NTSB Examines PRDs in East Palestine DerailmentWritten by Carolina Worrell, Senior Editor
National Transportation Safety Board (NTSB) investigators recently examined and tested pressure relief devices (PRDs) removed from the five vinyl chloride monomer (VCM) tank cars involved in the Feb. 3 derailment of a Norfolk Southern (NS) train in East Palestine, Ohio.
According to NTSB, investigators recovered the PRDs, which “regulate the internal pressure of rail tank cars by releasing material when under pressure, reducing the potential for a catastrophic tank failure,” and tested them at a Texas facility.
The examination and testing revealed the following:
- “NTSB testing found anomalies with the function of some PRDs that may have compromised their pressure relieving capability. This will require further testing and evaluation to assess the impact on the operation of the PRDs.
- “According to the manufacturer’s part specifications, one of the installed PRD’s internal spring was coated with aluminum, which is not compatible with vinyl chloride.
- “While aluminum debris from melted protective housing covers entered the PRD discharge areas, there was no evidence that melted aluminum entered the tank. The NTSB continues to assess if the debris impacted the PRD operation.
NTSB’s safety investigation into the probable cause of the NS derailment is ongoing. Additional actions, the agency says, may be recommended to prevent future derailments as the investigation continues.
Additional information on the investigation is available here.