• The clamping devices used to hold the rails firm should not cause any damage that might lead to the formation of cracks in the rail.
• During the welding process it is not permitted to interrupt the burn-off once the process has begun and upsetting must be performed immediately with the sufficient upset force.
• The excess upset must be trimmed off automatically and the weld must be in compression during trimming.
  
• All welds must be carried out according to programmed and automatic sequences. The welding parameters are determined by means of welding tests and should not be altered once approval has been given.

Certification of the welding head

For the main part of the certification, 12 welds are made on the rail profiles 60E1 or 60E2 of steel grade R260. Then, the quality of these welds is tested by an accredited weld testing institute.

To ensure reproducibility, the welding parameters are selected one time and must not be changed.

The certification procedure includes the following tests:

• Visual inspection
• Trimming and investigation of the upset bulge
• Offset at the weld
• Magnetic particle test or dye penetrant test
• Bending test
• Macro test
• Micro test
• Hardness test P –30HV30, +60HV30 (P: average measured hardness of the rail before welding)
• Fatigue strength test

For each welding head a separate certificate is required.