Summary:
A UK concrete cutting specialist with extensive experience in wire sawing recently undertook an unusual job cutting out 2.5 tonnes of unwanted cast iron from a 10 m diameter cast iron cylinder. This is a report on how diamond wire sawing proved up to the task.
Background:
D-Drill (Master Drillers) Ltd based in Coventry, has been in the business of concrete sawing and drilling for 40 years and now operates from 10 branches throughout the UK. Most of the company’s work entails the removal of concrete by conventional diamond drilling or circular sawing methods although like many other companies D-Drill now uses diamond wire sawing more and more due to its versatility.
Every now and then though, a highly unusual request comes through the door, such as when Neil Wood (Branch Manager)at D-Drill’s branch at Wigan, Lancashire was contacted by a company which specialises in the manufacture of heavy ferrous components for the paper mill industry.
The problem:
The company had experienced a problem when pouring a 10 metre diameter, 10 metre high cast iron cylinder, which is poured in one go using sand blocks to form the mould. During the pour, a bung gave way in one of the formation shutters, which resulted in the overspill of cast iron, effectively forming a bulge in the casting. This company has been manufacturing its own castings for over 30 years and this is the first time this has ever happened.
The area of overspill was 4 metre across by 2 metres in height, with a maximum thickness of approximately 400 mm at the centre tapering down to zero at the edges. When it was realised that the bung had given way it was cooled down quickly with water. Although necessary, this action probably resulted in making the iron strength harder.
Before approaching D-Drill the company had tried other remedial methods with no success. Attempts to stitch drill it off with 25 mm diameter steel drills were found to be laborious and were taking far too long. Thermic lancing was also tried, but this also proved to be too slow and had the added risk of lack of control on the cutting route the lancing would take.
With a value of around a quarter of a million pounds, the company was facing a substantial loss if this overspill couldn’t be removed and it was a last resort when it approached D-Drill.
The solution:
The first thing D-Drill did was to contact one of its regular diamond wire suppliers, Hilti (Great Britain) Ltd as it was known that Hilti manufactured a diamond wire - the Hilti DWC 100% Steel - suitable for cutting ferrous materials. Unlike conventional sintered diamond wire used for cutting concrete, this wire has electroplated diamond beads
A site visit was arranged together with Hilti technical representatives to view the job and assess whether the Hilti wire would cut through this particular steel. Once this had been confirmed, the cylinder manufacturer began work on making a suitable jig to fit inside the cylinder to accommodate D-Drill’s wire saw which would enable the diamond wire to cut flush with the required inside diameter.
The jig pivoted on a central point with the wire running from two horizontal pulleys over the height of the mass of overspill to be removed. The in-house manufacturing department managed to complete the jig over a weekend and D-Drill were set up and ready to commence cutting by the following Tuesday.
Using a Hydrostress wire saw driven by a CR3 power pack, the cutting was completed over 20 shifts on site. Work continued around the clock, as time was of the essence. In total it took approximately 220 hours to complete the job.
The cutting consumed 80 metres of wire to cut through an area of 8 m2. Wire speed at 18 m/s, was slightly lower than the normal 27 m/s used for cutting concrete, and the cutting rate was anywhere between 10 - 50 mm/hr across the internal face of the cylinder. Wire length between each pulley was about 2 metres.
Once the wire sawing was completed, the separated mass of cast iron was craned out of the cylinder and recycled. The weight of the segment removed was approximately 2.5 tonnes.
The final result was a fully usable cast iron cylinder delivered to the client as if nothing out of the ordinary had happened. Without a doubt, diamond wire sawing and the skill and expertise of D-Drill had saved the day.
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Picture captions:
Fig 1 Overview of the specially made jig in position to cut the overspilled cast iron shown on the right
Fig 2 A complex pulley arrangement was employed by D-Drill to ensure correct positioning and tensioning of the diamond wire
Fig 3 Close up of the pulley and diamond wire at the cutting face (a) and the wire starting its cut through the bulge (b)
Fig 4 Close up of the pulley and diamond wire starting its cut through the bulge
Fig 5 Two views of the cut section that was removed, which was 2 m high, 4 m wide and weighed 2.5 tonnes
