A railgrinder (or rail grinder) is a maintenance of way vehicle or train used to restore the profile and remove irregularities from worn rail track to extend its life and to improve the ride of trains using the track.
Rail-grinding equipment may be mounted on a single self-propelled vehicle or on a dedicated rail-grinding train which, when used on an extensive network, may include crew quarters. The grinding wheels, of which there may be more than 100, are set at controlled angles to restore the track to its correct profile.
The machines have been in use in North America, the United Kingdom and Europe since the early 20th century. They are made by specialist rail maintenance companies who may also operate them under contract.
The early 2000s saw several advancements in rail maintenance technology, most notably the introduction of track reprofiling by rail milling trains for which advantages in accuracy of the profile and quality of the processed surface are claimed. A second technology which is gaining widespread acceptance in Europe, Germany in particular, is "high-speed grinding". While it cannot reprofile rails like milling or other grinding trains, its working speed of approximately 80 km/h allows defect removal and prevention to be achieved with little or no impact on other scheduled traffic.
Hand-held rail grinders
The ERICO Company manufactures hand-held rail grinders and drills for the railway industry as maintenance of way tools. ERICO uses Honda four-stroke engines to power their railway drill and rail grinder. Rail grinders are used for rail preparation prior to the attachment of bonds, and serve as a multipurpose tool capable of rail prep, maintenance and repair.
Grinding quality index
The grinding quality index (GQI) is a software-based template used to measure the profile of a rail. This allows the desired rail profile to be compared to the actual rail profile. GQI software makes use of laser-based hardware mounted to the front and rear of the rail grinder. The use of laser-based hardware on maintenance of way vehicles such as rail grinders allow workers and contractors take precise measurements of the rail profile before and after grinding. The GQI is rated from 0 (low priority) to 100 (high priority). Grinding Quality Software is able to record and document measurements independently and provide a GQI rating for each rail on the track for before and after each pass on the grinder. The advantage of using GQI software is the ability to produce post-grinding reports for later usage by planners to help further prioritize and monitor grinding profiles in the future. GQI reports also provide analysis on the consistency of profiling to determine if grinding operations are consistently improving or deteriorating the rail profile. The usage of GQI software also provides the ability to produce accurate assessments of rail grinder effectiveness in real-time which allows for work to be prioritized more efficiently and be executed in a timely manner.
In the railway industry, there are risk factors involved with the prolonged usage of maintenance of way vehicles by vehicle operators during day-to-day track maintenance and construction. A common risk factor is prolonged exposure to excessive whole body vibration and shock exposure to the vertical and horizontal axes of the lumbar spine and vertebral endplate which can lead to spinal injury and or long-term damage to the vertebral bone structure. The American Conference of Governmental Industrial Hygienists has in the past proposed threshold limit values for whole-body vibration with certain guidelines also being based on ISO-2631 standards, but no official exposure threshold limits for maintenance of way vehicles have seen widespread publication or enforcement. The ACGIH-TLV limits worker whole-body vibration exposure to no more than 8 hours in duration. In the European Union a new risk assessment model (VibRisk model) for structural failure of the lumbar spine in the lower back was proposed as a result of vibration risk research. The VibRisk model provides more specific risk assessments of vertebral endplate failure on individual lumbar levels taking into account driver posture. When compared the risk assessment proposed using the VibRisk Model posed a higher risk of vertebral endplate failure at different lumbar levels than ISO-2631 Part 5 standards suggested. The main contributing factor that VibRisk incorporates that the ISO-2631 Part 5 standards are lacking is the recognition of operator posture as an additional stress factor when exposed to vibration and multiple shocks.
Rail corrugation is a type of track wear that develops from track and train wheel set contact over time. Once this process has started it will begin to grow exponentially worse as time progresses. The wear that develops due to the wheel set contact between railways takes its form in the many troughs and crests it leaves behind over time which may or may not develop into rail corrugation depending on the circumstances. The estimated tendency for wear is calculated by taking into account fluctuations in track and wheel set contact which causes the amount of wear to vary. The dynamic properties of different lines of the track can lead to varied degrees of rail corrugation through the use of high-speed wheel sets. In a study of high-speed railroad tracks, four types of tracks were studied for their tendency to develop corrugation (RHEDA 200, AFTRAV, STEDEF, and high performance ballasted track) and of the four considered the ballasted track was the one least prone to rail corrugation with the AFTRAV track being the second most reliable as well.
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- Zarembski, Palese and Euston. (2005). Railway Track and Structures: Monitoring grinding effectiveness, v 101, n 6, p 45-48
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- Correa N.; Oyarzabal O.; Vadillo E.G.; Santamaria J.; Gomez J. (2011). "Rail corrugation development in high speed lines". Wear. 271 (9–10): 2438–2447. doi:10.1016/j.wear.2010.12.028.
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