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Sheet Metal Rolling Vertical for Tank Builders

During a rolling cycle in a vertical, coil-fed system, the leading edge “curls” in front of the bending rolls.The freshly cut trailing edge is then pushed to the leading edge, nailed and welded to form the rolled shell.
Everyone in the field of metal fabrication is probably familiar with rolling machines, whether it’s an initial clamp, three-roll double-clamp, three-roll translation geometry, or the four-roll variety.Each has its limitations and advantages, but they also have one feature in common: they roll sheets and sheets in a horizontal position.
A less familiar method involves scrolling vertically.Like other methods, vertical scrolling has its own limitations and advantages.These advantages almost always solve at least one of the two challenges.One is the influence of gravity on the workpiece during the rolling process, and the other is the low efficiency of material handling.Improving both can improve workflow and ultimately increase the competitiveness of manufacturers.
Vertical rolling technology is not new.Its roots go back to a handful of custom systems built in the 1970s.By the 1990s, some machine builders offered vertical rolling mills as a regular product line.The technology has been adopted by various industries, especially in the field of tank production.
Common tanks and containers that are typically produced vertically include tanks and containers for the food and beverage, dairy, wine, beer, and pharmaceutical industries; API oil storage tanks; and welded tanks for agriculture or water storage.Vertical rolling greatly reduces material handling; generally produces higher quality bends; and more efficiently feeds the next production stages of assembly, alignment, and welding.
Another advantage comes into play where material storage capacity is limited.Vertical storage of boards or sheets requires far fewer square feet than boards or sheets stored in a flat surface.
Consider a shop that rolls the shells (or “routes”) of large diameter tanks on horizontal rollers.After rolling, the operator spot welds, lowers the side frames, and slides off the rolled shell.Since the thin shell bends under its own weight, the shell either needs to be supported with stiffeners or stabilizers, or needs to be rotated into a vertical position.
Such a large amount of handling—feeding sheet from a horizontal position into horizontal rolls, which is then taken out and tilted for stacking after rolling—can create a variety of production challenges.With vertical scrolling, the store eliminates all intermediate processing.Sheets or sheets are fed and rolled vertically, glued, and then lifted vertically to the next operation.When rolling vertically, the tank shell does not resist gravity and therefore does not sag under its own weight.
Some vertical rolling occurs on four-roll machines, especially for smaller diameter tanks (usually less than 8 feet in diameter) that will be sent downstream and worked in the vertical direction.The four-roll system allows re-rolling to eliminate unbent flats (where the rolls grab the plate), which is more pronounced on small diameter shells.
Most vertical rolling of storage tanks uses three-roll, double-collet geometry machines, using sheet metal blanks or direct feed from coil (an approach that is becoming more common).In these setups, the operator uses a radius gauge or template to measure the radius of the enclosure.They adjust the bending rollers as they touch the leading edge of the web, and then again as the web continues to feed.As the coil continues to be fed into its tightly wound interior, material springback increases, and the operator moves the rollers to cause more bending to compensate.
Springback varies by material properties and coil type.The inner diameter (ID) of the coil is important.All other things being equal, a 20-inch coil.Compared to the same coil wound to 26 inches, the ID is wound tighter and exhibits greater rebound.ID.
Vertical scrolling has become an integral part of many tank field installations.Using a crane, the process usually starts with the top course and progresses towards the bottom course.Note the single vertical weld on the top course.
Note, however, that vertical pot rolling is very different from rolling thick plate on horizontal rolling.For the latter, the operator strives to ensure that the edges of the strip are matched exactly at the end of the rolling cycle.Thick plates rolled to tight diameters are not easily reworked.
When forming the tank shell with coil vertical rolls, the operator cannot let the edges meet at the end of the rolling cycle because, of course, the sheet comes directly from the coil.During rolling, the sheet has a leading edge, but not a trailing edge until it is cut from the coil.In the case of these systems, the coil is rolled into a full circle before actually bending the rolls and then cut after completion .After this, the newly cut trailing edge is pushed to the leading edge, secured, and then welded to form the rolled shell.
Pre-bending and re-rolling in most coil-fed units is inefficient, meaning that their leading and trailing edges have drop sections that are often scrapped (similar to unbent flat sections in non-coil-fed rolling ).That said, many operators see scrap as a small price to pay for all the material handling efficiencies vertical rolls provide them.
Even so, some operators want to make the most of the material they have, so they opt for an integrated roll leveler system.These are similar to four-roll straighteners on a coil processing line, just flipped over.Common configurations include seven- and twelve-high straighteners that use some combination of idle, straightening, and bending rolls.The straightener not only minimizes the scrap drop section per shell, but also increases the flexibility of the system; that is, the system can produce not only rolled parts, but also flat, flat billets.
Leveling technology cannot replicate the results of the extended leveling systems used in service centers, but it can produce material that is flat enough to be cut with a laser or plasma.This means that manufacturers can use coils for vertical rolling and flat cutting operations.
Imagine an operator rolling the shell for a tank section receives an order for a batch of blanks for a plasma cutting table.After he rolls the shell and sends it downstream, he configures the system so that the leveler doesn’t feed directly into the vertical rolls.Instead, the leveler feeds flat material that can be cut to the desired length, creating a flat blank for plasma cutting.
After cutting a batch of blanks, the operator reconfigures the system to resume rolling tank shells.And because he rolls flat material, material variability (including varying degrees of springback) is not an issue.
In most areas of industrial and structural fabrication, manufacturers aim to increase the volume of shop fabrication to simplify and simplify field fabrication and installation.However, for the manufacture of large tanks and similar large structures, this rule does not apply, mainly because of the incredible material handling challenges that such jobs present.
Operating at the job site, coil vertical rolls simplify material handling and simplify the entire tank manufacturing process .It’s much easier to transport a metal coil to a jobsite than to roll out a series of huge sections in a workshop.Additionally, on-site rolling means that even the largest diameter tanks can be manufactured with just one vertical weld.
Bringing the leveler to the field allows for more flexibility in field operations.This is a common choice for on-site tank production, where the added functionality allows manufacturers to build tank decks or bottoms on-site from straightened coil, eliminating transportation between the shop and job site.
Some vertical rolls are integrated with on-site tank production systems.The jack lifts the previously rolled course upwards without the need for a crane.
Some field operations integrate vertical rolls into a larger system—including cutting and welding units used with unique lifting jacks—removing the need for a site crane .
The entire tank is built from the top down, but the process starts from the ground up.Here’s how it works: The coil or sheet is passed through vertical rolls just inches from where the tank wall is in the field.The wall is then fed into guides that carry the sheet as it is fed around the entire circumference of the tank.The vertical rolls are stopped, the ends are cut, and the individual vertical seams are positioned and welded.The stiffener assembly is then welded to the shell.Next, the jack lifts the rolled shell up.Repeat the process for the next shell below.
Circumferential welds are made between the two rolled sections, and the tank top pieces are then assembled in place – while the structure remains close to the ground, only the two uppermost shells are made.Once the roof is complete, jacks lift the entire structure in preparation for the next shell, and the process continues – all without the need for a crane.
When the operation reaches the lowest line, the thicker plates come into play.Some on-site tank producers use 3/8 to 1 inch thick plates, and in some cases even heavier.Of course, the sheets are not in coil form and can only be so long, so these lower sections will have multiple vertical welds connecting the rolled sheet sections.In any case, with vertical machines on site, the sheets can be unloaded in one go and rolled up on site for direct use in tank construction.
This tank building system epitomizes the material handling efficiency achieved (at least in part) by vertical rolling.Of course, as with any technology, vertical scrolling isn’t available for all apps.Its suitability depends on the processing efficiency it creates.
Consider a manufacturer that installs a non-coil-fed vertical roll to do a variety of jobs, most of which are small diameter shells that require pre-bending (bending the leading and trailing edges of the workpiece to minimize unbent flat).These jobs are theoretically possible on vertical rolls, but pre-bending in the vertical direction is much more cumbersome.In most cases, vertical rolling is inefficient for a large number of jobs that require pre-bending.
In addition to material handling issues, manufacturers have integrated vertical rolls to avoid fighting gravity (again to avoid buckling of large unsupported enclosures).However, if an operation only involves rolling a board strong enough to hold its shape throughout the rolling process, then rolling the board vertically doesn’t make much sense.
Also, asymmetric work (ovals and other unusual shapes) is usually best formed on horizontal rolls, with overhead support if desired.In these cases, supports do more than just prevent gravity-induced sag; they guide work through rolling cycles and help maintain the asymmetric shape of the workpiece.The challenge of operating such a job in a vertical orientation may negate any benefit of vertical scrolling.
The same idea applies to conical rolling.Rolling cones rely on the friction between the rollers and the varying amount of pressure from one end of the rollers to the other.Scrolling a cone vertically, gravity adds even more complexity.There may be unique situations, but for all intents and purposes, rolling the cone vertically is impractical.
Vertical use of three-roll translation geometry machines is also generally not practical.In these machines, the two bottom rolls move left and right in either direction; the top roll can be adjusted up and down.These adjustments allow these machines to bend complex geometries and roll materials of various thicknesses.In most cases, these benefits are not enhanced by vertical scrolling.
When choosing a plate rolling machine, it is important to research and consider the intended production use of the machine carefully and thoroughly.Vertical rolls are more limited in functionality than traditional horizontal rolls, but in the right application offer key advantages.
Compared with horizontal plate bending machines, vertical plate bending machines generally have more basic design, operation and construction characteristics.Also, rolls are often oversized for the application to incorporate crowns (and the rounding or hourglass effects that occur in workpieces when crowns are not properly adjusted for the job at hand).When used in conjunction with decoilers, they form a thin material for an entire shop tank, typically no more than 21 feet 6 inches in diameter.Field-installed tanks with much larger diameter top courses may have only one vertical weld, rather than the three or more of plate production.
Again, the biggest advantage of vertical rolling is that the tank or container needs to be built in a vertical orientation due to the effects of gravity on thinner materials (eg, up to 1/4 or 5/16 inch).Horizontal production will force the use of reinforcing or stabilizing rings to maintain the round shape of the rolled part.
The real advantage of vertical rolls is material handling efficiency.The fewer times an enclosure needs to be manipulated, the less likely it will be damaged and reworked.Consider the high demand for stainless steel tanks in the pharmaceutical industry, which is now busier than ever.Rough handling can lead to cosmetic problems or, worse, a product that can destroy the passivation layer and create a contamination.Vertical rolls work in tandem with cutting, welding and finishing systems to reduce handling and contamination opportunities.When this happens, manufacturers reap the benefits.
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Post time: Mar-29-2022
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