RIDC Tuxford, Network Rail’s rail innovation and development centre at High Marnham, is where new on-track machines and heavy plant are put through their paces and certified for operation on the national network. Rail Engineer was there recently (issue 148, February 2017) to look at Network Rail’s new ballast cleaning train.
Now this reporter has been invited back for an exclusive viewing of a Loram C4400-series rail grinder, the first of a fleet of three machines that Network Rail has ordered from American rail grinding specialists ‘Loram Maintenance of Way’, based in Minneapolis.
Compared with the high output ballast system that was on show last time, C44-01 is relatively small, consisting of only four cars, but what it lacks in length it makes up in complexity and sophistication.
First, let’s consider why Network Rail needs such a fleet of grinding trains.
Those with a knowledge of recent rail history in the UK will, unfortunately, recall the Hatfield crash, the sad loss of life it caused and the chaos which followed. This led to the demise of Railtrack and its replacement by Network Rail.
Not surprisingly, this accident was investigated very thoroughly, and it was found that the rail failure that derailed the train had arisen because of rolling contact fatigue (RCF) cracks in the rail.
RCF damage that appeared similar was found in many places all over the rail network, and needed to be rectified quickly. Clearly, there was also an urgent need to prevent the growth of similar rail cracks in the future.
Much of the cracked rail that was identified was replaced by re-railing, but it was simply not practical or economic to replace all of it. Neither would it have been feasible, for practical and economic reasons, to control the problem in the future by re-railing alone. Some other measure was required.
Looking at developments elsewhere in the world, one option used by other railways was rail grinding. This technique had been used in the UK, in a relatively limited way, for other reasons, such as the removal of rail corrugations or to generate surface roughness to improve adhesion. However, it had not been used to control the growth of cracks such as the RCF damage.
Rail grinding can be carried out using machines controlled by manual operators, but the scale of the operation that was now required meant that special rail vehicles or trains were sourced. These are fitted with banks of grinding heads, each angled differently so that, between them, they leave the correct profile on the ground rail head.
Because rail grinding creates large volumes of dust, a mix of steel and abrasive particles, and since it generates high temperatures (250ºC), special measures are needed. These include dust collection and disposal systems, spark arrestor devices and water spray mechanisms that can be used to extinguish any lineside fires that may be ignited.
Grinding is noisy, so noise attenuation measures are also very necessary.
Research into the RCF damage mechanism confirmed that the dangerous cracks could be controlled by periodically grinding off the layer of cracked steel from the running surface of the rail, maintaining a small gap between the gauge corner and wheel, thus preventing cracks from reaching a depth that could lead to rail failure.
Other aspects of the research indicated that a major contributor to the initiation and growth of RCF cracks was a mismatch between the profiles of the rail head and the wheel profiles of the trains running on it.
Rail grinding was known to be an effective means of reprofiling the rail head, to return it to the right shape to work well with the wheel profiles of the trains. Given appropriate wheel profile management by train operators, this would ensure a huge reduction in the incidence of RCF damage. It would not eliminate it all, because there are other causes besides the profile issue, but that which did still occur would be safely controlled by properly managed rail grinding.
Rail grinding trains were available at this time, and Railtrack, followed by Network Rail, availed themselves of these very successfully.
An indication of how successful the latter’s rail management has been is given by the history of rail failure statistics. Around the time of the Hatfield crash, rail breaks on the national network were averaging 1000 per year. Current figures are typically around 100 and, more often than not, these are due to failure of the foot of the rail and not the head.
Not all of this improvement is due to rail grinding, but a high proportion must be credited to it.
Currently, Network Rail has a significant fleet of rail grinding trains – five switch & crossing grinding trains, three trains that carry out preventive rail grinding cyclically, and three that are sent out to specific, targeted sites in response to an identified need. Preventive grinding, the main defence against RCF, is planned on a two-yearly cycle of regular treatment and is often carried out in traffic,
without requiring any possession.
However, the existing trains are getting old, most can travel in traffic at only 50mph, and are no longer competitive in terms of their rates of production. Consequently, some years ago, Network Rail began planning to renew part of the fleet with three modern trains. This resulted in a CP5 business plan item to develop, procure and bring these into use.
CRG-01, the first of these Loram rail grinders that Rail Engineer saw under test at Tuxford, is a four-car consist, one of two such which form part of the order with Loram. Both of these are in the UK already, the second being CRG-02 which, at the time of our visit, was at Derby undergoing checks. The third train, a seven-car variant (PLG-01), is currently under construction in the USA.
The four-car units have two grinding cars, each of which carries two grinding ‘buggies’ containing four grinding stones per rail, so that there are a total of 16 stones per rail on each car, or 32 in all.
There are control/driving cars at each end of the train, both fitted with air-cooled axle-mounted AC traction motors. One driving car carries the propulsion power pack, while the other has welfare and workshop facilities, including messing, toilet and washing facilities, and lockers for the crew’s gear.
Cummings tier 4 diesel engines driving threephase AC generators provide 480V power, and the train also has two Atlas Copco air compressors. Large water tanks provide for the fire suppression equipment, and the volume of water available will often be the limiting factor in determining how much work a train can complete in a shift. However, the capacity on these machines is double what was previously available.
Grinding cannot continue once the water has been used if there is any risk of lineside fires.
Clever technology enhances the capabilities of the trains. The main chassis frames include hollow, rectangular longitudinal members. Some of these are used as ducts for the dust suppression system, while others carry cooling air to the traction engines.
The train’s control system measures the rails using laser scanners to evaluate the rail profiles and the position and width of the running bands, whilst an eddy current crack detection system measures any RCF cracks present. Using that information, the optimum grinding profile outputs can be determined automatically.
The trains are designed to reduce, to the absolute minimum, the requirement for anyone to go out onto the track. For example, each of the grinding buggies has a sensor at each corner that detects that the buggy is correctly sat on the rail when it is lowered. The fire suppression equipment, mounted on each grinding car and at either end of the train, is operated remotely from the control cabs, and there are CCTV cameras to provide the driver and controllers with images of the surroundings of the train.
That said, at each end of the train there is a fire hose that can be brought into use if it becomes necessary for a member of the team to go onto the lineside to control a fire in person.
The four-car trains can remove up to 0.5mm of steel from the railheads at a pass, though it will not often be necessary to remove so much in normal use. As the seven-car train will have a total of 64 stones in its four grinding cars, it will have twice that capacity, but is more likely to use this to permit it to travel at greater speed whilst removing a given depth of steel than could the smaller units.
All of the trains are designed to operate safely on electrified lines, whether overhead or third rail. They will have a higher production rate than the existing trains, and will be able to travel in traffic at 70mph, enabling them to transit from location to location significantly faster than the existing units and resulting in significantly higher availability.
However, the increase in transit speed is a significant issue for Loram and the Network Rail project team, led by Leevan Finney. The rules about train braking are much more demanding and it is quite tricky to produce a braking system which meets the requirements for a 70mph transit speed whilst still being able to provide the necessary fine speed control at the low speeds necessary for the grinding operation. Chris Lidberg, Loram’s project engineer, and his colleagues Todd Hanks and Jeff Erickson, were dealing ably with the challenges of testing out the braking and other systems. Whilst Rail Engineer was on site, the first 40mph braking test was successfully achieved.
Each train will be expected to operate 290 shifts per year with only routine servicing, such as the replacement of grinding stones, removal of collected dust and the like. There will be only one major maintenance overhaul for larger tasks.
The trains are managed by Colas Rail under a separate contract with Network Rail. Jim Reid, rail grinding delivery manager, explained that the crews will be fully trained to maintain and repair their trains, up to and including being able to remove one of the big diesel engines, or even a buggy, and replace it with a new one should that ever be necessary.
Incidentally, the trains also have provision for control from track level, using a hand held remotecontrol unit that can be plugged into the side of a grinding car between the two grinding buggies.
This allows movement of the grinding equipment for cleaning, to check its operation or to facilitate changing worn stones.
All in all, these new trains should well justify their cost by helping to ensure the safety of the network more efficiently, with reduced noise and increased service life, whilst causing less disruption to traffic.
The first of the new units should be ready to enter service in June 2017. Network Certification Body (NCB), the notified body and designated body for the project, is also providing plant assessment body certification. Daniel O’Brien, NCB lead assessor on the project said: “We have been working closely with Loram throughout the design, manufacturing and testing phases of the project; and despite the main production facility being in Minnesota, USA, we have developed an excellent working relationship with the production team.”
NCB has assessed all aspects of the vehicle ranging from structural integrity to on-board safety systems, involving a wide range of TSIs, Euronorms, railway industry standards and railway group standards. NCB has already issued the ISV (intermediate statement of verification) certification to support dynamic testing, which has enabled type tests such as brake testing and ride characteristic testing to be conducted to support final certification.