Even if you repair low rail corrugation damage, it often returns. With Top of Rail Friction Management, you can address the root cause of low rail corrugation to ensure it doesn’t come back – reducing long-term noise issues and repair costs.
By Richard Williams, Area Sales Manager Rail
Recently, a colleague and I were asked to investigate noise complaints on an urban rail line. The offending piece of track was a tight curve outside a station and our investigation soon revealed the cause – track corrugation on the low rail. In this situation, how can you fix the corrugation so that it doesn’t come back?
In this blog post, I look at why corrugation occurs, how to diagnose the root cause and how Top of Rail Management can stop certain types of corrugation – especially low rail rutting corrugation – from returning.
Corrugation theory: What is corrugation damage?
Corrugation is one of the most common types of rail damage – and therefore one of the most expensive for rail line operators. It can occur on straight or curved tracks and is often exacerbated by heavy traction or braking.
There are different types of corrugation, all characterised by fixed ‘wavelength’ or visual spacing.
Rutting mainly occurs on the low rail in curves. It is caused by the flexural resonance of a wheelset, excited by high lateral tangential forces. Wear is periodic, develops very rapidly and is usually exacerbated by applied traction and high angles of attack by bogies.
P2 resonance is caused by the train’s un-sprung mass bouncing on the track. It can affect any type of network track – either straight or curved – and is especially common on metro tracks due to low frequency ‘rumble’.
Pinned-pinned resonance occurs as the track vibrates between sleepers, like a flexing beam. The high frequency/short wavelength of the corrugation can lead to ‘roaring rail’ noise.
Track form specific: Some types of track construction can cause their own types of corrugation. They often develop after a change in the track’s form – for example, either side of a weld.
Diagnosing corrugation: What is the root cause?
The challenge with corrugation is that each case is unique to the track layout, train type and speed at any given location. Certain types of corrugation are common in certain track configurations (e.g. low rail rutting in tight curves) but diagnosing the root cause may not be straightforward.
This is where noise comes in. In most cases, the first sign of corrugation is increased noise levels on the portion of track where the corrugation is developing. Analysing this noise can tell you what type of corrugation you have.
Using a Wavelength Fixing Mechanism (WFM), you can establish the unique vehicle/track dynamic that causes corrugation. This allows you to “fix” both the wavelength and position of the corrugation on the track.
How to stop low rail rutting corrugation: Top of Rail Friction Management
The standard repair for any type of corrugation is to grind or mill the top of the rail. This is an expensive repair that requires manhours on track and a disruption to services. Unfortunately, it is only temporarily effective, as it fails to address the root cause. This means the corrugation is likely to return and will need to be repaired again.
Luckily, Top of Rail Friction Management can be used to stop certain types of corrugation – especially low rail rutting corrugation – from returning.
Top of Rail Friction Management is achieved by the application of a specially designed consumable material. This Top of Rail friction control material creates a film on the track which acts as a “3rd layer” between the wheel and rail surfaces to ensure that the coefficient of friction (CoF) at the rail crown and wheel tread interface is around 0.3-0.4. These materials are not lubricants and work by controlling CoF to reduce steering forces and rail wear, which in turn leads to lower fuel or power consumption and reduced noise.
When applied to the top of a corrugated low rail after grinding or milling, a Top of Rail Friction Control Material can stop the corrugation from reoccurring, significantly lowering through life maintenance costs. This makes Top of Rail Friction Management the most cost-effective way of dealing with recurring low rail corrugation. As a result, it is increasingly being used by rail operators to stop corrugation from returning and many even apply it on tracks as a preventative measure to tackle the root causes of corrugation damage.
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If you would like to find out more about Top of Rail Friction Management, get in touch with us at RS Clare. You can also check out our Top of Rail Friction Control Material webpage here.