Slow and not operator friendly and whilst not completely unsafe our risk assessment of our projects highlighted potential problems. In order to achieve the production of approx 300lm in a 4hr working window we would require an unacceptable level of labour intensity. Labour which would be moving quickly in a restricted area carrying very hot material by hand. We decided to risk assess the current method out of the project and decided to try and devise a safer and quicker system.

First of all we purchased 250gallon pre heater tanks which heat the material and then maintain temperature control by thermostat. We mounted these on trailers which we could easily move with site transport.

Then we attached a specially developed heat lance to extrude the hot bitumen directly into the chase in a continual stream. Extrusion nozzle only needs to be guided by applicator. Although material at 160 deg is passing through the lance it is armour protected so that it cannot burst and it is cool to touch. Machine is towed along length of chase as it is sealed by the lance operator.

The traditional method of infilling the chases (13mm wide by 100mm deep) was to use hot oxidised bitumen at 160 deg C poured into the chase using a steel watering can. In order to achieve the target production (300lm per 4 hr shift) we estimated as many as 12 men with watering cans were required. We felt that this would place a higher than acceptable risk on these men as they would have to walk back and forward to the bitumen boiler with very hot bitumen in a steel watering can many times a night in close proximity to one another. An incident or a trip, fall or a collision between operatives was considered high risk and we set out to look at an alternative safer method of bitumen application.

We discussed the problem within our contracts managers and supervisors and came up with some ideas. It was difficult to find a solution due to the nature of the material. At 160 deg C oxidised bitumen is very fast flowing but will cool down rapidly when away from a heat source. We decided to go to the specialist hot materials handling industry and find out if there was a special type of pipe or hose that could be adapted to fit on to a large bitumen boiler. The hope was that if we could find such a hose we could fit a special type of nozzle to deliver the bitumen directly from the boiler to the cable chases without the need to manhandle many small quantities of bitumen.

After many attempts and re-design works the system was perfected and first used on the 23-05 runway refurbishment at Stansted. On average 250lm was achieved in a 4.5 hr possession the maximum achieved was 485lm with 3 men using one bitumen application machine.

This level of production proved vital in the overall success of the project making sure asphalt could be laid on time and on programme.