The Journal April 2018 Volume 136 Part 2

Transcription

1 ARTICLE AS PUBLISHED IN The Journal April 2018 Volume 136 Part 2 If you would like to reproduce this article, please contact: Alison Stansfield MARKETING DIRECTOR Permanent Way Institution alison.stansfield@thepwi.org PLEASE NOTE THE OPINIONS EXPRESSED IN THIS JOURNAL ARE NOT NECESSARILY THOSE OF THE EDITOR OR OF THE INSTITUTION AS A BODY.

2 Progressive assurance for S&C renewals AUTHOR: Nick Matthews Programme Engineering Manager S&C North Alliance The key to delivering higher speed handbacks is accuracy and getting each step in the installation of the track Right First Time. The difference between handing back with a temporary speed restriction and reopening at full speed comes down to working within much narrower tolerances and ensuring that ballast is consolidated effectively before the line is reopened, rather than allowing the ballast to settle under normal traffic. The S&C North Alliance is a partnership between AmeySersa and Network Rail to deliver switch and crossing (S&C) renewals across the North of England and Scotland. Established in 2014 under a 10-year agreement, the Alliance approach combines the best of European processes and technology, UK rail design and engineering expertise, and safety practices aligned to Network Rail s Life Saving Rules, to improve safety, performance and reliability for passengers. By moving away from the more traditional client-contractor dynamic, the Alliance approach has improved collaboration between designer and installer, established joint accountability and firmly embedded the client as an active participant in the partnership. This true Alliance way of working, has allowed the team to focus on delivering a Right First Time, high quality approach to switch and crossing renewals and associated works. This increased focus on quality has enabled lines to be reopened at higher speeds than were previously possible after engineering work. High speed handbacks are not only good news for passengers who experience fewer delays, and for employees working in safer environments but the increase in quality is also significantly more efficient in the long term. This is because the Right First Time approach reduces follow-up and rework, improves reliability of the asset and reduces the whole life cost of the installation. Within the first year of the partnership, the S&C North Alliance increased its average hand back speed after S&C renewals from 50mph to 80mph and delivered the UK s first 90mph S&C handback at Craigentinny, near Edinburgh. Since then, the Alliance has set about making handing back at line speed the norm, reducing delays for passengers and delivering several million pounds of schedule 8 savings for its route customers. In September 2016, the S&C North Alliance were tasked to complete a S&C renewal on the East Coast Main Line at Belford, of five turnouts over two 54-hour weekend possessions. The team made rail history by reopening the Down Main over 510bpts at line speed of 125mph immediately after the core renewal the first time this has been achieved on a S&C turnout in the UK. The DVs turnout Pts 510b on the Down Main were deliberately targeted for the 125mph handback as it was a set of trailing points on a straight. See image 1. After a detailed Lessons Learned was conducted following the Belford 125mph handback In February 2017, the Alliance was tasked to complete a complex S&C Renewal at Sandy in Bedfordshire, a busy section of the East Coast Main line approximately 40 miles north of Kings Cross. The work at Sandy was technically much more difficult than Belford as it included one turnout and three S&C crossovers, a mixture of facing and trailing switches over two 54 hour weekend possessions. Seven point ends (see table 1) and associated OLE adjustment is a challenging volume for a 50mph handback for any renewal team. However, building on their success at Belford the S&C North Alliance Doncaster team, under the leadership of Eldon Atherton, took on the challenge to handback the entire Sandy renewal at linespeed of 125mph. In order to achieve 125mph handback all the normal renewal activities associated with 50mph hand to be completed but installed to 125mph construction tolerances. All the welds had to be completed in the core works. Furthermore, a way had to be invented to parallel tamp and dynamically track stabilise (DTS) the long through bearers of the crossovers. The team at Sandy made rail history by reopening all the lines on Monday and again on the following Monday at line speed of 125mph immediately after the core weekend the first time this had been achieved on a complex S&C project in the UK and a worldwide first ever parallel DTS and Tamp of S&C. See image 2. Collaboration with our supply chain and partners was key. The Alliance team worked closely with Network Rail s IP Track Central Engineering and Delivery team who developed and supported the trials of the advanced technology that was used to ensure that machinery and processes could be used effectively on S&C sites. Working with the supply chain was also important to ensure that the high tech plant was available and, where necessary, adapted to work on a S&C renewal. A PROGRESSIVELY ASSURED, RIGHT FIRST TIME APPROACH The key to delivering higher speed handbacks is accuracy and getting each step in the installation of the track Right First Time. The difference between handing back with a temporary speed restriction and reopening at full speed comes down to working within much narrower tolerances and ensuring that ballast is consolidated effectively before the line is reopened, rather than allowing the ballast to settle under normal traffic. To make a 125mph handback on S&C a possibility, the Alliance team as both designer and installer - reviewed every step of the track renewal process in detail to work out how best to achieve the narrow tolerances required. This has resulted in a series of incremental improvements that helped to deliver the first 125mph handback at Belford and made the attempt to replicate this on the more complex layout at Sandy a realistic and safe goal. Throughout the two core weekends, the team adopted a robust progressive assurance process which was measured and signed off at every stage of the construction process by a named Responsible Person for that stage. 53

3 Image 1: First Ever 125mph handback of S&C at Belford (All photographs reproduced courtesy of the S&C North Alliance) This created an evidence file which was critical for the Authorised Person (speed raiser) to be able to assess the line as fit for reopening at 125mph, in addition to their normal checks and balances. In order to sign off each phase progressively and ensure Right First Time construction, a method of measurement and a tolerance set had to be agreed. The tolerances applied had to be achievable and verified with known technology, and increasingly had to narrow though each construction stage. For example, it would be impossible using a 3D Total Station Controlled dozer to get the bottom of the excavation to a finished +/-5mm to its absolute design position. However, for finished line and level an even greater precision is required. If, at any stage of the S&C construction, the tolerances are not met then the work done is rectified immediately to meet the tolerance. However, if time is an issue and rework cannot be achieved then the opening speed of the line is reduced to the tolerance band achieved. For certain stages, an Authorised Person is allowed the discretion to override the tolerance, but for other stages the tolerance is absolute and the opening speed must be set accordingly. Table 1: Sandy S&C Table 2 The method and tolerance required for each stage of the construction is outlined as follows. Table 3 54

4 Image 2: SB Rails 09 4s Unimat 09-4x4/4S Parallel Tamping and DTS at Sandy Image 3: Robust Separator and Geogrid Image 4: Stiffness Trace from Bomag Roller Image 5: Bomag Variomatic Roller FORMATION AND EXCAVATION If available the excavation may be controlled by 3D machine guided excavators. If not, then it must be controlled by marking the excavation width with a continuously sprayed line. The excavation depth should be controlled by a minimum of dip measurement using a scanning laser as a datum. The trimming of the excavation shall be undertaken by a 3D laser machine controlled dozer to achieve the tolerances shown in the table 2. Any areas of poor formation shall be noted including any remedial action taken. BOTTOM BALLAST Ballast shall be installed to the finished design level of the bottom ballast to a tolerance of +/10mm for speeds between 65mph and 125mph and to a tolerance of + 10 / - 40 mm for speeds between 0 to 60mph. The design level of the ballast shall be achieved by use of a 3D laser machine controlled dozer. During the placement of the bottom ballast the technical staff will ensure that the dozer is always pushing ballast across the full width of the blade to ensure that no depressions are left in the finished ballast level. The delivery of ballast will be such that small quantities of ballast can be offloaded and reloaded to ensure that the required amount of bottom ballast can be placed. The technical staff will undertake spot checks at a minimum of 5 metre intervals to ensure that the bottom ballast has been installed to the design level. The bottom ballast surface is to be recorded by the dozer or surveyed by the technical staff using a detail pole and total station or similar equipment. The bottom ballast surface or survey must be attached to the RFT progressive assurance signature sheet. See table 3. CONSOLIDATION / COMPACTION OF BOTTOM BALLAST The ballast shall be compacted by means of using Triple Wacker Plate(s), Vibrating Rollers (image 4) and Dynamic Track Stabilisation (DTS) (image 2) in accordance with table 4. In areas that the Vibrating Roller cannot access, the area of the bottom ballast must be subject to a minimum of five passes over the entire surface of a Single/ Triple Wacker plate. In areas where the Vibrating Roller is used then a target stiffness of 80MN/M2 should be inputted into the Roller control system. See image 3 The Roller cannot be used on category 3 structures and is limited to a maximum and structural assessment is required for category 2 structures. Bottom ballast compacted by means of a Triple Wacker must be subject to a minimum of five passes of the Wacker plate over the entire surface areas. 55

5 Image 6: 3rd Arm tamping In order to maintain productivity it may be necessary to compact the bottom ballast in stages related to panel length. The Responsible Person must assure themselves that five passes have taken place. The S&C North Alliance are working Southampton University, Datum Group and Torrent to understand if a reliable measure of ballast stiffness that can be used for assurance can also be established for use with Triple Wackers. BOTTOM BALLAST LEVEL AFTER COMPACTION The compacted bottom ballast surface is to be recorded by the technical staff using a Detail Pole and Total Station or similar equipment. This survey information must be reviewed by Authorised Person or Responsible Person who must be assured that the bottom ballast level has not dropped greater than 50 millimetres. Table 4: The compaction requirements shown in this table are mandatory 56

6 TAMPING For speeds of 65mph to 125mph the site shall be subject to a minimum of one pass of double tamping the construction tamp and one pass of single tamping the finishing tamp. For speeds up to 60 mph the site shall be subject to two passes with a minimum of one pass of double tamping the construction tamp. However, best practice is two passes. The site supervisor or site engineer is to walk through the site with the tamper operator before tamping commences. They should point out any obstructions and ensure that the tamper operator is satisfied they are marked up correctly and understand what work is required. Furthermore, any bearer/sleeper and rail height changes must be clearly marked so that the tamper operator can adjust his tine depth settings. The supervisor or site engineer must ask the tamper operator if the tamper is in calibration and if the pre-use lining checks have been carried out. The lining check is essential. If the calibration is not proven then this must be recorded on the phires form and escalated via the on call system. All sleepers and bearers should receive an 8 point tamp. The S&T Manager must ensure that any S&T equipment that prevents a full 8 point bearer tamp is removed or not fitted until after tamper has operated. If this is not practical then any bearer that has not received a full 8 point tamp must be hand tamped between passes. (See image 7). Image 7: Back drive removed to allow for 8 point tamping If the bottom ballast level is lower than 50 millimetres below the sleeper bottom design value after consolidation then the opening speed of the line must be restricted to 60mph. There are two reasons for this restriction: 1. The maximum lift a tamper should apply is 75 millimetres 2. Excessive drops in ballast level post consolidation (greater than 50 millimetres) could indicate a soft spot in the track bed. This soft spot under traffic will rapidly develop into a track geometry fault S&C PANEL AND PLAIN LINE ALIGNMENT BEFORE TOP STONE DROP When placing track panels or installing rail, the supervisor shall ensure that the rails ends are tightly butted at the rail joints. The alignment of the S&C and Plain Line shall be controlled by the technician using a Total Station and Detail Pole or similar equipment and installed within a lateral tolerance in accordance with table 5. Adjustments to the track alignment are to be made with approved equipment for sluing track such as hydraulic slue jacks. A survey is to be carried out by the Technician of the lateral track position. These tolerances need to be achieved before the top stone is dropped. TWIST CHECK BEFORE TOP STONE DROP The risk of derailments of an Auto Hopper is very high if the twist over 3 metre is greater than 1 in 150 (20 millimetres). To mitigate this risk a full twist check must be carried to ensure the 3Ametre twist though out the worksite is no greater than 1 in 200 (15 millimetres). Therefore, the supervisor is to ensure that before Auto Hoppers are used a full 3 metre twist check of the worksite (including turnout lines) must be carried out. Any 3 metre twist greater than 1 in 200 must be rectified before Auto Hoppers are used. This twist check must be carried out after each Auto Hopper pass. The twist check is a mandated requirement. Note: If progressive assurance has been followed then the twist values recorded should always be below the 1 in 150 maximum. The tamper third arm should always be used to support long bearers. (See image 6). If the tamper is equipped with a brush this should be used to clear the rail head of ballast and dust. If the tamper operator is unwilling to engage in the above activities this should be recorded on the phires form. To assist in data analysis of the combinations, the tamper / DTS will carry out a pre- and post-tamp geometry recording run on all points. However, these recording runs are not essential and can be cancelled if bar chart timings are at risk of being exceeded. For each chainage, the variance of the installed track position from design shall be recorded for the parameters of line, level and cant. The geometric tolerances achieved must be the agreed North Alliance Right First Time Tolerances shown in the table 6. The tolerances in TRK/2102 should be the target during the core works and must be achieved during the follow up tamp. After each tamping pass the track should be surveyed every 5 metres using a Detail Pole and Total Station or similar equipment. The as-built information must then be passed to the Authorised Person who must be assured that the geometrical track position is fit for the planned opening speed. It is acceptable for isolated step values for top and line to be greater than the indicated table. 57

7 Image 8: Datum Group Voidmate Remote Void Meter However, if two consecutive step values for top and line are greater than indicated in the table then the Authorised Person shall limit the opening speed in accordance with table 5. DYNAMIC TRACK STABILISATION (DTS) For speeds greater than 95mph DTS must be used. Optimum DTS performance is only achieved when the ballast cribs are level with the top of sleeper and a ballast shoulder is in place. The site supervisors must ensure this as far as is practical. Maximum DTS should be applied after or during the first tamper pass (construction tamp) to ensure maximum ballast consolidation. Maximum DTS is only allowed to be used during combined DTS Tamper or after the first tamper pass (separate tamper). A second subsequent DTS pass must be carried out in automatic mode. Automatic mode ensures the design geometry is followed by the DTS and prevents excessive accelerations being transmitted though the S&C system. The though route and turnout route must be subject to the same number of DTS passes. The DTS ramping up/down should duplicate the run in and out of the tamper. Table 5 Table 6: S&C North Alliances RFT Tolerances 58

8 If there is a category 3 structure within the worksite. The DTS should be ramped out 20 metres ahead of the structure and should not be ramped in again until 20 metres after the structure. If the existing track system is of poor quality then the DTS should be ramped down 20m in advance. All work carried out by the DTS is recorded. The resulting trace should be reviewed by the Authorised Person as part of the commissioning process. After the final DTS pass, the PWay, S&T and E&P engineers are to examine and rectify all equipment to ensure no components have worked loose. This includes all temporary bonds. ASSESSING THE OPENING SPEED The person undertaking the duties of the Authorised Person is responsible for determining the speed at which the works shall be opened to traffic. In making this decision, the following items must be complied with in addition to those that would be considered for any other hand back decision: The consolidation report shall show that no soft areas of formation have been left untreated. The measurement trace from the Roller or DTS can be used for this purpose The level readings for the pre-compacted ballast should be the designed sleeper bottom level The bottom ballast must have been subject to a minimum of six passes with the Wacker Plate or treated with a Vibrating Roller Confirm the post compaction and post tamping ballast levels. These should not vary significantly and must be no greater than 50 millimetres. If greater than 50 millimetres then the maximum opening speed should be no greater than 50mph The as-built geometry must be acceptable for speeds greater than 60mph, based on the parameters set down in Table 2. During the first follow up tamp the as-built geometry must be brought into compliance with NR/l2/ TRK/2102 All joints must be welded for speeds greater than 50mph. There must be no temporary joints left in situ, back hole drilled or otherwise INSPECTION If the line is opened to traffic at speeds greater than 50mph the Authorised Person shall remain on site to observe the passage of at least five trains to confirm that the opening speed is appropriate for the track condition. If this is not the case then appropriate steps shall be taken to reduce the speed and take any other action necessary to ensure the safe passage of trains. The track position is to be continuously monitored and surveyed in planned line blocks for the first 24 hours. This track position must be measured after the first train has passed. Void Meters (preferably remote Void Meters see image 8) are to be fitted at the interface between the new and existing track, on the crossing nose and switch toes. The Datum Voidmate system allows 24/7 remote monitoring of voids. A series of alarms is set so that a situation that could potentially lead to an ESR being applied can be predicated early, and a safe system of work can be planned to rectify the fault to maintain line speed. Within the extent of the works if voiding occurs that is greater than 7 millimetres within the S&C (3m ahead of the switch toe and 3m beyond the last though bearer) or 14 millimetres outside of the S&C (Plain Line) then the line speed must be reduced appropriately until rectification work is carried out. After the first 24 hours the track shall be inspected under traffic at least once under the direction of an Authorised Person certificated to the line speed the track is operating at. The passage of trains shall be observed over each line during each inspection. Where voiding is observed, Void Meters shall be installed to record the actual deflection and the readings taken shall be compared to previous and future results to ensure that the voiding is not increasing. The Contractors Responsible Engineer (CRE) shall review the results of the inspections daily and, in discussion with the Authorised Person and site technical staff, determine whether the current speed restriction remains appropriate and whether other works are necessary to preserve the prevailing speed restriction. Resource must be available to carry out daily inspections. If required by the Authorised Person, monitoring shall continue for a minimum of 5 days following handback at speeds of 60mph or greater. CONCLUSION PRECISION ENGINEERING AND EFFECTIVE USE OF TECHNOLOGY To reopen the line at Sandy at 125mph, a number of advanced engineering techniques were used to install the track to its exact designed geometry and ensure the ballast was effectively consolidated to provide a solid base: Using 3D dozing while excavating to formation level and placing the bottom ballast to within an agreed tolerance of its absolute design coordinates. This technology is a more effective and precise way of excavating as it saves the tamper from undertaking large alignment shifts which can undo the consolidation of the bottom ballast. Production waste such as over-digging is also minimised, resulting in less spoil, less ballast and fewer ballast wagons used. Use of the Variomatic Bomag Roller to uniformly compact the bottom ballast. The Bomag provides an objective measure of the load bear ability (stiffness) of the track bed a quality control measure that had previously been unavailable. Placing the track panels to within 5 millimetres of their absolute design position using GPS rather than expecting the tamper to make large alignment adjustments. The world first use of DTS. Following the successful used of combined DTS tamping on a single turnout, two /4S Dynamic Tampers were used in parallel to tamp two crossovers. In a world first, the two machines worked simultaneously to lift the crossover rails at the through bearers on both sites of the crossover in parallel. This was essential to ensuring track quality and mitigated the risk of leaving the bearers unsupported or distorted by the uneven movement. This process bedded in the track and ballast without the usual traffic settling period, by applying forces equivalent to 200 high speed trains passing over the tracks consecutively. Fully welding and stressing the track for the line speed within each core weekend. BENEFITS The S&C North Alliance now has the capability to hand back fast lines at their line speed of 125mph immediately after the engineering work is completed. To achieve the quality standard required to hand back a site at 125mph, the installation must be completed to a very high standard and Right First Time. Track installed to a higher quality has greater longevity, improved reliability, performs better and has a lower life cost overall. For passengers, reopening at full line speed of 125mph immediately after the work, eliminates delays associated with temporary speed restrictions. This is critical on busy high speed passenger routes such as the East Coast Main Line. For our customers, allowing the trains to run to their normal timetable immediately after engineering work has enormous financial benefits. The work at Sandy alone saved 600,000 in schedule 8 compensation payments. For the workforce, completing the work Right First Time is ultimately much safer. It removes the need for speed restrictions, follow up work tamping and remedial work, taking workers away from trackside and away from harm. 59

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