1. Start with the process goal

The product description lists three functions for a skin pass mill in a galvanizing line:

• Surface roughness: creating the surface roughness the galvanized sheet requires, which supports quality in a later color coating process.
• Flatness: improving the flatness of the galvanized sheet.
• Mechanical properties: improving the mechanical properties of the galvanized sheet by decreasing or eliminating the yield plateau and stretcher strains.

Write down which of these goals matter most for your product. If your line feeds a color coating process, roughness control is likely a priority. If your customers complain about stretcher strains or flatness, put elongation and flatness control at the center of the specification.

When this guide does not apply: the confirmed material describes the mill as equipment for a skin pass mill galvanizing line. If you are sourcing for a different line or process, the source material does not show that the mill fits. Ask the supplier for application-specific documentation before you go further.

2. Match strip width and rolling force

The configurations include strip widths such as 1800 mm, 1680 mm, 1550 mm, 1450 mm and 1150 mm, and rolling forces such as 4000 kN, 5000 kN, 6000 kN, 8000 kN, 10000 kN and 12000 kN.

When you write the inquiry, give:

• the maximum strip width of your line;
• the strip grades and thickness range you process;
• the rolling force or elongation your process needs.

The supplier can then say which configuration applies. Strip thickness range, line speed and roll dimensions are not in the confirmed material, so request them in writing.

3. Check the automatic control functions

The confirmed product description lists these control functions:

• AFC – automatic constant rolling force control
• AEC – automatic constant elongation control, carried out through rolling force control
• APC – automatic position control
• ATC – automatic constant tension control

For flatness, the mill uses a positive/negative work roll bending system, and the bending roll system uses servo control. If you need consistent elongation to remove the yield plateau, ask how the AEC loop is set up and tuned for your strip grades.

4. Review welded seam handling

Welded seams pass through the skin pass mill on a continuous galvanizing line, so seam handling affects roll life and uptime. The description lists two options:

• Quick roll gap opening and recovery when the welded seam passes, plus automatic online calibration, quick online roll change and hydraulic locking.
• A soft rolling mode that lets the welded seam pass without opening the rolls. If rolling force is below 2000 kN, the seam passes directly. If rolling force is above 2000 kN, force is reduced to 2000 kN and the seam then passes without opening the rolls. The source says this mode is meant to prevent damage to the roll surface.

Ask which seam-handling mode is offered for your configuration and how it fits your welding practice.

5. Confirm the electrical and HMI scope

The description states:

• the drive control uses full digital inverter speed control with Siemens or ABB speed control devices;
• basic automation uses a Siemens or ABB PLC with a touch screen;
• an HMI collects, displays and stores mill data.

If your plant has a standard automation platform or data-integration needs, say so early. Confirm which vendor's components will be supplied and what data the HMI can export to your plant systems. The confirmed material does not state the interface details.

6. Define wet or dry skin passing and auxiliary systems

The mill can skin pass in wet or dry mode to suit process needs. It has a high pressure water system, an anti-crimping roll and an anti-cross breaker roll. The auxiliary systems include a medium pressure hydraulic station and a high pressure servo station.

Tell the supplier whether you plan to run wet or dry. Also confirm the utility needs (water, hydraulic and electrical) and the installation footprint, since the confirmed material does not give these figures.

Selection checklist

Next steps

Buyers in the United States, Europe, the Middle East and Southeast Asia should also check local electrical, safety and documentation requirements with their own engineering teams. The confirmed material does not say that the mill meets any specific regional standard. For specifications, quotations and project scope, contact Beijing Yang Wang Li Xin Sci&Tech Co.,Ltd. through www.bjywlx.com.