The Massachusetts Bay Transportation Authority (MBTA) announced Monday that the Red Line car derailment on June 11 was due to a broken axle. There was poor electrical connectivity between two pieces of the axle, weakening it over time, according to the report detailing the incident.
The derailment caused significant service disruptions and was the beginning of a long summer for the MBTA—two more derailments occurred within the following two months.
The connectivity issue was between the ground ring and the ground brush—electricity exits through these two pieces after it has entered the third rail and provided energy to turn the motor. A working ground ring is smooth, but the broken one was distorted due to electrical arcing—an uncontrollable electrical discharge.
An ultrasonic inspection was performed on all of the Red Line cars after the incident, and will be completed on all Orange, Blue, and Green Line cars within the next three weeks, the report said. Ground ring inspections are also being conducted on all Red Line cars.
Maintenance inspections will be performed on 8,500 miles of track, annual inspections of the axles—including ground ring inspection—will be conducted, and ultrasonic inspections will happen every two years going forward, the report said.
The car derailed near the JFK/UMass stop, damaging the signal system. The signals on the Red Line are slowly being restored, however, the project isn’t complete yet. The restoration of the signal between North Quincy and JFK is anticipated to be completed sometime in October, according to the MBTA’s report.
The car was inspected visually in May of this past year, as well as in March.
“There is some ambiguity as well unto the level of detailed inspections being done of the ground ring and I think it’s our responsibility to really make it clear to our technicians on what they need to be inspecting for and the level of detail and precision that we need to be inspecting for on these ground rings,” said Jeffrey Gonneville, the MBTA’s deputy general manager at a MassDOT Board and the Fiscal and Management Control Board meeting on Monday.
This was the first time this kind of derailment has happened at the MBTA, Gonneville said. During the visual inspection, the ground ring is not directly visible. They are changing the procedure for how it’s checked.The ultrasonic inspections were done every two years in the past—this car’s was due for one this summer.
“That is on us,” Gonneville said to reporters on Monday. “That is on the MBTA to ensure that we’re giving our technicians the right procedures that they should be following.”
A car on the Green Line derailed in the same week as the Red Line derailment this past summer. Another Green Line car derailed near Riverside on Aug. 7, and service was suspended due to a fire near the track on the Orange Line on Aug. 23.
The MBTA announced a plan to close major T lines every weekend throughout the fall to conduct repairs and renovate the dated infrastructure.