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Presentation on theme: "THE BENEFITS OF UNDER SLEEPER PADS (USPs) FOR HIGH SPEED TRACKS"— Presentation transcript:

10/03/2013 BENEFITS OF USPs

THE BENEFITS OF UNDER SLEEPER PADS (USPs) FOR HIGH SPEED TRACKS 1. DEFINITION 2. WHY USPs? 3. A BRIEF HISTORY 4. POLYURETHANE RUBBER 5. RETURN ON INVESTMENT 6. CONCLUSION Note : the hereafter LCC and ROI estimates must be understood as hypothesis based on current on-line informations, conferences and press articles which FIMOR has no way to verify in full. Please send any remarks and comments to : we shall try and use them to the best interest of the rail industry 10/03/2013 BENEFITS OF USPs

3 Improved maintenance of track geometry
1.Definition « Under Sleeper Pads » (USPs) or Attrition Reducing Pads? In France, the SNCF engineers who pioneered USPs and their use, first called them “ Attrition Reducing Pads” or “ PRAs” • There are several types of USPs having specific functions in specific contexts. Thus, the USPs of type A are used exclusively for HST while USPs type S (Medium / Soft) or V (Soft / Very Soft) are mainly designed for urban transport and slab tracks. • The present document deals mainly with the ’A’ type, the one designed for High Speed Tracks. USP Reference USP Type Improved maintenance of track geometry Ballast Protection Reduction of wave defects Vibration reduction - Without USP = A (PRA) Hard / Medium + + + M Medium S Medium / Soft V Soft / Very Soft Source : RFF et UIC 10/03/2013 BENEFITS OF USPs

4 1st answer: some well known advantages:
2.Why USPs ? 1st answer: some well known advantages: On bridges Under tunnels Under turnouts In transition zones Saving on ballast weight and height Better stress distribution 10/03/2013 BENEFITS OF USPs

5 2nd answer : significant savings on maintenance works
2.Why USPs ? 2nd answer : significant savings on maintenance works The French designation as “Attrition Reducing Pads” was truly describing the main functions of USPs for HST: to avoid the ballast settlement under speed, vibrations and vertical strain. USPs have 2 main functions: Reducing the transmission of dynamical stress on the rail towards the ballast, Amortizing as far as possible the load of trains on the overall track system 10/03/2013 BENEFITS OF USPs

6 Distributing train pressure way more evenly:
2.Why USPs ? Distributing train pressure way more evenly: Wooden sleepers once offered a tender surface for the sharp angles of the gravels to penetrate. The contact points were hence quite sufficient for the sleeper to rest. Nowadays, concrete sleepers, required by HSL, are solid and prevent the ballast edges to penetrate it. As a consequence, the stones edges blunt against the ciment. Moreover, the percentage of the sleeper surface which does rest on the ballast is a mere 6%, which in turn contributes to the increased pressure on the ballast and provokes the degradation of the track profile. Further, the ballast erosion generates fines which tend to block the natural rain water drainage allowed by the ballast structure, increasing the stiffness of the entire track system, and accelerating in turn the track decay... 10/03/2013 BENEFITS OF USPs

7 USPs, secures ballast durability
2.Why USPs ? USPs, secures ballast durability Rubber pads bonded under concrete sleepers help distribute train pressure over the ballast by a factor of three compared to conventional sleepers without pads: It has been measured that more than 20% of the sleeper surface lays on the ballast if the sleeper is equipped with pads instead of the barely 6% mentioned. This ratio from 1 to 3 corresponds roughly to the maintenance savings generated by sleepers with pads. Detailed figures will be presented in the next slides. This correlation depends however of the intensity of (stress X duration), essentially: • The supported tonnage (as per UIC classes) • The train speed (slow, median and maximum speed) • The nature homogenous or mixed of the traffic (TGV, ICE, freight only or a mixed pattern) 10/03/2013 BENEFITS OF USPs

8 The concept of USP has been around for 20 years !
3.A brief history The concept of USP has been around for 20 years ! • In the earliest days, a French patent (SNCF + SERP) was experimented on a few problematic sites. This patent discloses the benefits obtained from rubber layers applied to sleepers, but the original spray system (on-site) proved to be painstaking and was abandoned. • Later, the concept was successfully industrialized off-site and the principle of «PRAs» (Attrition Reducing Pads or USPs) started to be known namely on HSLs. • For more than 11 years, the USPs were used with spectacular results, particularly on a dozens of kms over the HSL “LYON-MEDITERRANÉE”, in extreme conditions (= high traffic and speeds up to 320 km/h). • In the same harsh conditions, the HSL EAST PHASE 1 has suffered some quick dilapidation without pads. Consequently, RFF has decided to incorporate USPs on Phase 2, on a leg of over 100 kms. 10/03/2013 BENEFITS OF USPs

9 Which method of bonding ?
3.A brief history Which method of bonding ? The principal difficulty is to secure the adhesion of the USPs onto the concrete sleepers in order to prevent the deterioration of the bonding through vibrations or lack of strength of the glue over the years. Several techniques have been developed to this end: • The first technique was a gravel interface, first casted into the rubber, then with the rubber onto the fresh ciment. • Several manufacturers have used a “geo-grid” mesh • FIMOR has recently patented a glue free pad, without any glue nor bonded material, therefore made with PU only, resulting in a strong homogenous pattern designed to be self-locking into the vibrating concrete with a consistent thickness. 10/03/2013 BENEFITS OF USPs

10 The FIMOR homogeneous pad
3.A brief history The FIMOR homogeneous pad The FIMOR patented a glue free pad, made with PU only, which provides several advantages: Easy and homogeneous grip in the vibrating concrete High tear resistance thanks to the studs Homogeneous thickness (<1 mm deviation) Uniformed hardness Economic production through the use of automation. 10/03/2013 BENEFITS OF USPs

11 High Speed Lines, a ruthless world
4.Polyurethane rubber High Speed Lines, a ruthless world In spite of the maintenance costs problem and the logistical difficulties (on average 3 or 4 hours during the night between the last evening train and the first train in the morning), the engineers were, originally, unsure about USPs usefulness. • How can a piece of plastic increase the overall resistance of the rail + sleepers + ballast assembly? • How will it resist to extreme pressure, to tampering and other track maintenance operations, and to extreme weather conditions: will the USP not crumble or become loose from the sleeper? We can understand these questioning if we think in terms of classic rubber or most thermoplastic polymers which have little chance to last more than 10 years. 10/03/2013 BENEFITS OF USPs

12 The strict criterium defined by the SNCF
4.Polyurethane rubber The strict criterium defined by the SNCF (This slide corresponds to the pads of category A for High Speed Lines). MECANICAL BEHAVIOR OF THE USPs Stiffness : according to the standards of SNCF, 0,370 N/mm3, static. Hardness: according to the standards of NF ISO 868 Tensile strength: according to the standard used in NF ISO 37 Shear resistance : according to the standard used in NF ISO FLAMMABLE RISK WITH THE USPs Rankings F and I according to the standard used NF F ISO CHEMICAL BEHAVIOR OF THE USPs Hydrocarbon resistance : according to the standard NF ISO 1817 Ozone resistance:according to the standard used in ISO method A Chemical agents resistance related to the sleeper manufacturing process: according to the standard ISO 175 SPECIFIC TESTS FOR USPs WEAR RESISTANCE The VIBROGIR (equivalent to a wear test ballast plate): SNCF standard The tear resistance of the USP off the concrete sleeper: SNCF standard Micro durometer shore 10/03/2013 BENEFITS OF USPs

13 High quality polymers for rugged use
4.Polyurethane rubber High quality polymers for rugged use Vibrations and noise damping T° -10°c to +40°c : Wide range of use PURs POLYETHERs THERMOSETs Damping capacity 1,7 times EVA from +10 to -10°c Resilience Tear resistence Abrasion resistance 2 times EVA 4 to 10 times most polymers Long life cycle Hydrolysis Tensile strength 10/03/2013 BENEFITS OF USPs

14 4.Polyurethane rubber Target: 50 years and more!
Examples of PUR applications for very long use • Support for bridges decks. • Envelope for submarine and transatlantic cables USPs can’t be removed and changed, they have to last as long as the sleepers, unlike rail pads. 10/03/2013 BENEFITS OF USPs

15 4.Polyurethane rubber 2 testing sites provide remarkable data Most of the figures used herunder have been presented in VTM conferences, on the internet and in technical magazines. 1°/ For well over 10 years, Polyurethane Rubber (PUR) USPs have been used at a speed of 320 km/h on the HSL LYON-MEDITERRANÉE (LN5) over a dozen of kilometers equipped with various heights of ballast layers. The wear of the ballast and the number of tamping have been reduced well over three times, including over the areas where the height of the ballast is reduced to 25 cm (instead of the standard 35 cm). 2°/ As a counter-example, one could see a very fast degradation for a speed of 320 km/h on the first part of the HSL EAST built without USPs. To be clear, there is no sound economical reason to incorporate USPs ONLY for tunnels or bridges, switches or other transition areas. 10/03/2013 BENEFITS OF USPs

16 So why do people wait for ???
4.Polyurethane rubber So why do people wait for ??? Today, USPs are being supplied only to the HSL EAST PHASE 2. Why? The use of Under Sleeper Pads means an additional initial capital investment, modest per kilometre but significant on an overall project. But NOT implementing USPs is typical of a short-term financial decision: any calculation which does takes into account the overall LCC and namely the maintenance costs of the track leads to the opposite choice. 10/03/2013 BENEFITS OF USPs

17 5.Return on investment To try to calculate the ratio cost/benefits of USPs, we will do the following hypothesis : We are in 2015 and we have decided to build a new HSL of 300 km… First, we should consider an additional investment for the USPs of about euro per km of track (1666 sleepers/km), Why should we do that ??? 10/03/2013 BENEFITS OF USPs

18 We will show only three simplified cases:
5.Return on investment We will show only three simplified cases: 1. Annual tonnage on the track: Low = 5MT/year, Medium = 10MT/year, High = 25MT/year Train speed: qualitative differences of wear appear in the following ranges: <SPD250, SPD250 to SPD300, SPD300 to SPD320 (over SPD320, we have no data) 3. Nature of the convoys: axle load, and mixed traffic or not, for instance alternating TGV and freight trains or different types of trains (ICE and TGV do not behave the same on ballast). NB: We are aware that other parameters should be taken into consideration: the choice of rails, the kind of pads between sleeper and tracks, the fastenings, the ballast height, the importance of suspended masses… 10/03/2013 BENEFITS OF USPs

19 5.Return on investment Consequently the 3 study cases are:
CASE 1 : “Low traffic” (UIC class)* AND/OR < SPD250 CASE 2 : “Medium traffic” * AND/OR SPD250 à 300 AND/OR mixed convoys CASE 3 : “Heavy traffic” * AND/OR SPD300 à 320 AND/OR mixed convoys at medium and high traffic LOW TRAFFIC = <10 Mt/ Year and <SPD250 MEDIUM TRAFFIC = 10-25Mt/ Year and/or SPD250 to SPD300 HEAVY TRAFFIC = >25Mt/ Year and/or SPD250 to SPD320 And/or mixed traffic ( ALSTOM and SIEMENS) HEAVY TRAFFIC MEDIUM TRAFFIC CHARGE ( Mt/Year) NOT TESTED ZONE LOW TRAFFIC SPEED ( KM/H) *These 3 cases are given as equivalent for the aging of the support structure of the track; one should look at them as forecast only, but all the more probable as 2 or more of the real figures and facts (high speed, mixed traffic) are actually realized. 10/03/2013 BENEFITS OF USPs

20 Input data for a period of 50 years HSL per single TRACK
5.Return on investment Input data for a period of 50 years HSL per single TRACK 1. Estimated expense due to USPs use (two per sleeper) mounting included : euro/km/track 2. Saving on ballast thickness of 5 cm = 21,50 euro/meter : this saving is DEDUCTED from the acquisition cost of the USPs in the following charts (hence the cost of USPs comes down to euro/km) 3. Average cost of tamping (BML): 7,50 euro/meter Frequency without USPs : Heavy traffic = every 2 years*. / Medium traffic = 3 years. / Low traffic = 5 years 4. Average cost of ballast renewal (RB): 110 euro/meter Frequency without USPs: Heavy traffic = on the 25th year / Medium traffic = the 40th year / Low traffic = without 5. Average cost of ballasted track renewal (RVB): 1200 euro/meter (per single track). Frequency without USPs: Heavy traffic = on the 40th year / Medium traffic = without / Low traffic = without 6. Inflation rate : 2% / year, not mentioned in the above figures (costs 2013) 7. Factor of reduction of the maintenance intensity thanks to USPs: 3 (according to the main available studies, the cost reduction factor on the above parameters as provided by USPs should reach 4 or even 5: 3 is a conservative figure! All the following ROI charts would look even quite more favorable...) * 2 years : this frequency is also conservative = in fact, on some SPD320 tracks, the % of ballast to tam each year reaches 60 to 65%! 10/03/2013 BENEFITS OF USPs

21 Overview return on investment of USPs (300km) UNIQUE TRACK
Profit on the maintenance cost in million euro YEARS LOW TRAFFIC -5,1 -3, ,6 2, ,4 MEDIUM TRAFFIC -5,1 -3, ,4 6, ,9 HEAVY TRAFFIC -5,1 -2, ,4 29, ,4 With 2% of annual updating LOW TRAFFIC -5,1 -3, ,1 2, ,4 MEDIUM TRAFFIC -5,1 -3, ,7 10, ,0 HEAVY TRAFFIC -5,1 -2, ,0 44, ,2 10/03/2013 BENEFITS OF USPs

22 Overview return on investment of USPs (300km) without inflation
Maintenance savings over 50 years – HSL 300 km - Unique track Low Traffic Medium Traffic Heavy Traffic MILLION EURO Smoothed curves over years YEARS Not counting other savings such as costs of delays 10/03/2013 BENEFITS OF USPs

23 Not counting other savings such as costs of delays
5.Return on investment Overview return on investment of USPs (300km) inflation rate + 2% annually Maintenance savings over 50 years – HSL 300 km - Unique track + 2% inflation Low Traffic Medium Traffic Heavy Traffic MILLION EURO Smoothed curves over years YEARS Not counting other savings such as costs of delays 10/03/2013 BENEFITS OF USPs

24 Which new paths should be explored?
6.Conclusion Which new paths should be explored? 1. Interest of USPs at low speeds • reducing the ballast thickness: up to 10 cm with very significant associated costs • reducing noise level in urban areas • searching for the ideal correlation stiffness/thickness of the ballast • optimise the stiffness of the whole stack by taking into consideration the rail pads. 2. Completing the present saving study by taking into consideration all the related expenses and direct costs and the savings on delays (1 minute delay costs about 1000 euro by TGV, and the maintenance operations generate significant speed reduction and subsequent delays). 3. Study a new generation of USPs, covering the entire bottom of the sleepers and even the lower part of it sides to increase the transversal stability of the track and achieve further tamping and ballast related savings. 4.Gaining control of the maintenance costs in the area of speed > 320 (up to 400 km/h?). Among other technical possibilities, checking the benefits of "asphalt+gravel" constructions, in combination with USPs 5. But issues are not technical only : it is necessary that economic models stop opposing the interests of short term investors to those of long-term track owners and users! 10/03/2013 BENEFITS OF USPs

25 6.Conclusion What is already proven
1. For more than 20 years the USPs (Under Sleeper Pads) went from the testing phase to the economical rescue of the HSL (SPD250-SPD320), especially by reducing the maintenance costs of the tracks. This consideration has determined the RFF decision to equip the 100 km of the HSL EST PHASE 2 with USPs, and to generalize it's use on the network being renovated from 2013 on. 2. The USPs cost have decreased significantly through progress in it's industrialization. If we take into account a reduction of the ballast thickness, the return on investment is fast: 5 to 10 years depending on the model. 3. Their profitability can be highlighted even in the case of low or medium traffic. The aim is still achieved: preserving the geometrical profile of the track while reducing maintenance. 4. At a speed around 320km/h, the USPs are a pre-requisite for the very profitability of the future exploitation: The geometric characteristics of the ballasted track are sustained. Each operation of tamping speeds up the degradation of the ballast. USP reduced the tamping frequency by factor 3 at least Our figures indicate that the maintenance savings, directly related to reductions of the ballast costs permitted by the USPs, sum up to 455 million euro (cumulated over 50 years and 300 km of two-ways track) before inflation million euro with maintenance costs actualized at 2%/year! 5. USPs mean better controlled spendings proportionally to the speed: they are a must for HSL as they help to keep the ticket price affordable hence preserving the competitiveness of the rail versus the other means of transport. Maintenance should not be mainly curative, nor even preventive: it ought to be predictive. 10/03/2013 BENEFITS OF USPs



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