First published in Bolted #1 2017.
The people of Nuremberg are proud of their underground system, which is among the most modern in Europe. The city, located in Bavaria, Southern Germany, has the only underground network in Germany where two of the three lines operate automatically, without train drivers. Nuremberg trains travel the equivalent of the circumference of the earth twice each day, carrying more than one hundred million passengers per year.
After 40 years of continuous use, it comes as no surprise that a renovation of the track beds is required to ensure passenger safety. The main beam, also known as a concrete stringer, which attaches the tracks to the tunnel floor, has simply sustained damage in too many places.
This is a daunting issue for the provider of the Nuremberg metro services, VAG (Verkehrs-Aktiengesellschaft Nürnberg). Normally, metro companies need to completely shut down a track for weeks during the renovation of such concrete stringers. Employing water pressure to remove the concrete, it is a time-consuming and extremely dangerous job, considering the many power lines inside the tunnel. Long delays caused by closed tunnels are costly for the track operators, adversely affecting train traffic and irritating passengers.
Coming to the rescue, a brand new innovation caught VAG’s attention just as they started planning the renovation. Local Nuremberg dowel and concrete bolt manufacturer TOGE Dübel won a railway innovation award for a new concept that enhances the sustainability of existing concrete bridges. Present in the audience, VAG representatives were intrigued and had the idea of trying the concept for the first time in an underground rail environment. Currently, work is under way at the first three stations: Bärenschanze, Gostenhof and Maximilianstrasse. Work on the second largest station in the network, the “Plärrer”, with 98,000 passengers daily, is planned for 2017.
Instead of complete reconstruction, concrete bolts measuring 36 centimetres and weighing 1 kilo are utilised as load-bearing components to improve the life span of the overall track bed construction. The bolts are fitted with a patented special thread that cuts into the borehole wall upon application. The force of the bolt is mechanically transferred to the anchor base and the concrete is fixed in place.
“Completely removing a concrete stringer and installing a new one could never be accomplished without service disruption,” says Waldemar Gunkel, Technical Director of TOGE and one of the two inventors of the new generation of concrete bolts.
“In Nuremberg, however, our system is only being installed between the hours of 23.00 and 04.00. By the morning, everything is running normally.”
During these working hours, only one track is shut down and trains are redirected via a single track, while the porous areas of concrete on each stringer are chipped away and replaced. Finally, the stringers are fixed into the ground utilising the concrete bolts. Since the bolts need to be drilled into the concrete, there is a risk of inclination as the drilling machine might not be positioned at an exact 90-degree angle. That’s why all concrete bolts that are being used in this first project are secured by Nord-Lock X-series washers. Their conical shape can compensate for the inclination, while the wedge effect prevents spontaneous bolt loosening due to vibration.
The Nord-Lock connection came via Deutsche Bahn – Germany’s national railway operator – where Nord-Lock original wedge-locking technology has long been prescribed as the standard.
Jochen Süssenbach, Nord-Lock Project Account Manager, sees great potential in this new approach to metro renovation. “We’re looking at a huge renovation of the tunnels that virtually doesn’t affect the timetable at all”, he says. “In terms of costs, it’s also a solution that beats any conventional method.”
So far, the renovation is running as planned. The first construction phase has even been completed a week ahead of schedule and the total time for construction carried out at all three metro stations will last six weeks instead of several months, which could have been the case with the previous method.
The concrete bolts themselves are designed to last for 50 years. No concrete will last that long, but further renovations will not be necessary for decades.
Describing TOGE’s Innovation Award-winning solution, Bavarian Interior and Transport Minister Joachim Herrmann said the following: “We have our fingers right on the pulse.” He hinted at the billion-dollar losses that Germany faces due to the poor condition of some 120,000 highway bridges and 30,000 railway bridges.
THE UNDERGROUND RAIL SYSTEMS are in a similar state. Just as in Nuremberg, most metro networks in Germany, as well as in the rest of Europe, were established in the 1970s. Gunkel thinks TOGE has found an important application for its concrete bolt: “This project gives us the boost to further drive our product development forward.”
Facts: The Nord-Lock Solution
Client: TOGE Dübel GmbH & Co.KG.
End customer: Metro services provider, Verkehrs-Aktiengesellschaft Nürnberg (VAG).
Location: Nuremberg, Germany.
Project: Renovating concrete stringers under metro tracks without affecting traffic.
Solution: Using concrete bolts with a patented special thread to reinforce the existing structure.
Nord-Lock Product: X-series multifunctional wedge-locking washers with enlarged outer diameter (NLX24sp)
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.
We know that safety is a priority to our customers. Our products are very easy to use and we appreciate that you want to be 100% sure that you are mounting them correctly, operating in the recommended temperature range, or know when to reuse them.
The following user manuals are available:
Download them now and never worry about your bolted connection again!
First published in Bolted #2 2016.
The development of new materials, for example glass-fibre reinforced plastic (GRP), has set new trends for the infrastructure of railway companies. Materials on the tracks, such as steel and timber, are increasingly being replaced by GRP for grates, walkways, bridge coverings, escape routes and service access ways. GRP makes these elements weather-resistant, slip-proof and thus safer.
Their simple, modular design, but also their low weight and high strength, make GRP profiles increasingly popular with railway operators for entire structures, such as railings, ladders, suspended stairways and work platforms. Another GRP advantage, compared to steel, is the fact that you don’t have to earth the entire structure, as the material is an electrical insulator. It is also resistant to corrosion, which significantly reduces the costs for maintenance.
Deutsche Bahn AG in particular has decided to make greater use of GRP in its infrastructure. This makes DB a trendsetter for Europe, since railway operators in neighbouring countries take cues from the continent’s largest railway industry company.
“This is a trend, because Deutsche Bahn has a complete understanding of this material’s advantages,” says Philipp Wilczek, Junior Partner and Sales Director at CTS Composite Technologie Systeme GmbH – a technology leader in the field of glass-fibre reinforced plastics. Products and structures made of GRP must be bolted together and these bolted joints can be problematic. To overcome this, CTS has decided to use the Nord-Lock X-series bolt-securing system. Maik Hartmann, Technical Director at CTS, explains: “Our material is low-maintenance in principle. However, in order to make the entire structure low-maintenance as well, we needed a solution for securing the bolts, so that we could expand the material’s advantages to the connecting elements as well.”
On or close to the tracks, shaking and vibrations from train traffic must always be expected. An increased loss of preload due to slackening (settlements and/or relaxation) should be considered when using new materials. Nord-Lock X-series washers combine the wedge-locking principle with a spring effect to prevent loosening caused by settlements and relaxation. This way, they enhance the advantages of CTS’s GRP products to offer the railway industry a safe option with many advantages.
First published in Bolted #2 2016.
Customer: The Hoyer Group
Product used: Nord-Lock stainless steel and X-series washers
Number of tank containers: over 30,000 worldwide
Number of tank trailers worldwide: more than 2,000
Application: Tank containers for liquid transport
To avoid accidents that would put people and the environment in harms way, it is crucial that the transport of liquids is managed safely and efficiently.
Started in Hamburg more than 70 years ago, the Hoyer Group has vast experience in handling chemical products, foodstuffs, gas and mineral oil. Today this global market leader in moving liquids by road, rail and sea operates over 30,000 tank containers and over 2,000 tank trailers worldwide. On the recommendation of a customer, the Hoyer Group has started to employ Nord-Lock stainless steel washers on their tank containers used on the European continent.
Frits Bakker works at the Engineering department at Hoyer Nederland BV in Rotterdam. “We faced a problem with valves on gas containers,” he explains. “A customer advised us to try Nord-Lock washers. Using these washers and a different seal material solved the problem. After this, we started to fit them on the bottom valves of our tank containers.”
The Hoyer Group will be using the Nord-Lock stainless steel standard washer, as well as the X-series version. They have a standard guideline to fit them on particular parts during maintenance. According to Bakker, the Nord-Lock washers help the Hoyer Group to avoid critical situations. He says that, “Obviously on tank containers it is vital that leakages don’t occur. In this respect, the washers are very reliable.”
The September issue of Bolted magazine is out now! Prepare yourself on a reading journey to explore interesting cases and insights from the world of bolt securing.
In this issue, our theme article focuses on coupling challenges. Couplings are essential in the power generation and shipping industries, and are arguably the most demanding of all bolting applications. Learn what the bolting experts have to say about couplings.
Engineers from the Nord-Lock Group answer questions on how to get the most out of your fasteners and cover the key advantages of hydraulic tensioning.
We witness the largest public works project in California’s history, where Boltight tensioners are installed on the San Francisco-Oakland Bay Bridge. We then move on to Oman to find out how broadcasting antennas owned by the BBC are being secured against windstorms. Last but not least, we ride on the time machine as we simulate 20 years of wear and tear on a wind turbine in just a fraction of that time.
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First published in Bolted #2 2013.
Q: Why is slackening becoming an increasing problem?
A: One of the main reasons for bolt loosening is slackening. Slackening leads to loss of preload and can be divided into three subgroups: Slackening caused by settlement, slackening due to relaxation over time or slackening resulting from gradual temperature changes (creep).
Settlements are related to surface roughness and surface irregularities. The pressure on the clamped surfaces after pre-loading causes any irregularities on the surface to start to flatten. When the irregularities have been flattened out the parts will be less tightened and the pre-load will decrease. If the reduction of pre-load is significant enough the joint may rotate loose. Low pre-load also increases the risk of fatigue failure.
Relaxation occurs when materials become more compact over time, resulting in additional loss of pre-load. This is common for materials such as polymers, composites, copper and soft metals.
Creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. It occurs as a result of long-term exposure to high levels of stress that fall below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and close to their recrystallization temperature. Creep always increases as the ambient temperature rises.
Today, increasingly more joints are exposed to more extreme conditions such as higher speed, high temperature and higher loadings. If components were still manufactured out of steel the ’old way’, they would be cumbersome and heavy. In order to reduce the total weight, components these days are made from composites, plastics and aluminium. This is why slackening is becoming an increasing problem. Nord-Lock has developed the X-series washers to counteract these slackening effects so designers no longer have to worry about how to compensate for slackening in the joints.
First published in Bolted #1 2016.
Wam Metals is a manufacturer and supplier of a wide range of specialized non-ferrous and ferrous components, servicing both the local South African and the international markets. The company has a long-standing and close relationship with logistics company Transnet’s Freight Rail Division, which specializes in the transportation of freight, mainly through its electrified rail network.
The contact splice conductors in the installations Wam Metals did for Transnet used to be designed to use locking plates to lock the bolts after being tightened. However numerous incidents occurred because of bad maintenance. The procedure stated that splices had to be tightened and later re-tightened, and only then could the locking plate be bent to lock the bolts.
The incidents revealed that the plates were usually intact and therefore, because of vibration in the overhead line, the bolts loosened and the contact wire pulled out of the splice.
Wam Metals requested approval from Transnet’s Engineering Department in April 2014 to change its specifications and to start using stainless steel Nord-Lock washers instead of the locking plates. Thorough tests were carried out. The washers from Nord-Lock performed as they should, with no slip occurring, so Transnet approved the use of the new product instead of locking plates.
To date, no incidents regarding hook-ups caused by contact splices – fitted with Nord-Lock washers – have been reported. Wam Metals currently uses NLX10 for the signal bonds, NL10ss for 107mm² contact splices and NL12ss for 161mm² contact splices and the rail and mast bonds.
For Wam Metals, the use of Nord-Lock washers on the contact splices means there is no need to re-tighten at a later stage. The same goes for signal, rail and mast bonds, which translates into reduced maintenance costs and fewer hook-up incidents.
For Nord-Lock, the experience from Wam Metals is highly interesting. It is really putting the company’s X-series to the test, in a new field where the company has not previously been widely involved.