The cost of securing access
Why access cover design can be a major influence on chamber safety
A fatal accident following a tripod collapse over a wet well led Green to undertake a detailed assessment of chamber and surface access cover safety. He found most covers offered "little or no protection" to men working on the edge of holes, sometimes up to 10m deep and often filled with water or sewage. Even opening hinged covers, he believed, "put men on the wrong side of the cover," with nothing between the worker and the void. As well as the inherent dangers of working by deep chambers the weight of many covers presented the additional threat of back injury when they were moved.
As a result of his research Green set about designing a hinged access cover which would eliminate the risk of falling while remaining practical for on-site engineers to use. Following design work which included looking at the hinge mechanisms on domestic items such as windows and garage doors, a prototype was developed and demonstrated to cover manufacturers.
The idea was taken up by steel cover specialist Brickhouse and developed into a centrally-sprung hinged cover which incorporated a removable chain barrier around the entrance and grid over the void. The cover is opened with a vertical lifting action from a stationary, balanced position Ð making it unnecessary to stand over the open shaft. The lift is spring-assisted, and the cover supported and withdrawn on a roller to reduce the physical demands on the operator. A lone worker can open the cover, which once raised acts as a shield between worker and chamber. The cover can also act as a platform upon which to work on equipment retrieved from the chamber, removing the need for slewing items clear of the opening.
The risks involved in accessing chambers and raising heavy items like pumps are highlighted by the series of regulations the new cover, called Guardsman, is designed to meet;
Richard Green believes Guardsman is "as safe as you can get," and AWG specifies the cover or its equivalent at all new sites. Cost, however, means retro-fitting will not take place.
Guardsman is more expensive than traditional covers and improved safety alone may not be sufficient to encourage water companies to make the investment. "Unfortunately," said Green, "water companies tend to go for cheap," but he believes the cover will pay for itself in four years because of a reduction in man-hours lost through accidents and back strain. Manning costs can also be saved because it does not require two workers to open the cover. Andy Buchan believes the water companies' attitude towards the cost of safety is less clear cut. Buchan is commercial director of Saint-Gobain Pipelines, which manufacturers and markets access covers under the Stanton PAM and Brickhouse brands, and he has found water customers vary from those who seek innovation and are willing to pay for it, to those who simply want the cheapest possible cover. "Safety," said Buchan "is an acid test, a challenge to water companies to see if they are interested in spending more to save their staff."
Like Richard Green, Buchan believes safer, more expensive covers, will over time save money. As an example he cites Stanton PAM's Opt-Emax access cover. Opt-Emax uses a pair of triangular sections to cover square or rectangular openings, and because the cover is split in two the weight which needs moving to access the void is halved from 25kg to 12kg. This and the hinge mechanism make access less of a physical task and are designed to reduce one-off and repetitive strain back injuries. As well as a cut in the man-hours lost due to injury, the split cover - like the Guardsman - can be manipulated by one engineer, so manning levels can be lowered. According to Buchan: "the more forward thinking water companies are the prime movers behind this sort of thing."