A Water Treatment Works, which provides 200 million litres of water a day to over 3 million homes and businesses, urgently required inspection and repair works on a large water contact tank just below ground level.Challenge
To keep the water clean, a very small dose of chlorine is added systematically to the water in the tank. The tank was drained for the urgent inspection and repairs but, due to a faulty valve, there was chlorine entering the empty tank. This created an extremely hazardous
atmosphere, making entry into the tank impossible without significant RPE and breathing apparatus.
Following a site survey and analysis, RVT proposed a strong positive pressure and air-change system, effectively utilising the "lanes" in the tank as a duct. This was achievable thanks to hatches at each end of the lanes which served as ideal entrance and exit points for the air. A pair of powerful Ventex® 600S high pressure fans and flexible duct runs were sited at these hatches to purge the tank with a high air change rate.