Composite manholes ‘safer than iron’
New materials are making access covers safer and less expensive, says Andrew Burton, general manager of Structural Science Composites, a manufacturer that has joined the Motorcycle Action Group for a new campaign
Chartered engineer John Newton, inventor of the composite cover, says: "Considerable design effort has been directed by SSC at developing the slip-skid properties of its composite covers. The tread design is thought to be the first non-directional pattern provided on a manhole cover.
"Unlike many anti slip-skid solutions, the treads are not a stick-on addition but are moulded as an integral part of the composite structure using embedded aggregate technology, and exhibit excellent slip-skid properties straight from the mould."
The aggregate that forms each tread has two unique properties. It has a hardness value of 9 on the Mohr scale, which is similar to that of a ruby, and provides exceptional wear properties.
The second property is the aggregate's resistance to polishing and it is this property that is responsible for maintaining the slip-skid value throughout the cover's life.
Whole-life costs are also an important factor. A recent market research study, carried out by Lancaster University, showed that a typical water company might have up to 1M manhole covers in its estate, mainly in metal.
Utilities might well experience theft and vandalism of installations as well as the repeat replacement and maintenance cost through wear and tear, along with rising insurance costs. The study found that in relatively high traffic areas, covers and frames were changed out on average every seven years. Cost comes mainly through the implementation and planning associated with a change out, rather than the procurement cost of the asset itself.
These costs often run into four-figure sums. The lifetime of an SSC composite cover and frame is four to five times that of its metal counterpart, taking into account reduced change out costs and the fact that composite covers have no value on the scrap market.
Recent research by research consultancy WRc said that, "The water industry spends over £40M annually on repair and maintenance of the ironwork that covers their sewer systems."
The following statements support the argument that ductile iron covers are not 'fit for purpose': "Our survey revealed that up to 85% of manhole covers on heavily trafficked routes had failed in some manner. It also highlighted the fact that there are a small but significant number of locations where the service life of the cover installation is measured in months rather than years." (WRc)
"There is no doubt that manhole covers are a danger to motorcyclists. The covers that are most often used are ductile iron and often start life with some grip to their surface. After time, with constant contact, the grip diminishes and leaves us with the smooth, dangerous surfaces that cause us problems." (Access Legal, Shoesmiths).
"Worn or damaged metal access covers are motorcycling's equivalent of playing a game of Russian roulette." (Paddy Tyson, MAG UK) From a legality aspect, under the New Roads & Street Works Act 1991, utility companies have a duty to maintain manhole covers to the reasonable satisfaction of the highway authority. Where a utility company has been negligent in the execution of its powers under the Act, resulting in personal injury, it will be liable in damages.
Local authorities do not actually own any more than about 10% of the manhole covers in the road, but they are in a position to affect planning policy, when it comes to new building projects and encouraging the use of certain materials. Section 58 (Defences) of the Highways Act, Highway Authority Defences to Claims from Defective Roads section states that there is no obligation to improve a highway, only to maintain it, and highway authorities are under a duty to maintain the highway in a fit state to accommodate the "ordinary traffic which passes or maybe be expected to pass" along them.
By raising awareness of the important safety, performance, liability and cost issues, the Get a Grip team's composite story continues to win over expert audiences at a large number of specially organised events and exhibitions around the country. Converts include specifiers, influencers, road users, MPs, government, local authority and council officials, transport engineers, water companies, and bikers.