BOLTED

Een discussieplatform voor het
optimaliseren van het borgen van boutverbindingen

Nord-Lock Group keeps the railway industry on track

First published in Bolted #1 2017.

Starting with ROLLING STOCK some 20 years ago, Nord-Lock wedge-locking washers are now found in all safety-related areas of the railway industry, such as bogies, coupling devices, brake systems, rail dampers, housing, and many more.

Nord-Lock washers ensure the functionality of bolted joints, even at the highest levels of vibration caused by rail traffic. One example is in railway switches, highly complex structures that must be used as long as possible with minimal maintenance, while exposed to the elements and to considerable stress.

Nord-Lock steel construction washers (NLSC) help railway companies avoid operational downtime, thus saving money. When renovating or replacing old bridges, small temporary bridges are assembled on site with a bolt preload of 100 percent to achieve secure bolted joints. However, these bolt connections can only be used once. Using Nord-Lock washers, the preload can be reduced.

Overhead line masts and signal masts must cope with severe dynamic loads caused by passing trains. Given the large number of masts, reliable bolt connections are crucial to reducing maintenance costs. With their special geometry, Nord-Lock X-series washers increase security, including on bolted joints with short clamp length, as well as in softer materials.

A recent application for the Nord-Lock X-series is noise-absorbing walls, which cope with extreme vibrations from passing trains. In Germany alone, 3,000 km of noise-absorbing walls are to be installed by 2030. A combination of concrete bolts and X-series washers is used to attach noise-absorbing barriers on existing bridge decks, many of which were not designed for noise barriers.

 

Video: Nord-Lock washers Junker vibration test

Video: Multifunctional Nord-Lock X-series washers

More: Nord-Lock Group solutions in the Railway industry

How the Expander System Group came to life and evolved

12 juli 2017
reactie

Tekst: Ulf Wiman

Foto: Stefan Jerrevång

The Expander System Group, the latest Nord-Lock Group acquisition, shares many customers with its new parent company and their history is remarkably similar. Founded in a remote part of Sweden, evolving from an innovative idea. In Expander’s case, a rusty nail was transformed into market-leading pivot technology. Founder and former owner Roger Svensson tells the story.

First published in Bolted #1 2017.

What is Expander’s business?
“Our patented Expander System is a state-of-the-art, cost-effective solution that permanently ends pivot wear in construction, forestry, mining and other heavy machinery. Fitted in the pivot, a double-locking expanding pivot pin assembly increases stability and safety and eliminates welding and line boring of worn-out pivot lug ears. The system has been field-tested for over 50,000 hours without failure.”

How did the company start?

“My father, Everth, and his twin brother Gerhard, did road work in the 1950s, starting out with one bulldozer. Machinery joints and pivots are prone to wear and tear, leading to expensive downtime and repairs, but they came up with a makeshift solution, knocking a rusty nail into the lughole to eliminate the gap. This worked surprisingly well, which inspired them to start developing the technology.”

When did you get involved?
“I learned about their ideas and immediately saw the potential. My father and I founded the company in 1986. At quite an early stage we got involved with computer engineers in the development of a parameter-controlled CAD system. This is an invaluable tool, as each Expander System is custom made to fit customer-specific applications.

In the 1990s we expanded geographically. North America is a huge market and in 1997 I moved there to get a business foothold. The launch was successful and in 2006 we established our own production facility in North America.”

Why did you sell the company?
“Enormous markets, such as South America, are starting to develop, but you need local presence. It was about either setting up my own network or selling to someone that already had a global subsidiary and distributor network. We already collaborated with Nord-Lock and after several discussions with Ola Ringdahl, CEO, Nord-Lock Group, I was sure that the Nord-Lock Group was a perfect fit.”

What does Expander bring to the Nord-Lock Group?

“There has been a major change in how people view repair and maintenance, which makes the market potential for the Expander System huge. We’ve only scratched the surface.

Also, we and the Nord-Lock Group have often shared customers, but solved different problems. Bringing our solutions together – and cross-fertilising them – will make our portfolio and product range so much stronger, which will benefit the customers.”

Facts: Roger Svensson
Role: Founder and former CEO, Expander System Group.
Age: 56.
Lives: Sedona, Arizona, USA.
Background: Studied Economics/Political Science at UCLA (double major). Member of the UCLA team that won the prestigious NCAA swimming championships in 1982. Held a couple of positions with other companies before starting Expander with his father in 1986. “I have always been an entrepreneur.”
Passion: Music: sings, plays guitar and writes his own songs. Is currently working on his debut album. Also paints and likes to write.

Torquing or tensioning – that is the question

6 juli 2017
reactie

Tekst: Nic Townsend

Foto: Nord-Lock ILLUSTRATIONS: Dan Hambe

Which is the best method for controlled tightening of a bolted joint?
Bolted plays hydraulic torquing off against hydraulic tensioning.
And the winner is…

First published in Bolted #1 2017.

Nearly everyone has tightened a nut at some point in their lives and can understand the basic concept of torquing. It is the oldest, simplest, and for most non-engineers, the only method of tightening bolted joints.

Whether by hand or hydraulics, compared to other methods, simple to understand basics of torquing make it overall a far more cost-effective option. This does not dismiss the need for training and understanding of the key factors in torque tightening.

“With one torque wrench and a range of sockets, you can tighten quite a wide range of nuts and bolt sizes,” says Robert Noble, Technical Director, Asset 55. “It offers quite a bit of flexibility, and it’s easy to explain to a technician how to use torque equipment.”

Given that it will be effective in the majority of applications, it is clear why it is often the default first choice.

Hydraulic torquing has its limitations, particularly friction, which Noble labels, “the number one enemy of torque.” Typically, friction accounts for 90 percent of the torque applied to the nut, which means only a small portion of torque will translate into useful bolt load. Because torquing is an indirect way of loading, it is difficult to predict the exact bolt load. Many factors should be taken into consideration, in particular the lubricant used, the need to avoid possible contamination and a good surface finish on the nut bearing surfaces. This must be overcome to ensure reasonable accuracy when using torque to produce preload and can be a significant disadvantage in critical joints.

Noble stresses that with good procedures, calibrated equipment and competent personnel, torque tightening can be used successfully on most joints. Much is made of bolt scatter, which will see the achieved preload on an individual bolt within +/– 25 percent of target, but on a flange with multiple bolts the usual result is to achieve an average bolt load within close range of target (providing good practice is followed and the coefficient of friction is assessed). “This is accurate enough for the majority of gasketed flange joints, so torque remains a very viable technique,” Noble says.

Hydraulic tensioning began in the 1970s, pioneered in part by British engineer Fred Heaton, who would go on to found companies Hydratight and Boltight. Over the next 20 years it gradually became more common and is now becoming the preferred method for tightening large critical joints in many industries, such as oil and gas, wind, subsea, or power generation.

Compared to hydraulic torquing, it is a more complex procedure that involves more specialised equipment. In certain applications tensioning can offer greater accuracy and control, as well as speed of assembly. It is particularly advantageous on flanges with multiple bolts. Using conventional torque, each bolt is tightened one-by-one in a pattern, which must be applied carefully to avoid the risk of putting too much load on one side of the gasket or flange. By attaching multiple tensioners, it is possible to tighten a number of bolts simultaneously for an even compression of the gasket.

“This is essentially where hydraulic tensioning came from,” says Nitin Patel, Projects and Commercial Manager, Boltight. “It allowed people to control the clamping force and if you could do it all in one go, around the whole circumference, that would be much better for the gasket, much better for the joint, and you could actually predict the load that is in that joint.”

Another perceived advantage of tensioning is improved accuracy, but as Noble points out, it’s not always that simple. “Unfortunately, the industry tries to use simple one-size-fits-all rules but they do not apply to the torque and tension criteria,” he explains. “Where the conditions are right, tensioning can become very accurate. Typically, that would be for bolts with a high length-to-diameter ratio – long, thin bolts – and where you have high bolt loads. In these applications tensioning is more accurate than torque. But conversely with short, fat bolts and low bolt loads, tensioning becomes less accurate.”

Tensioning also has its disadvantages, namely load loss, which occurs when the tensioner is released and the load transfers to the nut. To compensate for this, the load loss is estimated and the technician applies the expected load loss in advance. This means that the bolt, gasket and flanges are subjected to greater stress than the targeted assembly stress. This has to be taken into consideration either at the joint design stage or prior to using the tooling. An alternative is to repeat the tensioning procedure to compensate for the settlements.

Hydraulic tensioning can also have practical and logistical drawbacks. Since it requires more equipment and specialised tools, it can be significantly more expensive. “Tensioning is not easily understood, other than by those who tension regularly,” says Noble. “You need specific tension tools and it’s difficult to design a tensioner range with the same flexibility as a torque wrench.”

So the truth is that there is no simple answer to which one is better, torquing or tensioning. It is best decided on a joint-by-joint basis.

“Blanket policies result in a lot of technical queries and in some cases the need to compromise on bolt load. Instead you need to do what is best for that specific joint,” Noble says and concludes: “Sometimes it comes down to looking at the application with open eyes, considering how you will actually get the equipment out to the site, the location where it has to be used and how it is going to fit into the application.”

Did you know that…
Friction typically accounts for 90% of the torque applied to the nut during hydraulic torquing?

Joint ventures
For bolted joints, several factors must be considered before choosing between torquing or tensioning.

  • Establish the target assembly load that the application needs.
  • Consider any factors that can directly influence your choice. In applications where it would be beneficial to avoid any torsional effect on the bolt, such as foundation bolts in concrete, tensioning would be the best option. Torquing, however, could be a better option if you are dealing with space constraints.
  • Don’t underestimate the physical and logistical constraints. For a tensioner to grip properly, at least one diameter of thread needs to be protruding through the nut.

 

Interested to know more?

► Boltight hydraulic tensioning system

► Video: Installing a hydraulic bolt tensioner

 

Washers keep airplanes in the air

First published in Bolted #1 2017.

Look up into the sky in the coastal city of Miri, in north-eastern Sarawak, Malaysia, and you may see Nord-Lock washers in action: inside a radio-controlled aircraft. These hobby airplanes are sold by Byond Horizon, a business that otherwise uses drones to take aerial photos and videos for companies.

“Unlike our drones, these recreational aircraft use gasoline-powered engines,” says Mr. M. Fadzly of Byond Horizon. “These engines cause a vibration problem. Since the frame is made of wood, which is soft, and the engine and its mounting are made of steel, the bolts holding them together can come loose after only four or five flights.”

Fadzly says that it can be difficult to access the plane’s engine, so the loosening is a real problem. A friend of Fadzly’s, however, works at Mayura Engineering and is a supplier of Nord-Lock washers.

“I ordered a box, tried them out, and now I recommend them to all of my customers when we are assembling their airplanes,” says Fadzly. “The Nord-Lock washers never need to be retightened, and they also make sure the engine stays in place. It would be quite dangerous if the engine were to fall out during flight.”

Fadzly not only sells the radio-controlled airplanes, he flies them himself. “I’ve been doing it since 1997,” he says. “It’s a passion, and a fun thing to do on the weekend. It gives you the feeling of flying a real airplane.”

►► Contact us to receive more information about Nord-Lock washers

Boltight subsea hydraulic bolt tensioners

Boltight manufactures both standard and custom built tooling for subsea applications. The subsea tensioners incorporate components that helps to save installation time, cost efficient, protects the environment and conforms to the requirements of the European Pressure Equipment Directive.

All subsea tensioners are assembled, filled with oil and have been pressure tested before dispatch. Boltight subsea tensioning tool is supported by a range of ancillary equipment such as high volume pumps, diver control valves, long length down line and hose reels.

Click here for more information about Boltight

Request for more information about Boltight

No downtime with innovative pivot pins

15 juni 2017
reactie

Tekst: Alastair Macduff

Foto: Rambooms

First published in Bolted #1 2017.

Customer: Rambooms
Range: >40 models from 450 kg to 20 tonne
End-customers: Crusher manufacturers and mines
Product used: Expander System Pivot Technology
Applications: Breaker boom systems

Rambooms Oy is a global supplier of breaker boom systems to crusher manufacturers and mines. Based in Finland, its products are used to break oversized rocks.

Pivot wear on these applications is a natural occurrence through time and repeated use, and the company had previously been using its own solution to prevent this. This solution, with a basic conical locking, had caused some issues. Rambooms’ own pins also arrived at its factory in pieces rather than assembled, which meant extra repacking work for personnel when sending the pins on as spare parts.

In 2009, the company took the decision to test the Expander System pivot technology and has been extremely satisfied with the results. The Expander pivot pins are already fully assembled when they arrive. This represents a significant time and cost saving in a competitive industry. Technicians have found fitting and locking much easier than the company’s previous solution.

The Expander System has offered Rambooms significant peace of mind, as it has had no customer issues with pivot wear since the company employed it. A marked improvement in delivery times has also been noted, as Expander always has the stock ready to ship.

“Our customers recognise the fact that the Expander pivot technology means good quality. This reflects well on us and our business,” says Samppa Varhomaa, Product Manager at Rambooms Oy.

The Expander System is locked into the pivot on the machinery when fasteners are tightened. The double-sided locking increases safety and stability, while both fitting and dismantling is simple.

Lubrication: The when and why for tensioning

8 juni 2017
reactie

Tekst: Amaris Neidich & Joseph Vernam

First published in Bolted #1 2017.

Q: How does lubrication affect hydraulic tensioning and multi-jackbolt tensioning?
A: With the traditional method of tightening a nut, using a spanner, lubrication is very important, as there are a lot of surfaces moving against each other – the threads of the nut against the threads of the stud and the underside of the nut against the surface of the joint. Overcoming these frictional forces accounts for approximately 90 percent of the work (energy input) applied to generating the load in the joint.

When a hydraulic tensioning tool applies a clamping load to a joint, lubrication has no effect as it is applied directly to the stud and joint. A tension force is a linear force applied in an axial direction, so there is no rotation required to generate the load. This allows the nut to be turned down against the joint face under minimal friction.

As there is no friction to consider, there is no need to reduce the coefficient of friction using lubrication. Also, the lack of friction in the application permits much more accurate and repeatable results.

With multi-jackbolt tensioners (MJTs), the use of a lubricant on the main bolt thread does not affect the preload. It is advisable to use a very light film of lubricant with anti-seize characteristics to facilitate tensioner removal.

A more tangible effect of lubrication for MJTs is from the required lubricant use on the individual jackbolt threads, jackbolt bottoms of the tensioner, and washer face.

Proper use of lubrication is crucial to safeguarding repeatable and precise preload control in Superbolt installations. Superbolt mainly uses a graphite-based lubricant with a low friction coefficient and steady performance to achieve a positive impact on the preload. The MJTs are delivered with lubricant pre-applied to the installed jackbolts. Additional lubricant is included for application to the jackbolt bottoms. For subsequent installations, reapplication of lubricant is required to provide the intended performance.

 

ASK THE EXPERTS
Do you have a question about bolt securing?
Put the Nord-Lock experts to the test.
Email your questions about bolt securing to
experts@nord-lock.com

Converting sea wave motion into energy

CorPower Ocean harvesting energy in the sea

First published in Bolted #1 2017.

ENERGY. With oceans covering more than 70 per cent of the earth’s surface, wave power is potentially a huge untapped source of renewable energy. The problem is that most wave energy converters are too large and costly to be commercially viable. Swedish company CorPower Ocean could have the answer.

The company’s compact Wave Energy Converter works by oscillating in resonance with waves, amplifying their motion and then converting that energy into power. CorPower Ocean founder, cardiologist Stig Lundbäck, invented the initial concept based on the pumping principles of the human heart. In the same way that a heart uses hydraulically stored energy to form back in place, the Wave Energy Converter uses a pneumatic pre-tension system to pull down the buoy after it has been lifted by a wave.

This allows for a relatively small device to harvest a large amount of energy. It is estimated that one buoy, eight metres in diameter, can generate around 250 kilowatts of power. That is enough electricity for around 200 homes.

“If you look at wave energy potential, somewhere between 10 to 20 percent of global electricity consumption could be provided by wave power,” says Patrik Möller, CEO, CorPower Ocean. “It has the potential to become the most competitive source of renewable energy. It offers five times more energy density than wind and ten times more than solar power. Waves have fewer variations and are more predictable than sun and wind, so you know a few days in advance what the energy flow will be.”

Currently, the Wave Energy Converter is undergoing tests with simulated wave loading, while a full-scale demonstration is being set up to begin in 2017. One of the key challenges has been keeping the buoy small and lightweight, while at the same time strong and durable enough to survive the toughest storms at sea.

This has presented a number of fastening challenges. On the mainframe inside the buoy, Cor­Power Ocean has elected to use Superbolt ­tensioners due to their lower torque requirements compared to a single bolt, which makes assembly far more manageable. Superbolt can also guarantee reliability over the buoy’s intended 20-year lifespan. At the base of the buoy, Nord-Lock washers are used, since they can maintain the correct tension over many load cycles over a long period of time.