Transkript
Welcome to Performance on Track, a podcast by voestalpine Railway Systems.
Welcome back to the Railway Systems podcast. In the first part of this episode, we started talking about the fundamentals of a fixation system.
Now in the second part, we will go one step further and focus on elasticity as well as the different sleeper types and slab track systems and why these aspects are so critical for performance, durability and also comfort. Once again, I am joined by our expert who is Robert Demal, Vice President of Product Management, Fixations at voestalpine Railway Systems.
And you mentioned in the last episode that elasticity plays a crucial role. What exactly is meant by elasticity in a fixation system and how is this concept applied in fastening systems? Yeah.
First of all, also welcome back from my side. So elasticity can be applied, let's say basically in three different layers. So starting with the first layer, this is between the rail and sleeper or bearer or slab track. So it's mainly for direct fixation where you apply the elasticity within the rail pad. The second layer would be for indirect fixation systems between the base plate and the sleeper or the slab track itself. So this is this more important for resilient slab track systems. The third layer is then underneath the sleeper. Those were under sleeper pads and this is mainly important for ballast protection For slab track systems.
There are also more layers which you can apply elasticity, but this is what I can explain. Later on, OK, even more layers, all right. And now that we are that we have these different layers and also different types of elasticity, why in general, why at all do we need to consider different elasticities? As I explained in our last episodes, there are different fields of application. So high speed or conventional rail heavy hole and based on those different fields of application, there is also different requirements on the system stiffness itself also which I mentioned the last term was between slab track and ballasted track. And especially for a slab track you need to you need to apply elasticity to the system because you don't have the ballast who covers more of the damping effect.
So that's why you have different systems with different system stiffnesses. And the important thing is that the system itself or the components matches for the system. So when you apply, for example, the elasticity in the first layer in the rail pad, you need also clips, rail clips, which can cover the deflection of the rail pad.
So simple speaking, softer rail pads needs clips with higher deflection range, higher fatigue limit compared to stiffer ones. It that makes sense? Yeah. So for an example, I can give you the SKL 12 clip, which is mainly used for indirect fixation. So the rate it fixes the rail to a base plate. So there you have usually quite stiff rail pads between and the fatigue limit of such an SKL 12 clip is only 1.4 millimetre because the main elasticity in such systems is applied then underneath the base plate in a resilient pad. So the rail pad itself between rail and base plate is usually quite stiff and you don't need clips which which are high deflection. Or on the other hand for in for direct fixation systems which high resilience or more resilience, there you have clips with higher fatigue limit the entire deflection. So for example high speed system with W 21 and then SQL 21 clip which has usually stiffnesses i the range of 40 to 70 kilonewton.
The clip itself has a fatigue limit of 2mm. So it's already higher than for slab track systems like the W300 system where you have really high resilient pets and the system stiffness is around 30 or 201K Newton. The SKL 15 clip can cover or has a fatigue limit of three millimetre already. Also with our G9 clip, it's the same fatigue limit. So the fatigue limit, and this is is important that the clip matches with the elastic pads underneath. So we always have to consider how all of these different factors play together. Yes, that's crucial, yeah. Because if you have improper elasticity this this can affect a lot of components. What would happen if we did not consider both the clamping force as well as also the elasticity? So first of all, when you have softer rail pads and clips, which doesn't have this high fatigue limit or cannot cover these deflections, then the clip can can break just the thesis one.
But it also when you have stiff systems, it also has has an effect than also on the rails because stiffest systems causes more corrugation, more head checks on the rails itself, but also underneath they destroyed the the ballast. So that's why it's really important to apply elasticity in the system. So we should definitely avoid having these these failures. Besides considering the elasticity, another very important topic in context to fixation systems are sleepers and also slab track.
Also, in the very first episode we talked about that a fixation system also includes concrete sleepers. Could you give an overview about the different types of sleepers and also their roles in the track system? For sure. So first of all, you may have heard the names, sleepers, bearers, ties and so on. And it's not the same. Pretty much, but a bit different. So starting with sleepers, the the name sleepers.
So sleepers the name is used for track sleepers. So track sleepers which is really a standardized mask product and installed in track bearers, the sleepers for turnouts are called bearers. So concrete bearers because they are in the turn out they're more specific, they are not standardized products, they are really so each individual because. Customized.
Yeah, see and in North America or the Arema markets, they are calling both types ties. So they have Trek ties and turn out ties. So this is just looking at the
the names of it. Even more confusing than. Bit confusing, but yeah, basically we are talking about the same product and then of course you have different types of materials. So starting with wooden sleepers. So wood for the sleepers, it was the classic sleeper design, let's say, which had been used in, in, in Europe or where they started the railways with.
But it's, it's also the, the most common one now in North America. Then we have concrete sleepers and bearers which are here now in, in in Europe and and many more countries around the globe are now the most common type. That's also those that we always see at yeah, yeah, at at train station, so. Yes, then you have steel sleepers in special locations on on steel racks, but also create common in in South Africa or in these markets. And then you have more and more now the synthetic sleepers, so plastic or reinforced plastic synthetic sleepers if a few sleepers, those types are more and more common now for to be installed on on bridges viaducts because they have less weight compared to the concrete Barristan sleepers. All right.
And if we now look more closely at slab track systems, we also see different system designs. So which types of slab tracks are available and what role does elasticity play in these systems?
So generally we can say there are four major types of slab track systems on the market. So starting with singing support systems which are casted directly on in situ concrete. So there you have only one stage of elasticity and this is, as I mentioned, between the base plates and the slab itself. Of course between the rail and the base plates there's a bit of elasticity applied, but the major elasticity comes between the the base plate and the slab itself. Then you have systems where the same fastening system is installed on a concrete sleeper or bearer and the bearer or concrete block is then casted into inserted concrete. So on the regarding the elasticity, it has the same level of elasticity, so only only one stage. Then you have systems where bearer or a concrete block it's additionally covered in a rubber boot like an LVD block. And then this complete system is then been pureed into into concrete. So there you have already 2 stages of of elasticity. So you have the one stage between the base plate and the concrete, and then you have between the concrete block a concrete sleeper and the inserted concrete or concrete slab.
Just out of curiosity, why would would you use rubber shoes here? Rubber shoes because it's it's more resistant because you have two, two layers of concrete or you have let's say the rubber is between two layers of concrete. And this material is, let's say,quite resistant against this. That's why you apply rubber. And then you also have systems with precast slabs, precast elements.
And there you also apply a two stage elasticity. You have it between the bastener and the and the precast elements. And then underneath the precast elements. These these types are the most common one let's say now and the last two types as I mentioned these are so-called mass spring systems. So as I said they have more elasticity in the system 2 stages and this is better especially for noise and vibration in emission are. So different types of slab track as well that would already lead us to some sort of conclusion about about this topic and also about this episode of our podcast.
As a final summary, what is your key message that you would like our audience to take away when it comes to fixation systems? I think you can imagine the key messages that you really apply more elasticity or let's say sufficient elasticity into a fastening system. But not only looking at the fastening system, it also matches them with improved sleeper design. So and this really helps to reduce the sleeper deflection in ballasted track systems and to improve the ballast protection. And this is important to have less maintenance effort, less maintenance costs for the operators. And it also guarantees a longer operational service lifetime of the whole infrastructure, because, as I mentioned, improve elasticity leads to higher risks of cracks, corrugation, head checks and so on. Or failures itself. So all of these really then leads to really significant cost saving savings for the operators and and asset owners guarantees also higher availability of their tracks.
Yeah. And with that, I would like to thank you for that very, very much for joining us and for sharing your expertise on fixation systems. We both hope that this two-part episode helped you better understand how fastening systems all work together as part of an integrated railway system. We hope that you learned a lot about elasticity as well, about different types of sleepers, etcetera. But also, as I want to emphasize here again, all of our webinars as well, this webinar on fixation systems is available online on our Railway Systems Academy platform. So you would also have the video there and the whole presentation with all of the concepts, all of the components, everything that we talked about also visually available there. With that, stay tuned for upcoming episodes of the Railway Systems podcast. Thank you very much for listening and thank you very much, Wilbert, for sharing your insights.
Also, thank you. Thank you very much from my side.
