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A new system for pumping out CFA lines which promises higher safety standards has been going through its paces at a High Wycombe project.

With piling systems that use air pressure to pump concrete posing a safety concern for site personnel, and with a rising number of serious incidents occurring across the construction industry, Stent has developed what it claims is a groundbreaking procedure for pumping out concrete lines with water.

Stent is using its new system at High Wycombe in Buckinghamshire, where it is installing a total of 1459 piles, ranging in diameters from 450mm up to 1200mm, for a new retail development for Multiplex Constructions (UK).

While piling companies commonly use compressed air to pump out concrete lines, Stent's CFA process manager Neil Burrows has been developing the new water pressure system since the beginning of this year.

'Compressed air is used to generate sufcient pressure to pump concrete through the lines, but it creates a hazardous environment for piling operatives, ' he explains. 'When the concrete has been pumped, the air forces the sponge ball out with an enormous force. This is not a sufficiently controllable environment and there is always risk of accidents.'

To minimise risk, barriers are normally erected around where the ball exits the system to try to contain its expulsion and any concrete owing from the pipes. The company says that while it has an unblemished record in this regard, there have been a number of serious injuries and even fatalities using the compressed air method.

'Stent wanted to look at developing a system that would primarily enhance safety, ' says Burrows.

'We now have a fully integrated system that achieves this aim and, as a consequence, it also improves our site efficiency.'

By using water to clean the concrete lines, Stent claims to have virtually eliminated the risks posed by compressed air. In the pumping line, four toughened foam balls and Prima Pump mix fluid create a sufficient seal between the water and concrete. This ensures the aggregate does not separate and cause a blockage. No water passes into the concrete because the Prima Pump mix is sandwiched between the balls and the concrete mix. As the concrete is pumped out of the lines, the sponge balls are gently ejected in a controlled manner and drop harmlessly to the ground.

'People were concerned that this process wouldn't work, as water cannot enter the concrete mix under any circumstances, ' says Burrows.

'When water is pumped into concrete the aggregate segregates and causes a blockage. However, by using the foam balls and Prima we create a seal between the water and concrete so it cannot enter the concrete mix.'

The contractor says the system not only eliminates the risk of injury to piling operatives near the rigs, but also to the public when rigs are situated close to people or moving traffic. 'To a degree, public safety can be compromised with air, ' continues Burrows. 'But as the water system simply ushes the balls out of the end of the pipes, they fall onto the ground without any force. There is virtually no risk of incident.'

To create the system, Stent worked with Premier Concrete Pumping to design a bespoke agitator with a tank and integral hydraulic valve system, which houses sufcient water to pump and clean pipes in a single process.

Stent's bigger rigs accommodate 1800 litres in the whole system.

The capacity of the holding tanks has increased to 2000 litres, while the fully integrated water tank allows a pipe to be fed into the concrete pump immediately after concrete has been pumped out of the agitator to clean the lines. Additional hydraulic pumps on the engines assit this hydraulic valve system.

Burrows says: 'We have now created the safest system for CFA piling and Stent is keen for other piling companies to learn from this development on the grounds of its safety benets.

'All piling operatives are fully trained and are required to reach a required level of competency before using it, ' he stresses. 'But as safety is an important issue for the whole industry, we are keen to share our expertise and make this system the industry standard.'

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