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Case Study - Wire Sawing

Queen Elizabeth Hospital- Birmingham- Wire Sawing Operations Case Study

Gnat's Diamond Drilling team overcomes difficult access problem with modified HILTI Wire Saw

The challenge faced by contractor Morgan Est, on a pipe realignment project in Birmingham, was how to remove- in less than two days- a section of brittle, 1100mm diameter cast iron water main, embedded in a concrete saddle and lying just 660mm from a similar live pipe carrying one of the city's main water supplies. The solution was to call in specialist Gnat UK Limited, who used a newly developed diamond wire sawing machine to cut through both cast iron and concrete in a fraction of the time needed by conventional milling machines and at one third of the cost. Additional advantages of the machine, an adaptation of Hilti’s WS10 compact wire saw, include ease of erection, cutting accuracy through the cast iron of less than 5mm and- crucially for the adjacent 100 year old live pipe- no potentially damaging vibration.

Morgan Est's contract centred on diverting a 275 metre length of twin pipe main, carrying drinking water to millions of Birmingham's population, around the future site of the city's new university teaching hospital. Maintaining the water supply was so crucial that Seven Trent Water would allow only 12 hour working windows while the 7 metre length of each pipe was cut out and replaced by a new junction section - with the adjacent pipe always remaining live.

Using percussion breakers or hydro demolition to remove the concrete saddle risked damage to the nearby live main. Cutting the 15mm thick cast iron pipe itself with a conventional milling saw would have resulted in an overall four-day operation. Gnat UK's new machine cut through the lot in less than two hours and completed the two cuts for each pipe section in just one day. Based on Hilti's established diamond wire cutters used for concrete, this more compact and mobile machine consists of a 5 metre long multi strand wire threaded through a series of five guide pulleys and driven by a linked hydraulically powered wheel. The 10mm diameter wire is kept under constant 6 bar tension by an integral pneumatically operated piston.

The really clever bit is the wire itself; strengthened to cut through a 100mm length of 15mm thick cast iron pipe in less than 15 minutes. Cylindrical metal beads, located every 30mm along the wire, are each heavily impregnated with up to 100 industrial diamond chips ' a density 30% greater than used in concrete cutting tools.
'Their machine proved effective, safe and accurate,' said Morgan Est site agent Jay Standen. 'There was really no other way we could have completed the work in the time available and I was pleasantly surprised how quickly it solved one of our major problems.'

Birmingham was the first commercial test of the machine cutting through cast iron. Its unqualified success leaves Gnat UK Limited, optimistic over a wide range of future uses.
'It can cut through virtually anything including steel, and we envisage good market opportunities ahead,' concluded the company's project manager Mike Hill.

Mike Hill can be contacted on: Tel: 0844 840 4440 or Mobile: 07738 622265