Rupture of a Heat Exchanger in a Refinery, Due to Hydrogen Attack
A petroleum refinery experienced a catastrophic rupture of a heat exchanger in the catalytic reformer / naphtha hydrotreater unit (the NHT unit). The heat exchanger, catastrophically ruptured because of High Temperature Hydrogen Attack.Highly flammable hydrogen and naphtha at more than 500 degrees Fahrenheit (260C) were released from the ruptured heat exchanger and ignited, causing an explosion and an intense fire that burned for more than three hours. The accident fatally injured seven employees (one shift supervisor and six operators) who were working in the immediate vicinity of the heat exchanger at the time of the incident.
Event Date
April 2, 2010
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The direct cause was carbon steel degradation and seal break due to high temperature hydrogen attack (HTHA).The reports speak of self-ignition of the naphtha/H2 mixture.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
heat exchanger PREHEATING THE NAPHTA
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
The workers were in the final stages of a start-up activity to put back in-service following cleaning a three bank of heat exchangers. The heat exchangers are used to preheat process fluid before it enters a reactor of the Naphtha Hydrotreater unit. While the operations staff was performing the start-up operations, the heat exchanger in the middle of the operating bank catastrophically ruptured. Because of the refinerys long history of frequent leaks and occasional fires during this start-up activity, the CSB considers this work to be hazardous and non-routine.
Currency
Lessons Learned
Lessons Learned
The Chemical Safety and Hazard Investigation Board (CSB) has issued a report which makes recommendations, summarized below, to the various recipients. To the Refinery the recommendation was to implement a process safety culture program that will assess and continually improve any identified process safety culture issues. Since the April 2010 incident, the company has installed new NHT heat exchangers with upgraded materials of construction to significantly reduce the potential for HTHA. In addition, an advanced process control system is in place to minimize fouling. The heat exchangers are also constructed using only one bank of exchangers. The entire NHT unit now must be shut down for cleaning, eliminating the hazards of online switching and creating a much safer approach for maintenance. The new heat exchangers also incorporate additional instrumentation to allow the monitoring of each heat exchanger for fouling and decrease the likelihood of operation in HTHA-susceptible conditions.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
The Chemical Safety and Hazard Investigation Board (CSB) report REPORT 2010-08-I-WA (May 2014).
Available at: https://www.csb.gov/tesoro-refinery-fatal-explosion-and-fire/
(accessed June 2020)