Production enterprises connected with the railroad industry and utilizing certified welding processes should introduce specific requirements and obtain certificates which qualifies them for welding rolling stocks and components. The series of norms consists of 5 parts containing: general requirements, the certification and quality requirements for welding plants, construction requirements, production standards, controlling and research. The certification of a welding plant is divided into 4 levels: CL1, CL2, CL3 and CL4. The level depends on the importance of the manufactured component. The CL1 certification level is the most rigorous for the manufacturer in terms of conditions.