Shinkansen Crack May Have Started Widening on Previous Day

June 28, 2018

Tokyo- A crack found in the undercarriage of a Shinkansen bullet train car on Dec. 11 last year may have started widening on the previous day, the Japan Transport Safety Board said Thursday.

The transport ministry-affiliated board is investigating the causes of the crack, which placed the Shinkansen undercarriage on the verge of fracturing.

In the investigation, the panel focused on the varying pressures of air springs that adjust the height of moving Shinkansen train cars.

When a crack is created, the pressure of a nearby air spring goes down.

A comparison of the air spring near the crack in question and other air springs showed that their pressure gaps tended to widen from Dec. 10 last year, the day before the crack was found at Nagoya Station in Aichi Prefecture, central Japan.

The crack was found in the undercarriage of one of the 16 cars of the Tokyo-bound Nozomi No. 34 Shinkansen train operated by West Japan Railway Co., or JR West.

Abnormal smell and sounds were noticed by some crew members after the bullet train departed Hakata Station in the southwestern prefecture of Fukuoka on that day. But the train continued operations until its arrival at Nagoya Station, where it was halted.

The transport safety board designated the case as a serious incident that could have led to an accident. This was the first such designation for a Shinkansen train.

In the month when the crack incident occurred, operators of Nozomi Shinkansen trains, including JR West, did not have in place a system to immediately grasp air spring pressure differences.

On Thursday, the board advised transport minister Keiichi Ishii to consider establishing a system for informing crew members about abnormalities based on air spring pressure and other data.

Undercarriage maker Kawasaki Heavy Industries Ltd. has been found to have shaved the bottom of the undercarriage during the manufacturing process, causing a lack of strength, which is seen as the primary factor leading to the crack.

The board newly pointed out that Kawasaki Heavy also failed to conduct required heat treatment after the welding operation on the parts of the undercarriage.

It said this failure may have contributed to the widening of the crack. Jiji Press