February 2009 Archives

Energy Conservation and Precision Machine Lubrication
by Mike Johnson, CMRP, CLS, MLT2

Machine lubrication practices offer a multitude of opportunities for energy conservation. Some of those opportunities are obvious and quantifiable, and some are not. Observing from a broad to narrow perspective, the manufacturing organization uses energy from a variety of source types, including coal, natural gas, petroleum, and electricity from a generating plant. Some of these energy sources are put to direct use, and some are used to create other energy sources, including pressurized oil, pressurized air, steam and accelerating chemical reactions.

Human energy, arguably the most important energy resource, is often left out of the discussion for energy use effectiveness. An extensive amount of human energy is expended lubricating production machinery.

Opportunities for energy improvement from the machine lubrication process can be both obvious and obscure. A gallon of oil or grease has a given energyband economic value that can be measured in BTU's and dollars. The impact from the use of a barrel of oil to float and separate interacting machine surfaces, or accomplish hydromechanical work, has an even greater economic value, but it is not always obvious. The human energy expended to place and replace the oil represents another type of energy and economic value.b These three topics will be explored in the following paragraphs, beginning with a broad view.


Tribology

The relatively new scientific field, Tribology, began to be formally recognized following the March 9, 1966, publishing of a report by the British Ministry of State for Science. The report suggested that the economic value to be derived for British Industry from improvements in lubrication design and practice was worth nearly a trillion dollars (equivalent, adjusted for inflation and exchange rate).

H. Peter Jost, and his team, offered their impression of the potential for improvements in a variety of areas, as shown in Figure 1. Following this study, Germany, Japan, China and Canada have each executed studies that have produced insight similar to that of the Jost Report.

Jost's study indicated cost reduction potential for several categories, including savings on energy purchases (7.5%) , general efficiency (1%), and lubricant purchases (20%), each of which will be expanded upon in this discussion. 43 years after this study, one could argue that the savings potentials for manufacturers are still available from most of these categories. For a few categories the potential is even greater, particularly savings from efficiency improvements and reduced repair costs. Let's consider the arguments for some of these savings opportunities.

Energy Savings Potential from Friction Reduction at Lubricated Parts

The theoretical basis for reducing energy consumption by improving lubricant effectiveness is strong. Personal experience suggests that the 7.5% potential for energy reduction noted in the Jost report may be attainable for some types of applications, but not for all. The challenges to the reliability engineer will be measuring the improvement with some degree of repeatability, and overcoming skepticism by engineering and operations managers. There are often a few things to consider.

The Nature of Machine Surfaces - Machine surfaces are rough. Figure 2 illustrates typical surface profiles for all machined surfaces. Even finely prepared bearing element and race surfaces exhibit undulations. As shown in Figure 3, machined surfaces have a wavelike profile. The average of the height of the ridges, value 'r', differs based on the OEM's finish technique. Element bearing finishes will have maximum surface heights in the 0.2 micron range, and average heights in the 0.4 micron range (RMS). Ground gear finishes will have surface heights approaching three microns, and averages heights approaching 0.6 microns (RMS).

Separating Machine Surfaces - The dynamic

 oil film thickness must always be greater than the heights of the combined surfaces in order to avoid frictional energy losses. The ideal condition would be an oil film that is three to five times thicker than the height of the combined surfaces. Component suppliers provide formulas and standardized tools that are useful in establishing minimum viscosity operating requirements. Reputable suppliers provide engineering support to their customers to help refine lubricant selections, and for most applications, the first run selections are not difficult.

Inadequate film conditions occur as a consequence of changes in load, changes in machine operating temperatures, changes in lubricant condition (particularly contamination with gases or fluids), and accidents in lubricant handling and application, which lead to viscosity errors. These condition changes www.uptimemagazine.com 31 often occur simultaneously, resulting in film collapse, machine component interaction and greatly increased frictional resistance.

Surface Protecting Lubricant Additives - OEM's and machine owners collectively recognize that conditions will cause the oil films to degrade and fail. Even though the oil film collapses, the machines will continue to run causing degradation of the machine surfaces.

In order to protect the contact area of the lubricated surfaces, lubricant suppliers employ the use of a wide variety of chemicals intended to chemically bond to metal surfaces to create an organo-metallic boundary layer. Although these tarnish-like films are very thin they do offer protection from excessive wear, and prolong machine component lifecycles.

The use of insoluble (solid film) lubricant additives provides another avenue for reducing frictional resistance from surface contact. Boric acid esters, Teflon, Molybdenum Disulfide and Graphic all have a well established track record for surface friction reduction.

Energy conservation claims have been made by several high performance lubricant manufacturers, including Lubrication Engineers, Engineered Lubricant, Whitmore's Lubricants, Royal Purple, Castrol Performance Lubricants, and several others. These companies create specialized additives that accomplish a variety of end results, including friction reduction from surface improvement. Most of these companies consider their additive technologies to be central to their survival and are tight-lipped about product composition, but there is no debating that there are additive agents that improve lubricity (the 'slipperiness' property) of the lubricant that then helps reduce energy consumption.

Energy Consumption Influence of Base Oil Type and Weight - In markets that have federally mandated energy efficiency requirements, such as automotive engines and refrigeration systems, base oil and additive choices are heavily influenced by the material's energy efficiency impact. It is widely known that oil viscosity directly influences energy consumption. As viscosity increases the amount of energy used to overcome viscous drag also increases.

It is less well known that the type of base oil (molecular composition) influences energy consumption in a couple of ways. Some polar stocks, specifically esters and polyglycols, have lubricity properties superior to conventional mineral oil and unconventional hydrocracked stocks. These fluids provide better surface protection with less bulk oil requirement.

Consequently, a lower viscosity grade may be adequate to provide similar levels of component protection versus a mineral oil option. The lower viscosity also enhances flow rate, an important characteristic for heat removal, which further enhances energy efficiency.

A similar impact may be experienced with the use of ester cylinder feed lubricants in high pressure process gas applications. The combined lubricity and polarity of ester stocks make these ideal choices for cylinder lubrication. Volumes and viscosities can be reduced, providing reduction in parasitic energy losses from friction and viscous drag.

Proving Energy Conservation in Production Machines - Documenting energy improvement results is not difficult, but it does warrant careful planning and measurements. It is essential to compare similar conditions when making final conclusions.

Steps to consider during the evaluation process should include:

1. Develop the data collection plan, and put it in writing. Develop the criteria for measurement and evaluation before the process begins.
   
2. Identify a, or multiple, machine(s) that operate with a narrow range of load, speed and throughput variability. Fluctuations will complicate test cycle comparisons.
   
3. Verify that the lubricant in use for the select machine (call it Product A) is, in fact, the correct type and grade of product for the application. (visit www.precisionlubrication.com for additional information concerning precise selection of lubricants.) 
   
4. Collect process data. At a very minimum, conduct energy readings (amps) for a period of at least 30 days. It would be best to coincidentally record ambient temperatures, operating temperatures vs ambient, machine loads, machine throughput (speed, units of production, RPM, etc...) and/or other process values.  Mechanical conditions and changes should also be observed and documented. All maintenance conducted on the machine during the test period should be documented.
     
5. Collect mechanical data. Data that is relevant could include sump, motor, drive, and bearing temperatures (thermal images), vibration levels and oil analysis data. All of the sample collection methods must be highly repeatable in order for the data to be dependable. Also, a sample set of less than 30 readings can bring the results into question. It is preferable to have too much data rather than too little. Make the conversion to the alternate product (Product B).
   
6. Make sure that the sump is completely clear of Product A, and that no other mechanical or electrical changes have been implemented that might impact the operation of the
   machine. 
   
7. Repeat the data collection activity and compare the results. 
   
8. Readings should be converted to monetary terms.

Energy Savings Potential from Lubrication Program Process Improvements

The value of process improvement may be worth every bit of savings derived from superior lubricant performance. Process improvements considerations should address:

• Using tools and technology (modernization) to replace human labor.
• Efficiency of the selection of tasks in total for machine care.
• Efficiency of each required task versus the actual scheduled tasks.

Labor Utilization Improvements through Modernization - A large percentage of lubrication programs operate on automatic pilot. When the practices are highly refined this can be a good thing. When practices are not, net labor hours required to fulfill practices tends to be high, and the results may not even cover the minimum requirements. Labor savings potentials are numerous.


Potential for savings include:

15% to 20% - Efficient Grease Relubrication Frequencies. It is common for grease relubrication practices to be inconsistent with component manufacturer's requirements.

Calculation of intervals based on machine operating environment and characteristics is an important first step. Reliability engineers are often surprised to learn that the scheduled frequencies for their slow rotation machines are too short, and the frequencies for their high speed (high nDm) applications are much too long. Balancing grease relubrication intervals alone may free up labor needed to make other systematic lubrication program improvements.

5% - Use of Automation for Short Term Grease Intervals. Grease replacement activities with an interval shorter than seven days should certainly be evaluated for automatic lubrication, either in the form of a single point grease cup, or in the form of simple multi-point systems. The choice is based on a cost comparison for installation and long term maintenance.

20% - Operator Based Care, Including Sump Level Checks and Top-up Activities. Level checks and corrections can, and should, be fulfilled by operators. While it is clear that operators are always busy, part of the operator's role should be to visit the machines, observe their condition, check the levels and report any observed problems. Organizing this task into routes is time consuming but not difficult, and should be done whether operators are involved in top-ups or not.

10% - Implanting Aggressive Oil Condition Control (filtration, cooling). Lubricant sump change intervals could be safely extended in many applications by a factor of three simply by cooling and cleaning the sumps. The relationship between wear debris, heat and oil oxidation is proven and intuitively obvious. Just 10 years ago, the standing practice for most facilities was to change oil on an annual basis. Integrated into the lubricant analysis program, lubricant sump filtration requires effort while the plant is operating, but returns highly valuable labor back to the planning department during outages.

The few items noted above account for 50% of the labor expected for machine lubrication. Freeing this labor for other purposes may require capital (for tools and systems) and certainly will require a change in mindset. During the evaluation of practice efficiencies (for a safe return of labor to the maintenance department), plant engineering should simultaneously redefine inefficient practices to reflect a plant 'Best Practice'.


Energy Savings through Material Conservation

If the engineering department executes the previous improvements, the potential for material conservation, reduced lubricant consumption, will already have been achieved.

Three highly visible targets for lubricant consumption improvements include:

Compressor Lubricant Usage - Reciprocating cylinder and sliding vane cylinder feed rates are often significantly above OEM suggested values. The excess causes varnish buildup on heat exchangers and coats pipes and air components with excessive oil residue.

Synthetic lubricants can be used to optimize the throughput and reduce the risk of varnish accumulation.

Hydraulic and Circulation System Leakage - Hydraulic system designers collectively agree that the majority, perhaps as much as 80%, of hydraulic system leakage is controllable, and much of it is a consequence of poor hydraulic fluid contamination control. Those 'difficult to identify' leaks can be found using fluorescent dye and black light technique. Retrofitting hydraulic circuits with leak resistant fittings, and instructing general maintenance mechanics and pipefitters on the proper installation and use of these fittings adds to the long term value of a leak control initiative.

Open Gear Lubricant Application - American Gear Manufacturers Association (AMGA) standard 9005-EO2 provides specific guidance on the required volume of open gear feed per minute of operation for several gear sizes and speeds. Measuring the current feed, and judging the potential for reductions in feed is initially a simple mathematical exercise. Judging the adequacy of the feed rate at various steps in the reduction cycle may require the assistance of the lubricant supplier, or a knowledgeable technical consultant.


Summary

Precision lubrication practices support machine reliability interests, produce best use cost, and improve labor efficiency. Electrical energy consumption can be reduced through the use of high performance lubricants and a careful measurement plan. Human energy consumption can also be reduced through careful evaluation and improvement of machine lubrication requirements, including the application of high performance lubricants for critical production machines.


Mike Johnson is the founder of Advanced Machine Reliability Resources Inc., a firm that provides precision lubrication program development, consulting and training. He has written and presented numerous technical papers at symposia and conferences throughout North America about how to use machine lubrication to drive machine reliability. Mike is happily married, plays and coaches soccer, and has 3 young children that consume his remaining time and attention. He can be reached at mjohnson@amrri.com or 615-771-6030.

References
1 - "Interview with Luminary Professor H. Peter Jost - The Man Who Gave Birth to the Word 'Tribology'". Fitch, J. Machinery Lubrication Magazine, Jan., 2006.

2 - "Lubrication for Industry, 2nd Edition",page13. Bannister, K. Industrial Press. 2007

3 - L. Rudnik and R. Shubkin, "Synthetic Lubricants and High Performance Functional Fluids, 2nd Edition", page 88. Marcel Dekker Publisher.

Vibration Analysis of Wind Turbines
by Jason Tranter

Wind turbines are dotted across the countryside, seaside, and even offshore. Many believe they are the answer to global warming and stopping the reduction of fossil fuel reserves. Whether you enjoy seeing them on the horizon, majestically spinning in the breeze, or believe they disturb the previously unspoiled landscape, for all of us in the reliability and condition monitoring fields, they pose a new challenge - we have to keep them turning!

In Europe, wind power currently supplies 3.7% of EU electricity demand1. In Denmark, for example, more than 20 percent of electricity is wind-generated. In Spain, the figure is 13 percent and in Germany it is seven percent2. In 2001, the European Union passed legislation setting a target for 21% of the EU's electricity demand to come from renewable energy by 20103.

The United States wind energy industry is growing at an exceptional pace, and that pace will only accelerate in the coming years. Within days of being elected, President Barack Obama announced a new energy plan which includes measures to "create five million new jobs by strategically investing $150 billion over the next ten years to catalyze private efforts to build a clean energy future"4. The plan also includes "an economy-wide capand- trade system to reduce carbon emissions by the amount scientists say is necessary"4.

The total installed capacity in the United States is 21,017 MW in 35 states. Over 8,000 MW more are under construction for completion this year or early next year. Over 7,500 MW were installed in 2008, and 5,249 MW were installed in 2007. The American Wind Energy Association (AWEA) stated that in 2008 American wind farms generated "just over 1.5% of U.S. electricity supply, powering the equivalent of over 5.7 million homes". It also states that "to generate the same amount of electricity using the average U.S. power plant fuel mix would cause over 28 million tons of carbon dioxide (CO2) to be emitted annually"5.

The U.S. is now the world leader in wind electricity generation. While Germany still has more generating capacity installed (about 23,000 megawatts), the U.S. is producing more electricity from wind because of its much stronger winds5.

With Government assistance, a continuing threat of global warming, and growing demand for power, we are sure to see an increase in the number of wind turbines around the world.

A Brief Guide to the Operation of a Wind Turbine

Wind turbines are remarkable machines. They are designed to operate, unmanned, in very windy locations; typically in remote farmland or at sea. As the wind blows, the yaw control points the blades into the wind, and the pitch of the blades is constantly varied to control the speed. Typically two large bearings support the main shaft driven by the blades. A gearbox increases the speed in order to drive the generator at 1800 RPM, for example.

1. Variable speed and load from one test to the next
2. Variable speed and load during the actual test
3. Difficult and limited machine accessibility
4. Complex gearboxes - planetary gearboxes being the worst
5. Very low speed shafts

Variable Speed and Load -- One of the key requirements for successful vibration analysis is to be able to compare the current readings to either a previously collected set of readings, vor to a set of alarm limits. We want to see how the vibration patterns have changed. In a standard power station, the majority of the machines will run at the same speed and load from one test to the next. Comparisons with older data are easy, and alarm limits can be generated based on experience with the machine, or based on statistical analysis of the history of data. But it is not that easy with a wind turbine.

As the wind speed varies, the load on the blades, shaft, bearings, gears and generator will change. The speed of the machine will also change. The result is that the peaks in the spectrum will not line-up with peaks in previous spectra, and the amplitudes of peaks are no longer comparable. Not only does the load affect the amplitude of the peaks in the spectrum, natural frequencies will either cause the measured vibration amplitudes to be higher or lower than when the machine was running under a different speed or load.

It is certainly possible to "order normalize" the spectrum, so that the speed-related peaks
in the spectrum will be aligned, but that does not address the changes in amplitude

The solution is to define one or more bands of operation where spectra (and time waveforms) collected within that band can be deemed "comparable". The "band of operation" may be specified by the RPM of the input shaft, or the power generated by the turbine, or perhaps another parameter. You will then need to wait until the required conditions are met before the vibration measurements are acquired. Alarm limits can also be defined for that "band of operation".

Variable Speed During the Measurement -- When the analyzer (or monitoring system) acquires the "time record" that is used to compute the spectrum (via the FFT calculation), it is assumed that the machine being monitored operates at a constant speed during that test.

For example, if you acquire a 1600 line spectrum with an Fmax of 1000 Hz, the analyzer will acquire 1.6 seconds of vibration data in order to compute the FFT (for just one average). An 1800 RPM generator will rotate 48 times during the test, but the 15 RPM input shaft will rotate just 40% of one rotation... In order to capture 10 rotations, we need an Fmax of 40 Hz (with resolution set to 1600 lines), and the measurement will take 40 seconds!

If the speed of the wind turbine varies during the test, the peaks in the spectrum can blur - the peaks will be wider than they should be, and the amplitude of each peak will be reduced. And this blurring effect may not be consistent from one test to the next. (Note: The blurring effect will be more noticeable at higher frequencies.)

Therefore, depending upon the nature of the turbine, and the wind conditions, this effect can either be tolerated, or the "order tracking" technique must be employed. Either the once-per-rev tachometer signal must be fed into the analyzer (with an internal "tracking ratio synthesizer") such that the analyzer varies its sample rate in proportion to the RPM, or a shaft-encoder must be used to generate a "pulse train" that contains, for example, 360 pulses per rotation of the shaft which is used to control the analyzer's sample rate.
Gearbox Measurements -- There is one more challenge when monitoring gearboxes; especially planetary gearboxes. In an ideal world the vibration sensor (accelerometer) would be placed close to the bearing and/or gear of interest. However not only do these gearboxes have a large number of bearings and gears, it is difficult to get an accelerometer close to certain bearings; the planet bearings for example. When analyzing spectra, either conventional spectra or demodulated spectra (or Peak Vue, SPM, etc.), it is necessary to resolve three issues:

1. Computing the speed of each shaft, and the gearmesh frequencies, can be quite a challenge with planetary gearboxes.
2. Computing the bearing frequencies will be very complicated due to the large number of bearings and different shaft speeds. Both jobs are made even more difficult if the manufacturer is not willing to provide the details of the bearings used and gear ratios.
3. The amplitude of the vibration measured when a planet bearing begins to fail, for
   example, will be lower than the vibration from a bearing in contact with the gearbox
   case due to the transmission path involved.

The Solution

Almost all of the vendors of portable data collectors and analyzers now manufacture online monitoring systems designed specifically for the wind turbine application. There are an awful lot of wind turbines, and each one requires its own monitoring system. These vendors all recognize both the challenge and the opportunity.

Systems are designed to monitor the speed of the turbines, and other process parameters, so that they can correctly determine when the turbine is operating in the pre-defined "band of operation".

In fact, many of these systems can define  multiple "bands of operation". Each band will have its own set of alarm limits, and all readings are tagged with their band of operation so that graphical comparisons can be performed. It is important to have multiple bands for two reasons

1. Unless the weather conditions are reasonably constant, the turbine will not be operating in any one band for a large proportion of time. By defining multiple bands, the system will monitor and check the turbine far more frequently.
2. The bearings, gearbox, and generator will react differently under different speed and load conditions. It is, therefore, very helpful to monitor the machine-train during the
   majority of operating conditions. For example, a problem with the support
   structure may only be detected when the turbine is operating at highest load.

The Challenge With All On-Line Monitoring Systems

All on-line monitoring systems face a number of challenges that can limit their effectiveness, but these challenges are compounded when applied to wind turbines. I have already discussed the issue related to varying speed and load, but let's take a look at some of the other challenges:

The Number of Monitoring Points -- One of the most critical decisions is selecting the number of sensors that should be installed on the gearbox, generator and bearings, and selecting their location. Every sensor costs money, and it requires another channel in the monitoring system. And when you multiply these additional costs with the number of wind turbines (see Figure 11), you can see that it is a very sensitive issue.

As with all vibration monitoring applications, it is essential that the monitoring system can at least acquire enough data to warn when the vibration levels are increasing - even if there is not enough data to actually diagnose the problem remotely. But, as discussed previously, when monitoring large planetary gearboxes, the spectral data can be very complex.

Knowing the failure modes of the turbine can help immeasurably. If you know which gears
and bearings are most likely to fail, then you can position the accelerometers accordingly.

The Central Monitoring Service -- The "central monitoring service" is the group of people who will respond to the alarms, analyze the data and make final recommendations. It is essential that this group has access to the required data and has the experience to make recommendations. Obviously a communication link must be established with the wind turbine monitoring systems.

Centralized or De-Centralized -- The monitoring system must not only acquire data when the turbine is operating within pre-defined bands, but it must compare the data to alarm limits and take the appropriate action. There are at least two approaches: perform all of these operations within the system that is installed in the nacelle and communicate directly with a central monitoring service, or install a more sophisticated system centrally within the wind park and use it to communicate with both the wind turbine monitoring systems, and with the central monitoring service. Many wind farms have a wired or wireless network, and the monitoring system may be allowed to tap into that network.

The Effectiveness of Alarm Checking Software -- Many vibration analysts running 'normal' vibration monitoring programs do not have an effective set of alarm limits set up for their machines which allows them to run an exception report that provides useful, actionable information. The solution is to manually analyze each and every measurement. This is not possible when performing on-line monitoring.

It is therefore very important that the alarm limits are set up carefully, and they need to be refined frequently. Too many on-line monitoring systems generate "thousands of alarm exceptions" - as a result faith in the system is lost. There are methods that can be used to set up effective alarm limits, such as statistical alarm generation, but that will need to be covered in a separate article.

Conclusion

Wind turbines are being installed at an amazing pace, and while some of the earlier reliability problems have been resolved, there is no doubt that reliability will be an on-going issue. Condition monitoring technologies such as vibration monitoring, oil analysis, and performance monitoring will play a very important role in the viability of wind farm operation. As long as monitoring system vendors and wind turbine manufacturers continue to improve their designs, focus on reliability, and share information, renewable energy from wind power will continue to grow as a source of affordable and clean energy around the world.

Best of all, any one of these will quickly save more than the cost of a task-specific software
solution.


Costly Misperception

Most often, there is a major disconnect between the "oil is oil" presumption of upper management and the inherent understanding maintenance and reliability professionals have for the complex nature of lubrication. When these professionals seek funding for a task specific program they are often told "there is no budget for that." Frankly, this is akin to shooting oneself in the foot. Think about it, for a plant with an energy consumption of $500,000 a year, a 10% energy savings from a properly designed task-specific Lubrication Reliability program would result in an annual savings of $50,000. Further, Smith draws this impactful conclusion "If a company's annual sales are $60 million, and total downtime is 10%, and 25% of downtime is due to lubrication, the lost opportunity cost due to lubrication is $1.5 Million."

With documented benefits and rapid ROI, it is hard to understand why corporations continue to neglect this profound opportunity for notable increases in operational efficiencies, competitiveness and profit.


References

1. Energy Reduction through Improved Maintenance Practices, Kenneth E. Bannister,
1999 Industrial Press

2. Exterminate Lube Problems, Ricky Smith, CMRP, Plant Services

Eric Rasmusson is President / CEO of

Generation Systems, Inc. He has over 30 years of high-tech and industrial software experience and is the principle architect of LUBE-IT Lubrication Reliability software solution. Eric launched Generation Systems in 1984 and now is guiding the company toward its 25th anniversary. His passions are increasing global awareness of the profitability of lubrication reliability, and enhancement of the award-winning LUBE-IT product. Eric also holds concern over the increasing complexity and bloat of industrial software. This, coupled with his sincere regard for end-users, drives him to innovate comprehensive, yet highly intuitive solutions.

Editors Note: We published this article with specific references to LUBE-IT Lubrication Reliability software in order to tell more people about potential solutions as maintenance and reliability information management evolves. We did not want to make it generic. There are other unique software products that we will also be presenting to you in Uptime. In order to bring you the full impact of the capabilities of some of these new technologies - we have decided to allow product specificity- not as an endorsement - but to create an enhanced understanding of the rapidly changing landscape of Information Technology.

Sustainability Through Ultrasonic Energy Conservation
by Allan Rienstra

In 2008, there arose a broad selection of solution providers specializing in helping the community of maintenance and reliability professionals to 'Go Green'. It is unlikely that the original mandate of most of these companies was to "help save the environment", but it does show how nimble entrepreneurialism adjusts to accommodate the demands of corporate social responsibility. The term corporate social responsibility eventually gave way to the broader catchphrase "sustainability" in 2008. Maintenance departments formed energy management teams to focus on the dual win of saving both money and the environment with efficiency initiatives. For them, and most of us, the definition of "sustainability" closely mirrored that of the trusted EPA; "meeting the needs of the present without compromising the ability of future generations to meet their own needs." In 2009, sustainability may well be redefined as "doing whatever it takes to keep our doors open for business."

A stubborn economic and environmental crisis grips the globe. There are obvious virtues to positioning our business as a provider of green solutions with benefits for both energy savings and reducing a factory's carbon footprint. This is the re-emphasis of an original mission statement made some thirty years ago when ultrasound inspection first appeared as an answer to curbing sources of waste energy in factories, but this time around the stakes are higher.

As consumers we have an insatiable thirst for electricity, and the fossil fuels consumed by its creation. That fossil fuels are running scarce is not just rhetoric. Conservation must be made as mandatory as the ongoing search for alternative energy sources is. Those alternatives will have to be planet friendly, as the reckless use of energy has loaded our environment with CO2 and other greenhouse gases, changing our planet forever. Expect continued and dramatic changes in global weather patterns illustrated by extreme storms, draughts, cold waves, and heat waves. And while the price per barrel of oil was low at the time of writing, expect higher prices to return as the globe moves through, and out of recession. Now is the time to look to your airborne ultrasound program for some assurance about your company's sustainability in 2009.


Airborne Ultrasound Inspection

Airborne ultrasound inspection refers to the technology of detecting and localizing the sources of ultrasonic phenomena for the purpose of identifying

a) sources of wasted energy

b) sources of mechanical failure

c) sources of electrical failure

d) faults within a machine

without intrusion or shutdown. These problems all have one characteristic in common; they produce noise in the ultrasonic range with peaks between 35-40 kHz. Ultrasound inspection is useful because it focuses on these specific noises while filtering away ambient plant noise, making it extremely handy in loud plants. This makes the technology available for use during peak production hours, reducing the need for overtime. It is advantageous to use this technology to pinpoint the source of problems because ultrasound is more directional than audible sound. Subtle changes to plant machinery can be heard in the ultrasonic frequencies first. Inspectors are rewarded with an earlier indication of a problem, and a larger window to schedule repair. So ultrasound inspection extends the abilities of human hearing and empowers companies to pursue some of the easiest wins in the sustainability business.

Going "green" and saving energy are two separate ideals that merge by circumstance, and focus on a campaign with huge potential wins. This battle starts in the air compressor room (supply side) and branches throughout the facility (distribution) to wherever air is needed (demand side). Along the way there are leaks, wasted dollars spent and energy consumed, all the while enlarging your carbon footprint. Take a look at the benefits of a well managed compressed air leak program.

Here are some compelling reasons to tighten your compressed air system.

• Compressed air production is the 2nd or 3rd highest source of energy consumption in most companies.
• On average, air compressors account for 18% of all industrial electrical consumption in European manufacturing plants. Some suggest that compressed air costs account for as much as 30% of a manufacturing plant's electricity bill.
• For every kWh spent on compressed air, an additional 0.8kg of CO2 per month is spewed into our atmosphere.
• 75% of the total cost of your compressed air system goes to your electricity provider. The other 25% is accounted for by capital costs and ongoing maintenance.
• On average, only 43% of compressed air produced gets used to satisfy real demand.
• On average, 34% of compressed air produced is wasted to leaks.
• The remainder is consumed by wasteful applications and artificial demand.

Reducing energy consumption starts with getting your system leakage under control, but should include more than just ultrasonic leak detection. To get a handle on the total opportunity represented by a greener compressed air system, a plant should hire a consultant to conduct a compressed air audit. A consultant examines the entire system, which is broken down as Supply, Distribution, and Demand. The auditor looks at your system objectively and will recommend improvements that, when implemented, will see more SCFM flowing to demand, and a positive impact to bottom line. Partnering with a quality compressed air auditor is a definitive step toward sustainability.

The United States Department of Energy (DOE) says "The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize high frequency hissing sounds associated with air leaks. These portable units are very easy to use." The main point here is that leaks create a high frequency sound which can be difficult to hear, and to pinpoint, without the aid of an ultrasound detector. Leaks produce turbulence when air flows from the high pressure side to the low pressure side. It is this turbulent flow, which we associate with the characteristic hissing sound of a leak, which generates noises with both low and high frequency sound components.

The low frequency sound components are audible to the human ear, but masked by the noise of the plant. The high frequency sound components (ultrasonic) are inaudible to the human ear, but are detected above the noise of the plant. Perhaps most important in our ultrasonic search for leaks is the directional nature of ultrasound. This gives inspectors the ability to hear leaks while the plant is operating, and to pinpoint their location quickly so they can be tagged or fixed.


Compressed Air Audits

Paul Edwards, a principle with Compressed Air Consultants, USA of Charlotte, NC is a compressed air auditor for whom I have a great deal of respect. He recently wrote, "Leaks are an important aspect of compressed air improvement projects and a good study documents the leaks without focusing on them... ...The real value in ultrasonic detection is in increasing the speed at which leaks can be located and tagged." Edwards sees ultrasonic leak detection as a speedy alternative to listening with the unaided ear, or even using water and soap mixtures to look for bubbles.

Leaks can be detected from as close as an inch or two, or as far away as fifty feet or more. The distance of detection depends on two factors: the energy of the turbulent flow, and the type of sensor used. The turbulent energy is dictated by the pressure of the system and the size or shape of the orifice (see Figure 2). Lower pressures will produce lower turbulent flow, but smaller orifice size will restrict flow and can actually increase turbulence. Think of a garden hose and what happens when you restrict the flow of water with your thumb. Less water flows from the hose, but with greater force. Likewise in an air line, a smaller orifice may mean less air, but more turbulence.

The leak may sound louder in the ultrasound detector's headset, but in fact the loss from that leak may not be much. To accommodate both close up and far away leaks, ultrasonic detector manufacturers produce different sensors for different situations. Flexible wand sensors are used for near inspections and tight access areas while parabolic sensors with laser sights are used to pinpoint leaks in overhead piping without the need for ladders.

• The Millstone nuclear generating plant in Connecticut unexpectedly shut down when a circuit board monitoring pressure in a steam line failed (April 17, 2005)
• During 2006, multiple batches of a Swiss company's watches were recalled - the estimated cost was $1bn
• The failure of the Galaxy IV communications satellite in 1998
• The FDA recalled a number of pacemakers in 1986
• Relays in AT&T telephone switching centers failed during the 1950s
  

• External compressive stresses such as those introduced by torquing of a nut or a screw can contribute to the formation of whiskers.
• Bending or stretching of the surface after plating has been applied.
• Differences in thermal expansion characteristics between the substrate and the plating material.
• Microscopic damage to the plating or the substrate material caused by handling or application of test probes etc.

• Operational Reliability
• Asset Management Programs
• Maintenance Effectiveness
• Preventive Maintenance Programs
• Maintenance Support
• Maintenance Training Programs
• Component Repair Facility
• Components Themselves
• Mechanical System Hardware
• Operator / OEM Engineering

Rogue Component Definition

A rogue component is defined as an individual repairable component, which repeatedly experiences short in-service periods, manifesting the same mechanical system fault each time it is installed, and when it is removed from the mechanical system, the fault is corrected.

The primary reason a component becomes rogue is because shop repair bench tests do not address 100% of the component's operating functions, characteristics or environment. Interviews with various component Original Equipment Manufacturers (OEM) revealed the bench test coverage is typically about 85% of the component's complete functionality. Even if all the functions were covered, the operating environment of the component when it is installed in the mechanical system is usually quite different than the repair shop, so if a failure is dependent upon a particular in-service environmental condition, it is unlikely that it will be duplicated during testing.

Additionally, the bench test is crafted to identify anticipated failures - focused on things that are expected to fail. For instance, it would not make sense to check all the screws or electrical ground straps each time the component comes into the shop, since the chance of failure for those pieces is practically zero and the cost of performing such extensive testing during each shop visit would be exorbitant.

When a component experiences a failure that was unaddressed or unanticipated by the shop testing procedures, a rogue is born. Since every test that is performed misses that specific aspect of the component's functionality, the fault will never be identified and resolved.


"Natural Selection" Phenomenon

There is a Darwinian-like "natural selection" process that ensures the rogue components are placed in the most disadvantageous position in the asset management program. The following depictions demonstrate the mechanics of this phenomenon.

Figure 1 shows a pristine condition where the component spare inventory and the in-service population are comprised of serviceable (Good) components that function as designed and expected (the In-Service Population shown in the diagram is a small representation of the general population). There are no rogue components yet.

In this situation, the asset management process will follow all the applied models. As a part fails in service, it is removed and replaced with a good part from the spare inventory. The component repair facility duplicates the problem with the failed unit, repairs it and returns it to the spare inventory. The "natural selection" phenomenon begins when a rogue component develops as shown in Figure 2.

When one of the in-service components develops a rogue failure, it is removed and sent to the repair facility. Since the failure is not addressed by the standard bench test or overhaul procedure, it is not duplicated and resolved. It checks normally, scoring a "No Fault Found" (NFF) and returns to the spare inventory as depicted by Figure 3.