The challenges

Sydney Metro Northwest is the first stage of the new metro system in Sydney, Australia. It is Australia’s biggest public transport project. Northwest Rapid Transit (NRT) has been awarded the Operations, Trains and Systems contract for this project. The first stage of the project is estimated at $8.3m (AUD). It runs from Rouse Hill to Epping and includes a 4km elevated Skytrain, a 270-metre cable-stayed bridge, and twin 15km tunnels. This is also Australia’s first autonomous (driverless) rail system.

NRT contacted Pyrotek to source acoustic absorbing materials for the rail tunnel and viaduct. The designers of the tunnel and acoustic consultants had specified acoustic absorbers on both walls of the tunnel, as well as in the four-foot section (between the tracks). This was done to give maximum passenger comfort and the aim was to provide very low noise levels for passengers.

As well as being excellent noise absorbers, any materials selected also needed to be fire safe. This means that the non-combustibility of the materials is important, as well as making sure that if the material does get hot that it does not emit smoke of toxic fumes. Many traditional absorbers, such as foams and polyesters, do not meet the required standards for rail tunnels, so alternate materials were needed. Also, the four-foot section was designated as an emergency exit pathway so any materials in this area also need to be ‘trafficable’, meaning that they can be walked on by pedestrians.

The solutions

When first approached by NRT, Pyrotek proposed two different materials. One for the tunnel floor (T1) and another for the tunnel walls (T2).

The product proposed for the walls (T2) was Reapor. This lightweight, high absorbing material is fire safe and is produced by bonding together millions of expanded recycled glass beads. The contract for this product was awarded to Pyrotek and the product supplied from April-December 2017. The material was imported from Europe by Pyrotek and stored in Australia until required for the project. In addition to this, Pyrotek also cut to shape the majority of the product in Australia to meet NRT’s requirement.

The solution for the T1 area on the tunnel floor (four foot) was less straightforward. Pyrotek proposed several materials for this application but all were rejected. The main reason for this was the strength of the product. The requirement that the product is ‘trafficable’ was one not encountered previously, so Pyrotek’s technical team stepped in and from their archives of technical knowledge developed a material with the correct properties. This material has all excellent fire safe characteristics of Reapor, with the additional advantage of being very strong. With some clever use of Pyrotek’s reverberation room in Sydney, the material was also tuned to give the optimum acoustic absorption at individual frequency bands. This allows the material to more specifically reduce the noise of the moving train. The T1 product is called Viterolite 900.
Viterolite 900 was presented to NRT and approved for use on the project. The contract was awarded to Pyrotek with supply from September 2017-June 2018. This allowed a 9-month manufacturing window for the product.

The results

Having received the contract, Pyrotek leased a site in Sydney to manufacture the product and designed the plant and equipment to manufacture this large volume of panels.

In July 2017, it became clear that the original delivery schedule no longer met NRT’s programme. Pyrotek was requested to accelerate the project and complete deliveries by the end of December 2017. This has been achieved and required the casting of over 100 tonnes of material each day, working 24/7.

NRT area manager Simon Tibbet said “Pyrotek has been a flexible and committed partner making sure we have received the acoustic materials for the Sydney Metro Northwest project on time. Being local and able to change plans as needed has been invaluable to the project and has helped with the planning of logistics and installation. Their ability to meet the revised delivery programme for the T1 panels has been critical to NRT completing this project on time.”