Corporate Engineering Ltd.

Rotational Covers Cure Odour Emissions


Source: Corporate Engineering Ltd.

Preventing odour from half bridge scrappers can be expensive. The introduction of rotating covers has provided a cost effective solution. Colin Chamberlain of Corporate Engineering explains why

Odour problems are at best an unwelcome nuisance. Covering the offending treatment processes can provide an effective solution but there are added complications when a process contains large moving components. When Premier International Foods identified they had an odour problem emanating from their 2 primary clarifiers they were quick to take action. As a leading canning company for all of the major food retailers they take their environmental responsibilities very seriously. Richard Smith, engineering services manager, identified two options for containing the odour. The first option was to enclose it in a building and the second was to build a cover over it.

'I wasn’t sure whether it was possible to put a cover on a clarification tank when it has a half bridge scraper,' admitted Richard. 'We were concerned about the reliability of a rotating cover, the strain it would put on the motors and whether an operator could walk across the cover to gain access to the launder channel. We invited major cover producers to discuss our requirements. Corporate Engineering were clearly experienced at producing rotating covers and we were certain that this was the optimum solution.'

There are several important benefits rotating covers offer, the most important being cost effectiveness. Erecting a building over a half bridge scraper contains the odour but also creates a number of further potential problems. Firstly, a building significantly increases the half bridge scraper’s footprint and can present maintenance and access problems. The atmosphere in the building is likely to be hazardous so motors need to be upgraded to prevent the possibility of explosion. In addition, there is increased potential for the corrosion of working components. Installation of a rotating cover avoids all of these problems.

'We have pioneered this technology, manufacturing and commissioning rotating covers both at sewage treatment plants and industrial wastewater treatment plants.' Reflects Colin Chamberlain, Managing Director of Corporate Engineering. 'The principle of the technology is simple. A GRP cover attached to the half bridge scraper and rotates with the bridge, driven by the bridge motor. The cover rotates on a series of wheels which track around the outer wall of the tank.'

While the principle of the cover is very simple, the technology to make the principle work is quite sophisticated. There are two areas that need careful attention to ensure the rotating cover will work efficiently for the lifetime of the scraper. The first is the rotation and tracking mechanism and the second is attaching the cover to the bridge to maintain the integrity of the bridge.

'We conducted a range of trails to ensure that the carriage system works reliably and safely.' Said Colin. 'The innovative element of the cover is the self correcting tracking technology. We have developed a system that ensures the cover rotates smoothly and consistently preventing wear on the bridge motor and delivering reliable long-term performance. As the bridge rotates the cover rotates with it and, in essence, the cover becomes an integral part of the bridge and vice versa. The carriage system has guards which prevent fingers being caught in it during routine inspection or maintenance by works personnel.'

The covers are assembled on site from sections specifically manufactured to suit the tank. Each application is unique and as such cannot be treated as an 'off the shelf' product.

'I was very impressed by the speed of installation. It took a week for each of our two clarifiers to be completed. Installation costs were minimal,' reflects Richard Smith. The covers are 11.6 metres in diameter and continue to operate reliably without any need to upgrade our motors. They have effectively contained the odour within the clarifiers and now form an important part of our odour control strategy for the plant'

Since successfully covering these two 11.6 meters diameter clarifiers Corporate Engineering have supplied a further eleven rotating covers ranging in size from 7.0 meters to 32 meters diameter. The 32 meter covers are believed to be the largest installed in the country so far (photograph above).

While many of the UK applications to date have been retro fitting covers to existing half bridge scrapers there are cost savings associated with specifying rotating covers for new plants. Rotating covers appear to offer effective odour prevention at affordable prices and there is growing confidence in the market that this simple technology will be widely specified in the future.

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