WCA January 2017

Material Savings The challenge for today ’ s manu- facturers is to determine what target is to be chosen within the scope of the specifications. If the criteria for determining the construction were based solely on the economics, the industry would gravitate to the unilay conductor schedule, and the smallest diameter that is allowed within that schedule.

8 wire sizes required using conventional system 2 wire sizes required using SIW system

❍ ❍ Figure 1

The roll form process allows unilay products produced up to 500mm 2 . Statistical analysis of strands compacted with methods (die or rollers) other than the roll form system has shown that a typical material variance of ±1% to ±1.5% must be expected. These results, therefore, lead to the need to oversize the conductors by at least three per cent in order to ensure that product does not fall below specification. This excess material is, effectively, given to customers free of charge. When utilising the Ceeco Bartell roll form system with its strand design software, the material variance is reduced dramatically. Giving a real and very tangible material saving over conventional compacting methods, this is particularly important with the current cost of aluminium and copper. This means that the minimum diameters specified in the IEC and ASTM standards can be achieved, while at the same time approaching but not exceeding the maximum resistance.

It should be noted that the concept of using a single input wire to manufacture a range of finished conductor sizes is not new; it is used within the confines of most manufacturing plants within the allowances of the current specifications. It has been used extensively in Europe where strand programmes using the single input wire diameter to cover a range of finished conductor sizes has been in existence for decades. The potential cost reductions using this process can be split into the following areas: • Process savings • Material savings Process Savings The obvious impact of the incorporation of roll forming into the stranding process is shown in Figure 1 . While still working within the constraints of the IEC and ASTM standards, the roll forming process allows the number of wires required to produce a range of conductors to be reduced dramatically. In this case, to cover 35mm 2 to 240mm 2 the number of wires has been reduced from eight to two. In a similar way, 35mm 2 to 500mm 2 the number of wires can be reduced from 12 to three. This reduction in the required number of wire sizes brings about major cost savings in the wire drawing area: • Creates a higher productivity in the wire drawing machine due to the elimination of multiple set-ups for the different wire diameters required for the traditional strand designs • Reduces the amount drawn wire scrap through wire size changeover • Creates a reduction in the wire drawing die inventory Similarly the roll forming process has a cost saving impact in the stranding process: • Lower volume of different wire sizes being produced to await the stranding process • Ability to use larger package sizes and switch from a bobbin system to a stem pack system • A reduction in down time due to loading, with the ability of automatic pay-off changeover while the machine is running • Quicker set-ups for different strand sizes due to the elimination of the movement of different pay-off sizes • Higher linear production speeds, when compared to conventional stranding methods • Reduction in manning levels in the stranding process

❍ ❍ Figure 2 : Strand simulator output 150mm 2 compact strand

❍ ❍ Figure 3

Economic analysis of 95mm 2 XLPE product Fill factor

86% 92% 96% 1=6=13 1=6=11 2=6=9

Configuration

Outer diameter (mm) Outer gap area (mm 2 )

11.7

11.39 11.07

15.88 0.710 0.663

Insulation cos t (US$/km)

131.35 109.55 106.83

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Wire & Cable ASIA – January/February 2017