Fabrication yards producing tubular structures rely on computer numerically controlled (CNC) oxyfuel cutting machines to accurately profile AWS cuts to pipes. These are a type of cut familiar to the offshore sector according to international welding standards.
The cut can vary from 0.610 to 2.035 mm or beyond for pipe outside diameters, and must be controlled carefully to ensure fitting and welding time and costs are minimized.
Historically, the machine operator has had to program all machining for each individual profile at the shop-floor machine. But due to increasing demands to organize production more efficiently, new systems are being introduced that cut profiling time further through pre-programming in the drawing office.
One such system employs a CAD/CAM connection called Tubecam, developed by HGG Profiling Equipment, which the company says can achieve at least a 20% reduction in conventional CNC programming time. The system uses the center-line definitions that are available within a typical CAD program and the operator generates a schematic center line-based drawing. All center lines (i.e., pipes) are tagged electronically with data such as position number, diameter, and wall thickness.
Via a toolbar programmed into the CAD system, the intersections are defined manually by simply selecting a pipe in the drawing, followed by all other pipes that have to be profiled prior to connection to this pipe. All intersections must also be tagged electronically with data such as profile type, welding opening, and shrinkage.
Still from a Tubecam CNC pipe cut planning operation.
The CAD drawing itself contains all 3D locations of the pipes. From here, the direct numerically controlled system generates one single data file that can be fed into the machine via the LAN cable, memory stick, or floppy disc.
The operator selects a file corresponding to the pipe collected from stock, loads this pipe, and starts up the machine. All profiles in the data file can be cut without programming or re-starting the cutting machine. At the completion of a profile, the cutting head moves automatically to the starting point of the next profile, leaving the operator only to approve the start of the next cut.
Middenmeer-based HGG’s clients include Aker Verdal and Aker Stord in Norway; Chiwan Sembawang/Penglai yards in China; Vietsovpetro in Vietnam; and Adyard Abu Dhabi.•
