MBTA: Weakened steel ring led to June derailment

Discovery has led to more stringent inspections

This story has been edited to include additional comments made after the findings were first disclosed.

A BRITTLE STEEL AXLE on the front of the third car of a 50-year-old Red Line train snapped on June 11, according to engineers who on Monday disclosed their findings about the cause of the subsequent derailment that has led to months of sub-par service.

The reason that axle broke appears to be a unique occurrence in the annals of the MBTA, according to Deputy General Manager Jeff Gonneville, and T staff is determined to keep it that way.

“It is our responsibility and our obligation to make sure that this never happens again,” Gonneville told reporters ahead of a Monday meeting on the subject. “This has impacted a lot of people’s lives over the last several months.”

An inspection last December revealed that the housing for something called the ground brush had somehow come off, and Gonneville now guesses that was how grease and train dust wound up in the component. The ground brush takes electrical current that has been used to power the motor that turns the wheels and transfers it to the ground ring on the axle, which sends the charge through to the rails to the earth where it dissipates.

The debris on the ground ring appears to have hindered the smooth transfer of electricity, and during a “prolonged period,” which Gonneville reckons occurred over a span of about six months, that particular ground ring became mottled and scarred from electrical arcing – which is a bit like the striking of miniature lightning bolts. This arcing hardened the steel and weakened it, making it brittle, according to Gonneville.

The MBTA’s inspection regime has been enhanced in the months since, but before the derailment, there wasn’t much attention paid to the state of the ground rings during each vehicle’s roughly three-month check-up, Gonneville said.

After the December discovery of the undone housing, there were two more inspections in March and May. In May, MBTA mechanics replaced two ground brushes on the vehicle. Gonneville suspects, but the records aren’t detailed enough to confirm, that one of those ground brushes was used on the weakened ground ring. In any case, the weakened ground ring remained on the car.

The broken axle of the Red Line car that derailed is visible in the foreground. (Photo courtesy of MBTA)

The repeated electrical arcing damaged the axle so much that it fractured, and that fracture created the early morning derailment, which caused only minor injuries to passengers but led to many other problems. After it derailed, the car in the middle of the train slammed into signal equipment right outside JFK/UMass, which regulate the safe passage of trains from one station to the next. Since the derailment, that process has been accomplished using MBTA personnel on the tracks and at each station communicating with each other to make sure trains can safely move from one station to the next.

Service is now almost back to normal, according to Gonneville, who said the only stretch in need of restoration of signal controls is the one between North Quincy and JFK, and that should be done in as little as two weeks, or at least by the end of October. The T restored signal controls between Fields Corner and JFK, which is a junction for two southern branches of the T’s busiest subway line, on September 11.

Red Line trains used to average about 30 minutes traveling between Braintree and South Station. Trip times soared to about 55 minutes after the derailment, but have since come down as signal work has been completed. Currently, the Braintree-South Station trip takes about 35 minutes.

Before the derailment, the Red Line cars had been due for their two-year ultrasonic inspection this past summer, which, had it occurred, would have turned up the damage to the axle steel, Gonneville said. Ultrasonic testing, which reveals flaws in metal, has since been ramped up so that it will occur annually on all subway cars. Before the derailment, the Orange Line was the only line that underwent annual ultrasonic testing.

Even if the axle didn’t break completely in two, the fracture to it would have been enough to cause the derailment, said Gonneville, who expressed some uncertainty over whether the axle was completely severed before the crash, during the crash, or after. The train’s undercarriage trucks were inspected at an Everett repair shop, and that’s where the T found the broken axle, said Gonneville, who thinks the axle was still barely in one piece when the inspectors discovered it.

Jeffrey Gonneville, deputy general manager of the MBTA, shows the mottled ground ring that he believes caused the Red Line derailment on June 11. (Photo by Andy Metzger)

On Monday, Gonneville said that ultrasonic inspections of the entire Red Line were completed soon after June 11, and testing of the Orange, Blue, and Green lines will be done in three weeks. The T has completed inspections of the ground rings on the oldest Red Line cars, and ground ring inspections on the rest of the fleet is underway.

While Transportation Secretary Stephanie Pollack appeared to ward off criticism about the flawed equipment going undetected, noting that the grounding ring isn’t easily visible, the T has tacitly acknowledged that its earlier system was inadequate by enhancing its protocols and schedules for inspections in the future.

Jimmy O’Brien, the president of the Boston Carmen’s Union, the T workers’ largest labor organization, suggested cost-cutting might deserve some blame, and claimed that cuts had been made to the ultrasonic testing program.

“The MBTA claims a commitment to investing in the system while simultaneously boasting about cost savings in the operating budget,” O’Brien said in a statement Monday. “Cuts to the operating budget and the elimination of jobs resulted in cuts to inspections and testing – including the Ultrasonic Testing that could have detected the problem that resulted in the Red Line derailment.”

In response, Gonneville said the ultrasonic inspections had been conducted every two years for as long as he could remember.

“We will do everything we need to ensure the safety of our fleet,” Gonneville said. It’s debatable whether annual ultrasonic testing alone could have prevented the cracked axle. The housing seems to have come loose between October 2018, when one of the regular inspections of the 50-year-old train car occurred, and December 2018, when the problem with the covering was noted.

On Monday afternoon, members of the MBTA Fiscal and Management Control Board and the Massachusetts Department of Transportation Board of Directors asked about what more could be done to ensure the safety of the equipment.

“The level of sophistication of these cars is very basic,” Gonneville said, of the older cars, but the more modern cars have a far more advanced system for dispersing the electrical current into the ground.

MBTA General Manager Steve Poftak said cost should not be an obstacle as the T attempts to improve safety.

“We very much regret that this incident occurred,” Poftak said. “We are ready to make any investments needed.”

Accelerating the ultrasonic testing could require hiring more staff, Gonneville allowed.

“Our vehicle-maintenance team is going to have to analyze whether or not they will need some additional staffing to go from that biannual to that annual testing,” Gonneville said.

MBTA control board member Monica Tibbits-Nutt asked whether the schedule of conducting ultrasonic tests every year or two years is an “industry standard,” and Gonneville said he would have to get back to her about that.

New Orange Line cars are trickling into service, and the T has hired the Chinese-government-owned firm CRRC to completely replace the Red and Orange line fleets.

In arriving at the damaged ground ring as the culprit for the crash, the T ruled out several other possibilities. The axle, which has been in service since 1992, is “not beyond a useful life,” and a metallurgical analysis didn’t indicate the age of that piece of equipment was the issue. There was no manufacturing defect in the equipment, nor was there a problem with the bearings that allow the axle to rotate, Gonneville said.

Any number of things could have caused the housing assembly to come off the component where the ground brush connects with the ground ring, and the T is “scouring through our maintenance records” to learn whether there are any other documented incidents of the covers being loose. So far, nothing has turned up, Gonneville said.

Meet the Author

Andy Metzger

Reporter, CommonWealth magazine

About Andy Metzger

Andy Metzger joined CommonWealth Magazine as a reporter in January 2019. He has covered news in Massachusetts since 2007. For more than six years starting in May 2012 he wrote about state politics and government for the State House News Service.  At the News Service, he followed three criminal trials from opening statements to verdicts, tracked bills through the flumes and eddies of the Legislature, and sounded out the governor’s point of view on a host of issues – from the proposed Olympics bid to federal politics.

Before that, Metzger worked at the Chelmsford Independent, The Arlington Advocate, the Somerville Journal and the Cambridge Chronicle, weekly community newspapers that cover an array of local topics. Metzger graduated from UMass Boston in 2006. In addition to his written journalism, Metzger produced a work of illustrated journalism about Gov. Charlie Baker’s record regarding the MBTA. He lives in Somerville and commutes mainly by bicycle.

About Andy Metzger

Andy Metzger joined CommonWealth Magazine as a reporter in January 2019. He has covered news in Massachusetts since 2007. For more than six years starting in May 2012 he wrote about state politics and government for the State House News Service.  At the News Service, he followed three criminal trials from opening statements to verdicts, tracked bills through the flumes and eddies of the Legislature, and sounded out the governor’s point of view on a host of issues – from the proposed Olympics bid to federal politics.

Before that, Metzger worked at the Chelmsford Independent, The Arlington Advocate, the Somerville Journal and the Cambridge Chronicle, weekly community newspapers that cover an array of local topics. Metzger graduated from UMass Boston in 2006. In addition to his written journalism, Metzger produced a work of illustrated journalism about Gov. Charlie Baker’s record regarding the MBTA. He lives in Somerville and commutes mainly by bicycle.

While the particular cause of the Red Line crash appears to be a unique occurrence for the MBTA, derailments themselves are not. A panel that includes former US transportation secretary Ray LaHood has been brought on to look at the T’s safety practices overall.

Bruce Mohl contributed reporting.