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Bearing News • Issue 1
“Once people
understand what air bearings are, our product sells itself.” Mr. Jared Ticotin, Director of Engineering at OAV Air Bearings Princeton, New Jersey / USA
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Bearing News • Issue 1
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The US Based Manufacturer
WHO BRINGS AEROSPACE TECHNOLOGY TO AIR BEARING SYSTEMS
INTERVIEW - OAV AIR BEARING Air bearings work on a thin film of pressurized air between surfaces and avoid the traditional bearing-related problems of friction, wear, particulates, and lubricant handling. Result: distinct advantages in precision positioning. We tried to find more answer concerning this technology during an interview with mr. Jared Ticotin, Director of Engineering at OAV Air Bearings located in Princeton, New Jersey. What is your role in the company? I lead the design and concept team. And I work with quality control and purchasing to make sure that we deliver a quality product on time.
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Bearing News • Issue 1
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Why are you chosen for this function? I was initially hired due to my background in aerospace. Since then I have gained valuable training, technical expertise, and experience with the company which made me a good fit to develop the best design solutions and to collaborate with the rest of the team so that we keep organized and everything runs smoothly.
Can you give us a short description of the air bearing systems and in which applications they can be used. Air bearings can be used for any systems with linear motion, rotary motion, multi-axis, pulley systems and many other types of systems. Off the top of my head the applications range from Coordinate Measuring Machines, to CNC Machines, to laser machines, to spindles, to conveyers, to wind tunnels, to optics and many other commercial as well as government, military & medical applications.
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What
is the main difference between air bearing systems and the conventional bearings? Unlike conventional bearings, air bearings do not make physical contact with any surfaces. They use a thin pressurized film of air between the surfaces. Because of this: there is no friction, there is an exponential increase in accuracy, no maintenance required which makes it more cost effective, no heat generation , clean air (which is why it is great for medical applications), high speeds, high repeatability, no noise, reduced vibrations, and
Bearing News • Issue 1
the list goes on but these are some of the most common differences.
When did OAV start the production and what was the evolution in the company? Before Air Bearings, we were known as O’Aviation Corp and we manufactured parts for the military, mostly small bearings. We still run this company and have gained 15 years of aerospace experience from it. OAVCO started about 3 years ago. We couldn’t help but notice not only that air bearings were an amazing technology but we also noticed that there was a lot of room for improvement, development, and innovation. With our background and expertise, we knew we were the perfect company to bring aerospace technology to this industry and bring air bearings to the next level.
What is your latest product development The products I am most excited about are the Roller Air Bearings and Thrust Air Bearings. Until OAV launched these products, there was no standard product line available that do the same thing. These products are designed for fixed location and rotary motion. You can use them for spindles, pulleys, conveyor systems, any kind of rotary system where you want to add the benefits of air bearings. Have you ever heard about the surgery machines? They are robotic machines that have several arms and at the end of these arms are the same tools that a surgeon would use. These machines can perform surgery on a patient. A roller bearing could be used to allow faster, more fluid and precise movement of these arms at each joint. Speed and precision is important during surgical operations. In some cases, you may need to open up an artery which can only be opened for so long then it will need to be shut closed before resulting in too much blood loss. OAV Roller Air Bearings provide the benefits needed to further develop this technology and make it a reality. This is just one example. The great thing about these products is that often they can replace conventional thrust and roller bearings.
he 3 biggest challenges you faced and how you T dealt with them (please give here a few examples of leadership and initiative, or some of the major decisions made) 1) We had to shift our market from the government to the private companies. We weren’t sure what to expect while
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working with private companies. We were accustomed to having to manufacture every part with 100% conformance. It was much easier to apply this tight quality control to our own product designs. In the end our strict background made for an easy adjustment. Marketing was also new to us. We needed to have a plan and make sure that we selected the right people at the management level who could get the company moving in the direction that we envisioned it. Once the perfect management and marketing plans were in place, we had overcome one of our biggest hurtles. 2) Because of our aerospace & defense background, we felt we had to apply the potential technology from aerospace & defense to make design improvements. We are always thinking about how we can make the products better and how can we manufacture them more efficiently so that we could provide them at a more affordable price. We focused our goals towards utilizing our background to always innovate and always improve. 3) Unlike any other company, we are using Aerospace Quality Material. We had a dilemma on whether or not it was worth the extra cost of using aerospace quality material. In the end, we felt it was necessary because our products will have the best performances on the market while maintaining competitive pricing.
Is there any project you truly enjoyed or a customer experience you are most proud of? Majority of what we do is custom air bearings and all of it is very exciting. But the first one that comes to mind is our very first success. All of the hard work we had put into these products over the years and we finally had the reward of hearing our customer say “wow, this product really works! This is amazing!”. A lot of people are amazed just from learning about air bearings. But to actually experience this customer’s reaction to our product after they physically tested? I can’t even find the words to describe the feeling.
ow do you motivate and convince potential H customers that air bearings systems can replace conventional bearings? We simply get our name out. Once people understand what air bearings are, our product sells itself. Majority of the time,
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customers come to us with an issue in their design. We call ourselves The Problem Solvers because we see a problem, we implement our air bearing technology, then the problem is solved.
ow do you see the future of air H bearing systems? Air bearing systems will continue to develop to break boundaries and reach applications which were previously not possible. I see air bearings being used in transportation systems, high temperature applications, complex machinery & robotics, engines, and more. Many more possibilities are out there and we are here contemplating this every day. One specific technology that comes to mind is The Hyperloop. Tesla has announced that they plan to use air bearings in their development of what will be the fastest train in the world. As it turns out, we’ve been talking about using air bearings on trains for a long time. So once the Hyperloop was announced we were very excited because we had already thought about it and knew this technology was possible. And we are very interested in developing it because we know this is one of many ways we could change the world with OAV Air Bearings.
I s there anything you want to add concerning the developing countries? Air bearings will have a major impact on the energy industry. With the added efficiency due to zero friction and reduced vibrations, air bearings could reduce the cost of energy making it more affordable. We hope that one day we could aid in the development of the technology that would provide power to those in need. In addition, air bearings may be used for clean energy sources.
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World
Bearing Market Page: 16
Bearing News • Issue 1
ANALYSIS
Renewed growth of the worldwide bearing market expected Looking towards the near future, analysts of the American consultancy Freedonia Group say that global demand for bearings will grow by almost 8 % per year; reaching a sales volume of $ 96 billion in 2016. A study by Global Industry Analysts Inc. expects it to pass the $ 100 billion mark in 2018. Roughly three quarters of that amount is taken by non-mounted ball and roller bearings. Roller bearing demand is expected to continue to outpace other product types, supported by sales of higher value, technologically advanced bearings and thus, roller bearings will continue to be the largest product segment.
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Since the beginning of the financial crisis in 2008, there have been fluctuations in the market. Problems in the Euro zone and the stagnation of US and Japanese economies made it difficult to stabilise, let alone to increase the demand for bearings. Now, a recovering basic industry together with positive trends in investment projects, will push up that demand again, on a worldwide level. But despite the fragile state of the financial markets and stagnation in the short term on the end market, the gradual increase in global economic activity together with the weakening of the financial crisis in the long term should increase the need for bearings. Improving the balance of the non-financial corporate sector and sustainable leveraging by banks, is expected to help the smooth flow of capital and the gradual strengthening of the positions of durable goods and applications, activating the demand for bearings. In addition, a trend on consumption reduction will affect the price of the bearings themselves because of low prices for raw materials and increased competition between bearing companies, which will be forced to reduce their profits.
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The bearing industry also realises the need to become more involved in producing specialised products, to meet specific needs of their market. Specialisation, high-quality equipment, new research and development projects are but a few themes to handle by the industry if they want to keep up with the evolution. Investing in new techniques and knowhow not only creates new specialised businesses, also for the general bearing business efforts are being made to shorten production times and speed up manufacturing processes.
Asian markets Between now and 2016, the greatest growth is expected in the Asia-Pacific region. The bearing market will rise by almost 10% per year and is estimated to reach $ 54 billion. That will be more than half of the global total demand. Developing countries will continue to see increased consumer access to finished goods, keeping the need for bearings on a rising level. The industry will see an increasing demand for railway, electronic, aircraft and automotive equipment in that region. China will grow faster than other countries in the region: Development of urban and industrial areas Bearing News • Issue 1
over the past years ensured a sustained use of bearings in a wide range of industries. Main factors are an expanding automotive industry and construction machinery, linked to a strong after-sales service of industrial equipment and vehicles. As a result, sales in China are expected to represent one third of the world’s total. Other long-term predictions even see China exceed the combined sales of Western Europe and North America. At the same time, the country remains the world’s major consumer of bearings. Keeping an eye on competition from upcoming countries such as India, China’s industry and government are implementing several plans to improve the manufacturing equipment for bearings, get better quality grinding machines and to increase research and development of new technology. Cooperation between smaller companies and groups is advised, in order to gain a stronger position in the market.
Western developed markets In the developed markets of Western Europe, the US and Japan, demand for bearings will also rise again. After a backdrop due to the economical crisis, with the fragile position of several banking institutions and stagnating end-user market, specialists expect a gradual growth of worldwide economic activity in general. Herman Van Rompuy, president of the European Union, mentioned last December that the crisis has seen its worst moments, and was positive about the confidence in the European Union. Nevertheless, several members of the EU still face serious obstacles to overcome before big changes can be expected. The Dutch Minister of Finance, Jeroen Dijsselbloem, as president of the Euro countries announced recently that several of the member states have promised extra measures to keep a hold on their budgetary agreements. On average, he expects a budgetary deficit of less than 3% of the GDP in 2014. It would be the first time since 2008 and a sign that their agreements and measurements are showing positive results. A recent report on the US market shows they expect a rise in demand by 4,4% per year to $13 billion by
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2017. Here as well they have good hopes for the automotive business, their largest bearing market. As on worldwide level, also for the US the demand for roller bearings remains the largest of the various product series. Demand for bearings in OEM applications will outpace the industry average, due to ongoing growth in US durable goods output. Many durable goods manufacturers are building or upgrading production facilities in the US, boosting demand for components such as bearings.
Main bearing consuming industries Increased production of machinery will stimulate gains, since these industries are heavy users of more advanced, high value bearing products. Consumer
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and producer will see a new expansion of durable goods, which will result in increasing demand for bearings and rising sales figures. Engine, turbine and power transmission markets are expected to grow the fastest, while automotive industry will also see improved conditions, especially in truck and bus production. Also wind energy is a rather new and fast growing segment. An SKF view on the global power transmission market estimates the global power transmission market to be around $ 25 billion. As a major bearing consuming industry, they expect the business to stay on the growth levels of the past 10-15 years, between 3% and 10%.
Bearing News • Issue 1
In this same branch, EPTDA’s (European Power Transmission Distributors Association) economic outlook at the end of 2013 indicated good conditions in UK, Russia, Turkey, the US and China should provide European businesses with solid export opportunities until about mid-2014. After a mild downturn in the second half of 2014, positive business cycle pressures will return in 2015. Economic expansion in the Americas and in Asia will generate increasing demand for European-made goods.
Better times ahead Overall, the bearing industry can start looking at a brighter and more profitable future, after the difficult past few years and the sudden drop in
2008. Competition will remain hard, smaller players on the market will have to be inventive to keep a piece of the cake for them, be it by developing new products and technologies, by specialising in a highquality segment of the market or, on the contrary, by merging with others to provide a wider range of products and services. Europe, US and Japan crawl out of the glooming crisis, and so economy starts to pick up. Investors get more active again, industries are investing themselves in new technologies and equipment. Manufacturing processes evolve to enhance and speed up production. All in all, the mood is positive, from the politicians’ side worldwide as well as the industry itself, each of them measuring up the past to turn things around for the near future.
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Sweet Success:
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Bearing News • Issue 1
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Kids like to run from house to house for collecting as much candy as their bags will hold during Halloween. They will be completely unaware that without bearings, their beloved chocolate bars would never exist.
Bearings plays a critical role in the production process of chocolate, ensuring the little ghouls and goblins enjoy the same quality taste each time they trick-or-treat. There are three important areas in the chocolate production process where bearings are used: • Transfer pumps • Conveyor rollers • Conching machines The conching machine is one of the most important in the entire process as it determines the final flavor consumers expect when they unwrap their favorite sweet treat. These machines can run for up to 60 hours mixing and kneading the chocolate mixture for flavor and consistency at average temperatures of 110 degrees. With this type of demand on the production equipment, bearing reliability and durability are imperative to maintaining a consistent temperature and texture. Ritbearing was approached by a chocolate manufacturer needing a stainless steel bearing that would be able to withstand frequent washings, sanitation, extreme temperatures and meet FDA regulations. The engineers were able to work closely with the chocolate manufacturer on the following areas to determine: • • • • • •
Correct bearing selection to maximize product life Speed and load ratings Life calculations Shaft and housing fits Material selection FDA-approved grease selection
Through its network of manufacturers, Ritbearing was able to offer the custom engineered bearing with a shorter lead time, lower minimum order quantity and was able to inventory the product according to the scheduled release. During the last Halloween week, Americans consumed over 90 million pounds of chocolate, thanks, in part, to the bearing industry. Ironically, soon after the jack-o-lanterns burn out, the bearings used in dental equipment will be given their time to shine as dentists across the country start to correct the effects of this sweet confectionery holiday Page: 24
Bearing News • Issue 1
5 Questions to Ask Your Bearing Supplier For your business, it is vitally important to have the right bearing supply partner that understands your needs and is willing to help find, supply and quickly deliver the right bearing for your application. Sorting through all the options available and which is the best for you and your application can be a time-intensive task.
We have narrowed down the five most important areas to evaluate your bearing supplier to ensure you are getting the best service possible : What markets do they currently serve? Almost everything that moves needs a bearing, but the right bearing can be the difference between operational and outstanding for your project. Companies like Ritbearing continually add new focus markets and work with their partners to develop new information and research to expand its available product solutions.
What type of manufacturers do they work with?
Do they offer custom engineered bearing solutions? If you have a small or niche application, most bearing manufacturers will expect you to select from an existing option and make it work. Customer responsiveness and your company mission just aren’t a part of their vocabulary. When you need more than an out-of-the-box bearing solution, wholesalers like Ritbearing have the resources available to address your individual needs and develop a product to match.
A responsive bearing supplier should have a deep manufacturer base to provide the best quality, price and products to fit your needs. Even the top manufacturers subsidize their bearing production, which means they too are limited on the solutions they can provide. Bearing wholesale companies like Ritbearing bring an entire network of quality manufacturers to match your application’s needs while still being cost competitive with the big brands like Timken, SKF and INA
How well do you know them?
How much time will your order take?
Depending on your needs and industry, you may have more questions to ask your bearing supplier but the common thread in all the answers you receive should be that you come first. How the supplier plans to help you achieve your goals should be at the beginning of every answer.
Big bearing manufacturers are like large ships; they move slowly and turnaround time is a long, arduous process. The time delay on your order is an important question to ask your supplier since acceptable lead times can go out as far as two years. Working with customer-focused companies like Ritbearing who understand the importance of a quick order turnaround can mitigate the risk of paying more in the long run. In fact, Ritbearing can typically fulfill orders, even customized bearing projects, in months, not years.
In today’s world of instant, impersonal communication, it’s easy to become just an account number. Face-to-face meetings are still important to Ritbearing and happen as soon as possible with new customers. Understanding who you are, your application and your expectations are vital to ensuring you receive the best service and product solution.
Ready to work with a bearing supplier that provides the answers you need to hear for these questions? www.ritbearing.com/blog Page: 25
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Bearing News • Issue 1
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Team Spitphya Wins With
CARTER Bearings
Carter Bearings sponsored Team Spitphya who has won the 2013 London Red Bull Soap Box Race. Dubbed the “world’s wackiest road race”, the Red Bull Soap Box Race is held in cities across the world. Last in the UK in 2003, this year’s event was held at Alexandra Palace in north London. 70 competitors were selected from several thousand applications and included a coffin, an 8 foot effigy of Usain Bolt, a slice of Victoria sponge cake and a rolling rugby scrum. Each team was judged not only on their time down the hill but also the creativity of their theme and ability to entertain 20,000 noisy spectators with a 20 second performance before their run. The course was run down 430m of North London hillside incorporating 3 jumps and a set of stairs designed to create as much carnage as possible. The crowds weren’t disappointed with numerous spectacular crashes throughout the day at speeds of up to 40mph. Blood was split and bones broken. Parc fermé tellingly comprised of two lanes, one for ‘keepers’ and a skip! Team Spitphya’s soap box, named the ‘Phyabird’ was inspired by land speed record breakers of the 20s and 30s; Malcolm Campbell, John Cobb, Henry Seagrave et al. Mark Wells, Ian Wride, Greg Seed, Roy Norton and Thomas Kasher, a group of workmates from motorcycle design agency Xenophya Design, employed the same processes that they apply in their ‘day jobs’ in the creation of the Phyabird. The tubular spaceframe was designed in CAD to fit perfectly around driver Greg Seed who was digitised using a FARO arm. A full scale clay model of the land speed racer style body was then created which was then
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Soap Box Race • London 2013
moulded in fibreglass and painted in Bluebird Blue. “We’ve ended up taking this project a bit too seriously - and allowed it to take over most of our lives.” Said team captain and Xenophya Director Mark Wells. “The goal was always to be first down the hill, no matter what the judges thought of us”. In the quest to be fastest Carter Bearings were approached for assistance in selecting low friction bearings, essential in maintaining speed in a vehicle powered only by gravity. Carter bearings provided a set of Isisz hybrid bearings which offered the perfect compromise of strength and performance. “The difference was massive” said Greg, “after swapping the bearings the cart rolls much more freely and just keeps going and going, you can feel there is much less resistance”. The Phyabird achieved it’s objective of being fastest in style. Greg piloted the cart down the course in 33.57 seconds, some 3 seconds faster than the runners up, hitting the final ramp at around 40mph and flying approximately 10 metres through the air! Combined with a judges’ score of 39 out of 40 for the performance this put Team Spitphya on the top step of the podium. “We’re elated to have won the event” said Mark, “it goes some way to justifying the immense amount of work that has gone into the build”. Team Spitphya would like to thank Carter bearings and all those that supported them in kindly donating components and time to help them to victory. With some minor repair work to do, the Phyabird will hopefully be appearing at soap box events around the country later in the year. Video footage of the winning run is available to view at • http://youtu.be/4byhapmPUhE • http://youtu.be/pjnm1kdWhJk
Bearing News • Issue 1
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Specially designed products with LESS IMPACT on the Environment
Ball Bearings Energy
& Saving Page: 31
Ball Bearings
& Saving Energy
Today there is a growing need for energy products with less impact on the environment. This demand will still grow in the future and improving the performance of machines and factories are challenges of tomorrow. It is in this context that JESA SA, a company specializing in the design and manufacture of ball bearings and polymer components measured in units, began to study technical solutions to make advanced performance ball bearings. The potential global energy savings is considerable, since it is in relation to components used on a large scale in a wide variety of applications.
possible capacity for a given dimension. They are suitable for a number of applications, however, they represent a compromise which is not optimal for precise applications. In some cases, they can present friction greater than what would be necessary for the proper functioning of the application.
For this development, a theoretical study was conducted internally and solutions were tested and validated on different test benches.
Internal Friction and Optimization of Components
In the scope of this project, scientific collaborations have also been conducted with Swiss universities and schools of higher education.
The causes of friction in a ball bearing Rolling bearings transmit a rotary motion between two bodies with little friction. This is thanks to the ball bearing which performs with minimal relative sliding upon surfaces. The friction, heat and wear is limited compared to other rotation guidance solutions, while also ensuring a high positioning accuracy and low noise. Despite this, certain factors generate friction which translates into a dissipation of energy and heat generation adverse to high performance of the final product. Standard ball bearings generally offer the best
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JESA SA provides bearings to measure which are developed on the basis of a specification. This approach offers the possibility to meet the demands of it’s customers with products optimized for their needs.
Joints: The main cause of friction in a sealed ball bearing is generally friction within the joints. This type of seal is often unavoidable since the bearings are exposed to a high level of contamination to ensure cleanliness necessary for their proper functioning. These elements generally consist of a thin sheet of coated synthetic elastomer type NBR, HNBR or FKM, selected according to the operating temperature. One or two flexible lips are in radial or axial support on the opposite ring to ensure airtightness. Research into pre-stressing optimization between the seal and friction equate to the best possible solution to increase the yield. One can reach up to a 50% reduction in friction thanks to the use of seals with an improved design without diminishing the seal. A special surface treatment is necessary to reduce the coefficient of friction of the material and thus reduce the friction. Another area of optimization is the roughness of the metallic surface in contact with the bearings. When
Bearing News • Issue 1
there is sufficient space, it is sometimes possible to replace seals and joints that are not making proper contact, which allows for a significantly reduced energy loss by ensuring the required tightness.
reduction in energy and life expectancy. There is no universal grease suitable for all applications. A grease measured accordingly, depending on the
Figure 1: Double joints without friction
Shearing of the lubricant in areas of ball bearing contact: The primary role of a lubricant is to prevent metal-onmetal contact of the rings and balls, by separating the surfaces with a thin film. The asperities of the surfaces are thus excluded and do not come into collision, which allows for significant improvement and a longer service life of the product. The most common lubrication is lifetime lubrication with grease which offers ease of implementation. However, lubrication with circulating oil is sometimes necessary.
Figure 3: Curve of Stribeck describing the different types of friction [Sksana Banakh, 2010, Treatments of surface and use in tribology, Course FSRM]
application, will optimize the lubricant film thickness and thus reduce the friction as well as extend the life expectancy. It is possible to specifically calculate the lubrication routine, taking into account the roughness of surfaces, the minimum thickness film of lubricant created according to the loads, relative rates, geometry and temperature as well as the characteristics of the lubricant.
Λ = parameter of film thickness h min = minimum thickness of the film of lubricant formed [mm] Sr = RMS roughness (= 1.25 x roughness Ra [μm]) paths of ball bearings [μm] SRE = RMS roughness (= 1.25 x roughness Ra [μm])
• For < 1, the lubrication system is limited • For < 1 < 3, the lubrication system is mixed Figure 2: Detail of surface ball-rings in contact with mixed lubricants. In this method occasional contact of surfaces is possible. [Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, CRC Taylor & Francis Group, 140]
The choice of the viscosity and the type of base oil is critical to ensure optimal lubricant film thickness. A too high viscosity will cause unnecessary friction and temperature increase, while a low viscosity will cause friction of mixed types and limited collision of the asperities of the surfaces which results in a severe
• For Λ < 3, the elastohydrodynamic
lubrication
system
is
Different methods exist for calculating the minimum thickness of the film of lubricant in the contact area. One of the most commonly used is that of Hamrock and Dowson:
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h min = minimum thickness of the film of lubricant formed [m] a = coefficient of pressure/viscosity [m2/N] Ηo = dynamic viscosity at atmospheric pressure [Pa ·] s U = the surface drive speed. [m/s] Average linear velocity of the rolling body (UA) and the speed at the point of contact on the inner or outer ring (UB) E’ = Young’s modulus reduced [Pa] W = load on the body rolling [N] e = Euler number k = parameter of ellipticity of contact ellipse, report of the a/b semi-axles. May be approximated by:
material at the front of the point of contact, which should be deformed elastically so rotation can continue. Energy consumption is partially recovered by the material as it returns to its position at the rear point of contact, but not entirely. The energy difference corresponds to a loss through dissipation. b. Micro-slipping
Rx = radius of curvature reduced in the x axis Ry = radius of curvature reduced in the axis y
Good surface tracks and balls are essential to ensure proper factors Λ > 3, without having to use an excessively viscous lubricant, and therefore to ensure a good rolling life duration while limiting friction. JESA SA is equipped with the most recent generation of machines, which provide a very highquality finish and achieve excellent surface states.
Mix of the lubricant within the ball and cage: A part of the friction is created by mixing lubricant with the ball bearings and cage, it is during this time that grease is most heavily distributed upon the bearings. The geometry of the cage, the ball size, and the amount of balls influence the mix. The type of NLGI class soap thickener used in the grease, as well as the initial volume of lubricant also have an impact on the friction. The application will also be decisive when determining these separate parameters. Internal geometry and friction in the points of contact of balls and rings > because the materials used are not rigid and contact pressures are very high, there are elastic deformations of balls and tracks in the areas of contact. This deformation causes two principle types of friction:
Figure 5: Detail of contact of ball bearing-path of ball showing the average RADIUS after deformation as well as two points A - A where there is purely rolling. [Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, Taylor & Francis Group, 45 CRC]
The area of contact between the balls and ball tracks has an elliptical shape more or less elongated depending on the radii of curvature selected for the ball in comparison to the diameter of the ball tracks. A relative slipping of surfaces is caused by the elasticity of the material, and only two points of the ellipse are rolling without slipping, in the case of a deep groove bearing radially loaded.
a. Hysteresis losses When a ball rolls on a surface, it forms a bead of
Figure 6: Detail of contact of ball-path of ball showing the lines of slipping and two points A - A where there is pure rolling. [Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, CRC Taylor & Francis Group, 46]
Figure 4: Rotation of cylinder and deformation of surfaces [Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, CRC Taylor & Francis Group, 129]
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Most ellipses are extended and there are more sliding speeds at the ends of the ellipse, which increases the friction. Bearing News • Issue 1
Figure 7: Detail of contact of ball-path of ball showing speeds of sliding amplitudes. [Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, CRC Taylor & Francis Group, 138]
Standard balls generally are created to maximize surface areas of contact between balls and rings, to reducesurface pressures and thus increase the carrying capacity of the bearing. Optimized performance is unfortunately impeded by friction that increases with the contact surface. Thanks to its advanced calculation tools, JESA SA is able to determine the optimal internal geometry to minimize friction, guaranteeing the lifetime performance thatâ&#x20AC;&#x2122;s expected.
Figure 8: Bench test for measuring friction torque
Friction of the cage on the balls and rings: The use of a cage allows limited friction by keeping the balls from rolling against each other, as is the case in a full ball bearing. The cage itself is in contact with the ball and sometimes also with the inner or outer ring, which causes energy loss as well as slipping by shearing off lubricant. The quality of manufacture of the cage, its geometry, as well as the manner, in which it is manufactured, have an influence on the friction generated. A range of engineering polymers and a low coefficient of friction are combined by JESA for the development of cages with low friction, which allows for reduced energy loss compared to a conventional steel cage, while providing better resistance against vibrations. A simulation of deformation of the highspeed cage can be carried out, if necessary, through finite element analysis software, in order to exclude any risk of excessive deformation resulting in unintentional contact.
Practical validation: It is difficult to accurately calculate the friction of a bearing, as the number of parameters that influence this value are more diverse. Certain programs are used to calculate a relatively accurate friction value for standard bearings, but the results may strongly
Figure 9 Cell test mounted on a rheometer
Figure 10 Cell installed for lifespan test
diverge from reality, for special bearings. JESA is equipped with a test bench to measure the friction of bearings for different methods of rotation. A practical validation calculation is made on this bench, so as to ensure the friction level of real products. A tribological test bench has been developed in collaboration with the School of Engineers in Freiburg and allows for precise quantifying of friction of various materials and coatings under load at variable speeds. An independent cell applies contact pressure of 0-4 â&#x20AC;&#x2DC; 200MPa on two rings of tests, through 2 x 3 beads. This cell can be installed on a rheometer for measurements of friction or coupled to a motor to perform life tests.
Specific example: Bobst SA is one of the world leading companies involved in the design and manufacture of machines for production of cardboard packaging. Some of
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special no contact double-joints provide a good seal to the cardboard without effecting friction.With such a product, it is possible to divide by 2, or even 3, the friction of the bearings. As one multiplies the amount of bearings per machine, significant energy savings can be achieved on the final product. The impact of the machine on the environment is reduced and lower operating costs are obtained. Figure 11: Folder-gluer BOBST [www.bobst.com]
these machines are large and utilize hundreds of bearings to support and guide flat belts, which are used to move the cartons through the machine.
Sources 1. Tedric A. Harris, 2007, Advanced Concepts of Bearing Technology, CRC Taylor& Francis Group 2. Gwidon W. Stachowiak, Andrew W. Batchelor, 2005, Engineering Tribology, Elsevier, ISBN-10: 0-7506-7836-4 3. Sksana Banakh, 2010, Treatments of surface and use in Tribology, courses FSRM Author: Laurent FrĂŠsard Spinning Solution Engineer at JESA SA
Figure 12: Detail rolling folder-gluer BOBST [www.bobst.com]
These bearings are specifically for low loads and
About the company
Figure 13 Special wheel developed by JESA SA
as standard bearings they are not adapted and optimized for heavy loads. JESA SA has proposed a special bearing optimized according to the needs and responsibilities of the customer. The construction and internal geometry have been revised as well as the quantity and type of lubricant used. These Page: 36
JESA, founded in 1969 by Mr Joseph Egger in Villarssur-Glane in the canton of Fribourg, is currently a limited company of the POLYGENA holding and has approximately 200 employees. Specialist customised solutions of precision ball bearings and units containing technical polymers, JESA has been a major player in this market for over 40 years. Present worldwide through sales offices in Germany, USA, France, Great Britain and also in China, its turnover is around 50 million Swiss francs. In 2010 and 2011, JESA invested about 8 million Swiss francs in production equipment at the forefront of technology to continue its journey toward operational excellence. www.jesa.com
Bearing News â&#x20AC;˘ Issue 1
www.sugawara-labs.co.jp
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Early Detection Of Critical Operating Conditions For Vibration Induced Premature Bearing Failures In Industrial Gearboxes By Sensor Monitoring Of Oil Aging Manfred MAUNTZ
Ulrich KUIPERS
Jürgen GEGNER
CMC Instruments GmbH; Hauptstraße 388 Eschborn; 65760, Germany
South Westphalia University of Applied Sciences, Haldener Straße 182 Hagen, 58095, Germany
University of Siegen, Institute of Material Science, Paul-Bonatz-Straße 9-11 Siegen, 57076, Germany
ABSTRACT An online web-based oil diagnosis system for the early identifying of critical operating conditions for premature failures of rolling bearings in industrial and particularly wind energy gearboxes by white etching cracks is presented. The new approach utilizes sensor detection of chemical aging of the lubricant and its additives due to causative vibration loading. The mainly large roller bearings in wind energy gearboxes fail pretty frequently way before their calculated L10 life by so-called white etching cracks. Material damage is characterized by mostly axial raceway cracks with occasional pock-like spallings and branching and spreading crack propagation from the surface to the depth driven by corrosion fatigue. The root cause of these premature bearing failures is vibration loading. The resulting specific mixed friction operating conditions involve the high localized friction coefficients that initiate tensile stress induced brittle spontaneous cleavagelike surface cracking. The basic idea of the new premature failure detection condition monitoring system is the early identification of chemical aging of the lubricant and its additives under the influence of vibration loading.
The OilQSens® sensor effectively controls the proper operation conditions of bearings and cogwheels in gears. The online diagnostics system measures components of the specific complex impedance of oils. For instance, metal abrasion due to wear debris, broken oil molecules, forming acids or oil soaps, result in an increase of the electrical conductivity, which directly correlates with the degree of contamination of the oil. For additivated lubricants, the stage of degradation of the additives can also be derived from changes in the dielectric constant. The determination of impurities or reduction in the quality of the oil and the quasi continuous evaluation of wear and chemical aging follow the holistic approach of a real-time monitoring of an alteration in the condition of the oil-machine system. Once the oil condition monitoring sensors are installed on the wind turbine or other industrial gearbox, the measuring data can be displayed and evaluated elsewhere. The signals are transmitted to a webbased condition monitoring system via LAN, WLAN or serial interfaces of the sensor unit. Monitoring of the damage mechanisms during proper operation below the tolerance limits of the components enables specific preventive maintenance independent of rigid inspection intervals. Page: 38
Principles of OilQSensÂŽ With the OilQSensÂŽ unit, components of the complex impedances X of oils, in particular the specific electrical conductivity k and the relative permittivity er as well as the oil temperature T are measured [1-3]. The values k and er are determined independently of each other. Oils are electrical nonconductors. The electrical residual conductivity of pure oils lies in the range below 1 pS/m.
Fig. 1: Sensor with triple plate design.
For comparison, the electrical conductivity of the electrical nonconductor distilled water is larger by six orders of magnitude.
Abrasive (metallic) wear, ions, broken oil molecules, acids, oil soaps, etc., cause an increase of the oil conductivity k. It rises with increasing ion concentration and mobility. The electrical conductivity of almost all impurities is high compared with the extremely low corresponding property of original pure oils. A direct connection between the electrical conductivity and the degree of contamination of oils is found. An increase of the electrical conductivity of the oil in operation can thus be interpreted as increasing wear or contamination of the lubricant. The aging of the oil is also evident in the degradation of additives. The used additives reveal high conductivity compared with the oil.
cannot be assumed to be known. To improve the comparability of measurements, a self-learning adaptive temperature compensation algorithm is necessary. An integral alteration of the oil quality can then be assessed by the temperature compensated conductivity value, whereas the type of contamination is not determinable. The relative permittivity is measured with the same basic sensor arrangement as used for the determination of the electrical conductivity.
Premature failures of rolling bearings due to vibrations and correlation with oil aging Bearings in industrial, e.g. wind turbine, gearboxes quite often suffer from a significantly shorter life than calculated by so-called white etching cracks [4]. These early failures are characterized by mostly axial raceway cracks, revealing vertical semi to fully circular cleavage-like lenticular brittle spontaneous incipient cracks in preparatively opened original fracture faces. Occasionally, pock-like spallings are associated with the surface cracks, as shown exemplarily in Fig. 2 [5]. The developing deep crack systems are open to the raceway, from which oil penetrates and promotes further corrosion fatigue crack growth as well as local secondary microstructural changes in the form of crack path decorating white etching constituents. It is evident from fractography and X-ray diffraction (XRD) residual stress analyses that the cleavage-like incipient cracks are caused by frictional tangential tensile stresses, which occur in subregions of the contact area in vibrationally induced mixed friction
The consumption of the additives is reflected in a reduction of the electrical conductivity and permittivity of the oil. The gradient, i.e. the time derivative, of the conductivity or the dielectric constant progression respectively represents a measure of the additive degradation and consumption. The full additive degradation is indicated by the slope of zero (bathtub curve). Then the measurement signal increases further with increasing pollution, water entry, etc. Ion mobility and thus electrical conductivity k are dependent on the internal friction of the oil and therefore also on its temperature. The conductivity k of the oil increases with temperature. The type of pollution and its temperature dependence
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Fig. 2: Inner ring raceway with typical axial cracks and few associated pocklike spallings.
Bearing News â&#x20AC;˘ Issue 1
operating conditions. XRD based material response analysis of run rolling bearings, suffering from white etching cracks on still largely undamaged raceways, reveal the causative vibration loading. It is further reported that lubricant aging occurs under the influence of vibrations. An example of an infrared spectrum of used oil from rig test run of a roller bearing is provided in Fig. 3 [6].
can only detect particles as small as 4 µm. In a very early stage of wear of bearings, gears, hydraulic cylinders, etc., however, particularly smaller particles are produced. A preventive maintenance lowing, rather than rigid inspection intervals, therefore requires recognition of even the smallest particles. These particles are far more common in the oils of functioning machines than larger ones. Oil aging can be involved in the failure, for instance, of rolling bearings [7].
Web-Based decentralized lubricant quality monitoring system
Fig. 3: Oxidation peaks in the infrared spectrum of a used oil run under vibration loading in a rolling bearing test rig.
The found O‒H and C=O oxidation bands indicate operational acidification of the oil, also reflected in the dissolution of MnS inclusion lines on the raceway, as a result of polycondensation reactions towards resinification and beginning lacquer formation. It is this aging of the lubricating oil and its additives that can be detected in an early stage by the OilQSens® sensor.
Approach for condition monitoring of additivated lubricating oils Fig. 4 schematically shows the temperature compensated time curve of the permittivity of
The integration into a suitable communication structure and the realization of an online monitoring system offers an interesting practice-oriented utilization of the oil sensor system. This is briefly discussed below. Preferred areas of application of the sensor system are energy production and automated technical plants that are operated locally, like e.g. wind turbines, generators, hydraulic systems or gearboxes. Plant employers are interested in continuous automated in vivo examination of the oil quality rather than interrupting the operation for regular sampling. Online oil status monitoring significantly improves the economic and ecological efficiency by increasing operating safety, reducing down times or adjusting oil change intervals to actual requirements. Once the oil condition monitoring sensors are installed on the plants, the measuring data can be displayed and evaluated elsewhere. A flexible decentralized monitoring system also enables the analysis of measuring signals and monitoring of the plants by external providers. A user-orientated service Fig. 5: The displayed ensuring the quantitative measured data.
Fig. 4: Temperature compensated permittivity.
additivated oil continuously contaminated by the addition of wear debris, water or oil acids from chemical aging. Once the additives are consumed, the vanishing shielding effect results in a characteristic re-increase. The most commercially available particle counters
Fig. 6: OilQSens® sensor system with communication module.
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evaluation of changes in the oil-machine system, including the recommendation of resulting preventive maintenance measures, relieves plant operators, increases reliability and saves costs.
evaluation of the bearing and gear wear and oil aging meet the holistic approach of a real-time monitoring of a change in the condition of the oilmachine system.
In a web-based decentralized online oil condition monitoring system, the sensor signals are preferably transferred through the Internet to a database server and recorded on an HTML page as user interface [8].
The measuring signals can be transmitted to a web-based condition monitoring system via LAN, WLAN or serial interfaces of the sensor system. The monitoring of the tribological wear mechanisms during proper operation below the tolerance limits of the components then allows preventive, conditionoriented maintenance to be carried out, if necessary, long before regular overhauling, thus reducing outages caused by wear while simultaneously increasing the overall lifetime of the oil-machine system.
Following authentication, a simple web browser permits access via the wired or wireless LAN. In case of alarm signals, an immediate automated generation of warning messages, for instance by e-mail or SMS, is possible from any computer with Internet connection. Fig. 6 shows the OilQSens® sensor system with communication module [9].
Summary The online diagnostics system measures components of the specific complex impedance of oils. For instance, metal abrasion due to bearing wear at the tribological contact, broken oil molecules, acids or oil soap cause an increase in electrical conductivity that directly correlates with the degree of pollution of the oil. The dielectrical properties of the oils are especially determined by the water content, which, in the case of products that are not enriched with additives, becomes accessible by an additional accurate measurement of the dielectric constant. In the case of oils enriched with additives, statements on the degradation of additives can also be deduced from recorded changes in the dielectric constant. Indication of damage and wear is measured as an integral factor of, e.g., the degree of pollution, oil aging and acidification, water content and the decomposition state of additives or abrasion of the bearings. It provides informative data on lubricant aging and material loading as well as the wear of the bearings and gears for the online operative monitoring of components of machines. Additional loading, for instance, by vibration induced mixed friction in rolling-sliding contact (rolling bearings, gears, cams, etc.) causes faster oil aging. Verified in roller bearing rig tests, the oil suffers from incipient resinification and significant acidification, as proven by infrared spectroscopy of used lubricant. For an efficient machine utilization and targeted damage prevention, the new OilQSens® online condition monitoring system offers the prospect to carry out timely preventative maintenance on demand rather than in rigid inspection intervals. The determination of impurities or reduction in the quality of the lubricants and the quasi continuous Page: 41
On a bearing and gear rig test, various load cycles are run and the functionality of the introduced electric online condition monitoring sensor system is tested successfully. The evaluation of the experiment is presented.
References [1] Gegner, J., Kuipers, U. and Mauntz, M.: Ölsensorsystem zur EchtzeitZustandsüberwachung von technischen Anlagen und Maschinen, Technisches Messen 77, 2010, pp. 283-292 [2] Kuipers, U., Mauntz, M.:Ölsensorsystem – Sensorsystem zur Messung von Komponenten der komplexen Impedanz elektrisch gering leitender und nichtleitender Fluide, dessen Realisierung und Anwendung, Patentanmeldung Nr. 10 2008 047 366.9, Anmelder: cmc Instruments GmbH, Deutsches Patentamt, München, Anmeldetag: 15. 9. 2008 [3] Kuipers, U., Mauntz, M.: Verfahren, Schaltungsanordnung, Sensor zur Messung physikalischer Größen in Fluiden sowie deren Verwendung, Europäische Patentanmeldung Nr. EP 09000244, Europäisches Patentamt, München, 9. 1. 2009 [4] Gegner, J.: Tribological Aspects of Rolling Bearing Failures, In: C.-H. Kuo (ed.), Tribology – Lubricants and Lubrication, InTech, Rijeka, Croatia, 2011, Chap. 2, pp. 33-94 [5] Nierlich, W., Gegner, J.: Introduction of the Normal Stress Hypothesis for Mixed Friction in Rolling-Sliding Contact, VDI Reports 2147, VDI Knowledge Forum, Düsseldorf, Germany, 2011, pp. 277-290, in German [6] Gegner, J., Nierlich, W.: Operational Residual Stress Formation in Vibration-Loaded Rolling Contact, Advances in X-ray Analysis, Vol. 52, 2008, pp. 722-731 [7] Gegner, J., Nierlich, W.: Mechanical and Tribochemical Mechanisms of Mixed Friction Induced Surface Failures of Rolling Bearings and Modeling of Competing Shear and Tensile Stress Controlled Damage Initiation, T+S Tribologie und Schmierungstechnik 58, 2011, 10-21 [8] Gegner, J., Kuipers U. and Mauntz, M.: New Electric Online Oil Condition Monitoring Sensor – an Innovation in Early Failure Detection of Industrial Gears, The 4th International Multi-Conference on Engineering and Technological Innovation July 19th – July 22nd, 2011, Orlando, Florida, USA 2011, Proceedings Volume I, International Institut of Informatics and Systemics, Winter Garten, FL, USA, 2011, pp. 238-242 [9] Gegner, J., Kuipers U. and Mauntz, M.: High-precision online sensor condition monitoring of industrial oils in service for the early detection of contamination and chemical aging, Sensor+Test Conferences 7.-9.6.2011, Nürnberg, AMA Service GmbH, Wunstorf, 2011, pp. 702-709
Bearing News • Issue 1
RACEWAY CROWNING IN ROLLER BEARINGS
• Simulation of contact pattern • Optimization • Development of a simplified method for families of similar applications
Abstract: Contact pressure distribution in bearings is determined by micro-geometry of the contact surfaces, related axial and radial loads and by misalignment between shaft and housing, while especially cylindrical and tapered roller bearings are very sensitive for misalignment which can be caused by both initial manufacturing deviations or by elastic deflection due to operation conditions. In most applications, loads and misalignment can hardly be influenced why optimization of microgeometry is very important for reaching proper contact pattern without any critical pressure peaks and thus providing sufficient lifetime of the bearing. By means of finite-elements-method, contact pattern due to operational loads and deflections can be assessed which allows discussion of different concepts for micro-geometry. Subsequently both optimized geometry can be determined and influence of tolerances can be estimated. Based on that, detailed specifications for micro-geometry can be developed for each particular bearing and application. As optimization based on sophisticated simulation of each particular case is very expensive, in a second
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step, a simplified method has been developed which allows transferring of results from one case to a family of similar applications. Subsequently, microgeometry of roller bearings can be controlled by reasonable effort and precision which is sufficient for a broad spectrum of applications.
1. Simulation: The numerical simulation shall provide precise information on contact pressure distribution which requires excellent mesh properties close to the contacts. For this reason, rollers and rings have been meshed using hexahedral elements with local refinement in those areas where contact can be expected. Elements in this region are almost rectangular while aspect ratio (ratio between longest and shortest edge) is limited to 4. The further partitions of rings and rollers, however, can be meshed using rather coarse elements. Apart from that, surrounding parts like shaft and housing have to be considered. Here, stress values do not need to be discussed as this is not the goal of the simulation. Nevertheless, global stiffness and subsequent deflection have to be calculated precisely as these quantities are most relevant for contact pattern. On the other hand, meshing of the
Bearing News • Issue 1
surrounding parts should consider total simulation effort for both modelling and calculation. For this reason, surrounding parts have been meshed using second order tetrahedral elements which are suitable for automatic meshing of complex geometry and provide accurate results with most common solvers. For all parts, acceptable simplifications have to be discussed. In context of contact simulation, especially chamfers, small radii, bolts etc. can be neglected. Also contact definition between rings and housings and shafts can be simplified. Here, tied contacts have been used at both interfaces. Figure 1: model of a cylindrical roller bearing As the objective of the optimization is to find geometry which prevents both edge contact and plastic deformation, both plasticity and edge definition of the rollers can be neglected. This allows higher mesh quality at critical positions and reduces calculation effort due to simplified mechanical theory. Subsequently, results will not be valid for improper versions; however, behavior of optimized version can be predicted properly.
2. Optimization: The goal of the optimization is minimization of peak pressure considering boundary conditions which means that pressure at edges of the raceway has to be significantly less than peak pressure â&#x20AC;&#x201C; here, one decided to define 50 % of maximum pressure as limits at edges of the raceway. Subsequently, transition to radii at roller faces may cause up to 100 % increase of local pressure. In general, two different phenomena have to be discussed: deflection of bearing parts due to high loads and misalignment between bearings rings towards each other due to shaft and housing deflection. For the first item, the best approach is to apply convexity on both rings while both circular, logarithmic and combined circular-straight profiles are very common. Convexity of rollers is not discussed so far as only total convexity of one contact pair is relevant for contact pressure distribution â&#x20AC;&#x201C; no matter which part takes with portion of total convexity. Subsequently, rollers have been assumed to be perfectly straight while crowning is applied only on the rings. However, investigation showed that in context of misalignment, one should design one contact pair rather straight while only the opposite contact is made with significant convexity. Subsequently, edge contact at the rather straight pair will be reduced by bending of the rollers. The advantage of this approach is that the flatter contact pair clearly defines roller position in the bearing and subsequently position of centre of gravity of pressure area. In case of two convex contact pairs, the position of the pressure area is likely to move in axial direction so that reduction of peak pressure by convexity is overcompensated by edge contact effect.
Figure 1: model of a cylindrical roller bearing
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The main conclusion in this context is that two completely different approaches are required depending on whether misalignment or high peak loads are the most relevant issue that has to be covered by crowning of surfaces. Subsequently, crowing concepts which are optimized for low speed heavy duty applications, e. g. wheel bearings of mining trucks, are not feasible for e. g. railway gearboxes, where rather high speed and high number of total revolutions at medium loads but significant elastic deformations have to be considered. Optimization does not only lead to identification of geometry which provides best possible contact pattern, it helps also to discuss influence of tolerances. Wide tolerances are desired for manufacturing reasons; however, the wider tolerances are, the higher maximum expectable pressure will be which will affect product performance. Based on data gathered during iterative optimization, a suitable compromise between both objectives â&#x20AC;&#x201C; maximum performance and minimum manufacturing costs â&#x20AC;&#x201C; can be achieved.
3. Development of a simplified approach for families of similar applications: If desired crowning parameters for one bearing including acceptable tolerances have been defined, transferring these parameters to similar bearings in comparable applications will be likely to save plenty of engineering effort. For this reason, a simplified method has been developed which helps to analytically calculate parameters for a whole family of application cases based on optimized parameters for a reference bearing. However, this approach is only valid for circular crowning and precision of this method is limited by difference between related geometry and loads. The first step of such an approach is to simplify the system that has to be discussed and to reduce the number of parameters. Here, the first simplification is to reduce contact between roller and convex rings to an equivalent system of a convex roller which is in contact with an ideal flat, using the assumption that diameter of rings do not significantly affect contact pattern. This means subsequently that diameters within one bearing family should be within a limited range. Further, both contacts of one roller are defined by different crowning parameters while contact Page: 44
pressure distribution is influenced by bending of the rollers. Consideration of bending, however, allows reducing this two-parametric system to only one parameter which will be a mean convexity of both contacts as convexity of one contact is likely to reduce edge pressure on the opposite contact as well. At the end of this approach, one assumes that the ratio of both crowning parameters has to be constant within one bearing family. Based on these simplifications, maximum contact pressure and contact width can be calculated according to Hertz theory dependent on contact force per roller, roller diameter and mean convexity. For tapered rollers, the mean roller diameter will be considered. For the purpose of finding equivalent crowning parameters, it is assumed that parameters are equivalent if maximum pressure is equal for such contact forces per roller which lead to contact width equal 80 % of raceway width. Using this assumption, required mean convexity can be calculated. Subsequently, inner ring and outer ring convexity will be defined using a constant ratio between these values for all bearings of one family. Finally, tolerances have to be adapted, while ratio between tolerance field width and mean convexity is kept constant too. In this context, it is recommended to slightly reduce tolerances in relation to geometrical difference towards reference bearing in order to cover the influence of simplification.
4. Conclusion: Using numerical simulation methods by means of finite elements method, raceway crowning of bearings can be optimized regarding particular applications. Here, one has to distinguish between influence from internal bearing deflection and from deflection of shafts or housing. Both influences on contact pattern have to be covered by completely different approaches. Apart from optimal parameters, a reasonable compromise between tolerances and bearing performance can be achieved. Within one bearing family, equivalent parameters for different bearings can be derived based on one reference bearing using a simplified approach. However, this approach is limited by differences between macro-geometry and operation conditions. More information can be find on www.elgeti-engineering.de
Bearing News â&#x20AC;˘ Issue 1
MANAGING YOUR STRATEGY Enluse provides a full range of tools and equipment to help you manage your lubrication activities. These range from innovative solutions like 3-D bullâ&#x20AC;&#x2122;s-eyes and oil sight glasses to check your oil levels, to filtering systems and breather dryers to stop airborne contaminants from entering the oil. Enluse is also an authorised distributor for the Reliability Institute providing a range of online training courses.
Desiccant breathers to protect the oil
Reduce airborne contaminants
Oil Sight glasses for level control
Online Training Programs
Mobile Filtering
Reliability Institute On-line Training Courses
www.enluse.com +31 (0) 76 57 81 280
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Bearing News â&#x20AC;¢ Issue 1
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Bearing News â&#x20AC;¢ Issue 1
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LUBRICATION MANAGEMENT FOR IMPROVED RELIABILITY Overview Lubrication practices within a plant have a direct effect on plant and equipment reliability. When a lubricant is working effectively in a machine – with no chemical degradation and with limited contamination within it, wear will be reduced and equipment reliability will be improved. The key to achieving a reduction in component wear and an increase in equipment reliability, is an effective and clean average lubrication film thickness – or in other words protecting and maintaining a good lubrication viscosity.
What is Lubrication Reliability? Any investigations conducted today on why bearings fail, will reveal the alarming fact that over 60% of the damages are lubrication related. The bearing is the rotating core of the machine and if we can reduce the lube related failures we will directly improve the equipment reliability, not to mention reducing the bearing consumption.
way, equipment reliability will improve. Meaning a Lubrication Reliability strategy is all about ensuring effective machine lubrication occurs within the machine resulting in reduced wear and failures.
It is all about Lube Film! SKF has stated that, “bearings can have an infinite
life when particles larger than the lubricant film are removed.” Meaning the removal of abrasive particles prevents bearing wear.
In a bearing with a good average lubrication film thickness, the metal surfaces are separated and the average thickness of this separation or film is very small, in fact it is about one twentieth of the thickness of a strand of human hair. See figure 1 When there are hard contaminants in the oil and
Bearings and other rotating components need a good lube film thickness to separate the metal components and reduce wear; however, generating a good film thickness is a chemically complex mechanism, which is dependent on many factors. However, when the lubrication works in a reliable Page: 50
Bearing News • Issue 1
Lubrication practices within a plant have a direct effect on plant and equipment reliability. When a lubricant is working effectively in a machine â&#x20AC;&#x201C; with no chemical degradation and with limited contamination within it, wear will be reduced and equipment reliability will be improved. The key to achieving a reduction in component wear and an increase in equipment reliability, is an effective and clean average lubrication film thickness â&#x20AC;&#x201C; or in order words protecting and maintaining a good lubrication viscosity.
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they are greater in size than average lube film, then 3 body abrasive wear starts to happen. This then leads to surface indentation and scratching, which is a process that can lead to bearing or component failure. A good average lubrication film thickness in a machine or component is the result of a lubricant operating with an effective viscosity. If the oil is kept clean, meaning that there is a very low level of abrasive particles in it and there is no degrading of the chemical composition of the oil, then the lubrication will do it’s job. – provide an average lubrication film thickness that will separate the metal components and eliminate or reduce wear. Viscosity changes are the result of oil degradation, contamination, or both and any change of a lubricants viscosity has a dangerous effect on any components reliability, as it can lead to the breakup of the lubricating film generation process and increase the wear potential.
Understanding Oil Contamination
The number one problem with lubrication today is contamination and this can be particle contamination or chemical contamination or both.
Particle Contamination The effects of particle contamination on bearing life is supported by a research project conducted by Doctor MacPhearson, which looked at the relationship between filter ratings and millions of bearing cycles to fatigue failure. See figure 2 The bottom line being the lower the contamination level the longer the bearing life.
Managing Particle Contamination There are 5 steps we need to consider in managing Page: 52
our oil cleanliness and contamination levels. These are: 1. Receipt of new oil. 2. Storage and conditioning of new oil. 3. Dispensing of the oil to the machines. 4. Stopping contaminants entering the machine. 5. Removing contaminants generated in the machine from wear.
Managing Chemical Contamination. As mentioned in the article earlier the oil can also be contaminated chemically, for example water entering the system or oxidation occurring within the process. These chemical contaminants will also affect the average lubrication film thickness and any well managed lubrication activity will use an Oil Analysis process to monitor the development of them. ROI or Return on Investment. A well structured lubrication strategy will require some investments. Depending on how advanced a company is with their existing lubrication strategy and their size, these costs can be anywhere from $20,000.00 to $150,000.00. A lot of money, however it is an investment that will be paid back. The following are three examples of where the investment payback will come from. • The eliminating of one failed electric motor, due to lack of lubrication. • The doubling of life of a number of gearboxes due to cleaner oil. • The reduction in bearing spend, by a conservative 30% annually. • The doubling in life of all hydraulic systems and pumps.
Conclusion Lubrication practices within a plant have a direct effect on plant and equipment reliability. When the lubrication is working effectively, wear will be reduced and equipment reliability will be improved. A Lubrication Reliability strategy focuses on all parameters that protect the average lubrication film thickness thereby reducing component wear and increasing equipment reliability. Please feel free to email Ian Knight for any additional information or queries you may have. You can email Ian Knight for more details: ian.knight@enluse.com
Bearing News • Issue 1
PM Procedures Without Effective
Repair/Restoration Procedures
is Insanity! Page: 53
PM Procedures Without Effective
Repair/Restoration Procedures
is Insanity!
In the field of maintenance the traditional approach has been to rely upon the intuitive knowledge and skill of the crafts-persons who conduct it. There is a great deal of pride of workmanship and, in all too many organizations, a great deal of psychic income in addition to significant overtime pay for successful emergency repairs to return equipment to operation after unplanned shutdowns.
“There is a mystique that accompanies all of this that many skilled crafts-person would like management to believe firmly. That is that there are too many variables in maintenance, making compliance with written procedures impossible and impractical; that the “way we’ve always done it” is the best and only way to conduct maintenance” Page: 54
This idea spills over into preventive maintenance, also. Crafts- persons believe that their own intuitive knowledge is preferable to a written procedure and/or a thoroughly defined checklist. Aside from these problems, most organizations have allocated no resources to creation and on-going support of procedures and checklists. Accordingly these organization are beating on the wrong way of conducting maintenance in order to assure reliability. This results in at least a lost opportunity for increased profits from existing assets and at worst a fatal management omission. Management is gambling with profits and losing big time with the approach that emphasizes “pride” of workmanship over an approach that has been proven to work. Lost in all of this is the concept of ensuring
Bearing News • Issue 1
and sustaining reliability as both corrective and preventive maintenance is performed. Ideas about how things fail that we used to rely upon as a basis for preventive maintenance have been shown in the four failure profile studies over the past 40 years to apply to only a minor percentage of failures. In gambling terms, this means that odds are very long against a “win.” From this it can be shown that time directed maintenance, in general, also should apply to only a minor portion of the failure modes which an organization must correct or mitigate. This is because we seldom know the profile for a failure and assume that most components exhibit a “wear-out” characteristic, but assign a frequency for maintenance anyway, as if they did.
Nowlan and Heap Study – Most Failures are Random Further it can be shown that intrusive, time directed maintenance can be detrimental to reliability because humans are involved and they produce “infant failures.” Non- intrusive maintenance and monitoring tasks should be sought, instead. Indeed, because of the distribution of the failure profiles described in this paper, the only logical approach for the mitigating failures in the majority of equipment is through the use of non-intrusive tasks supported by the use of procedures to assure consistent results.
“As modern predictive maintenance tools and analysis methods have come into use, most of which are non-intrusive, the requirement for procedurebased maintenance becomes even more important”
Analysis of data from modern tools such as vibration monitoring, lubricant and wear particle techniques, infra red observations, motor electrical condition monitoring and almost all other technologies depends for accuracy upon knowledge of the operating state of the equipment. Operating conditions and surrounding environmental parameters must be carefully established and recorded in order that thorough analysis can be performed. This can only be established by adherence to carefully written, detailed procedures and checklists. Such procedures may be “imbedded” into equipment designed for data collection. However, procedures for connecting data must be carefully prepared and followed in order that there is complete agreement between imbedded and non-imbedded details.
“Should Repeatable and Effective Procedures be the standard for most Maintenance organizations or should we keep doing what we are doing and expecting a different result” I know many organizations spend a lot of money, time, and energy to develop “Failure Mode Focused PM Procedures” and yet spend little or no focus on the corrective procedures which must be applied to correct any deficiencies or abnormalities (corrected to known specification or standard) identified through PM Inspection or Condition Monitoring Inspection. If this does not occur we know frequent failures will occur. Imagine the outcome of a Procedure Based Maintenance Organization where frequent and unexpected failures become a thing of the past. Your equipment would have a better chance of running failure free for a longer period of time through Procedure Based Maintenance. We apply Preventive Maintenance, Predictive Maintenance, let’s add Procedure Based Maintenance and make it a standard we must follow.
It is time to change! Ricky Smith Principal Advisor Maintenance/Reliability GPAllied • www.gpallied.com
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Increased Input In
European
BearÄąng Industry
New trends in economical and technological developments often announce themselves unnoticed at first. Could we see the rebirth of the bearing industry in Europe in the near future? The interest of investment groups, combined with the desire of developing markets to gain ground on the European market, might well lead to such a renewed situation.
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Bearing News â&#x20AC;˘ Issue 1
Asia has known an exponential growth the past decade on the bearing market. Western companies until today are investing in infrastructure and technology in those regions. Recent economical crisis however, made for a stagnation in sales. The Chinese Bearing Industry Association already reacted by announcing structural changes in development of new machinery and aiming more and more towards specialisation. And even when the initial doubts of European consumers about Chinese production are starting to disappear, it is a matter of fact that a strong demand remains for a product that originates from their own European production facilities. Not long after a country like Romania saw itâ&#x20AC;&#x2122;s bearing industry plummet to historical depths, there now are signs of a new interest towards investing in Europe again. Several reasons lay at the background of this upcoming trend. Seen the need for specialisation in China, wages will rise and product price will go up as a consequence. Logistics are still not evident and transit time of goods remains a disturbing element for a market that needs to see their goods delivered on command and preferably just in time. Third important factor remains quality. Know how and technology in Europe stand for higher quality levels, and the earlier mentioned confidence in â&#x20AC;&#x2DC;ownâ&#x20AC;&#x2122;
product may help to ignite this trend. A group of Italian investors for example, is currently looking for potential partners interested to invest in manufacturing bearings and bearing components in any one of the European countries. Target is to install the final part of the manufacturing process (e.g.: finishing or assembly plant) to serve the European market from a within. They try to attract South American or Asian companies to establish a position in Europe, interested in developing niche products for special applications, like large size spherical or tapered roller bearings. A similar idea grows in Germany, where interested parties think about setting up assembly lines for automotive bearings. Imagine a guaranteed quality control, highly reduced transit-times, less logistical paperwork and import taxes to take in account. Combine it with the growing interest of companies in developing economies to produce more in and for the European market. The result might well be that we might see part of the bearing industry return to Europe to offer an alternative and fast distribution channel to their customers for high quality product where specialist know-how is required.
Jake Fisher
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Are failures like these happening in your plant? Lubrication Reliability By implementing a lubrication reliability strategy in your plant will have the effect of eliminating bearing failures and reducing equipment wear - with the effect of improving your equipment reliability. Enluse BV has the knowledge and the product lines to help you implement a lubrication reliability strategy in your plant.
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Using Ultrasound to Improve Lubrication Practices Page: 59
Using Ultrasound to Improve Lubrication Practices Keeping a handle on lubrication is easy, right? All one needs to do is make sure the right lubricant is used in the right amount and at the right time. Not so fast; if only it were that simple.
It has been estimated that 60-90% of all bearing failures are lubrication related1. Bearing failures most often lead to unplanned downtime which can impact production as well as affect all related components around the bearing. Downtime is costly. While the cost varies by incident and by plant, it can add up. Since the most common cause of bearing failure is lubrication related, it’s clear to see that lubrication is serious business. And for the longest time, that “serious business” has been conducted in a way that on its face makes perfect sense—but in fact borders on haphazard. Many technicians, unfortunately, have relied on “preventive”, time-based lubrication alone. That is, every X number of months, the grease gun comes out, and the bearings are lubricated. After all, under-lubrication can be lethal, causing equipment failure, costly repairs and replacements, significant unplanned downtime, and lost profits. But by relying solely on time-based lubrication, or even a combination of planned maintenance and temperature readings to serve as a proxy for lubrication status, one runs the risk of something just as bad, if not worse: over-lubrication. In fact over-lubrication has been reported both anecdotally and in presentations at various conferences to be the primary cause of premature bearing failure. Page: 60
Relying on time-based, periodic lubrication assumes bearings need to be greased at defined time periods. Often this evolves into a well-intentioned guessing game at best. Adding more lubrication to a bearing that is already adequately greased is a real risk. By using ultrasound technology (along with standard practices such as removing old grease and replacing it with new), technicians can combine standard time-based maintenance with condition-based, predictive maintenance, gaining in the process both a clearer picture of what’s really going on and better reliability.
How Ultrasound Works Ultrasonic equipment detects airborne and structureborne ultrasounds normally inaudible to the human ear and electronically “transposes” them into audible signals that a tech can hear through headphones and view on a display panel as decibel [dB] levels. In some instruments, such as the Ultraprobe 15,000, the received sound can also be viewed on a spectral analysis screen. With this information a trained technician can interpret the bearing condition in order to determine what, if any, corrective action is needed. Bearing News • Issue 1
Bearing Lube Example I
Bearing Lube Example I: This is a Time Wave Form
of a recorded ultrasound of a bearing in the process of being lubed. The approximately 1 minute sound file shows the bearing before and after lubrication.
Bearing Lube Example II
Bearing Lube Example II: Another Time Wave Form
of a bearing in the process of being lubed over 13 seconds. Again, a distinct before and after lube can
Bearing Beginning of Over Lube
be seen.
Bearing Beginning of Over Lube: This recording
shows the bearing dB & amplitude increase as more
Drive Bearing Lube History
lube is added and has reached the threshold of over lubrication.
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Drive Bearing Lube History: This chart shows a
trend of decibel readings taken on a drive bearing. The readings are plotted against a baseline dB, a low alarm dB, and a more critical high alarm dB. Ultrasound technology has many advantages. • It can be used in virtually any environment; • Learning to use ultrasound technology is relatively easy; • The technology is relatively inexpensive; • Modern ultrasonic equipment makes it easy to track trends and store historical data; • Ultrasonic technology has proven itself to be extremely reliable in predictive maintenance, saving thousands upon thousands of dollars and hours of lost productivity.
How Ultrasound Produces Better Lubrication Practices Ultrasonic technology helps the lubrication technician take a lot of the guesswork out of lubrication needs. Ultrasound is a localized signal meaning when a sensing probe is applied to a bearing, it will not be affected by “crosstalk” and allows the technician to hear and monitor the condition of each individual bearing. Ultrasound looks at each individually, much the same way medical ultrasound can detect exactly which artery is clogged or which vein is leaking.
over-lubrication, the technician will then apply lubrication, a little at a time, until the dB level drops. Many departments set up their “Condition-Based” lubrication programs by incorporating a two- stage approach. The reliability inspector uses a relatively sophisticated ultrasound instrument to monitor and trend bearings. A report of bearings in need of lubrication is produced. The lube tech then uses a specialized ultrasound instrument that alerts the tech when to stop adding grease. (These instruments can be affixed to a regular grease gun or worn in a holster.) To improve efficiencies, it is a good practice for the technician to note when the equipment was last greased and how much grease was used to calculate roughly how much lubrication is used per week. By using ultrasound to lubricate each and every time, he technician produces historical data that can be used as a guide from previous calculations, helping the department to determine whether the lubrication schedule can be modified, perhaps saving manhours, and whether the manufacturer’s suggested
As an example of ultrasound’s efficacy, consider this. A maintenance manager at a large firm reports that, since adopting ultrasound technology and practicing ultrasound-assisted, condition-based monitoring rather than “running to put out the fire,” his plant has gone from close to 30 rotating equipment failures per year to zero in three years. But how does ultrasound work, exactly, vis-à-vis lubrication? The first step is establishing both a baseline decibel level and a sound sample. This is ideally done when moving through a route for the first time by first comparing dB levels and sound qualities of similar bearings. Anomalies will be easily identified. Once established, each bearing can be trended over time for any changes in either amplitude or sound quality. Generally speaking, when the amplitude of a bearing exceeds 8 dB and there is no difference in the sound quality established at baseline, the bearing needs to be lubricated. To prevent potentially disastrous Page: 62
Bearing News • Issue 1
lubrication amount is accurate (if less is needed, there’s cost-savings potential). And while most of this discussion has focused on the dangers of under and over-lubrication, ultrasound is just as reliable in picking up other potential bearing failure conditions. The technician, using ultrasound, can hear telltale “grinding” sounds and other anomalies, which are often accompanied by an amplitude increase. With regards to lubrication, the advantage of ultrasound is that it is able to isolate bearings and determine their individual needs, thus reducing the possibility that some bearings are too “dry” and prevent others from over lubrication.
Why You Should Begin Using Ultrasound—Today
It is always a daunting proposition to make a new investment in technology. Will it pay off? Will my staff actually have an easy time using it? Is it a flash in the pan or a truly reliable modality that will stand the test of time? While more and more plants are using ultrasound and adopting a predictive and proactive rather than reactive mindset, there are still many that are figuratively using crystal balls and outdated methodologies. The end result is poor reliability, unnecessary man-hours, downtime, and lost productivity and profit. While ultrasound can’t cure all reliability ills, it has proven itself—in a plethora of settings—to be a valuable and powerful diagnostic tool that technicians must add to their toolkits. When it comes to something as important to reliability as lubrication, the question really becomes, “Can you afford not to use ultrasound technology?” Consider the plant that went from close to 30 bearing failures a year before using ultrasound to having no bearing failures for three years once bringing ultrasound into its maintenance arsenal. It’s no coincidence. Ultrasound works. For more information on ultrasound technology and to access valuable resources, including a sound library, presentations, and articles, visit UE Systems’ website at www.uesystems.com. Author: Adrian Messer - UE Systems
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Technical Trends of Oil/Air Lubrication for Steel Making Equipment
Oil/air lubrication system is one of the lubrication methods for rolling bearings installed in steel making equipment. Recently, expansion of the application of this system has been accelerated not only for continuous casting machines but other applications because this system has been recognized by customers to be applicable to various conditions unique to steel making equipment. It has been confirmed that oil/air lubrication applied to continuous casting machines signifi cantly reduces bearing wear. Also it is expected that the oil/air lubrication can contribute to energy saving due to minimum lubricant consumption and smaller starting and operating torque. Based on considerable experience as a diversifi ed bearing manufacturer, JTEKT has developed the optimum oil/air lubrication system for rolling bearings. This paper presents application examples and effectiveness of the oil/ air lubrication system for steel making equipment.
T. MIYACHI & T. URANISHI 1. Introduction
2. Overview of Oil/Air Lubrication
JTEKT began developing oil/air lubrication system in 1990 with the objective of improving the lubrication performance of rolling bearings for steel making equipment. Bearings for steel making equipment are often used in severe environments therefore, as a result of engaging in activities to solve various technical issues relating to oil/air lubrication together with our customers, we have had many successful application cases of bearings on various steel making equipment, including continuous casting machines, hot and cold strip mills. This paper presents application example and effectiveness of oil/air lubrication system for steel making equipment.
2. 1 The Principle of Oil/Air Lubrication
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Figure 1 shows the transfer principle of the oil/ air lubrication. The characteristics are as described below. 1) The oil is supplied into the pipe in droplets and transferred by air flow. 2) The oil supplied to the final lubrication point is in the form of droplets and enabling oil consumption to be kept to a minimum. This system has more promise of producing energy saving effects than other lubrication methods. Bearing News â&#x20AC;˘ Issue 1
Table 1: Characteristics of each component in oil/air lubrication system
Fig. 1: Transfer principle of oil/air lubrication system
Fig. 3: Mixing device
Fig. 2: Basic configuration of oil/air lubrication system
Fig. 4: Distributor in oil/air lubrication system
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3) Moreover, because the air, which transfers the oil, is also supplied to lubrication points, the positive pressure is created inside the bearing and the sealing performance can be improved. In the steel making equipment, this sealing effect contributes signifi cantly to improving bearing lubrication performance (life). 2. 2 Components of the Oil/Air Lubrication System JTEKT’s oil/air lubrication system is basically consisted of the devices shown in Fig. 2. Table 1 describes the functions of each component. With this as our standard confi guration, this oil/air system has a degree of freedom in its design, therefore it can be adjusted to suit the layout of the various steel making equipment.
3. Examples of Application on Various Steel Making Equipment 3. 1 Application on Continuous Casting Machines The bearings applied on the continuous casting machines use a grease lubrication method however, by applying the oil/air lubrication, the following merits can be expected. 1) Longer segment exchange interval due to significant alleviation of corrosion and wear on the bearings 2) Reduced unexpected incident ratio caused by the bearing damage due to significant alleviation of corrosion and wear on bearings 3) Reduced operation cost due to lower lubrication consumption 4) Reduced maintenance cost due to less man-hours required for disassembly and cleaning of bearings
With the grease lubrication, the “breathing”*1 of the seal creates the negative pressure inside the bearing, reducing sealing performance and allowing slab cooling water penetration. Meanwhile, with the oil/ air lubrication, the positive pressure is maintained inside the bearing because of the constant air supply achieving high seal performance. As a result, the penetration of slab cooling water is suppressed and the corrosion is signifi cantly reduced. The wear occurrence is greatly affected by the strength of the oil film by the deterioration of the lubrication condition due to the penetration of cooling water. In the oil/air lubrication, the oil with high extreme-pressure property can be used and combined with stabilization of the lubrication condition due to the abovementioned high sealing performance, the wear is improved significantly. *1 breathing of the seal Pressure fluctuates inside bearing when air expands or contracts due to temperature rising or falling. This fluctuation causes air to go back and forth from inside to outside of bearing. Figures 6 and 7 show the results of the field tests. Figure 6 gives the visual comparison results of the bearing between with the grease lubrication and with the oil/air lubrication. The oil/air lubricated bearing showed no corrosion had occurred, confirming it had excellent sealing performance. Furthermore, the amount of the wear on the outer raceway of the bearing was significantly reduced, as shown in Fig. 7. These field test results make it safe to assume that, in the case of continuous casting machines, the oil/ air lubrication signifi cantly contributes to improve the bearing life.
5) Friendlier on environment due to oil collection The oil/air lubrication is particularly effective for improving the bearing life. Two examples of such improvement are given below. Figure 5 shows the investigation results of the factors for the replacement of the bearings which are operated with the grease lubrication. Approximately 70% of the replacement is caused by the corrosion and the wear. The corrosion is mainly caused by the penetration of slab cooling water into the bearing.
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Fig.5: Factors for replacement of spherical roller bearings
Aside from the oil/air devices, JTEKT, based on our experience as a bearing manufacturer, is involved Bearing News • Issue 1
in the design of oil/air systems including bearing peripheral devices. We engage in the three activities listed below in order to meet the various demands relating to continuous casting machines.
such as a multicoupler allowing several pipes to be attached at one time and an oil fi lling device required for off-line maintenance work.
1) Layout Design Responding to Each Segment Configured The continuous casting machines are confi gured from multiple roll assembly units called â&#x20AC;&#x153;segmentsâ&#x20AC;?. The layout of the rolls within such segments is not completely identical. Moreover, as the rolls for slab continuous casting machines are separated into multiple parts, the several bearings are required to support them in various locations. JTEKT, by developing the oil/air distributor, has established the layout design for the correspondence of the diverse roll confi guration in the segments (Fig. 8).
Oil/air pipe layout example
Fig. 6: Corrosion comparison after field test Fig. 8: Example of layout in segment
3) Design of Oil Supply and Drain Holes in Bearing Housing In the oil/air lubrication, to maintain the lubrication ability of the bearing, it is necessary to secure the
Fig. 7: Wear comparison after field test
2) Enhancement of Units Considering Maintainability In the continuous casting machines, the segments are replaced periodically to maintain their condition. To make segment replacement work easier, JTEKT has also made developments for peripheral devices
Fig. 9: Example of oil supply and drain holes on bearing housing
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sufficient oil level inside the bearing. JTEKT has designed the optimal oil supply and drain holes in the bearing housing (Fig. 9). 3. 2 Application on Hot/Cold Strip Mills In hot and cold strip mills, the rolling bearings are used in not only the strip mill itself, but also the accessory equipment such as guide rolls and transfer devices. The effectiveness of oil/air lubrication is examined for such application. On the strip mill itself, the oil/air lubrication could be applied to the back up roll bearings which are not often replaced. Currently, on the hot strip mills, many back up rolls use the oil fi lm bearing. Moreover, large forced oil system is the main lubrication method, therefore the overall strip mill size becomes large. It will be effective in making equipment more compact if the rolling bearings will be used on the back up rolls and the oil/air lubrication will be adopted. In case of cold strip mills, already many rolling bearings are used on the back up rolls (Fig. 10). The mainstream methods of the lubrication are the forced oil circulation systems and the oil mist, with hardly
Table 2: Comparison of oil/air cosumption for back up roll bearing of
cold strip mill
Apart from examples of application on strip mills themselves, there are also examples of the application with the transfer tables for the hot strip mills. The main objectives of applying the oil/air lubrication method in this case are the improvement of bearing life by better sealing performance and the reduction of motor power consumption due to low torque. Moreover, by collecting the supplied oil, it is possible to minimize equipment maintenance costs by reducing processing costs of the oil discharged around the equipment and so on. In the application example of Fig. 11, as well as constantly monitoring the oil supply condition, the system also collects the oil supplied, therefore providing both reliable
Fig. 10: Back up roll bearing for cold strip mill
any examples of the oil/air lubrication. However, it is feasible that in the future a shift may occur from the oil mist to the oil/air lubrication in order to improve the environment and reduce operation costs. Table 2 gives a comparison between the oil and air consumption of the oil mist and the oil/air lubrication. The table shows that the application of the oil/air lubrication could have an energy saving effect. Page: 68
Fig. 11: Application example for transfer table
Bearing News â&#x20AC;˘ Issue 1
lubrication and easy maintenance. Another example of the oil/air lubrication being applied to the cold strip equipment is on the auxiliary rolls in the strip stand periphery. The spherical roller bearings are widely used for this application. By using the oil/air lubrication, high speed performance is improved compared with the conventional grease lubrication method. And there are expectations that the strip speed can be increased and the maintenance interval can be extended. Regarding the high speed aspect, the results of bench test showed that oil/air lubrication could achieve rotational speed as 400 000 dmN (equivalent to strip speed of 2 800 m/min) (Fig. 12).
lubrication, as the air supply causes oil leakages from the seal area easily, an ejector pump is used to suck the oil/air to prevent the oil leakage.
4. Conclusion JTEKT has studied the effectiveness of the oil/air lubrication for the bearings on the steel making equipment while developing various technologies. As a result, many customers that deal with steel making equipment, especially continuous casting machines, are very satisfied with the benefi ts to be gained. JTEKT, in order to meet the customerâ&#x20AC;&#x2122;s various demands, would like to continue to improve the oil/air lubrication technology and the product appeal from the lubrication method (oil/ air lubrication) and the lubrication target (bearings) point of view. And we would like to develop the oil/ air lubrication system which can further contribute to the stable operation of the equipment and the energy saving.
Fig. 12: Bearing temperature rise results
3. 3 Application on Strip Mills of Nonferrous Metal The same effects as mentioned above can be expected when the oil/air lubrication is applied to strip mills nonferrous metal, for example aluminum and copper rolling mills. The below is an example of how oil/air lubrication responds to the particular requirements of nonferrous metals. Particularly, as the products of the foil strip mills are required to have a lustrous surface fi nish, it is necessary to suppress the friction loss with rolls as much as possible. That is a reason why light contact seals and non-contact seals are sometimes applied to lower the rotational torque of guide rolls, etc. The trade-off, however, is that the lubricant leakages may occur. In the normal oil/air
IDENTIFY AND LABEL IT! The key to ensure that the right oil and grease gets into the right machine, is to allocate for each oil and grease itâ&#x20AC;&#x2122;s own distinct colour. Enluse can start you on the way to implement an effective Lubrication Reliability program by making your wall mounted colour-coded lube chart. We also supply a wide range of labels to identify any lube points in your entire plant.
10 coloured labelling convention wall chart
Dispensing Labels
Fill Point Labels
Coloured and Transparent Grease Guns
Coloured Grease Nipple Protectors
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Spherical Roller & Axial Spherical Roller Bearings The base of ZKL´s production program are the spherical roller and the axial spherical roller bearings. The basic series are completed with other bearing construction groups such as single or double row ball bearings (including the versions with so called angular contact), cylindrical roller bearings, selfaligning bearings, axial ball bearings, tapered roller bearings, spherical plain bearings, bearings with shields, storage units, etc.
Radial bearings The spherical roller bearings belonging to the 222 and 223 in EW33J design series are very interesting. The new types of double row spherical roller bearings produced by the manufacturer were optimized, as regards the internal construction, with the aim to achieve maximum basic dynamic and static loading Page: 71
capacity whilst providing high limit frequency of rotation. The focus is placed on achieving high reliability, the reduction of power losses resulting in lower heat and vibrations. The E design bearing series achieves up to one third higher dynamic load capacity, which allowed a service life extension by 140 %. The bearings differ from the former design by a higher number of rolling units, the use of symmetrical shape with a greater diameter and length, the separation of individual roller units (provided by means of steel pressed cages), and the internal bearing rings without the central guiding flange.
Few years ago, the company started the production of bearings for the Czech Railway Company, and it is homologated in order to supply bearings to the German railways. The non-standard technical solutions include the production of special spherical bearings as per the individual requirements of the clients in order to perform supplies for the first production in Europe and in the USA. ZKL Company also introduced on the market the double row spherical roller bearings for vibrating machines and devices operating in highly demanding conditions.
Goal: high revolution frequency ZKL also introduced a new generation of axial spherical roller bearings with optimized internal construction with the aim to achieve maximum basic dynamic and static loading capacity whilst providing high limit frequency of revolutions. ZKL focuses on achieving high reliability, the reduction of power losses resulting in lower heat development and vibrations. The new innovation level of the axial spherical roller bearings in E design makes the ZKL bearings in EJ design fully replaceable with SKF bearings with metal cage. Great benefit represents the option of the bearing greasing in EJ design with plastic lubricants. Using the E bearing design guarantees that the bearings in the machines have a longer service life, allows material and weight savings, together with a lower consumption. Moreover they show a lower heat emission, achieve higher operating revolutions, are less noisy, and require lower costs for maintenance. Additionally to the double row spherical roller and axial spherical roller bearings, which are a crucial part of the company production program, and in compliance with the requirements of customers and of the whole industrial development, ZKL extended its production to many special bearing types. This includes standardized bearings for special machines and devices, for the automotive industry (for personnel, cargo and special vehicles), the railway industry, in the lifting and handling technology, in the power industry including nuclear, for the machine-tool and forming technology, in mining and metallurgical devices, in the agricultural technology, and many more. For example, special single row ball bearings can be used for the railway vehicle axles. Page: 72
ZKL Group is the largest Czech producer of large-size spherical roller bearings, special and split bearings in Central Europe. With its own Research and Development the company deals with the analyses of trundle inner geometry, the contact stress analysis in respective contact points of bearing components, and tribology issues.ZKL Group during its more than sixty-five year tradition has become a proven and reliable supplier with certification for a variety of industrial companies. Produced range of both standard and special bearings of the ZKL brand name secures the most demanding customer requirements in a wide field of individual industries. Examples of the industries to which ZKL delivers its products are e.g. metallurgy, power engineering, heavy engineering, automotive industry, transportation, mining and raw material processing, agriculture and many more. In all activities the company applies friendly approach to the environment. For more information visit: www.zkl.eu
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World’s Biggest
Bearing Interchange & Application Database-BIAD REVOLUTIONARY:
Interchange & Application Database Developer Mr. Mayur Shah • Bearing Expert at Amcom Enterprise Canada
World biggest Bearing Interchange & Bearing Application Database (BIAD) is currently under development. The Database will be a revolution for bearing selection, finite element analysis and bearing life calculations. A useful tool for all
bearing traders and users worldwide. Page: 82
Bearing News • Issue 1
The database will cover the designations and bearing frequencies information of more than 1000 bearing companies worldwide. Apart from the interchange between the designations, the database will also be able to provide the bearing frequencies information based on given RPM in more than 96 categories /types of bearings. The total data in first phase would be more than (1.8 Million) 1.800.000 for interchange designations and around (0.44 Million) 436.000 for bearing frequencies. Apart from above databases, the BIAD will also be able to simulate the Finite element analysis of bearings which will have a turnaround time (procession time) between 8-16 hours, based on load conditions.
Typical User Scenario: Users of the database will be able to search for any bearing in the database and select the companies for interchange required from 1000 companies, 1) Look and check up for the same bearing designation for Bearing Frequencies and Harmonics Data at a given RPM . 2) Look and search in database for the same bearing designation with respect to its application. Means this particular bearing is used for which applications. 3) User can also look for interchange based on Application area
Application Areas: • • • • • • • • • • • • • • • • • • • • • • • • • • • •
Aerospace Agriculture Cars & light trucks Compressors Construction Electric motors Food & beverage Home Appliances Industrial fans Industrial pumps Industrial transmissions Machine tool Marine Material handling Medical & health care Metals Mining & mineral processing Oil & gas Portable power tools Pulp & paper Racing Railways Skates Solar energy Traditional power Trucks, trailers & buses Two & three wheelers Wind energy
Within the designations interchange of 1000 companies (selectable), the database will be able to loop up for the same bearing designation the bearing frequencies data, application data and finite element analysis along with bearing life calculations. The database is currently under development and testing phase and shall be released during 2014.
The database will cover the designations and bearing frequencies information of more than 1000 bearing companies worldwide. Apart from the interchange between the designations, the database will also be able to provide the bearing frequencies information based on given RPM in more than 96 categories /types of bearings. The total data in first phase would be more than (1.8 Million) 1.800.000 for interchange designations and around (0.44 Million) 436.000 for bearing frequencies. Page: 83
Unique Bearing Design
Proves Successful in Universal Joint Application An innovative bearing cup design concept has demonstrated feasibility by successfully performing in various U.S. Army Field Test applications and environments. The universal joint cups employing this design concept are referred to as Geometrically Contoured (GC) cups for the design approach which structurally modifies the wear surface in order to improve load carrying and reduce wear and friction. They are made from powdered materials alternately known as porous materials. The balls and rollers normally used by these bearings are eliminated. (Fig. 1)
Fig. 1. GC bearing cup (left) compared to standard universal joint bearing cup with needle bearings.
The basic principles involved in the Geometrically Contoured Bearing involve control of wear debris at the micro and macroscopic levels. At the microscopic level, it prevents the actual generation of these wear particles in the first place. This is done by selecting a powdered material with the desired size and shape powders that are chemically compatible with the composition of the lubricant selected. These must promote the proper interactivity with the macroscopically determined contour design. At the macroscopic level, the GC Bearing removes the destructive wear debris that is generated and normally trapped between the contacting surfaces. The removal of the debris significantly reduces surface deterioration and wear. This is done by the
contoured surface which provides pockets for their continuous removal and deposit. Traditional bearing wear control design methodology is based on the use of wrought metal structures, using rollers or ball bearings. The size and shape of the wear debris is generated by the rubbing action of mating surfaces or the rolling stress of the rollers or balls. It is unpredictable and random. The surface wear behavior process for components made from powdered metal materials behaves differently. This results directly from the use of powders whose generated debris particles reflect the powders dimensions, thus differing greatly from the wrought metal debris. The powdered metal wear debris particles, unlike an alloyed material, are largely predictable. A universal joint bearing cup, does not operate simply to reduce friction. It is also required to transmit power, i.e. transmit large torques. In the case of the HMMWV u-joints, these heavy torque loads can be as much as 4 to 5 times a normal automotive load of 445 to 668 N-m (100 to 150 ftlb.).This unique approach to wear control and reduction, while improving performance, eliminates the need for periodic maintenance and replacement of HMWVV (Humvee) universal joints. It reduces unit costs significantly by eliminating the need for roller needles and lubrication channels, in addition to savings in inventory, logistics and maintenance. The concept holds considerable promise for bearings in general. It has been granted six patents and two are pending. Genesee Northern Research LLC is currently working to develop additional applications for this unique bearing technology. Michael F. Pyszczek Genesee Northern Research LLC www.geneseenorthern.com
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Cloud Monitoring
Maintenance
Cloud on the
Maintenance
Cloud on the
All of us know the importance of condition monitoring and the need to perform a good inspection plan that allows us to detect the machine problems on time, based in the P-F curve. To define the inspection periods we can use the risk based inspections principles or reliability programs. But we can increase our condition monitoring program effectiveness by a continuous monitoring program with send of real time information to the cloud, these programs are named Cloud Monitoring. Because the inspection plan is the most critical part of a condition monitoring program, due the uncertainty of the reliability calculus and, mainly, the difficulty of the P-F curve interpretation due the variety of failures of an equipment. We must add the difficult to perform right measuring, either ultrasonic, oil analysis, vibrations analysis, thermography or other techniques, and the difficulty
Fig. 1: The P-F Curve.
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to understand the results. Cloud Monitoring programs avoid these problems, increasing the condition monitoring program effectiveness, providing real time information, logging the measure results continuously and allowing them to be studied and reviewed on-line by specialists.
How can we get it? Cloud Monitoring is based in an electronic acquisition data unit that receives information, continuously, through sensors placed in the equipment that we want to study. There is a wide range of sensors, as the electrical diagnostic (phase angle and current signature) that we can use in electrical motors, accelerometers to detect misalignments and unbalances in mechanical components, ultrasonic to detect micro cracks, surface
Fig.3: Fractal diagnostic of a bearing performance. (from Predictive Systems Engineering Ltd.)
Bearing News â&#x20AC;˘ Issue 1
PREDICTIVE SYSTEMS ENGINEERING SYSTEM AT GLANCE
CLOUD COMPUTING (ALERTS; REPORTS; EXPERT ASISTANCE)
Fig. 2: Cloud Monitoring System (from Predictive Systems Engineering, Ltd.) Page: 94
roughness, lack of lubrication, electric currents or fluids leakages; ultrasounds for leakages, vibrations to detect wears and turbulences or cavitation formations, temperatures or, even, lubricant condition. These sensors provide a continual signal, so to place and adjust them to obtain the maximum effectiveness is easy. An example is the fractal diagram; it is an accumulated diagram obtained in the course of a number of revolutions, the form of the diagram relates a normal operation or abnormalities. The acquisition data unit transforms the signals from the sensor, using specific software, and send them to a web site where we can see, real-time, the results of the measurements and the historical data, we can review them anytime and anywhere, only visiting a web page; these results can be easily processed using any spreadsheet. We can program the system to send the alarm signals, by e-mail or SMS, if it reaches some limits. This methodology is suitable to any industry and any location, because it doesn’t require a complex installation, it doesn’t need maintenance and low installation cost.
Application: This technology is easily customizable so it is suitable for every applications, as Power Industry (i.e. fossil power, turbines, wind turbines,…), Process industry (including chemical industry), Mining industry, Oil & Gas, Pulp & Paper, Steel industry, etc. The combination of different predictive techniques allows monitoring all type of problems, mainly in rotatory equipment. So, if we study a compressor we can control all its failure modes by a combination of spectral analysis of motor current and phase angle, ultrasounds, temperatures and vibration analysis and spectral analysis of voltage; the system performs an early discovery of minor disturbances (left side of the P-F curve) that allows to plan and schedule the maintenance task and acquires spare parts and tools on time, it does cloud monitoring a useful tool for a just-in-time policy and reduces both maintenance and inventory costs.
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Even, if the failure is imminent, it allows us to take immediate actions or to perform autonomous actions. Cloud monitoring is also suitable for safety, especially in ATEX environments, by connecting oxygen, toxic or inflammable gas detectors that allows performing a continuous environment control reducing risks and increasing the effectiveness by eliminating human operated controls. The monitoring system also can perform an alarm and/or operate and emergency system (i.e. ventilation fans) if the level of dangerous gases increase dramatically.
Main benefits Cloud monitoring is, mainly, a tool to prolong the life cycle of the equipment and to reduce the maintenance costs. It provides benefits to the asset management plan as: • Risk mitigation and cost reduction by elimination of unexpected breakdowns. • Ensure the spare parts, tools and technicians are available to perform the maintenance tasks by detecting minor disturbances. • Increasing the equipment uptime and availability. • Avoid false alarms. • Automate evaluation of failure root causes. • Prediction of residual life cycle that support logistic. • Elimination of emergency shutdown and reduction of secondary damage. • Allow joining data with SCADA system or CMMS.
About the Author: Jorge Asiain Sastre. Mechanical Engineer, Master in Automotive Engineering and Certificate in Asset Management Principles. CEO of Alter Evo Ingenieros (www.alterevo.es) and Professor of Electro-Mechanical and Materials Department in the School of Engineering of the Universidad Europea de Madrid (www.uem.es)
Bearing News • Issue 1
A closer look at the coming evolutions of the Chinese Bearing Market. Page: 96
Bearing News â&#x20AC;˘ Issue 1
Whatâ&#x20AC;&#x2122;s Happening in the
Chinese
Bearing Industry Page: 97
What’s Happening in the
Chinese
Bearing Industry
Bearings are basic components of most industrial equipment. Around 80% of the world bearing market belongs to 8 important multinational industries. Main production units are situated in Germany, Sweden, China, Japan and the US. During the past decade and after several years of development, China’s bearing industry has known an exponential growth. They obtained an important position in the worldwide ranking, with a turnover of over $20 billion. China’s bearing production can roughly be situated in the provinces of Shanghai, Shandong, Zhejiang and Jiangsu, where you can find about 80% of the nationwide bearing industry.
Nevertheless, as so many others, this industry has not seen the best of times during the year 2012. Recess in global industry and demand have caused the first half year of 2012 to be an extremely negative half-year period. Worldwide economical crisis resulted in increasing stocks and decreasing profits. Some of the larger manufacturers saw their losses go to 35% and more. Total national gross profit over this period dropped to 41.87%.
number of barriers. Not only do they have to deal with a tough price competition due to the large number of mainly smaller companies, they also realise the need for better production technology and automation. Research and development, for example to improve the quality of produced steel, lubrication applications, product specialisation, are not easily accessible, except for the main companies of the industry.
Most factories kept their production up the trusted levels and faced a sudden overproduction of many of standard quality series. Stocks in general increased with over 11%. As a direct result, many companies saw a significant drop in their prices, lowering the general profit margins, in an attempt to lower their inventories.
The National Grinding Machine Tools Producers also put their views in the open. Their main market is the bearing industry itself and they follow the developments with close interest. The organisation also agrees that structural changes are at hand. The markets for cheap, mass production bearings are saturated. Further expansion can only lie in developing medium and large size bearings of high quality. Whereas now the main target markets are situated in automotive and appliance, this would mean an expansion to machine tooling, alternative energy, mining and off-road industry, aerospace, etc., both on national and on international playfields.
Numerous national players in the Chinese bearing industry are taking measures to strengthen their position in the domestic and international markets in order to increase further expansion abroad. Many manufacturers in China need to overcome a Page: 98
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Surely, this involves the loss of one of the main market advantages of the Chinese industry: low production costs and thus low prices. On top of that, the large number of small manufacturers keeps price competition at high levels. Increasing demand for higher quality means investments have to be made to produce higher quality bearings for specific applications. They realise that the average technology level has to be upgraded. However, many companies still lack the possibilities to invest in experience, skills, machinery and other resources.
position in the market as fastest growing sector, preceding India, draws on the support of the Chinese government. To stabilise the steel market, structural adjustments are called for. Price control, increased investment possibilities, availability of credit, all will have supporting effects. Many European manufacturers are already taking the opportunities to invest in Asia, in particular China and India. To ensure this trend for the future, government policy measurements alone will not be enough.
Chinese bearing manufacturers are aiming for high-tech, high-margin and high-precision bearings
Main issue to resolve by the industry itself is that modern grinding machines of high quality are still too expensive to import for many smaller companies. Despite the fact that the Chinese bearing factories mastered the production of over 70 thousand types
The need to keep and improve their
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and sizes, their products are poorly represented in the market of high-tech, high-precision and highmargin bearings. Chinese experts tend to believe that the national bearing industry will be able to take a significant position in the world market through the establishment of one of the most high-tech and capital-intensive industries in China. To reach this goal, several recommendations and suggestions have been made by The Association of Chinese Bearing Industry and the related industrial institutes and organizations. These have to trigger the transition into producing high-tech, high-margin and high-precision bearings, for which demand continues to grow worldwide. Among these recommendations are: • The transition to multi-place machines for the forging of bearing rings with diameters ranging from 50 mm to 300 mm; • Use of induction heating for forging, which allows accurate temperature control and maintains a record of process parameters in real time;
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• Use of CNC machining centres for machining parts with diameters up to 300 mm in the production lines. • Ensure stability in the production process of the parts and rolling elements by using highprecision machine tools; • Implement high-speed and co-grinding, for the grinding of bearing parts • For large amounts of processing, implement the use of auxiliary equipment for automatic line connection; depending on the type, size and requirements of the product; • To develop proper assembly lines for tapered roller bearings. • Actively develop ongoing assembly of bearings; • Facilitate the introduction of new generation, more efficient high-speed electric spindles, to assure environmentally friendly and low-loss lubrication in production. Chinese industry has a challenging task, on short term and on the longer term, if they want to keep their bearing export on competitive levels. To do this, not only the machinery will have to be updated to
Bearing News • Issue 1
higher quality standards; research and development will need a boost, investments in know-how of production processes and closer integration with main target industries should at the same time be considered. If this will also lead to the disappearance of some of the smaller businesses, remains to be seen. One of the recommendations made by the Chinese Bearing Industry Association already was to have (smaller) companies work together in investments and innovation, with the support of national politics, to achieve the realisation of these goals. In the later part of 2012, follow-up and progress on these issues and others was discussed during a meeting between construction machinery and bearings industry. On behalf of the China Bearing Industry Association, Mr. Lu Gang had a speech about current development of bearing industry, transformation and upgrading, technology and quality progress, and how to meet the needs of users. He required enterprises to take a positive attitude to face the current situation, complete the process and quality improvement, make technical preparation, study the product
trend of main equipment enterprises, research the technology trend of bearings and main equipments home and abroad, collect potential energy for the development of enterprises. Mr. Ban Yungang, senior engineer of FuWa Heavy Industry expressed the need to discuss specific technical questions with bearing enterprises in view of further technological improvement and development. Main points of interest were the efficiency of pulley bearings, installation tolerances, and the effects of temperature on the lubrication.
Maintaining position in the world wide bearing market. Fact is that competition stays hard, new technologies and know-how are expensive, and many companies are still overcoming the financial problems of a worldwide economical drop. Larger players will have a significant advantage in catching up with the needs of the moment. Still, realising the problem is half the solution, and with the help of foreign investments, China remains a competitive player in the bearing market. They have now to realise the
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breakthrough into the 21st century by developing more specialised, application-specific, higher quality bearings. A challenge for sure. An NSK announcement at the end of 2012 of their plans to start to begin South Korean production of low-cost, high-precision bearings, could already be a sign that other important bearing manufacturers are starting to anticipate on these Chinese evolutions. With a production cost at 80% of that in Japan, they hope to challenge the growing competition with bearings comparable in quality to Japanese production, made from lower priced steel. The company estimates that world-wide demand for automobile-transmission systems will increase at least 30% by 2019. Recent developments through 2013 also prove that several companies have indeed made the necessary planning and/or investments. We see new industries developing high-tech machinery to suit the bearing producers in their need to specialise. Factories come up with long term investment plans, production of spindle bearings is growing, and first signs of specialisation start to appear. Apparently, China is not hesitating to put theory into good practice, in their effort to stay ahead of upcoming countries like India and others in the region.
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