A new generation of Swedvent underground ventilation fans and ducting system from GIA Industries offers reduced noise levels. Improved silencer design offers noise reductions of at least 3 dB(A) for the full range of fan motors rated between 10 and 500 kW to meet 75-85 dB(A) at 7m. The improved sound damping has been achieved with a specially designed silencer filled with processed mineral wool to reduce high frequency sounds.The ventilation system features advanced impeller design incorporating a large hub, short blades and, accurately measured spacing between the blades to give the fan an enhanced ability to counteract high pressure systems. The dynamically balanced impeller rotates in purpose – designed guide vanes to eliminate turbulence.Individually adjustable aluminium blades allow the same fan to be used for a number of different tunnel conditions by adjusting the blade angle. For example, a 1,250 mm diameter fan can be set to deliver 16-44 m³/s. The range of Swedvent fans is available with 630-2,240 mm diameters and 1.5-200 m³/s capacities. They are built in a rugged anti-corrosion treated design to withstand aggressive environments. The GIA Swedvent range of fans is particularly suited to long drifts allowing two or more fans to be installed in series offering increased power to counteract the possible high pressures in the tunnel ducting.The Swedvent ventilation system also features GIA’s flexible, pvc-coated polyester fabric ducting available in diameters from 300 to 3,000 mm and lengths of 10 up to 200 m; to ensure a pliable, easy to handle duct, with a relatively low weight and highly durable ducting.Increased tear strength is also assured with an enhanced yarn in the base fabric every second centimetre. The flexible ducting system is also manufactured in two different standard qualities and two antistatic qualities which meet SIS650082 fire resistance.Both duct ends are fitted with a split, heavy duty, PVC-type zipper and made with protective flaps on both the inside and outside to ensure an absolutely airtight ducting. The ducting can be used several times on different projects, and, if it should fail, is very easy to repair. The airflow is shut off causing the ducting to collapse: a fabric repair sleeve is then applied to the damaged area and closed using its zip joint. When the airflow is returned the sleeve stays firmly in place.