sensors areused to quantiy the magnitude o vibration or how rough or smooth the machine is running. This isexpressed as vibration amplitude. This magnitude o vibration is expressed as:

Displacement The total distance traveled by the vibrating part rom one extreme limit o travel to the other extreme limit o travel. This distance is also called the peak-to-peak displacement.

Velocity A measurement o the speed at which a machine or machine component is moving as it undergoes oscillating motion.

Acceleration The rate o change o velocity. Recognizing that vibrational orces are cyclic, both the magnitude o displacement and velocity change rom a neutral or minimum value to some maximum. Acceleration is a value representing the maximum rate that velocity (speed o the displacement) is increasing.Various transducers are available that will

sense and provide an electrical output reectiveo the vibrational displacement, velocity, oracceleration. The specifc unit o measure tobest evaluate the machine condition will be Figure 6.5.1. Vibration severity chart



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dependent on the machine speed and design. Several guidelines have been published to provideassistance in determination o the relative running condition o a machine. An example is seen inFigure 6.5.1. It should be said that the values defned in this guideline, or similar guidelines, are notabsolute vibration limits above which the machine will ail and below which the machine will runindefnitely. It is impossible to establish absolute vibration limits. However, in setting up a predictive

maintenance program, it is necessary to establish some severity criteria or limits above which actionwill be taken. Such charts are not intended to be used or establishing vibration acceptance criteriaor rebuilt or newly installed machines. They are to be used to evaluate the general or overallcondition o machines that are already installed and operating in service. For those, setting up apredictive maintenance program, lacking experience or historical data, similar charts can serve as anexcellent guide to get started.

As indicated earlier,many vibration signalsare generated at onetime. Once a magnitudeo vibration exceeds some

predetermined value,vibration signature analysiscan be used in defning themachine location that isthe source o the vibrationand in need o repair orreplacement. By usinganalysis equipment andsotware, the individual vibration signals are separated and displayed in a manner that defnes themagnitude o vibration and requency (Figure 6.5.2). With the understanding o machine design andoperation, an individual schooled in vibration signature analysis can interpret this inormation todefne the machine problem to a component level.


Depending on the application, a wide variety ohardware options exist in the world o vibration. Althoughnot complicated, actual hardware requirements dependon several actors. The speed o the machine, on-linemonitoring versus o-line data collection, analysis needs,signal output requirements, etc., will aect the type oequipment options available. Regardless o the approach,any vibration program will require a sensing device

(transducer) to measure the existing vibration and translatethis inormation into some electronic signal. Transducersare relatively small in size (see Figure 6.5.3) and can bepermanently mounted or afxed to the monitoring locationperiodically during data collection.

In some cases, the actual translation o the vibration to an electrical signal occurs in a handheldmonitoring device. A metal probe attached to a handheld instrument is held against a point ointerest and the instrument translates the motions elt on the probe to some sort o electrical signal.Other portable devices use a transducer and handheld data-collection device. Both styles will provide

Figure 6.5.2. FFT Example of graph breaking down vibration level at differentfrequencies

Figure 6.5.3. Typical vibration transducers



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some sort o display where thevibration magnitude is defned.

Styles and equipment size varygreatly, but equipment is designedto be portable.

In addition to instruments designed to measure vibration magnitude, many manuacturers provideinstrumentation that will perorm signal analysis as well. Some equipment is a stand-alone designand perorms analysis in the feld independent o computer interace while other equipment designsinterace tranducers directly with a PC where analysis sotware is utilized to interpret the signal data.


Vibration monitoring and analysis can be used to discover and diagnose a wide variety o

problems related to rotating equipment. The ollowing list provides some generally acceptedabnormal equipment conditions/aults where this predictive maintenance technology can be ouse in defning existing problems:

Unbalance

Eccentric rotors

Misalignment

Resonance problems

Mechanical looseness/weakness

Rotor rub

Sleeve-bearing problems

Rolling element bearing problems

Examples of typical hand-heldvibration sensing meters. Notereadout providing immediate levelindication.

Some signal acquisition and analysisequipment interface a PC directly with thesensors.

Typical Vibration Analyzer Note liquidcrystal display providing actual vibrationwaveform information in addition to machinecondition analytical capabilities.


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6.5.7.1 Training Equipment

Resources

Wilcoxon Research, Inc.

Gaithersburg, MD

Telephone: (301) 330-8811 or 1-800-945-2696Web site: www.wilcoxon.com

Computational Systems, Inc./Emerson Process Management

Web address: www.compsys.com

6.5.7.2 Service Companies

Industrial Research TechnologyBethlehem, PA - Pittsburgh, PA -

Cleveland, OH - Detroit, MI - Chicago, IL -Charleston, SCTelephone: (610) 867-0101 or1-800-360-3594Fax: (610) 867-2341

6.5.7.3 Training/Internet

Resource Sites

Vibration Institutewww.vibinst.org

6262 S. Kingery HighwaySuite 212, Willowbrook, IL 60527Telephone: (630)654-2254Fax: (630)654-2271

www.plant-maintenance.com

Training material Industry links Free sotware

- FFT/CMMS/Inventory control Technical articles Maintenance-related articles

DLI Engineering Corporation

U.S. wideTelephone: 1-800-654-2844 or (206) 842-7656Web address: www.dliengineering.com

Commtest, Inc.Knoxville, TNTelephone: 1-877-582-2946Web address: www.commtest.com

Computational Systems, Inc./Emerson Process Management

835 Innovation DriveKnoxville, TN 37932

Telephone: (865) 675-2110Fax: (865) 218-1401

www.reliabilityweb.com

Training material Industry links Free sotware

- FFT/CMMS/Inventory control

Technical articles Maintenance-related articles

www.maintenance-news.com

Industry links Technical articles Maintenance-related articles

http://www.wilcoxon.com/http://www.compsys.com/http://www.vibinst.org/http://www.plant-maintenance.com/http://www.dliengineering.com/http://www.commtest.com/http://www.reliabilityweb.com/http://www.maintenance-news.com/http://www.maintenance-news.com/http://www.reliabilityweb.com/http://www.plant-maintenance.com/http://www.vibinst.org/http://www.commtest.com/http://www.dliengineering.com/http://www.compsys.com/http://www.wilcoxon.com/


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6.6 Motor Analysis

6.6.1 Introduction

When it comes to motor condition analysis, inrared (IR) and vibration will not provide all the

answers required to properly characterize motor condition. Over the past several years, motor condi-tion analysis techniques have evolved rom simple testing into testing techniques that moreaccurately defne a motors condition. Motor aults or conditions like winding short-circuits, opencoils, improper torque settings, as well as many mechanically-related problems can be diagnosedusing motor analysis techniques. Use o these predictive maintenance techniques and technologiesto evaluate winding insulation and motor condition has not grown as rapidly as other predictivetechniques. Motor analysis equipment remains airly expensive and proper analysis requires a highdegree o skill and knowledge. Recent advances in equipment portability and an increase in thenumber o vendors providing contracted testing services continue to advance predictive motoranalysis techniques. Currently, more than 20 dierent types o motor tests exist, depending onhow the individual tests are defned and grouped. The section below provides an overview o twocommonly used tests.

6.6.2 Motor Analysis Test

6.6.2.1 Electrical Surge Comparison

In addition to ground wall insulation resistance, one o the primary concerns related to motorcondition is winding insulation. Surge comparison testing can be used to identiy turn-to-turn andphase-to-phase insulation deterioration, as well as a reversal or open circuit in the connection o oneor more coils or coil groups. Recent advances in the portability o test devices now allow this testtechnique to be used in troubleshooting and predictive maintenance. Because o dierences in insu-lation thickness, motor winding insulation tends to be more susceptible to ailure rom the inherentstresses existing within the motor environment than ground wall insulation. Surge comparison test-ing identifes insulation deterioration by applying a high requency transient surge to equal parts o awinding and comparing the resulting voltage waveorms. Dierences seen in the resulting waveormsare indicative insulation or coil deterioration. A properly trained test technician can use these dier-ences to properly diagnose the type and severity o the ault. In addition to utilization o this motoranalysis technique in a predictive maintenance program, it can also be used to identiy impropermotor repair practices or improper operating conditions (speeds, temperature, load).

Surge comparison testing is a moderately complex and expensive predictive maintenance tech-nique. As with most predictive maintenance techniques, the greatest saving opportunities do notcome directly rom preventing a catastrophic ailure o a component (i.e., motor) but rather the lesstangible cost saving benefts. Reduced downtimes, ability to schedule maintenance, increased pro-

duction, decreased overtime, and decreased inventory cost are just a ew o the advantages o beingable to predict an upcoming motor ailure.

6.6.2.2 Motor Current Signature Analysis

Another useul tool in the motor predictive maintenance arsenal is motor current signatureanalysis (MCSA). MCSA provides a non-intrusive method or detecting mechanical and electricalproblems in motor-driven rotating equipment. The technology is based on the principle that a



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conventional electric motor driving a mechanical load acts as a transducer. The motor (acting as atransducer) senses mechanical load variations and converts them into electric current variations thatare transmitted along the motor power cables. These current signatures are reective o a machinescondition and closely resemble signatures produced using vibration monitoring. These current signalsare recorded and processed by sotware to produce a visual representation o the existing requencies

against current amplitude. Analysis o these variations can provide an indication o machinecondition, which may be trended over time to provide an early warning o machine deterioration orprocess alteration.

Motor current signature analysis is one o the moderately complex and expensive predictive tech-niques. The complexity stems in large part rom the relatively subjective nature o interpreting thespectra, and the limited number o industry-wide historical or comparative spectra available or spe-cifc applications. This type o analysis is typically limited to mission critical applications and/orthose with lie/health/saety implications.

6.6.3 System Applications Improper seal/packing installation

Stem packing degradation Improper bearing or gear installation

Incorrect torque switch settings Inaccurate shat alignment or rotor balancing

Degraded stem or gear case lubrication Insulation deterioration

Worn gear tooth wear Turn-to-turn shorting

Restricted valve stem travel Phase-to-phase shorting

Obstructions in the valve seat area Short circuits

Disengagement o the motor pinion gear Reversed or open coils.


As indicated earlier, motor analysis equipment is still costly and generally requires a high degreeo training and experience to properly diagnosis equipment problems. A acility with a large numbero motors critical to process throughput may fnd that ownership o this technology and adequatelytrained personnel more than pays or itsel in reduced downtime, overtime cost, and motor inventoryneeds. Smaller acilities may fnd utilization o one o the many contracted service providers valuablein defning and maintaining the health o the motors within their acility. As with most predictivemaintenance contract services, cost will range rom $600 to $1,200 per day or on-site support.Finding a single motor problem whose ailure would result in acility downtime can quickly oset thecost o these services.


Training or motor analysis is usually highly specialized and typically available through a varietyo system manuacturers and vendors.



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6.6.6 References/Resources

The reerences and resources provided below are by no means all-inclusive. The listedorganizations are not endorsed by the authors o this guide and are provided or your inormationonly. To locate additional resources, the authors o this guide recommend contacting relevant trade

groups, databases, and the world-wide web.

6.6.6.1 Equipment Resources

Computational Systems, Inc./Emerson ProcessManagement835 Innovation DriveKnoxville, TN 37932Telephone: (865) 675-2110Fax: (865) 218-1401Chauvin Arnoux, Inc.

d.b.a. AEMC

Instruments200 Foxborough BoulevardFoxborough, MA 02035Telephone: (508) 698-2115 or (800) 343-1391Fax: (508) 698-2118Email: [email protected] Service Companies

Industrial Technology ResearchBethlehem, PA - Pittsburgh, PA - Cleveland, OH - Detroit, MI - Chicago, IL -Charleston, SC - Hamilton, ONTTelephone: (610) 867-0101 or (800) 360-3594Fax: (610) 867-23416.6.6.3 Internet Site Resources

www.mt-online.com

Technology overview Technology vendors Industry articles

AVO International4651 S. Westmoreland RoadDallas, TX 75237-1017Telephone: (800) 723-2861Fax: (214) 333-3533Baker Instrument Company4812 McMurry AvenueFort Collins, CO 80525Telephone: (970) 282-1200 or (800) 752-8272Fax: (970) 282-1010

www.reliabilityweb.com

Service companies Training services Sotware links (including Motor Master)

mailto:[email protected]://www.mt-online.com/http://www.reliabilityweb.com/mailto:[email protected]://www.reliabilityweb.com/http://www.mt-online.com/


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6.7 Performance Trending

6.7.1 Introduction

In addition to the general preventive maintenance we perorm, or have perormed on our

vehicles, many o us log and trend important parametric inormation related to the health o ourvehicles and use this inormation to determine maintenance needs. We calculate and trend our carsmileage per gallon o gas. We track engine temperature and oil pressure. We track oil usage. Thisinormation is then used to defne when vehicle maintenance is required. Maintenance activitiessuch as tune-ups, thermostat replacement, cooling system ushes, belt replacements, oil sealreplacements, etc., may all be originally stimulated by vehicle parametric inormation we trend.

Using this perormance trending approach can also be a valuable tool in maintaining the healthand operational perormance o the components in our acilities/plants. By logging and trendingthe dierential pressure across a supply or discharge flter in the HVAC system, we can determinewhen flter replacement is required, rather than changing the flter out at some pre-defned interval(preventive maintenance). Logging and trending temperature data can monitor the perormance o

many heat exchangers. This inormation can be used to assist in the scheduling o tube cleaning. Itmay also serve as an indication that ow control valves are not working properly or chemical controlmeasures are inadequate. Perhaps a decrease in heat exchanger perormance, as seen by a changein delta-temperature, is due to biological ouling at our cooling loop pump suction. An increasein boiler stack temperature might be an indication o tube scaling. We may need to perorm tubecleaning and adjust our chemistry control measures. Changes in combustion efciency may beindicative o improperly operating oxygen trim control, uel ow control, air box leakage, or tubescaling.

The key idea o perormance trending is that much o the equipment installed in our acilitiesis already provided with instrumentation that can be used to assist in determination o the health/condition o the related component. Where the instruments are not present, installation o apressure, temperature, or current sensing data loggers can be relatively straight orward and ratherinexpensive. A particular good resource to better understand portable meters or data loggers andtheir vendors is the report titled Portable Data Loggers Diagnostic Tools or Energy-Efcient BuildingOperations (PECI 1999).

6.7.2 How to Establish a Performance Trending Program

One o the frst steps o any predictive maintenance program is to know what equipment existsin your acility. First, generate a master equipment list, then prioritize the equipment on the listto defne which pieces o equipment are critical to your acilitys operation, important to personnelsaety, or can have a signifcant budget impact (either through ailure or inefcient operation).

Evaluate what parametric data should/could be easily collected rom installed or portableinstrumentation to provide inormation related to the condition/perormance o the equipment onthe master list based on your equipment prioritization.

Determine what, i any, o the defned data are already collected. Evaluate i any relatedparametric inormation is currently being tracked and i that inormation provides inormationregarding the condition or efciency o a component or system. Terminate the collection oinormation not useul in the evaluation o a components condition/efciency unless required byother administrative requirements.



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Defne and install instrumentation not currently available to monitor a critical componentscondition/efciency.

Log the inormation at some requency defned by plant engineering or operational sta. Forexample, the requency may be every 4 hours while operating or may simply be a single reading ater

reaching steady-state conditions, depending on the data evaluation needs.

Provide collected data to individual with knowledge and background necessary to properly trendand evaluate it.


Generally, any plant component with installed, or easily installed, instrumentation useul inevaluating the components condition, operation, or efciency can be trended. Inormation can alsobe obtained using portable instrumentation, (e.g., an inrared thermometer or a variety o stand-alonedata logging devices). Some general applications might be:

Heat exchangers Filters

Pumps

HVAC equipment

Compressors

Diesel/gasoline engines

Boilers.


The cost to establish an eective trending program is minimal and can provide one o the largestreturns on dollars expended. Most plants have much o the instrumentation needed to gain the para-metric inormation already installed. Todays instrumentation oers many cost-eective opportunitiesto gather inormation without having to incur the expense o running conduit with power and signalcabling. The inormation gatherers are generally already on the payroll and in many cases, alreadygathering the needed inormation to be trended. For the most part, establishing a trending programwould require little more than using the inormation already gathered and currently collecting dust.When portable data-logging systems are purchased, the payback or the little extra money spent isquickly recovered in increased machine efciency and decreased energy cost.


Training or perormance trending is very application-specifc. Most trending is done via pre-installed system sensors, an existing building automation system and/or the use o portable dataloggers. All o these systems will unction dierently with education and training typically availablethrough equipment vendors or distributors.



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6.7.6 Case Studies

Operational Efciency Opportunity Using Data Logger Data to Validate Boiler Operation

(FEMP 2007)

Objective: Use data logger (5-minute run-time, time-series data) to validate proper boileroperation.

Situation: Federal acility with boiler heating/process loads. End-use run-time data loggerinstalled. Data reported are rom peak-season loading conditions.

Findings: Reviewing the 5-minute run-time data (data collected with stand-alone magnetic feldenabled logger placed near boiler combustion-air blower motor) reveals excessive cycling o boiler;Figure 6.7.1 presents these data. A bar in the fgure rising rom 0 to 1 indicates the boiler cyclingon, the bar returning rom 1 to 0 indicates the boiler cycling o. Thereore, each bar in the graphrepresents one on/o cycle.

Outcome: Processing these data reveals an average o 6.5 on/o cycles per hour ar in excesso the recommended 1-2, depending on load conditions. Further exploration uncovered gross boilerover-sizing due to partial decommissioning o building/process loads. The outcome recommendationincludes installation o smaller, properly sized, and more efcient boiler to carry load.

6.8 References

FEMP. 2007. Metering Best Practices Guide: A Guide to Achieving Utility Resource Efciency. DOE/EE-

0323. U.S. Department o Energy, Federal Energy Management Program, Washington, D.C.

NASA. 2000. Reliability Centered Maintenance Guide or Facilities and Collateral Equipment.National Aeronautics and Space Administration, Washington, D.C.

PECI. 1999. Portable Data Loggers Diagnostic Tools or Energy-Efcient Building Operations. Preparedor the U.S. EPA and U.S. DOE by Portland Energy Conservation, Incorporated, Portland, Oregon.

Boiler Frequency Cycle Indicator"1" represents boiler-on event, "0" represents boiler-off event

0

1

2

6:05

AM

7:00

AM

7:55

AM

8:51

AM

9:46

AM

10:41

AM

11:36

AM

12:31

PM

1:27

PM

2:22

PM

3:19

PM

4:15

PM

5:10

PM

6:07

PM

7:03

PM

7:59

PM

8:55

PM

9:50

PM

10:45

PM

11:41

PM

12:37

AM

1:31

AM

2:26

AM

3:21

AM

4:15

AM

5:10

AM

6:04

AM

Time

On/OffIndicator

Figure 6.7.1. Boiler Cycling Frequency Data

Chapter 6 Predictive Maintenance Technologie

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