Section 179.100-9 - Welding(a) All joints shall be fusion-welded in compliance with the requirements of AAR Specifications for Tank Cars, appendix W (IBR, see §171.7 of this subchapter). Welding procedures, welders and fabricators shall be approved.29 FR 18995, 12/29/1964, as amended at 65 FR 58632, 9/29/2000; 68 FR 75759, 12/31/2003