More studies are needed on whether tank trailer wetlines should be banned or not, said Clyde Richard of Accident Analysis Inc.
He discussed the wetline issue at the National Tank Truck Carriers (NTTC) Conference and Tank Truck Equipment Show May 9-11 in Chicago IL.
The Pipeline and Hazardous Materials Safety Administration (PHMSA) proposal would mandate wetline purging systems on newly-manufactured or existing tank trailers transporting flammable liquids.
Little data is available about tank penetration in vehicle accidents, personnel danger in retrofitting tank trailers, and financial costs to meet the proposal, and the Department of Transportation appears to have no plans for further data gathering, he said.
He pointed out that if a tank is penetrated in a vehicle accident, having dry lines would not necessary prevent further dangers. Tests indicate that an impacting vehicle would retain 98% of its forward speed after coming in contact with the wetlines.
He anticipated that a crash into the trailer with enough force to penetrate the tank would likely end in a fatality — whether there was a resulting fire or not.
In addition, the wetline purging systems now under consideration would require welding on the tank trailer, which raises concerns about the safety of retrofit programs, he added.
“Even tanks cleaned and purged before welding can present potential dangers,” he said.
Richard also pointed out that an electronic control system involved in a purging system would have to withstand varying weather and road situations that might interfere with its ability to function accurately.
NTTC has filed comments on the proposal before PHMSA and said that the agency's estimate of wetline accidents and societal costs estimates are “grossly exaggerated.”