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An introduction to plate leveling



Most in metal fabrication know the importance of proper leveling. The processes used to create sheet metal at the mill produce a sheet with trapped stresses, a virtual tug of war of tension and compression. A sheet becomes flat when those forces are at an equilibrium across all directions of the plate.Get more news about metal plate leveling machine,you can vist our website!

To achieve this equilibrium, coil processors can employ various corrective leveling technologies—tension leveling, temper pass leveling, even stretcher leveling—but roller leveling remains the dominant technology.

Most corrective leveling technologies focus on sheet metal that’s 0.25 in. and thinner, but what about plate leveling? Anyone in heavy fabrication, such as large tank fabrication or pressure vessel work requiring heavy rolling, knows the challenges when a plate being cut or formed releases stress. The process becomes less predictable. But technology to level plate—sometimes up to 6 in. thick—can help make heavy fabrication much more predictable, faster, and less costly.

Historical Context
The demand for plate leveling goes back dec-ades. Plate several inches thick, designed for ships and submarines going back to before World War II, needed to be flat before fabrication began, hence the need for leveling, which usually occurred at the mill. Over the years plate leveling became more critical as the materials became more complex. Tanks and ships are prime examples, as well as other products fabricated over the years for the oilfields, natural gas plants, the water utility industry, food processing plants, bridge building, and elsewhere.

Some areas of food and chemical processing use clad plate, incorporating a thick base metal section of carbon steel and a cladded layer of stainless steel around the inside diameter, to prevent corrosion and chemical reactions to acid on the inside wall while allowing components to be welded to the carbon steel on the OD. Some tanks are lined with rubber or glass. Large-diameter pipe made of high-strength plate, critical for offshore drilling, also needs leveling.

A few manufacturers work in the extreme thicknesses of stainless steel, even plate consisting of multiple alloys fused together. A company called Dynamic Materials Corp., for instance, fuses 0.25-in.-thick stainless with carbon steel that’s up to 3 in. thick. Not surprising, given its stock ticker—BOOM—the company fuses the stainless to carbon steel in an underground chamber through a unique form of explosion welding. All this creates extraordinarily strong, thick plate that, before being cut and formed in a fabrication shop, needs to be leveled.

In all this work, 0.25 in. is considered thin. Most of this plate is thicker, and much of it is multiple inches thick. Put a raw, 3-in.-thick plate—full of uneven, trapped stresses—through a three-roll or four-roll bending roll, and there’s little chance you’ll produce a perfect cylinder with ease, with the prepped edges meeting just at the right place for subsequent welding.

Regardless of the process, if an operator starts with a plate that’s bowed in the middle or has any number of other shape defects, that process is likely to become more arduous and much more expensive. It’s why an operator starts by using a long (8 feet, for instance) straight edge to ensure a plate is level in all directions before starting any forming or fabrication.

Industry plate flatness standards specify a certain degree of flatness; 0.25-in. variance over 8 ft. is a common specification. But many plate fabrication operations require much tighter flatness tolerances, sometimes down to a small fraction of the industry standard. This is where precision plate leveling comes into play.