Application Stories

Lincoln STT® Process Welds China's Longest Pipeline

Cleveland, OH – Construction crews in China recently completed that country’s longest pipeline, the West-East Pipeline Project (WEPP). This 4,000-kilometer gas pipeline will link China’s economic hub of Shanghai to the Changqing gas field in northwest China. The project, completed with Lincoln Electric’ STT® (Surface Tension Transfer®) welding equipment, will play a key role in supplying energy to east and central China, as well as aiding in the development of west China.

Before construction of the $24.1 billion pipeline began, Lincoln representatives approached the project management team to introduce the company’s Surface Tension Transfer (STT) process for root pass welding. STT is a GMAW, controlled, short-circuit welding process which permits open gap root pass welding of pipe with greater ease of operation, more control over heat input, very good penetration with complete edge fusion and excellent bead control. In addition, the process results in faster travel speeds and with less welding fume and spatter than other available processes.

Using STT can also reduce welding costs. For example, on steel, recommendations call for the use of low cost 100 percent CO2 shielding gas. It is also often possible to use a larger diameter electrode than some processes, which are typically sold at a lower price than smaller diameter wires. The STT process is one of Lincoln’s Nextweld®: The Future of welding is here™; processes designed to improve quality and improve productivity.

After repeated successful root weld demonstrations on the 42 in. (1,067 mm) diameter, X60 and X70 grade pipe, the team chose STT for the project. Lincoln supplied welding equipment to join the 1.25 in (26.3 mm) thick, 40 ft. (12.2 m) long pipe sections. Lincoln units used on the job site included the Invertec® STT-II, Invertec V350-PRO: Designed Smart. Built Tough.Pipe (consult with your Lincoln technical sales rep) and DC-400 multi-process power sources, SAE-400 engine driven welder, as well as the LN-23P and LN-742 wire feeders.

Because the WEPP workforce consisted of 32 different construction crews, most of whom were not familiar with the STT process, Lincoln embarked on an extensive testing and certification process at China’s central pipeline training center near Beijing.

Following completion of the project in October 2003, the pipeline will begin pumping a trial supply to various areas of the country in November.

The Lincoln Electric Company, Cleveland, Ohio, is a world leader in the design and manufacture of arc welding equipment and consumables, robotic welding systems, plasma and oxyfuel cutting equipment.