Federal investigators found some anomalies with the function of pressure relief devices (PRDs) from five of the vinyl chloride monomer tank cars involved in the Norfolk Southern train derailment in East Palestine, Ohio.
Investigators with the National Transportation Safety Board (NTSB) said that further testing is required to assess the impact of these anomalies on the operation of the PRDs.
PRDs regulate the internal pressure of rail tank cars by releasing material when under pressure, reducing the potential for a catastrophic tank failure.
NTSB investigators examined and tested five of the devices, finding that:
- there were anomalies with the function of some PRDs that may have compromised their pressure relieving capability
- PRDs with anomalies will need to be tested further to determine their impact on the operation of the devices
- one of the installed PRD’s internal springs was coated with aluminum, which isn’t compatible with vinyl chloride, and
- while aluminum debris from the protective housing covers entered the PRD discharge areas, there was no evidence that melted aluminum entered the tank.
Investigators are still assessing whether the aluminum debris impacted the operation of the PRD.
More information can be found on the NTSB investigation webpage.