The president of the Rail Accident Investigation Commission (CIAF), Iñaki Barrón, has confirmed that the leading hypothesis regarding the Adamuz (Córdoba) crash identifies a broken weld as the root cause of the derailment of the Iryo train last Sunday.
Technical investigations are focused on the joint between a 1989 rail and another installed in 2023, where the failure is believed to have occurred. The fractured rail was the newer one, produced by ArcelorMittal under the Ensidesa brand.
In an interview with the College of Civil Engineers’ magazine, Barrón stated that “all the evidence points to a fracture—not so much of the rail itself, but of a welded joint.”
The failure of that weld would have caused the derailment, after which the train was struck, either simultaneously or just seconds later, by a Renfe Alvia class 120 travelling in the opposite direction.
Did the weld meet technical requirements?
Engineer Gareth Dennis noticed a contradiction in the documentation released by Transport Minister Óscar Puente concerning the weld. According to Dennis, the joint may not have been made with the appropriate charge for the lower-grade rail.
However, the Ministry of Transport has defended Adif’s procedure, insisting the weld was executed in line with internal specifications and the UNE-EN 13674-1 standard.
According to the official statement, the company used the aluminothermic charge corresponding to the lower-grade R260 steel, as set out in the NAV 3-3-2.1 standard. The ministry attributed the contradictory documentation to a “clerical error.”
Nonetheless, several experts have pointed out that aluminothermic welding is less reliable than flash butt welding, although the latter tends to create higher residual stresses.
Juan José del Coz, professor of Construction Engineering at the University of Oviedo, notes that aluminothermic welds are involved in roughly 40% of track breakages recorded on major railway networks.
Barrón defends the CIAF’s independence
With more than four decades of experience at Renfe, Barrón emphasised the CIAF’s independence and said that the commission would thoroughly investigate the weld’s condition and whether the fault could have been detected earlier. “We’re going to get to the bottom of this,” he assured.
The CIAF president also expressed surprise upon learning that the Madrid–Seville line renewal was not comprehensive, as many had assumed. “Some turnouts and rail sections have been replaced, but not all of them,” he said, requesting detailed clarification from Adif on the selection criteria.
Transport Minister Óscar Puente countered by insisting the renewal was comprehensive and accused the opposition of “ignorance” on railway infrastructure matters. Although Puente himself has claimed that all rails were replaced, parts of the original track remain—something not necessarily problematic if they were in good condition.
The investigation remains focused on kilometre post 318 of the line, where the suspected defective weld lies. The results of metallurgical analyses and laboratory tests to be carried out in the coming days will be crucial in determining whether that weld failure was indeed the trigger for the accident.