Ventilation System Designed and Supplied for Five Month Sewer Works Project

Project Overview

RVT was brought in to design and provide a ventilation system to protect workers conducting an overhaul of a sewage system in Yorkshire.

The work was being carried out in a live -flow sewer chamber, where discharges of fats and oils were blocking siphons. The plan was to unblock the siphons by removing an existing walkway and other steelwork and installing a smaller, new walkway to prevent further obstructions.

As well as being an unpleasant environment to work in, real dangers to health existed in the form of noxious, and even explosive, gases. It was vital to provide a supply of good quality air so that the work could continue safely.

The correct balance also had to be found between applying enough pressure to remove contaminates from the siphon, while being careful not to apply so much forced air in that it could disturb pockets of gases and create the risk of gas explosions.

Challenge

Over and above the normal challenges of supplying air to confined spaces, the design of the ventilation needed to allow for the impact of changing weather conditions and rates of sewage flow.

There was also the danger that if fresh air was supplied into the confined space under too much force, it could disturb pockets of gases, and thereby increase the risk of explosions.

Solution

RVT considered all the danger factors and designed a tailor-made plan of action which centred on the installation of a powerful ventilation fan to replace pungent, stagnant and contaminated air with a welcome flow of fresh air. They gave careful consideration to the dynamics and dimensions of the sewage tunnel itself, measuring its exact distance and size, in order to control the air flow effectively and deliver air at the correct pressure.

This would ensure workers at the site worked in a healthy environment, free from unpleasant and potentially harmful contamination from toxic gases, as well as removing the risk of explosions. Gas levels were monitored to ensure the ventilation was working.

The Ventex 450 CF (Centrifugal Fan) chosen to drive the air is capable of generating airflow of 20,500m/hr so was ideal to force a supply of fresh air through ducting into the furthest end of the sewer tunnel. In addition, the positive pressure created by the fan ensured contaminated air was continuously replaced.

RVT took all the details, went away and came back with the correct solution, backed up by detailed calculations, to select the most reliable safety equipment to suit this specific task. As always, they provided a professional solution and quality kit we could rely on.”