A faulty cylinder could be to blame for a CNG gas bus explosion in Brisbane last month, still under investigation by two teams
By David Goeldner | February 2, 2012
The CNG bus explosion at Brisbane City Council’s Virginia Depot which disrupted the city’s route service operations is under investigation by two teams.
It appears the explosion may have been caused by a faulty cylinder.
At 1am on January 21, bus V815 experienced a ruptured cylinder causing damage to four other buses parked in the vicinity.
“All five of the damaged buses will be repaired and returned to service,” a Brisbane City Council
spokesperson says.
Brisbane Transport (BT) removed 569 compressed natural gas-powered buses from service on Saturday immediately after the gas tank rupture.
The cause of the incident has yet to be determined and investigations are ongoing, but the current hypothesis, according to BT, is that it was the result of an isolated occurrence related to a defect in the specific cylinder.
The bus had been refuelled to 255 bar fill pressure at 27°C ambient shortly prior to the rupture.
According to the spokesperson, the fill pressure was below the results of the manufacturer’s batch tests reported in the certificate for the cradle assembly that contained the ruptured cylinder.
Cylinders from the same manufacturing batch as the cylinder that ruptured have been quarantined and are not in service, although all gas cylinders across the bus fleet are undergoing visual inspections.
Brisbane Transport has established two investigation teams, which will both report to an investigation governance group consisting of senior officers from Brisbane Transport and the Gas and Petroleum Inspectorate in Mines and Energy.
Other external experts will be brought in as required to assist both investigations.
Brisbane’s Lord Mayor Graham Quirk announced shortly after the incident that the city’s council was progressively moving back to diesel-powered buses.
However, BT has only been procuring diesel buses since October 2009.
“The speed of replacement of the CNG buses is dependent on funding from the Queensland Government for new bus acquisitions and growth bus requirements to operate the fleet,” the spokesperson says.
Funding for BT’s fleet replacement and expansion is provided by the Queensland Government through TransLink.
According to the spokesperson, Brisbane City Council is still waiting for growth projections and funding commitments from TransLink beyond the 2011-12 financial year.
“Retirement of the CNG buses will also be considered in the context of the retirement of older diesel buses,” says the spokesperson.
While no-one was injured at the Virginia depot, the Brisbane gas bus explosion follows a CNG-related fire last year in NSW on an STA bus.
The Sydney gas bus fire shut the city’s transport system down during a busy peak hour period after the incident was revealed by a driver’s union official.