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Ventilating Totley Tunnel
Ventilating Totley Tunnel
Factair recently completed its largest ever ventilation project at Totley Tunnel. Factair were working for ameyCOLAS who were completing a track and formation renewal contract on both roads from Grindleford station towards Totley.
At 3.5 miles in length, Totley Tunnel is the longest mainline railway tunnel, that runs its entire distance under land, in the United Kingdom. The tunnel is located on the outskirts of Sheffield and was completed in 1893. During its natural construction a natural cavern was discovered near the centre of the tunnel which is several hundred square feet in area and it was decided to incorporate this into the design and a large ventilation shaft was installed up to the surface at this point. This part of the tunnel is now fittingly described as “The Cathedral”.
With 4 additional ventilation shafts at the Totley end of the tunnel Factair’s engineers soon realised this was going to be a challenging project to ensure the entire work site was adequately ventilated. Factair’s engineers calculated that at any one time there was up to 12 Megawatts of diesel engines powering the equipment operating within the tunnel. When you consider the dust and fumes being generated from the work undertaken, not to mention the frequently moving plant equipment within a confined space, you can appreciate these are places where you certainly need to keep your wits about you.
Unusually prevailing conditions in the area meant air tended to be drawn in from both ends of the tunnel and ventilated out through “The Cathedral” ventilation shaft. As the length of the renewal work on one of the roads extended beyond “The Cathedral” Factair had to ensure air did not become stalled within the tunnel when its forced ventilation counterbalanced the incoming natural ventilation.
Normally Factair would temporarily install ventilation systems adjacent to the portal which would blow from one end of the tunnel all the way through to the other. The system would have sufficient power to keep the whole column of air within the tunnel moving at a minimum of 80 metres per minute, thereby ensuring the air within the tunnel was continually being replaced and limiting the build up of dust and fumes. This arrangement has a number of advantages over fans deployed locally within a tunnel. Firstly it avoids the possibility of the fumes and dust only being shifted along the tunnel but not out of it. Secondly it ensures there are no additional obstructions within the tunnel, keeping the workspace clear for the movement of plant and personnel.
For Totley Tunnel Factair had to provide a system which could be varied to suit the changing natural conditions, this resulted in 18 of its 1.2 metre diameter electric fans being installed in the Cess adjacent to the Grindleford portal, delivering a maximum total airflow of 1.5 million cubic metres per hour! In addition a self contained 1.8 metre diameter engine driven fan was located in “The Cathedral” which produced an additional 180,000 cubic metres per hour. During the blockade the electric driven fans were run in varying numbers, to maintain a safe working environment, whilst also ensuring air speeds did not become too high and cause a significant wind chill in the cold winter conditions. The diesel driven fan was used to assist the induction of air into “The Cathedral” past the 4 previous ventilation shafts. As the work progressed through the tunnel and beyond “The Cathedral” the airflow was managed to ensure that the natural airflow from the Totley end continued to ventilate those working in this area.
During the blockade Factair’s engineers remained on site to ensure the equipment operated continuously and to regularly test air quality, wherever there was a worksite within the tunnel. The pollutants tested included carbon monoxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, airborne dust particles, volatile organic compounds, acetylene, hydrogen sulphide as well as the oxygen level; also the key members of staff such as machine operators, machine controllers and COSSs were individually issued gas detectors which monitored the main pollutants. This element of the service is vital and is designed so that at no point do those within the tunnel never have to leave the worksite unnecessarily unless pollution levels have risen above those stipulated in EH40. The readings during the blockade are then compiled into a formal report which provides a useful health and safety record.
For the dustiest applications such as controlling auto-ballasters or for staff with existing respiratory problems such as asthma, Factair also provided battery powered air fed helmets. These self contained units deliver filtered breathing air to the face of the user and feature an integral hard hat, hearing protection and eye protection to EN397.
With this comprehensive ventilation system Factair was able to ensure ameyCOLAS was able to complete the renewal work within the tunnel without any disruption due to problems with the atmospheric conditions. Should you have a tunnel renewal project, where you suspect fumes and pollution could be a problem, then Factair is on hand to recommend a solution and provide a no obligation site survey and quotation. To contact the company call 01473 746400.
