TPT November 2011

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November 2011 101 ›
Article
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 3rd
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.
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
Figure 7: Sizing roll arrangement (4-roll design)
Figure 8: Travelling milling cut-off unit with milling cutter blade
Table 1: Size range of new 12¾" ERW line
Diameter
(mm)
Thickness
(mm)
Steel
grade Standard / Application
127 ÷ 219 8.0 ÷ 16.0 S355 DOM
127 ÷ 323 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 S235N ÷ S355N Structural Carbon steel
EN 10129 S275M ÷ S460M HSLA
API 5L B ÷ X70
API 5CT J55 ÷ N80