№ 6 (June 2006)
Russian Electrodes LEZLBgp for Oil&Gas Products Pipeline Welding
The scope of electrode welding in the construction and repair of oil-and-gas products pipelines is growing rapidly. On-route conditions of conduit joint welding in oil-and-gas products pipelines determine rigid requirements to the electrodes, recommended for such operations.
By I.S. Ioffe
These are as follows: welding arc stability, ease of its restarting, absence of apron forming tendency, back bead formation, clinker separation and joint formation in all directions in the process of welding pipes in fixed position. Besides, the stable high quality of the electrodes is of paramount importance.
Since the Soviet Union, the most widely spread electrodes for welding conduit joints of oil-and-gas products pipelines were the ones by Kobe Steel of Japan, the LВ-52u make. Domestic electrodes of a similar type, the UONI-13/55 make, were not approved for such kind of operations. The attempts of Paton Intstitute to develop the Soviet counterparts of LB-52u electrodes of ANO-T and ANO-TM makes did not result in decrease of Japanese electrodes application. Then, ESAB of Sweden offered the electrodes of OK53.70 make, used specially for welding conduit joints , and they are still in use. The attempts of BЪhler, Elga and of some others to offer their makes for the above purposes did not lead to their wide application.
In the recent years the electrodes of the MTG-01K make, based on one of the Oerlikon makes (Switzerland), have been put into production at Sychevsky Electrode Plant, which is a part of the Gazprom group. These electrodes enjoyed a certain distribution in welding of oil-and-gas products pipelines. However, the main part of such welding operations is still being carried out by the Japanese LB-52u and Swedish OK53.70 electrodes.
OAO Losinoostrovsky Electrode Plant has developed the LEZLBgp electrodes for welding conduit joints and put them into mainstream production. Production of these electrodes is based on Russian raw materials and industrial technology.
As compared to LB-52u electrodes at similar welding processing parameters Р combustion softness and arc elasticity, seam formation, including the ceiling position, back bead formation Р the above electrodes provide better clinker separation, especially from cutting.
As compared to OK53.70 electrodes, the LEZLBgp-s can provide high welding processing parameters even under lower currents. This allows for forming quality seams when welding joints with increased gaps and deplanation.
The specified electrodes have undergone a set of tests in the leading research institutions of Russia - VNIIGAZ and VNIST and received NAKS permit for welding conduit joints.
Transneft added the LEZLBgp electrodes to the register of materials approved to be used at the company's enterprises.
The metal mechanical properties, its chemistry and joints are shown in Tables 1 and 2.
Diffusive hydrogen content, according to the VNIIGAZ data, amounts to less than 5.0 ml/100g.
High welding processing parameters of the LEZLBgp electrodes, proved by consumers' references, and their relatively low price as compared to similar types of electrodes make the LEZLBgp electrodes quite competitive with the imported counterparts.