TPT March 2016

AR T I C L E

Dalian Field

Double-car cut-off machine aims to help increase competitive power over the next 20 years By Guowu Gao, chief engineer at FD Machinery

Only the flying saw is limited because the process of cut-to- length on 4-8m tubes cannot be accurately completed in a short space of time, so the line speed is always restricted. Taking a Dia76mm pipe mill as an example, when wall thickness of 3mm for tube, 60x60mm or pipe Dia76mm, if it is equipped with single car flying saw the line speed economically can be 50-60m/min. When wall thickness is 1mm for tube 20x20mm or pipe DIa25mm it can be 100-120m/min. A few pipe mill makers call for higher line speed, but this is at the expense of saw blade life and incision quality without practical usage or benefits. Pipe mills with double-car flying saws can have a speed of 120-150m/min and 200-240m/min or higher for the above-mentioned size tube production with saw blade life and incision quality that is not decreased. The benefits of double-car flying saws is not only in improving the maximum line speed but also in levelling line speed features to make line speed of cutting big size and thick wall thickness tubes similar to that of small size thin wall thickness in a single line. This is a more meaningful improvement for those who mainly produce big sizes. The producer can use the new flying saw to get double the efficiency it could previously, and the ratio of investment and benefit is cost-effective. When speaking about line speed usually we assume it is for 6m product lengths, but some tube and pipe makers may produce 3m or shorter lengths. For a line equipped with single-car flying saw, a fall of the speed in production will be far more than that of the length shortened, which will not only seriously affect the efficiency of the production line, but also

xx FD Machinery has been developing a new double-car flying saw since 2014. The first saw has already been commissioned for an ERW pipe mill at Mitwalli Steel Products Co in Saudi Arabia, with line speed up to 150m/min. The machine has now been successfully in production since the middle of last year. The second set of saws will be installed at a similar mill and will be put into production in early 2016 for the same company. The third set will operate at up to 200m/min and will be used at APL India for an existing mill. The flying saw has been praised by the customers thanks to its excellent performance in increasing line speed and due to the longer saw blade life achieved. Performance and applications Double-car flying saw: as the name implies there are two cutting cars equipped in one production line and they operate as per their own control model and finish the cutting on pipes or open profiles alternately. Because of the use of two independent cutting cars on the same line the job that was originally performed by one cutting car is replaced by two cutting cars. The duty cycle of one car is twice as long as a single car and overall cutting time is more than doubled. Due to the extension of cutting time the saw blade life is extended as well as the cut end quality, which is better than before. Therefore, if the cutting time and incision quality remain unchanged the line speed is also improved. The most common choice is for the speed, blade life and cutting quality to be improved at the same time to make the line speed and cutting time increase together. It is well known that the bottle-neck for line speed in tube and pipe and roll-forming mills is often the flying saw because the mill speed can be improved without limit and technology such as the HF welder can be upgraded to meet the requirements of any high speed mill currently in operation (although most roll-forming mills are not equipped with a welder), and high-speed pipe packing machines can solve product collection problems with ease.

Double-car flying saw

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M ARCH 2016