Siemens S60+ barrier boom development

Climate change and the increased risk of storm damage and high wind strength is just one of the challenging issues that Britain’s railways need to manage. Studies show a decline in days with minimal wind, indicating an increase in windy conditions. Research also suggests climate change will likely lead to more intense storms with stronger winds.

Another challenge for rail is to safely manage level crossings. Level crossing booms of 8.5 metres and above have, under excessive wind loading, displayed problems. This is not surprising given their height when the road crossing is open. The problems include lateral deflections, interference with the barrier closing time, barriers not fully closing the highway, and increased risk of barrier failures. The wind loading has even caused spurious trips of the level crossing obstacle detection system in some parts of the country. Siemens has therefore produced a revised S60 barrier design to address the identified issues. The new design is called S60+.

Risk reduction

Great Britain’s level crossings are among the safest in Europe, but they still pose a significant safety risk to the public, and the law requires railway businesses to manage level crossing risk effectively. Therefore, level crossing asset management is one of the priorities of the Office of Rail and Road (ORR) safety regulator. The ORR’s guidance on level crossings, ‘Principles for managing level crossing safety’, is focussed on continued improvement of level crossing risk management, and it emphasises that risk should be reduced through the design of a level crossing.

A study led by a team of Met Office climate scientists says that the North Atlantic Oscillation (NAO) could reach unprecedented magnitudes by the end of the century, leading to severe impacts in northern Europe. NAO is a large-scale atmospheric pressure ‘see-saw’ in the North Atlantic and is a key driver of winter weather patterns in the UK. It is measured by the gradient between high pressure over the Azores and low pressure over Iceland, and controls the strength of the prevailing winds.

Network Rail expects it will become increasingly difficult to respond to extreme weather events and for railway assets to withstand extreme high winds. So, it will spend £2.8 billion on resiliency and planned maintenance activities during Control Period 7. There are over 1,000 level crossings with barriers on the mainline rail network and they all need to be managed safely and improved to reduce the safety risk to As Low As Reasonably Practicable (ALARP). This is increasingly important given the greater volumes of both road and rail traffic. 

Rugged and reliable

The S60 barrier machine is an established design which has gained a reputation as a rugged field proven unit with an excess of 11,000 worldwide installations. It has been used on Network Rail infrastructure since it gained approval in 2014 and over 88 installations have been provided around the GB network.

Power consumption is either 15A at 12V or 8A at 24V, which are relatively low voltage and currents enabling both cost and space savings on the cable core size and backup batteries. The machine uses electrical direct drive, which improves sustainability due to the lack of hydraulics, and it has simpler maintenance procedures as draining hydraulic fluid is not required.

While the machine is very reliable, it is designed so that maintenance access is at eye level with a swing down door. All vital components are mounted off the floor to reduce any damage from flooding and new motor brushes, when required, can be fitted in a few minutes. 

The eye level access, plug coupled modules, absence of hydraulics, and on-board diagnostic LEDs, enable quick and easy installation and maintenance. The barrier machine is pre-assembled to the mounting post before delivery to site which makes it less time consuming to install. Additionally, the S60 is one of the lightest barrier machines on the GB railway, which leads to a lower cost and less labour-intensive installation. Network Rail says the S60 is one of the most reliable barrier machines on its network.

The boom lights are plug coupled and major bearings are sealed for life. Spare parts stock mainly consists of motor brushes, PCBs, and switches. Boom skirt service kits are available to replace any broken rods – reducing the need for complete boom replacement. With boom lengths without skirts of 2 to 12 metres, and with skirts 2 to 8 metres, the S60 can be deployed on both manned and automatic crossings.

S60+

Siemens has produced the revised S60+ design that includes a stiffer boom aimed at addressing the wind loading and deflection issues. The imposing design of the larger diameter boom was chosen to make it sturdier and more robust, which is beneficial for deterring trespassers.

Golden High Hedges crossing near Donington, on the Lincoln to Peterborough line in Lincolnshire, was a crossing where data suggested some failures were due to the barrier being held up in high winds and exceeding the 10 second operating time. Golden High Hedges crossing was therefore chosen as the trial site for the improved S60+ design. This has now been in use and subject to intense monitoring for over a year and is shortly expected to receive full product approval.

Prior to the in-service trial, the S60+ barrier design was subject to extensive testing in the Siemens Chippenham factory. The testing involved a total of 616,915 cycles and, for a crossing such as the trial site at Golden High Hedges, many components had seen the equivalent of 56 years in service. The test machine was fitted with a 9.2 metre boom which is longer than the typical boom on the network (9.1 metres) and the longest boom at Golden High Hedges is 8.544 metres.

The Network Rail requirement was for a rigid construction, so that the gap between each boom should not exceed 30cm with a specified trespass force. The boom should also not be damaged by a wind speed of 50 m/s and not deflected more than one metre with wind speeds of up to 35 m/s.

These requirements have been met by the new design. The problem with high winds preventing the barrier from dropping to close the crossing is no more, as the barrier is now driven down 70 degrees, instead of just 30 degrees previously, which means it falls under gravity for the remaining distance. The stiffer, more rigid boom design also improves trespass management, making it far more difficult for anyone to force themselves through the barriers.

An additional counterbalance and a modified cage has also been designed, together with a different hand crank system to enable good access and a different wind catcher. A traditional BR843 barrier machine to S60 base conversion bracket is now also available. This will enable an easy ‘like for like’ replacement, if required, with no base change.

Network Rail says climate change is one of the biggest challenges facing the railway today and the weather over the past few years has seen unprecedented rainfall and storms. Climate change is projected to increase the frequency and severity of extreme weather, and Network Rail is planning how to keep passengers and services safe and moving. The Siemens S60+ barrier machine and its improved boom is just the sort of asset and initiative that the railway will need more of.

Image credit: Siemens