Product category:
Design and Development Consultancy
News Release from: DavyMarkham
Edited by the Engineeringtalk Editorial
Team on 28 March 2007
Cutter head provided for enormous boring
machine
Sheffield engineering company DavyMarkham has produced the giant cutter head support and final drive housing support for the world's largest hard rock tunnel boring machine.
Sheffield engineering company DavyMarkham has produced the giant cutter head support and final drive housing support for the world's largest hard rock TBM (tunnel boring machine), to be deployed on a landmark Niagara Falls hydroelectric project The GBP 500,000 contract was placed by the Robbins company of Ohio, with whom DavyMarkham has a long-standing business association, dating back to the joint venture production of two marine running TBMs for the Channel Tunnel
Last year, Canadian hydroelectric company Ontario Power Generation announced the appointment of major European construction company, Strabag of Austria, to build a 10.4km hydro tunnel stretching under the world famous city of Niagara Falls, from the upper Niagara River to the Sir Adam Beck power stations at Queenston.
Running parallel to the two existing water tunnels, built during the 1920s and 1950s, it will reach a maximum depth of 140m and will be one of the largest tunnels ever built in North America.
During construction an estimated total of 1.6 millionm3 of rock will be removed and, upon completion, it will increase the Beck power generating capacity by 1.6 billion kWh per year, sufficient to supply 160,000 extra homes.
Strabag s using the specially-designed Robbins TBM to bore a tunnel of 12.5m finished diameter the machine was assembled on site to reduce overall construction costs and meet the project's tight delivery schedule.
The open, hard rock TBM will incorporate Robbins' proven floating gripper design and the cutter head will be powered by a 4725kW variable frequency drive system, expandable to 5040kW.
The machine's average advance rate is around 12-15m a day, with the spoil likely to be used by Ontario's clay brick industry.
DavyMarkham supplied the cutter head support and final drive housing, which bolt together to form the TBM's front-end drive module housing and carry Robbins' 500mm cutters.
In addition to collaborating on the 8.4m diameter Channel Tunnel machines, which proved to be the fastest TBMs on the whole project, the Sheffield company has previously worked with Robbins on such diverse tunnelling projects as Boston's Big Dig highway tunnel, a 10m TBM for the Manapouri underground power station in New Zealand, the Lesotho highlands water scheme in Southern Africa and the New York Queens subway tunnel.
For the Niagara tunnel project, DavyMarkham manufactured a cutter head support fabrication measuring approximately 7.2m in diameter, 1200mm deep and weighing 85 tonnes, and a final drive housing of the same diameter, which is 1100mm deep and weighs 44 tonnes.
The cutter head support houses the 15 motors/gearboxes that continuously rotate the cutting tools at relatively low rev/min, breaking the rock face into chips that are collected in a rear-mounted chamber.
The final drive housing carries the main bearing, to which the cutterhead adaptor is fitted, and is sealed internally and externally to prevent the ingress of dirt or water, with galleries through the fabrication for routine oil lubrication.
Steel plate in thicknesses up to 150mm was used for both units, which required 1300 machining hours and 6700 man hours in total.
Semi-automatic MIG welding was used for the fabrications, which were fully stress relieved before machining on DavyMarkham's large vertical and horizontal borers, then non-destructive tested using ultrasonic and magnetic methods.
Delivery of the finished components was direct to Niagara Falls, in line with Robbins' on-site assembly techniques.
Tunnelling work is currently progressing on schedule, with new, clean electricity expected to be produced by late 2009.
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