Ventilation Supplied During Inspection and Repair Project at Water Treatment Works

Project Overview

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. A solution was required where safe entry could be achieved without the encumbrance of other bulky equipment. To add to the challenge, the inspection and repairs required completion in just one day.

Solution

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. To create a positive pressure environment, clean air was continuously pumped into the tank via the entrance points, and then the contaminated are was leaked out through the exit points. This system was quick to install, extremely effective, and allowed the work to go ahead without delay and with no risk to site operatives’ health