Standardization News

An independent U.S. government agency uses everything at its disposal, including ASTM standards, to determine the causes of transportation and pipeline accidents.

An airplane battery catches on fire.

A gas pipeline explodes.

A bridge collapses.

When incidents like these happen, the U.S. National Transportation Safety Board¹ mobilizes.

Not far from ASTM headquarters this May, NTSB mobilized again after an Amtrak train derailed in Philadelphia as it headed north to New York City. The train's clocked speed exceeded 100 mph when it crashed, and resulted in the loss of life as well as numerous injuries. NTSB is still investigating.

NTSB responds, as in these situations, to transportation and pipeline accidents around the United States, and even internationally. Its mission: to determine the likely causes of transportation accidents, issue and promote safety recommendations aimed at preventing future accidents, and to help accident victims and their families. Their investigations rely, in part, on standards.

NTSB: A Brief History

In 1926, with the Air Commerce Act, the U.S. Congress first charged the Department of Commerce with investigating the causes of aircraft accidents. Decades later, Congress brought together all government transportation agencies into one in 1967 with the NTSB as part of the new department. In 1974, NTSB became an independent agency.

NTSB's mission has stayed the same although their work has expanded over the years to include highway, marine, pipeline, hazardous materials and railroad accident investigation. In 1996, NTSB added the responsibility of coordinating federal assistance to families of accident victims.

Since its founding, NTSB has worked on more than 130,000 aviation accidents as well as thousands of other transportation accidents. In a single year, NTSB may work on more than 3,500 investigations, with some using standards to determine hardness, tensile strength and other material properties.

Standards and the Process

When NTSB finds out about a major accident, the work often begins with a regional field representative who heads to the site. Depending on the scope of the accident, a "go team" may assemble at NTSB headquarters in Washington, D.C., to head to the scene as quickly as possible.

This group of three to more than a dozen, brings together needed expertise, such as fire, metallurgy, human performance, survival factors, operations, structures, power plants, systems, general counsel, and public and government affairs. Someone from NTSB's Materials Laboratory Division might be part of the group when a materials or metallurgical issue will likely need to be addressed.

Michael Budinski, chief of the Materials Laboratory Division, describes how his group and ASTM standards become part of the investigative process. The materials engineer or metallurgist assigned to the investigation team decides what will be needed for any lab testing that will take place, he says.

"At the scene, their role is to try and figure out what pieces of evidence we need to bring back," says Budinski. "Where do we need to cut it? How do we need to pack it? How do we need to ship it? How do we need to preserve it, wash it, clean it, so we can get it back to the lab in good condition?"

With the evidence in the lab, the team evaluates it and chooses appropriate tests, whether mechanical or chemical or both. "We work as a team on obtaining the standards and determining what needs to be done," says Kristi Dunks, Ph.D., NTSB transportation safety analyst/senior air safety investigator. Perhaps they'll look at fractures under a microscope to see how cracks develop. Or they'll test for hardness, how well a material resists change in shape or form.

Materials lab team members may be experienced with particular standards, such as ASTM tests for hardness, or methods for tensile testing, or they might look at the Annual Book of ASTM Standards for possible procedures to use. Or, they might call staffers at an organization - ASTM or the American Society of Mechanical Engineers, for example - to inquire about an appropriate standard to use for a specific material.

"If an investigation involves a premature failure of a component outlined in a standard, we go to the standard to see what it was supposed to designed to, and then we can move to the next step," Dunks says.

"We take a clean material sample that's not burned or affected by heat, and we'll do a litany of ASTM tests on it, or whatever the prevalent standard is," Budinski says. The safety board may make recommendations for revisions to standards based on their experience.

The Dreamliner Battery Issue

Standards had a role when the new Boeing 787 Dreamliners first rolled into service. When a Dreamliner battery caught fire on Jan. 7, 2013, while the plane was parked at the gate, it sparked an investigation by NTSB. Nine days later, with a second Dreamliner battery fire, the Federal Aviation Administration grounded the entire fleet. (In the NTSB investigative process, the airline company, battery manufacturer, component manufacturers, other safety boards, the U.S. Federal Aviation Administration and other groups were all part of the effort.) When the NTSB materials lab got involved, it focused on the craft's auxiliary power unit battery.

In the course of its failure analysis work, the lab disassembled the burned battery, and tested the copper busbars, which conduct electricity. The lab was checking for regions affected by localed heating, with busbar sections prepped for microhardness testing and microstructural evaluation according to ASTM standards. As reported, the cross sections were mounted, polished and tested according to E384 (Test Method for Knoop and Vickers Hardness of Materials). The mounted samples were then microetched as prescribed in E407 (Practice for Microetching Metals and Alloys), but no heat-related changes were observed.

The testing "ruled something out but it could have easily ruled something in," says Budinski. A battery cell proved to be the fire's cause. Short circuiting led to thermal runaway that cascaded to adjacent cells, which resulted in smoke and fire.

More Investigations with Standards

In some NTSB investigations, standards can demonstrate that a material is, or is not, suitable for purpose.

When a tractor-trailer's oversize load struck the Interstate 5 bridge over the Skagit River in Mount Vernon, Washington, in May 2013, part of the bridge collapsed into the water. A through-truss bridge, the structure comprised 12 spans, with specifications citing ASTM standards for the bridge supports above the road lanes. Here the NTSB lab used ASTM's A370, Test Methods and Definitions for Mechanical Testing of Steel Products, in confirming that the steel's properties were as they should be.

Another example: ASTM standards proved pipe didn't meet specifications in the September 2010 San Bruno, California, gas line explosion. The NTSB investigation showed the evening explosion and ensuing fire originated with a fracture in a short pipe section known as a pup. NTSB analyses with ASTM standards, following metallographic specimen preparation according to ASTM standard E3, contributed to the work. ASTM tensile and hardness testing were also conducted. "We could show that these pipe pieces did not conform to the operator's or other known specification for pipe," Budinski says. "The ASTM standard tests that we did revealed this material discovery."

A Final Word

As of early June 2015, NTSB was planning a press briefing related to the Philadelphia Amtrak crash with its Special Investigation Report: The Use of Forward Collision Avoidance Systems to Prevent and Mitigate Rear-End Crashes. In addition to safety recommendations, the agency will report on its findings when the investigation is complete. And its work will continue.

REFERENCE

1. Learn more about the National Transportation Safety Board, including its process, investgation reports, press releases and safety recommendations.