When we talking about large diameters pipe, It usually refers to the pipe in welded like LSAW pipe or SSAW pipe; More over, it also includes large diameter seamless pipe in some circumstances.
It shall be noted that for a high pressure pipeline large diameter seamless pipe is preferred. Since in welded type it is not expected as seamless types to bear the big pressure (the weakest point of the welded pipe is the welded seam on it). The welded seam can break or crack at anytime hence, people are looking for seamless large pipes for various things.
Large Diameter Steel Pipe OD range
Large diameters refer to pipe above 457 mm (16 inch) and 508 mm (20 inch)
For large diameter seamless pipe also refer to the pipe that more than 16 inch or 20 inch.
As we know maximum diameters for ERW pipe usually is 457 mm 16 inch, so we can say the pipe diameters is larger than this OD are known to be large diameters pipes.
For LSAW and SSAW large steel pipe: From 508 mm 20 inch to 2540 mm 100 inch.
Since the pipe larger than these sizes, will not be manufactured only by hot rolling, an additional process hot expanding will be applied. This way could enlarge the pipe diameters in a short time, with low cost and high efficiency, therefor it has became a modern way of manufacturing large seamless pipes.
Though the price of the large diameter seamless pipe is bit higher than the welded ones but the increasing ability and benefits are making it appropriate for any usage. In the array of commercial application of pipes, the importance of the seamless large pipes are increasing including pipelines oil rigs, building of ships, offshore rigs, machinery parts, pressure vessels, parts of machineries, equipment of oil field etc.