Heavy Fabrication

Heavy fabrication is throughput-limited at the prep stage. The welders are usually faster than the bevelers feeding them; the inspection bottleneck is usually faster than the seam removal step preparing for it. Every machine on this page is sized to remove the prep bottleneck, not to handle some exotic geometry.

What the work actually looks like

Pressure vessels, wind-tower sections, bridge plate girders and heavy structural assemblies all share the same prep sequence: cut plate to size, prep edges, weld, mill the reinforcement flush, inspect. Walls are heavy (25 to 80 mm typical, sometimes more), seams are long (6 to 18 metres typical), and the schedule is volume-driven.

The constraint is rarely complexity. It is how fast each plate edge gets ready for the welder, and how fast each seam gets ready for the inspector.

Pressure vessel and reactor shell prep

Pressure vessel longitudinal seams above 25 mm wall are where J-prep and compound bevels save real money — see V vs J prep economics. The decision is wall-thickness driven, but most fab shops stay on single-V too long out of habit. On 30 mm carbon at GMAW, switching from V to J typically pays back the head cost in the first project on fill metal and arc time alone.

For shell strake prep the DMM hydraulic heavy edge miller covers the 25–60 mm wall band with the rigidity to hold the J geometry. The DMM-900 vertical edge miller handles the heaviest sections. Full machine selection in the plate beveling machines category.

Wind-tower section welding

Wind-tower can-to-can welds and bottom flange welds run on the same prep philosophy as pressure-vessel shells — heavy wall, long circumferential seams, X or compound bevels for distortion control. Production volume drives the economics: a project of 50 towers means hundreds of can-to-can joints, and the prep machine throughput is the limiting factor on schedule.

For long-plate can seams the GL traveling edge miller walks the cutter along clamped plate. For the heavier flange-to-can butts the DMM hydraulic heavy edge miller adds the rigidity for X-bevel work.

Weld seam reinforcement removal

ASME Section VIII Div 1 and 2 surface-finish requirements on pressure-vessel seams need the weld reinforcement milled flush within ± 0.1 mm height along the entire seam — a tolerance hand-grinding cannot hold on a 6-metre run. The realistic tolerance band on a grinder is ± 0.5 to 1 mm with 15–30% rework rate; the realistic band on a walking HDL-5D weld seam planer is ± 0.1 mm with rework below 2%.

The break-even is clear on volume: above ~50 metres of controlled flush-seam per month, the planer pays back within a year. Full trade-off in the best weld seam removal tools. For grinder-versus-machined prep on the upstream side see cold beveling vs grinding.

Bridge and structural plate fabrication

Bridge and structural welding (AWS D1.1, EN 1090) runs on similar heavy plate with similar throughput constraints. The fab shops that move from grinder prep to machined prep typically see weld inspection pass rates jump from ~75% to ~98%, which compounds back to fewer welder reassignments per shift.

Selection between rolling-shear and edge-milling depends on the production mix — see rolling shear vs edge milling. For mild-steel high-volume single-angle work, the KBM rolling-shear plate beveler is the fast answer; everything else goes on an edge miller.

Dross removal from plasma and laser cut plate

Most heavy fab shops now run plasma or laser cutting for plate blanks. The blanks arrive with dross on the bottom edge and an oxide scale on both faces; downstream forming and welding cannot use them as-is.

A wide-belt slag removal system clears dross plus oxide layer in one feed-through cycle on plate up to ~40 mm thick. For lighter dross and edge break on thinner stock, the QC roller-brush deburrer covers the same workflow.

What ships on a typical heavy fab project

A working package for a pressure-vessel, wind-tower or bridge shop typically pairs:

• A DMM hydraulic heavy edge miller or DMM-900 vertical edge miller for thick-plate prep.
• A GL traveling edge miller for long-plate can or shell seams.
• An HDL-5D weld seam planer for post-weld reinforcement removal.
• A wide-belt slag removal system if plasma-cut blanks are produced in-house.

For sizing against your specific plate thickness range, seam volume and inspection regime, send the spec to the quote form or talk to an engineer.