A pipe cutting plasma machine includes a V-rollers platform configured to move and rotate a pipe located thereon; a gantry having a plasma torch configured to cut the pipe located on the V-rollers platform; and a visual dynamic positioning system, operatively connected to the gantry, configured to detect and measure, before the plasma torch cuts a first through coupling hole in the pipe, bowness of the pipe located on the V-rollers platform. The visual dynamic positioning system includes an imaging device configured to image the pipe and generate image data signals therefrom, an image processor configured to detect and measure, based upon the generated image data signals, the bowness of the pipe and to generate control signals corresponding to the detected and measured bowness of the pipe, and a gantry controller configured to bi-directionally move the gantry based upon the generated control signals.

In a field of welding technology, a welding method for a sea pipe with high efficiency and comprehensive performance under shaking of a pipe-laying ship is specifically disclosed. The welding method is as follows: performing ultra-short arc GMAW all-position welding on the sea pipe within a range of heat input of 0.2 kJ/mm0.3 kJ/mm, while setting a peak current, setting a peak current descent rate to 50 A/ms70 A/ms, and setting the necking time to 3 ms7 ms in the GMAW waveform to 285 A370 A. A welding effect of overall low heat input and partial high heat input is formed, and the stability of all-position welding of the sea pipe is guaranteed, which realizes stable welding of the sea pipe under the condition of pipe-laying ship shaking, and improves the fatigue resistance and corrosion resistance of the sea pipe.

The present invention relates to a preheating device for welding oil, gas, and geothermal wellheads of varying diameters and thicknesses which is applicable to the oil, gas, and geothermal industry. The preheating of head and coating pipes to be welded do not cool down quickly. The cooling speed reduction prevents structures or joints from being less susceptible to cracking by maintaining the necessary heat thus preventing the integrity of the joints from being exposed. The preheating of head and coating to be welded maintains a uniform and constant temperature avoiding temperature changes, thus making the structures or joints less susceptible to cracking by maintaining the necessary heat and preventing the integrity of the joints from being exposed.

A method of joining dissimilar material pipes includes applying a brazing metal filler to an end of a first pipe, press-inserting the end of the first pipe, with the brazing metal filler applied, into a second pipe, and plastically deforming and joining overlapping plastic deformation portions of the first pipe and the second pipe in a joint assembly, where the first pipe is fitted to the second pipe. This method offers joined dissimilar material pipe, which provides improved sealing capacity and perform well under high pressure and extremely low temperatures.

A method of preparing a pipe-section for welding to another pipe-section to form a pipeline comprising a plurality of said pipe-sections, the method comprising at least the steps of: (i) providing a pipe-section having first and second pipe-ends; (ii) defining a first portion L1 of the longitudinal length of the pipe-section from the first pipe-end being in the range 3% to 40% of the overall length of the pipe-section; (iii) defining a second portion L2 of the longitudinal length of the pipe-section from the end of the first portion L1 towards the second pipe-end; (iv) heating at least the first portion L1 to at least a first temperature T1 of at least 500 C. for at least 2 minutes; (v) maintaining a second temperature T2 of the second portion L2 during step (iv) below the first temperature T1. The invention is able to reduce the strain capacity during reel-laying of a pipeline formed from a plurality of pipe sections formed by the invention.

A backing welding process curve based on a narrow-gap U-groove and its application and product are provided. The backing welding process curve is used for welding the narrow-gap U-groove. On the basis of a CMT reference curve, at least one current pulse is introduced before and after the short-circuiting phase respectively, to increase the root weld width and avoid root concavity. Meanwhile, the peak current and cycle time are increased to enhance welding heat input, while the peak current rise rate and peak current fall rate are reduced to prolong the peak current action time.