Specific features of applying machine welding with drop transfer in repair of operating pipelines

Introduction. Repair of pipelines under pressure of pumped media by means of welding is relevant to reduce the complexity of work. However, it may reduce the safety of work. To solve this issue, the authors consider applying the technological processes of machine welding with controlled drop transfer.

Aim. To determine the main parameters of technological processes of machine welding with controlled drop transfer, affecting the safety of welding.

Materials and methods. The authors developed a theoretical model for calculating the working thickness of a pipeline wall under pressure which they used for calculating the strength during welding. The dependence of the pipeline wall thickness at the edge of the penetrated hole on the internal pressure was also used in the calculations.

Results. It was found that machine welding with controlled transfer of metal drops allows the wall penetration depth to be regulated by changing the welding variables. This significantly increases the safety of welding on pipelines under pressure of pumped media, compared to other types of welding. The developed welding processes ensure the safety of welding operations by means of a smooth and accurate control of the wall penetration depth. This is achieved by the correct selection of the background and peak current, control of the drop transfer process by arc voltage, control of the amount of weld metal and the heating temperature of welded structures.

Conclusion. Recently, a number of repair technologies have been developed to improve the quality of welds in the construction and repair of trunk pipelines. The highly significant results of research on the development of machine welding technology with controlled drop transfer allow this technology to be recommended as an effective way to improve the safety of welding operations on pipelines under pressure of pumped media.

1. Sobachkin A.S. Safety of welding works on pipelines under transporting medium pressure. Problemy sbora, podgotovki i transporta nefti i nefteproduktov = Problems of Gathering, Treatment and Transportation of Oil and Oil Products. 2018;(3):135–140. (In Russian).

2. RD 25.160.00-KTN-037-14. Welding during the construction and repair of oil trunk pipelines. Moscow: Transneft; 2014. (In Russian).

3. Mustafin F.M., Blekherova N.G., Bykov L.I. Modern pipeline welding technologies. 2 ed. Saint Petersburg: Nedra Publ.; 2010. (In Russian).

4. Rizvanov R.G., Fairushin A.M., Zaripov M. Z., Karpov A.L. Improving the manufacturing quality of petrochemical devices by using vibration treatment in the welding process. Bashkirskii khimicheskii zhurnal = Bashkir chemistry journal. 2005;12(1):27–29. (In Russian).

5. Gusev E.V., Mukhametzyanov Z.R., Razyapov R.V. Technique for Determination of Rational Boundaries in Combining Construction and Installation Processes Based on Quantitative Estimation of Technological Connections. IOP Conference Series: Materials Science and Engineering (MSE). 2017;262:012140. https:// doi.org/10.1088/1757-899X/262/1/012140

6. Fairushin A.M., Karetnikov D.V., Zaripov M.Z., Abdullin T.Z., Akhtyamov R.M., Fazylov M.R. Method of decreasing residual strain in welded metal joints. Patent No. RU 2424885 C1. Data publ 27 July 2011. (In Russian).

7. Tronskar J.P., Guan O.H., Tomqvist R., Bruce W.A. “Live” repair of gas pipeline with deep girth weld crack. In: ASME 2015 Pressure Vessel & Piping Conference, July 19-23, 2015, Boston, Massachusetts, USA. Vol. 6B: Materials and Fabrication. https://doi.org/10.1115/pvp2015-46005

8. Bruce W.F., Etheridge B.C. Further Development of Heat-Affected Zone Hardness Limits for In-Service Welding. In: Proceedings of IPC 2012, 9th International Pipeline Conference September 24–28, 2012, Calgary, Alberta, Canada, Vol. 3: Materials and Joining. https://doi.org/10.1115/ipc2012-90095

9. Raschke A. Technical safety and welding simulation of welding work on high-pressure gas pipelines in operation. In: 14th Pipeline Technology Conference, 18-21 March 2019, Berlin, Germany.

10. State Standard 8050-85. Gaseous and liquid carbon dioxide. Specifications. Moscow: Standards Publishing House; 1985. (In Russian).

11. Gareeva O.A., Yamilev M.Z., Lyagov A.B., Klimov P.V. Improving the safety of operation of pipelines subject to corrosion cracking. Neftegazovoe delo = Petroleum Engineering. 2011;9(2):58–61. (In Russian).

12. Nasibullina O.A., Gareev A.G. Development of a method for estimating the residual life of main gas pipelines with defects of corrosive origin. Neftegazovoe delo = Petroleum Engineering 2016;14(2):174–178. (In Russian).

13. Nasibullina O.A., Gareev A.G. Destruction patterns of ×70 steel sample, possessing cracks of corrosionmechanical origin, under cyclic loading. Materials Science Forum. 2019;946:20–24. https://doi.org/10.4028/ www.scientific.net/msf.946.20

14. Nasibullina O.A. Introduction to the basics of corrosion. Ufa: Neftegazovoe delo Publ.; 2019. (In Russian).