This paper aims to throw light on research into a narrow-gap welding technology which applies 135 method for L415 ME steel pipes for hydrogen transmission. Limits, non-destructive, and mechanical test results were discussed. The selected parameters enabled groove-free joints from 20.3 mm pipes reaching ISO 5817 level B. Radiographic and ultrasonic tests revealed no discrepancies. Welding provided 566 MPa tensile strength, exceeding base material, without hardness variation or martensitic structures. Base material hardness was ~200 HV, with welds reaching ~240 HV. Impact toughness averaged 300 J, meeting the requirements. Qualification for hydrogen pipelines demands compliance with EN ISO 12732 and EN ISO 15614-1. Automated dual-wire systems ensure EN ISO 15614-1 the compliance. L415ME steel's favorable composition allows for robust structural solutions that guarantee joint integrity and strength. The novelty of this paper is a new automated narrow-gap welding technology for hydrogen pipelines, combining joint design modifications, multi-head systems, and oscillatory movements to improve performance and reduce cracks.