By Daigo Isono and Shu Saito / Yomiuri Shimbun Staff WritersA crack so deep it was just moments from breaking apart was found in a bogie (see below) of West Japan Railway Co.’s Nozomi 34 (N700 series) Shinkansen train traveling from Hakata to Tokyo.
The fact that the train remained in operation for as many as three hours after abnormalities were detected may have worsened the situation. JR West must conduct a sufficient investigation to determine the cause of the problem, and implement countermeasures to prevent a recurrence.
Possibility of metal fatigue
The crack was discovered in a bogie frame of the Nozomi’s 13th carriage on the evening of Dec. 11 when the train stopped at Nagoya Station. The U-shaped crack was up to 14 centimeters long in a frame that is 17 centimeters tall on each side and 16 centimeters wide on the bottom.
Also, a joint part used to transmit motor rotation to the wheels was discolored, indicating it may have been burned.
Hitoshi Tsunashima, a Nihon University professor and expert on railroad engineering, said: “The crack in the frame was probably caused by metal fatigue and grew as the train was running. This in turn may have caused a misalignment in the wheel shafts, and put strain on and burned the joint part due to the heat and friction.”
Bogies are essential for the train to run safely.
In May 2016, four wheels of a train on the Tobu Tojo Line derailed in Itabashi Ward, Tokyo. An approximately 18-centimeter-long crack was found in the frame of its bogie, believed to have been caused by faulty welding.
The Japan Transport Safety Board deemed the latest trouble of the Nozomi to be a “serious incident,” the first-ever such designation for a Shinkansen. The size of the crack suggests there was a high possibility that the Nozomi — and its about 1,000 passengers — could have been involved in a serious accident.
From 1998 to 2000, train inspections on the Toei subway lines and Yamagata Shinkansen line and other lines revealed numerous cracks in their bogie frames, leading the Land, Infrastructure, Transport and Tourism Ministry to create an inspection manual in 2001.
In inspections for Shinkansen — conducted in line with the manual — magnets and iron powders are utilized to check for damage to the train’s easily cracked welded spots and other parts. The inspections include a “general inspection” wherein the car is disassembled either after every 1.2 million kilometers traveled or once every three years, and a “bogie inspection” conducted either every 600,000 kilometers traveled or once every 1½ years.
Built in 2007, the car involved in the latest incident had traveled 6.92 million kilometers and had just undergone a general inspection in February 2017. Early in the morning on Dec. 11, the train was given a routine visual inspection, but no abnormalities were detected.
JR West is now trying to determine specifically what kind of check was performed on the cracked part.
The affected area “is subject to continued strain and requires thorough inspection,” Tsunashima said. “Also a system needs to be introduced to constantly monitor the status of the car, in an effort to detect any abnormalities of the train in operation in their early stages.”
Another issue seen as problematic in the latest incident is that the train was kept in operation for three hours even after abnormalities were detected, traveling a distance of roughly 740 kilometers before it was stopped.
The train departed Hakata Station at 1:33 p.m. on Dec. 11. When it left the next station, Kokura, at 1:50 p.m., a crew member noticed what was described as a burning smell.
After the train left Fukuyama, a passenger in the 13th carriage reported smoke. Three maintenance staff who boarded the train at Okayama also reported hearing abnormal sounds. Some people called for an inspection of the bottom of the train, but the train was kept in operation because the smell was deemed faint and the sounds intermittent.
At Shin-Osaka Station, where the train was handed over to the control of JR Tokai, the maintenance staff disembarked and a different conductor and driver took over. The Central Japan Railway Cp. (JR Tokai) driver noticed an unusual smell near Kyoto, and an emergency inspection was conducted after the train arrived in Nagoya at 4:50 p.m. When staff checked underneath the car, they finally discovered the problem.
“Because Shinkansen operate at high speeds, more careful judgment is required,” said Satoru Sone, a specially appointed professor at Kogakuin University and an expert on transportation system engineering. “The problem is that the train was kept in operation despite multiple signs that something was wrong. There needs to be a thorough investigation into how the situation was handled.”
Train troubles continue
The latest Shinkansen incident is part of a recent spate of major disruptions to railway transportation, making the transportation ministry increasingly concerned about potential risks.
Minister Keiichi Ishii expressed his intention on Dec. 19 to establish a panel of experts for railway safety.
The Tokyu Denentoshi Line in Setagaya Ward, Tokyo, experienced a power outage on the morning of Nov. 15. The railway was forced to suspend services between Shibuya and Futakotamagawa stations for about four hours, affecting more than 120,000 people. It was apparently due to damage that occurred during installation of power line covers that later spread, resulting in a short circuit.
On Dec. 16, an overhead wire on the Keihin-Tohoku Line in Tsurumi Ward, Yokohama, was cut, resulting in suspended operations for nearly seven hours. Errors in overhead wire work conducted nearby are said to have caused a short circuit. The Tokaido Line in Aichi Prefecture and the Tobu Urban Park Line in Chiba Prefecture also experienced disruptions to operations on Dec. 12 when their trains’ pantographs were damaged.
Behind this string of incidents, the ministry sees such structural problems as the deterioration and complication of railway equipment and the aging of the workforce on the ground. It plans to establish a panel of experts to analyze these problems.
A senior ministry official said: “Many industries share the common challenges of fewer young recruits and veteran staff retiring in droves as a result of the aging population and the chronically low birthrate. We need to figure out what specific kinds of problems this trend is causing in the railway industry.”
At a Dec. 20 meeting, the ministry urged 32 railway operators, including JR companies, major private railway firms and public subway companies, to thoroughly ensure safety.
A piece of equipment used to run a train car, comprising such items as a motor, gears and frames to secure the wheel shafts. A bogie supports the weight of the car and transfers the acting force to the car when the driver hits the brakes. It plays an important role in ensuring a safe, stable ride by influencing the train’s maximum speed, the speed at which it runs on a curved rail, and passenger comfort.