Henkel has developed many rail-specific solutions, formulated in compliance with the BS Fire Approval standards which were introduced following the catastrophic 1987 Kings Cross underground station fire. Here we take a look into the solutions available and their rolling stock and rail applications.
For anyone involved in designing for the rail sector, 1987 was an important marker – it was the year of the catastrophic fire at Kings Cross underground station that led to the introduction of new and stringent British Standard (BS) Fire Approvals. These regulations now govern the use of all construction products specified for rail applications.
For companies such as Henkel, this move has led to the development of dedicated products for the sector. As a provider of industrial adhesives, sealants, surface treatment and sound deadening coatings, its products are used for a broad diversity of applications in the rail industry.
Not all, however, need BS Fire Approval – the determining factor is the quantity used, and less than 400g of the product per car makes them exempt. So, for traditional Henkel Loctite applications such as threadlocking and threadsealing, no fire approval is needed. However, with bonding and sealing technology now proving either a superior alternative – or good complement – to mechanical fastening, the company has developed many rail-specific products. These are formulated in full compliance with BS criteria because they are used in considerably greater quantity than the 400g threshold.
Structural bonding products within the Henkel Teroson range are a case in point. This range contains dedicated products that are fire resistant – signified by the FR suffix – with a good example being the new Terostat MS 939 FR. Not only is this a flame retardant version of its standard counterpart, it is also a member of Henkel’s new Health and Safety family. These products are free from hazard labels and, for some months, have been available for thread-locking, thread-sealing, gasketing and retaining.
With the introduction of the silane modified polymer, Terostat MS 939 FR, the rail industry can now call on a label-free structural bonding product which also meets its own fire approvals. Henkel’s UK MRO manager, Geoff Bickerton, explains: “This product is proving ideal for bonding coving – the rail equivalent to skirting board – to the floor and vertical wall of the carriage. It provides an effective seal that stops the ingress of water into underfloor cable trays during deep cleaning.”
There are many reasons why train builders choose structural bonding instead of, or in combination with, conventional jointing methods. More uniform stress distribution over the entire bond face is one of them. It has a very positive effect on the static and dynamic stress achieved, eliminating the localised stress peaks caused by welding or riveting alone.
Whilst welding may change the structure and therefore the mechanical properties of materials, structural bonding does not. It is also weight saving, able to join dissimilar materials, forms a protective film to prevent corrosion and acts as an electrical and thermal insulator.
Another product regularly used to join dissimilar materials and provide a highly durable seal is Terostat Butyl, supplied as a tape or kneadable formulation. A prime application for this plastic sealant is on the bellows that create a gangway between carriages. As well as being bolted to the respective carriage ends, the bellows frames are also sealed to provide good resistance to water.
Due to its inherent tackiness, Terostat Butyl product adheres to metal, glass, ceramics, mineral substrates, wood and plastics. A key benefit for the bellows application is its high flexibility even at low temperatures, and it provides excellent protection to the galvanic corrosion which these structures are susceptible. It is also ideal for sealing electrical enclosures.
Dedicated corrosion protection
Corrosion prevention is as important to the rail industry as it is to the automotive sector. Henkel has developed industry-leading pre-treatment and surface coating technology for cars and it is now starting to apply this knowledge to rolling stock. Bickerton explains: “Corrosion warranty on modern cars owes its longevity to pre-treatment and using similar technology we have now put together a complete paint system for train builders. With the asset value of a train at around £1 million per carriage it makes sense to give it the highest protection against the elements.”
For this purpose a rail-approved Loctite Nordbak polymer composite has been developed by Henkel. This is a two part epoxy coating, whose durability is assured by the inclusion of ceramic beads or fillers. Its key advantage is to create a sacrificial and renewable working surface that protects the structural integrity of the original substrate.
In combination with pre-treatment this is proving ideal for protecting a wide range of under-train structures such as axels, air receivers and motors.
On the track
In addition to the construction of rolling stock, Henkel also supplies products for the building of rail infrastructure, a good example of which featured at the Infrarail 2012 Exhibition. In fact Henkel Cerosit CF900 has just been specified to bond fixtures onto 1000km of new slab track in China.
T: 01442 278235