First published in Bolted #2 2017.
SAFETY. The JFE Steel Corporation’s West Japan Works is one of the largest and most advanced steel mills in the world. Like all steel plants, the operating conditions are exceptionally demanding on machines and equipment, and potentially hazardous for personnel – especially the hot rolling mill, where molten steel is flattened and stretched into thin sheets. The temperature of the steel will reach at least 450°C (842°F).
Until recently, the fasteners that connected the decelerators and pinion stands on the hot rolling mill, were tightened using a 300-kg weight, which was suspended from the ceiling via a crane. The weight would be pulled from a makeshift scaffold, before letting it hit the wrench like a hammer. Overall, the procedure involved five people: three to pull the weight, one to fasten the wrench, and one to operate the crane. It took an hour to tighten each bolt, and the multiple safety risks for the personnel involved were considerable.
Switching to Superbolt multi-jack tensioners has turned one of the riskiest maintenance tasks in the plant into one of the safest. Each connection can now be secured by one person in just 15 minutes. With eight bolts on each mounted application, the overall reduction in downtime and increase in productivity is significant.
In fact, Superbolt multi-jack tensioners have proven so successful that they have been implemented in JFE Steel’s other hot rolling mills in Fukuyama and Chita.
First published in Bolted #2 2017.
As prices continue to be down in the steel and metals industries, developing a successful partnership with a major customer can go a long way to securing profitability for a small business. The Danish company Viggo Bendz is based in Høng, on the west coast of Sjælland, the largest and easternmost of Denmark’s islands. The company employs eight people and delivers solutions and equipment for crushing, demolition and sorting. Poul Erik Jakobsen is owner and CEO. He took over the running of the business in 2006, just three years after it was formed. “When I started,” he says, “we were mainly dealing with excavators. Then one day I had a realization that the company would not survive in the future if we only sold certain kinds of bolts. We needed to expand our range in order to compete.”
The ability to anticipate change has been important to Viggo Bendz from the outset. Currently, one half of their business is parts for excavators such as teeth, buckets, cutting edges, hydraulic hammers and grabs. However, the other 50 per cent of their turnover comes from machines and complete plants for the environment and recycling business. Contractors are the main users of the Expander System bolts that they distribute, yet they have been well aware of Expander System’s potential in the recycling business, where Stena Recycling is one of the main players.
Located in five markets – Sweden, Denmark, Norway, Finland and Poland – Stena Recycling is committed to sustainability in their business practice. The two companies have had a long relationship, with Viggo Bendz supplying standard bolts for over a decade. However, they recently offered Stena Recycling the Expander System to test on their so-called ‘orange peel grabs’ (see picture). With this kind of machinery subject to wear and tear through constant and prolonged use, Stena Recycling have now taken the opportunity to employ a solution that will reduce the need for maintenance and will increase the safety and machine life cycle, Jakobsen believes. He says that, “By introducing the Expander System, Stena Recycling is saving money. Because of the quality, it represents a long-term investment for them. The industry is tough at the moment, due to the market price for steel and metals. Longer machine life obviously means both greater sustainability and profitability.”
The importance of supplying a sustainable solution to today’s market is something that Viggo Bendz knows well. The waste recycling business is one segment that is at the forefront of sustainable work practices, as companies increasingly focus on resource management and turning waste into new raw materials. More organizations are looking toward employing technology that enables this process and fits in with their sustainability strategy. Being able to supply a pivot solution that improves the durability and longevity of moving mechanical parts, means contributing something vital to the business of customers and to the environment as a whole.
As for being a smaller independent company in the current business climate, there are significant advantages according to Jakobsen. “We are focusing on quality products, which means that it is not always the cheapest solution for the customer. It is vital to us that we provide excellent service. Because of our size, we can be flexible and change direction quickly to help our customers and our own business if we need to.”
Being a distributor for the Expander System suits Viggo Bendz’ business model. They have a market presence all over Denmark, covering industries such as construction, mineral and scrap recycling. Currently Expander System accounts for around 200,000 euros of their annual turnover. Like almost every modern business, raising the company’s profile nationally has meant increasing their online presence. “We are focusing a lot on social media now,” continues Jakobsen. “Once a week we try to upload a case story to Facebook. Every time we upload an Expander System case, we get a couple of new customers. This is something that we must continue to use to our advantage.”
With pricing being crucial to compete succesfully in the market for the foreseeable future, Viggo Bendz is both positive and pragmatic about its current position. “Yes, it is all about price,” Jakobsen says. “However, with Expander System we do not have so many direct competitors. Being able to offer reliable, long-term solutions gives us the chance to target customers in waste recycling and other sustainable businesses. Even travelling around locally, you see how many grabs and different machinery are in operation. This potential is exciting for us.”
FACTS: THE SOLUTION
CLIENT: Viggo Bendz.
END CUSTOMER: Stena Recycling.
PROJECT: To provide solution for pivot wear on grab machinery.
NORD-LOCK GROUP PRODUCT: The Expander System.
The Expander System: cost-effective and sustainable
With its focus on sustainability and cost-efficiency, the waste recycling industry is tailor-made for long-term bolting solutions. Grab machines work constantly and repetitively, collecting, sorting and distributing waste of all kinds. Naturally, they develop pivot wear over time. Standard bolt fittings and joints become worn, leading to enforced machine reparations, which in turn lead to downtime.
The difference with the Expander System is that it is installed directly into the existing mounting on the machines, and involves a simple process which avoids welding and line boring. As well as being cost-effective in terms of longer machine life and increased uptime, it also adheres to sustainability principles, requiring less equipment and repeated repairs. By prolonging the lifetime on cylinder rod ends and moving mechanical parts, Expander System contributes to the increased safety and productivity of hard-working grab machinery.
The Expander System is installed on over 10,000 types of machines, covering more than 80,000 different pivot applications so far. The most common industries where they are being used are construction, manufacturing, oil & gas, mining, marine and agriculture.
Within waste recycling, The Expander System is not the only Nord-Lock Group solution to be hard at work. Several companies currently employ Nord-Lock Group products, including large UK waste services company Biffa. They have been using the wheel nuts on all their Mercedes trucks since 2012, having found them safer, more reliable and cheaper to source than standard locking wheel nuts.
First published in Bolted #2 2017.
Q: Can I use Nord-Lock stainless steel washers with steel bolts?
A: You can, as there is no difference in thread pitch between steel and stainless steel bolts. However, it is always best to use the same material for all parts of the joint. If you use a stainless steel washer together with high-strength fasteners of grade 10.9 or 12.9, you might deform the washers. These are only surface-hardened, and with a very high pre-load, the softer inside might incur “plastic deformation”. Steel bolts of grade 8.8 or lower might work in many applications, since the mechanical strength of grade 8.8 is similar to the one for stainless steel washers.
Another important aspect to consider when designing a bolted joint, including stainless steel washers and steel bolts, is corrosion, especially so-called galvanic corrosion, which may reduce the product life dramatically. Galvanic corrosion damage is induced when two dissimilar materials are coupled in an electrolyte. When a galvanic couple forms, one of the metals becomes the anode and corrodes faster than it would by itself. The other material becomes the cathode and corrodes slower than it would alone. Nord-Lock steel washers with Delta Protekt coating use the principle of controlled galvanic corrosion. Zinc material in this coating protects the cathode (the washer steel material).
First published in Bolted #2 2017.
SUPERBOLT has its origins in the US steel industry and has been providing a wide range of bolting innovations for a variety of industries since the 1970s. Its ongoing success within Nord-Lock Group’s portfolio is based on a knowledge of customer challenges and a commitment to supplying practical solutions to the market.
Launched in December 2016, HyFit and VersaTite tensioners continue Superbolt’s tradition of versatility. Superbolt multi-jackbolt tensioners have been on the market since 1984, allowing bolted joints to be tightened mechanically, without specialized skills or heavy tooling. HyFit is hydraulically actuated, while VersaTite uses both mechanical and hydraulic tightening. Easy to fit and remove, they are offering safe and efficient operations and increased uptime to customers worldwide.
“To have both mechanical and hydraulic options is a huge advantage in many industries,” says Steve Brown, Global Product Manager, Expansion Bolts. “HyFit is ideally suited for use on high-speed couplings on gas and steam turbines, and on marine propulsion drives. Traditionally fitted bolts must have a close tolerance. The fitting and removal of these are often problematic and can lead to damage of the couplings and costly downtime for customers.”
Both HyFit and EzFit (previously named EB, mechanical Expansion Bolt), are designed to offer a simple easy-to-fit solution that, once tightened, will provide a long and reliable lifespan.
VersaTite, as the name suggests, is a versatile tensioner that allows customers the flexibility of both hydraulic and mechanical tensioning and removal. Combining the speed of hydraulic tensioners and the accuracy of the Superbolt mechanical variant, it has been developed to improve operations in several industries since its launch at the Power-Gen International show in December 2016. “This type of ‘all-in-one’ technology represents the next step for Nord-Lock Group in terms of providing the market with a new generation of bolting solutions,” Brown says.
First published in Bolted #2 2017.
CUSTOMER: SUBSEA INNOVATION, UNITED KINGDOM
APPLICATION: OFFSHORE STRUCTURES
BOLTIGHT PRODUCTS: 14 UNITS OF M120 AND 10 UNITS OF M150 BOLT TENSIONERS
PROJECT: STRUCTURAL PIPELINE REPAIR CLAMPS FOR EPRS
Boltight solutions continue to be employed on more and more specialist applications in a multitude of markets worldwide. One example of this is Subsea Innovation, a UK-based company that serves the offshore industry. This company has been supplying subsea structures for over 25 years, and recently secured a multi-million-pound contract in Australia.
For this project, Boltight has supplied tailormade bolt tensioning equipment for structural split repair clamps. These are part of the Emergency Pipeline Repair System (EPRS) for gas pipelines off the north and northwest coasts of Australia. Boltight designed and produced two sizes of tensioner to suit M120 and M150 bolts. These tensioners are used to tighten the main bolts located around the clamp body and are activated remotely using a hydraulic control system.
The tensioners have been designed as per Subsea Innovation’s specifications, with Boltight adding its experience of supplying such solutions. The long-stroke, double-acting design means that they operate in both directions, so they can be reset without recovery to the surface. They are ideally suited for subsea use.
Boltight worked with Subsea Innovation to agree on testing and operational specifications, ensuring that the applied bolt tension is correct and that the overall EPRS system operates properly when called upon. All parts were supplied by Boltight within a strict delivery window.
The EPRS in Australia will act as a contingency if the main lines transporting gas need to be repaired.
First published in Bolted #2 2017.
Any machine with moving pivots will eventually experience lug wear. The most common are applications subjected to heavy loads and vibrations, such as mining and construction equipment. Other common applications include industrial presses, wind turbines and moveable bridges. Any moving pivot in just about any application will experience lug wear at some point – the higher the demands, the faster the onset. When it happens, it will lead to a loss of precision and control.
There are three main reasons why lug wear is inevitable when using conventional straight pins:
The most common solution to lug wear is to repair the lugs with welding and line boring. The first step of this is to unload the pivot and dismount the pin. Then the line boring equipment needs to be lined up and “mounted” to the equipment. The worn lugs are rebored, filled up with weld, and finally rebored with a fine cut to the original diameter and tolerance. After removing the line boring equipment and repainting the lugs, a new replacement pin is installed. This whole process can take anywhere from a few hours to a few days, depending on the size and complexity of the installation. During this time, the machine is inoperable.
Despite the time and costs, this method is generally accepted as unavoidable. “It’s just something everybody does because everybody else does it, and they’re not even aware that there is another way,” says Jonny Wiberg, development & research engineer, Expander System. “Repairs are just accepted, and people don’t even look for another solution.”
Over the years, engineers have searched for better solutions to the lug wear problem. None of the previous attempts has proven universally effective. One option is to use a pin that fits as tightly as possible into the lug’s holes, practically eliminating the play between the two, and ensuring the best possible pressure distribution for a straight pin. Not only does this make the pivot expensive and the pin difficult to mount; over time, the lug hole will expand anyway.
Using the temperature method, the pin is frozen and then allowed to get warmer and expand once installed, creating a perfect press fit in the lugs. Tolerances of both pin and lugs need to be exceptionally tight – down to some hundredth of a millimetre, or tolerance grade 6. This significantly increases the cost of the pivot. Pivots with frozen axles are often considered maintenance-free, but they are impossible to maintain, as the axle can’t be removed.
Another solution is to improve the strength of the lugs with bushings. However, this will only prolong the onset of lug wear, and will not eliminate the problem completely, as the bushings need to be replaced several times during the equipment’s lifetime.
None of these solutions will completely remove the need for costly and time-consuming lug repairs. In contrast, the Expander System can potentially eliminate lug wear once and for all. It works by using a pin with tapered ends and expanding sleeves on each side. When it is installed, the sleeves expand radially, so that they fill the lug to create an exact press fit.
As the sleeves of the Expander System expand into the lug, they can take up unevenness or deformation, eliminating the need for welding and line boring. This significantly reduces the time needed for installation as well as the machine downtime. The most time-consuming process for installing the Expander System is the dismantling and removal of the original pin – a process that is also necessary before welding and line boring. In a recent example, the Swedish Expander System company was asked to do a cost comparison for a 70-millimetres axle. Considering the cost of the expansion bolt, the cost of pin removal and installation, plus the income loss from downtime, the total cost of the Expander System solution was calculated at around 500 euros. A conventional pin was around a third of the purchase price, while the costs of removal and installation remained the same. The time needed for line boring, in addition to the time taken for the transportation of line boring equipment, and the loss of income from significantly higher downtime, all contributed to a total cost estimation of over 2,300 euros.
Using the Expander System will not totally eliminate the need for boring, but for the welding process. It will eliminate the lug wear problem for the lifetime of that pivot. Using conventional pins, lug wear would inevitably return and the repair procedure would need to be repeated. In a typical application, this happens three to four times during a machine’s lifetime or every 3,000 or 4,000 hours. This means that the cost savings can amount to thousands of euros – for each machine.
How a rusty nail led to an award-winning innovation
In the 1950s, twin brothers Everth and Gerhard Svensson were building roads throughout Sweden, and becoming increasingly frustrated with the downtime and repairs caused by lug wear. One day, when a pivot pin was coming loose, Everth improvised and took an old rusty nail to fix the pin in the lug hole.
As a temporary solution, the rusty nail worked quite well and inspired Everth to develop the Expander System. For many years, the twin brothers used expander products as they continued to build roads. However, it wasn’t until 1986, when Everth’s son Roger realized the ingenuity of his father’s solution, that the concept was patented and the company Expander System Sweden AB was founded. In 1987, the Swedish Minister of Industry awarded the Expander System with the Innovation Development Award, in memory of Alfred Nobel. Today, the Expander System is installed in millions of machine joints globally.
Getting over 6,000 extra operating hours
Lug wear is a widespread problem for machinery pivots. It has cost users of machinery lots of money through the years – for repairs as well as for downtime. This is something that the Expander System can put an end to.
The Expander System will in most cases cost more than a traditional straight pin. But when all costs are fully calculated, including the time and costs associated with welding and line boring, and the loss of production due to downtime, the Expander System will prove to be significantly more cost-effective. The full extent of savings depends on many different variables, but it is fair to say that the higher the frequency of lug wear and the higher the costs of downtime, the greater the potential savings.
For Swedish construction machine supplier Maskinia AB, every minute of downtime for machine repairs means lost income. This is why they have been using the Expander System since 1999.
Recently, an excavator was brought in for repairs after 3,700 hours of operation. Using the Expander System, the boom mounting axle was replaced in just 6 hours. By contrast, the repair would have taken 3–4 days if it was replaced by a traditional pin, using the common method of welding and line boring.
Lars Malmén, Aftermarket Manager at Maskinia, says that, “The Expander System admittedly costs more than a traditional axle, but if you include repair time and stoppages with loss of income, the difference is clearly to the advantage of the Expander System. If you add the fact that Expander offers a 10-year function warranty, you can count on at least 10,000 problem-free operating hours – compared with the 3,700 that is regarded as normal for a traditional pin.”
The 2017 September issue of Bolted magazine is available now! As with every issue we have filled the magazine with interesting cases and insights from the world of bolting.
In this edition, our theme article focus on lug wear which is a common issue for pivot joints. But why does it occur, what solutions exist and do they solve the root cause of the problem?
You will find out more about Expander System in our customer case, where we visited Danish company Viggo Benz who delivers solutions and equipment for crushing, demolition and sorting.
Also, see how Nord-Lock washers secure containers that transport radioactive substances, where there is no room for equipment failure.
Last but not least, don’t miss out on how and why we now offer lifetime warranty throughout our product range.
Want to receive your complimentary copy of the Bolted magazine? Subscribe here now!
First published in Bolted #2 2015.
A: The fatigue capacity of a bolted joint is very small, as compared to its static capacity. To improve fatigue resistance, designers can increase the thread capacity and decrease the alternating stresses at the threads.
To increase the thread capacity, it is recommended to use a rolled thread instead of a cutting process. To increase the bolted joint capacity, utilize multiple smaller fasteners instead of a single larger fastener.
The capacity is also increased by using an improved connector, such as a Superbolt MJT (Multi-Jackbolt Fastener) or Flexnut, which improves the load distribution in the threads and adds elasticity to the bolted joint.
The best way to improve fatigue resistance is to reduce the alternating stresses at the threads. There are three main ways of doing this: Assembly design, assembly tightening, and assembly security.
The assembly design process provides an opportunity for improvement of the load distribution on bolted joints and to reduce the level of external stresses supported by each joint. To facilitate that, keep these principals in mind:
1. Use the highest possible preload
2. Minimize the bolt to load eccentricity
3. Use the largest possible contact surfaces
4. Use the largest possible clamping lengths
5. In most cases, use a preload higher than the working load
Other assembly design options include the use of necked-down studs or bolts, and the use of elastic washers, which counter the effects of relaxation, creeping, and thermal differential elongation.
With regard to assembly tightening, achieving the necessary preload is the main factor in reducing alternating stresses. It is recommended to use calibrated tools with high accuracy. It is also recommended to use a proper lubricant to achieve preload accuracy, and to reduce the risk of seizing. A suitable tightening sequence should be used to mitigate the risk of un-evenly loaded bolts and to ensure overall bolted joint integrity.
Regarding assembly security, it is recommended to secure the bolted joint against loss of preload. Further, secure the assembly against environmental effects, such as corrosion that could initiate a fatigue crack. This may be done through the selection of suitable materials and/or coatings for parts and fasteners.