TPT November 2011

A rticle

Figure 8 : Travelling milling cut-off unit with milling cutter blade

Precise cutting-to-length of the tubes and square and rectangular section is effected by means of a travelling milling cut-off unit. Two milling cutter blades, 380mm in diameter, perform a burr-free quality cut (Figure 8). 4. Production results After a joint technical clarification, the tube welding plant was ordered in November 2007 and supplied in March 2009. The start of production was in July 2009. From the start, the plant produced the intended quality at the designed speed. After an initial training period, the plant, from the strip preparation line through to the cut-off unit, is run by five operators (per shift) in total. To date, the following dimensions (Table 1) and grades (Table 2) have been produced. The dimensions/products, in particular, are products which represent a special market segment. The plant achieves an average operating time of 70%, with an output per day of up to 500 t in the running-up phase. Thanks to the rigid plant design and the reproducible plant setting, optimum production settings are quickly achieved, resulting in a very small number of defective tubes. Arvedi intends to achieve a future annual output of 150,000 t in 2-shift operation. The products manufactured to date are characterised by their very high quality.

Figure 6 : Sizing section

The de-twisting stands serves to stabilise and correct the seam in the 12 o’clock position. The sizing stands are identical with the fin- pass stands. The 4-roll design (Figure 7) allows the sizing of round tubes as well as the shaping of special section tubes with rectangular and square cross-sections. Round tubes are straightened by off-centre positioning of the 3 rd sizing stand whereas special sections are straightened on the downstream universal straightening Turk’s head. All stands and side closers are motor-adjusted and are positioned via the quick-setting system. Positioning is computer-controlled and reproducible. The roll change is performed by means of the changing carriage. For changing, the changing assemblies, consisting of the roll, shaft, shaft bearing assembly and bearing, are automatically moved into the changing position, pushed onto the changing carriage in a horizontal direction to the operator side, and replaced with the prepared changing sets equipped with the new rolls. This concept allows the use of individual rolls and the reduction of the changing time to a minimum. The system permits a total changing time from good tube to good tube of approximately 90 minutes.

Figure 7 : Sizing roll arrangement (4-roll design)

Table 1 : Size range of new 12¾" ERW line Diameter (mm) Thickness (mm)

Steel grade

Standard / Application

127 ÷ 219 127 ÷ 323

8.0 ÷ 16.0

S355

DOM

4.0 ÷ 16.0 S355 & HSLA Mechanical and structural with dimensional tolerances ½ of that specified by the standards

100x110 ÷ 250x250 120x80 ÷ 300x200 Table 2 : Standards and grades Standard

Grade

Note

EN 10129 EN 10129

S235N ÷ S355N S275M ÷ S460M

Structural Carbon steel

HSLA

API 5L

B ÷ X70

API 5CT

J55 ÷ N80

101

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N ovember 2011

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