Two U.S. transportation agencies have jointly issued a safety advisory regarding hazmat packages known as nurse tanks following a 2023 incident that saw such a tank rocket more than 300 feet from its original location.
The advisory from the Federal Motor Carrier Safety Administration (FMCSA) and Pipeline and Hazardous Materials Safety Administration (PHMSA) focuses specifically on nurse tanks manufactured from Jan. 1, 2007 through Dec. 31, 2011 by American Welding and Tank (AWT) at its Fremont, Ohio plant.
These AWT tanks were the subject of a prior FMCSA investigation and enforcement action regarding improper manufacturing procedures.
Post-incident testing points to ongoing problems with welds
The incident that led to the advisory occurred on Aug. 23, 2023 when a 2009 AWT nurse tank containing anhydrous ammonia experienced a catastrophic failure while on a farm co-op lot. The failure led to a release of all of the product and the tank shell to rocket more than 300 feet from its original location.
No injuries were reported, but the event indicates the potential continuing problems of AWT nurse tanks that have been in service for more than a decade, according to the joint safety advisory.
The owner of the nurse tank involved in the incident contracted a third-party testing company to examine their other AWT nurse tanks that were manufactured between 2008 and 2012.
Seven out of eight of these tanks showed extreme stress corrosion cracking, porosity and voids in the welds where the heads and shells of the nurse tanks were joined. Only the 2012 tank passed.
The nurse tank owner submitted the results to engineering experts who were involved in the prior FMCSA research into AWT nurse tanks. Based on the review by the experts, the owner voluntarily placed their nurse tanks out-of-service.
This farm co-op’s parent company conducted similar testing on 142 AWT nurse tanks it owned that were manufactured between 2007 and 2012. One hundred of these tanks failed the test. All of the tanks manufactured in 2012 passed.
Agencies ‘strongly recommend’ owners conduct periodic tests
Based on these findings, the FMCSA and PHMSA “strongly recommend that owners of AWT nurse tanks manufactured between Jan. 1, 2007 and Dec. 31, 2011 that are exempted from periodic inspection and testing requirements … conduct voluntary periodic visual inspection in accordance with 49 CFR §173.315(m)(2)(i); thickness testing in accordance with 49 CFR §173.315(m)(2)(ii), and pressure testing in accordance with 49 CFR §173.315(m)(2)(iii).”
Owners of affected AWT nurse tanks who are unable to conduct voluntary pressure testing should conduct either radiographic or ultrasonic testing, according to the safety advisory.
The safety advisory recommended performing this testing at least once every five years on affected nurse tanks.
