This page contains a Flash digital edition of a book.
News Pneumatic conveyor used for tunnel fill

Aptech has supplied two pneumatic conveying systems as part of a major gas pipe project in the Greater London area. The systems were designed to backfill 6ft and 8ft tunnels with ground glass or sand. Rather than relying on the traditional method of using liquid grout to fill tunnels of this type, the use of a dry fill was favoured. Once grout is set, ground movement can cause it to crack, resulting in potentially damaging levels of stress being imposed on the gas pipe. A dry fill would allow the pipe to move. Then there was the question whether it would be possible to pneumatically convey dry fill the distances required.

“Aptech were the only company to

develop a solution that we had confidence in.” says Chris Rixon, advisor to the project. “Following small scale trials, we were impressed with the final designs and ability to manufacture pneumatic conveying systems that would fill the tunnel effectively. “To have used liquid grout would have required building bulkheads along the tunnel at frequent intervals and then pumping in grout to fill behind them. Even then, this method makes it difficult to fill to the roof and provide a complete and stable fill. Originally a year had been allowed to fill the tunnels with liquid grout, but Aptech completed the dry fill in just four months.”

Aptech’s design included support and movement of the conveying pipe in the tunnel. A cable also runs down the tunnel to instruments at the end of the pipe. Robert Skelton, Aptech’s managing director says: “These machines operate at high pressure, so can convey long distances. Instead of a rotary valve which would wear, they use a screw conveyor to meter the sand into the conveying pipe. The two machines, for small and large tunnel filling, were designed, built and put straight to use. For other applications, this high pressure method of pneumatic conveying is suitable for conveying cement, minerals and biomass.” The sizing of the conveying systems uses Aptech’s unique pneumatic conveying software. This analyses each section of the conveying system, predicting velocity and pressure change at every stage including changes in pipe diameter.

The two systems were distinct insofar as the smaller, lower pressure system was designed to discharge ground glass or sand from 1Te big bags and convey it at up to 14Te/hr to fill tunnels up to 300m long. The larger, higher pressure system was designed to transfer the dry fill from silos to a delivery system, weigh and convey it at up to 60Te/hr to fill tunnels up to 1000m long.

With over 30 years of experience specialising in the design, supply and installation of process systems and equipment, Aptech has established itself among the leading players in powder and solids handling. Through using the latest technology, their comprehensive range of products deliver technically advanced yet cost effective solutions.




Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52