Four workers were killed around noon in a refinery when replacing corroded pipes on a 46 m distillation tower while the fractionator continued to operate, with large volumes of flammable vapour and liquid flowing inside the tower and its attached piping.
Earlier that morning, under the direction of a maintenance supervisor, workers had removed a section of corroded naphtha piping 34 m up the tower, near where the piping joined the fractionator. After a first cut at 10 a.m., a second cut was made 30 min later 8 m below the first one when petroleum naphtha a volatile hydrocarbon mixture that ignites spontaneously at 232°C, began to ooze out, forcing the workers to reseal the pipe immediately. After breaking for lunch, around 11:30 a.m., the workers climbed 12 to 30 m up scaffolding alongside the tower. They tried to drain the piping system of naphtha by opening a pipe flange 11 m up and directing the leaking fuel into a vacuum truck using makeshift plastic sheeting and a bucket. The operation proceeded without apparent problem for 30 minutes, when suddenly a large volume of naphtha, propelled by vapour pressure from the operating fractionator, shot out of the open pipe overhead, spraying the workers. It ignited on the hot surface of the fractionator (260 °C) and engulfed the five technicians in flames.
Although emergency teams arrived quickly, no one could approach the victims for 20 minutes because of the fire. One man died at the scene, three died at the hospital and another, who had thrown himself off the scaffolding to escape the flames, survived with critical injuries.
The Chemical Safety Board (US CSB) investigated the accident and found critical safety issues :
- several naphta leaks had occurred since February 10th. Each leak was treated separately as an emergency, but none of the interventions managed to completely staunch the flow of naphtha. Shut-off valves malfunctioned repeatedly, and drain valves were found to be clogged beyond use or repair. Ultrasound and X-ray tests showed that both the piping and the valves were severely corroded and needed to be replaced.
- Although the unit operator argued for shutting down the process before attempting to replace the deteriorated piping, a maintenance supervisor decided to do the job while the hot fractionator continued to run. This fateful decision did not receive any oversight or scrutiny from the facility’s management.
- In the 13 days that elapsed between the first occurrence of the leak and the fatal accident, the personnel missed numerous opportunities to reassess the hazards of the pipe replacement work and take necessary measures (such as shutting down the fractionator).
- No systematic job planning and authorization process was in place at the refinery to ensure that maintenance work received appropriate scrutiny before going forward. In particular, no formal hazard evaluation was conducted before or during the maintenance project, and managers and safety specialists were not sufficiently involved in decision-making and oversight.
The valves and piping had corroded at an excessive rate because an upstream vessel known as the crude oil desalter which removes salt, water, and solids from the oil feed was being operated beyond its design limits. The operator had namely routinely processed excessive volumes of crude oil with high water content, overtaxing the desalter. As a result, water and corrosive materials like ammonium chloride were carried over into the fractionator, where they began to deteriorate the piping and valves. No specific evaluation, known as management of change (MOC), had been carried out to identify if the operational changes (feeding different material into the process, increasing the amounts being processed and making long-term adjustments to valve positions) could worsen the corrosion of piping and valves.
The CSB made a number of safety recommendations including :
- the implement a program to ensure that hazardous non-routine maintenance is conducted safely,
- a written hazard evaluation by a multidisciplinary team before any hazardous job is started,
- a high level of approval for high hazard jobs including a written protocol for making shutdown decisions,
- the improvement of the refinery management of change and corrosion control programs
The operator was fined 2 M dollars for safety violations or compensations.