A new safety alert has been issued by a federal agency focusing on the potential hazards of emergency discharges from pressure release valves at chemical manufacturing facilities.
The U.S. Chemical Safety and Hazard Investigation Board (CSB) issued a new safety alert on emergency discharges from pressure release valves based on information gathered from four investigations.
This alert advises facilities that “while a discharge from emergency pressure-relief systems can help protect equipment from unexpected and undesired high-pressure events, it can also seriously harm or fatally injure workers and cause extensive damage to a facility if the discharge is not made to a safe location.”
All four investigations highlighted in the alert “underscore the importance of thoroughly evaluating emergency pressure-relief systems to ensure they discharge to a safe location where they will not harm people,” according to CSB Chairperson Steve Owens.
The investigations are from four incidents that resulted in 19 deaths and 207 injuries. They include:
May 2018 ethylene release at Kuraray America
The May 19, 2018, ethylene release that ignited at the Kuraray America ethylene and vinyl alcohol copolymer plant in Pasadena, Texas injured 23 workers.
This incident occurred during the startup of a chemical reactor system following a turnaround, which caused high-pressure conditions inside the reactor and activated its emergency pressure relief system. That caused a discharge of flammable ethylene vapor horizontally into the ambient air in an area where a number of contractors were working.
November 2014 methyl mercaptan release in La Porte, Texas
About 24,000 pounds of highly toxic methyl mercaptan were released on Nov. 15, 2014, from an insecticide production unit at the DuPont chemical manufacturing facility in La Porte, Texas.
The release killed three operators and a shift supervisor inside one of the facility’s manufacturing buildings.
CSB investigators found that, separate from the release incident, there were a number of safety issues at the plant, including that several emergency pressure-relief systems at the facility were designed to discharge hazardous materials in a way that posed a risk to workers and the public.
May 2009 flammable vapor release in West Carrollton, Ohio
Highly flammable vapor was released May 4, 2009, from a waste recycling process at Veolia ES Technical Solutions in West Carrollton, Ohio.
The vapor ignited and violently exploded, injuring four employees. After the initial explosion, multiple other explosion occurred, significantly damaging every structure onsite. Residences and businesses in the surrounding community were also damaged.
Uncontrolled venting from emergency pressure-relief valves allowed tetrahydrofuran (THF) vapors to accumulate to explosive concentrations outside process equipment and they eventually found an ignition source, according to CSB investigators.
March 2005 explosions at BP refinery in Texas City
On March 23, 2005, during the startup of an isomerization unit following a maintenance turnaround, a series of explosions occurred at the BP refinery in Texas City, Texas, killing 15 workers and injuring 180 more.
A distillation tower flooded with flammable hydrocarbons and was over-pressurized during the startup, causing the tower’s emergency pressure-relief system to activate. This created a geyser-like release from the vent stack and formed a flammable vapor cloud that ignited and exploded.
3 key lessons based on these incidents
The CSB’s alert uses these incidents to illustrate three key lessons for chemical facilities:
- follow existing good practice guidance
- evaluate whether the atmosphere is the appropriate discharge location or if there are safer alternatives, and
- ensure hazardous chemicals vented into the atmosphere discharge to a safe location.
Companies should also evaluate and update their emergency pressure relief systems, when appropriate. This will help prevent future incidents and protects workers and surrounding communities from harm.
