A SSC Thrubeam Crestapol GRP composite pedestrian manhole cover in London’s Parliament Square.
A SSC Thrubeam Crestapol GRP composite pedestrian manhole cover in London’s Parliament Square.

The EN-approved SSC composite manhole and drain covers use Scott Bader’s Crestapol acrylic resin transfer moulding (RTM) resin in a patented Thrubeam design which produces a stiffer beam in combination with the reinforcement.

The covers which are typically three to four times lighter than an equivalent steel or reinforced concrete cover but have load bearing capabilities to meet BS EN124:1994 Standards Group 4 Class D400. This standard specifies that an access cover must be able to cope with static loading from cars, vans, lorries and HGVs if installed in areas such as carriageways, hard shoulders, factory sites and industrial estates; to pass BS EN124 Class D400 an access cover or grating must withstand a 40 tonne test load. 

Non-corrosive covers

The RTM process helps give the covers improved strength-to-weight ratio, surface details and anti-slip finish. SSC covers are also inherently non-corrosive, non-conductive, and avoid problems relating to theft for their scrap value, which is a real issue with metal covers.  

“After extensive new product development trials and testing different UPR and epoxy resin systems, we were very pleased that Scott Bader was able to develop a special grade of its Crestapol high performance acrylic resin for SSC that met all our needs,” said Andrew Burton, general manager of SSC. “The custom Crestapol grade we now use firstly provides a level of physical properties to match our Thrubeam technology and meet BS EN124 test standards. Secondly, the resin’s rheology and very fast cure rate at moderately elevated temperatures enables us to manufacture our composite covers consistently, and with a high level of confidence that parts will meet our quality standards.”