Located in Texas, Gerdau Midlothian ordered a new loop former table for its mill which produces reinforcing bar #3 up to #11, and plain rounds 5/8” up to 3 1/4”.  Russula supplied the engineering, mechanical equipment, installation supervision and commissioning support. The new looper was installed between stands # 16 and # 17 in the finishing end of the 340,000 tpy bar mill. 

The purpose of the mechanical upgrade was to replace a looper table that was installed when the mill was originally built in 1975 with a new, modern uplooper. Since the existing looper table was larger than contemporary designs and lacked critical features, Russula provided a customized design uplooper with a rollerized trough, base and adjustable exit guide to fill in the space between the stands.

Keep the oil in and the water out

Many mills today roll with suboptimal loop formations because they are unable to quickly and easily adjust the height of the eccentric and persuader rolls. The combination of heat, scale, water, and oxidation formation often cause the common screw adjustment of the hold-down rolls to seize and the only way to change the position is to attempt to clean the screw, or simply replace it. Conventional persuader stops typically are adjusted by a bolt and lock nut which have a similar problem in becoming frozen in place by contamination and can happen as early as weeks after the installation. 

Considering Gerdau Midlothian rolls a wide range of sections from 13-38mm, easy adjustment of the looper roll positions was an essential requirement in the design of the uplooper. Russula eliminated the seizing issues caused from exposure to the steel rolling environment by designing a fully sealed eccentric shaft assembly for reliable and simple floor and hold-down roll adjustments. In addition, the persuader arm roll assembly utilizes common components with the eccentric assemblies while the roll height adjustment is performed effortlessly with a newly designed, fully sealed, adjustable persuader travel stop assembly.

Change out the cartridge assembly in minutes

The eccentric roll assemblies can be changed out in a matter of minutes. Undo six bolts, replace with a spare cartridge and the mill can return to production immediately. The positioning of the eccentric rolls is adjusted from the operator’s side of the uplooper. Seven numbered positions provide visual clues of the roll positions and the operators can easily recognize a change in height adjustment, eliminating a source of human error that can happen if the roll setup is adjusted incorrectly between shifts and product size changes.

Interchangeable spare parts

The assemblies of the persuader arm and eccentric rolls are identical. Internal components such as bearings, seals and shafts are the same, reducing the quantity of spare parts that maintenance needs to keep in stock. Interchangeable parts reduce spare parts stock without having to compromise asset availability.

Tension free rolling

The actual value of the loop height is measured by a photoelectric scanner near the apex of the loop height, which falls between a range of 150-200 mm.  This value is compared with a set-point and the difference is used to correct the speed of the upstream stand in relation to the downstream stand to achieve the desired loop height for tension free rolling. 

Successfully operating since January 2018

The new uplooper was successfully commissioned in January, 2018 by the Gerdau Midlothian and Russula team. The uplooper was designed taking into consideration future replacement of the other two loop former tables which were installed when the Midlothian mill was built.  This new uplooper will be interchangeable with the future ones providing Gerdau greater flexibility and spare parts optimization.