Final report into 2021 fatal acid release published

30 May 2023

The US Chemical Safety and Hazard Investigation Board (CSB) released its final report into the 27 July 2021 fatal acetic acid release at the LyondellBasell La Porte Complex in La Porte, Texas. The CSB’s report found that the inadvertent removal of pressure retaining components of a valve caused the release of 74 tonnes of an acetic acid mixture, killing two contract workers.

Image: CSB

Additionally, one other contract worker and one company employee were seriously injured. The facility’s property damage, including loss of use from the incident, was estimated to be $40 million (£32m).

CSB Chairperson Steve Owens said: “As this tragic incident shows, even a simple task can turn deadly if it is not performed properly. There have been similar incidents around the country involving plug valves being inadvertently taken apart when removing connected equipment. It is time to improve the design of these valves and take other protective actions, such as signage and training, before more workers are killed or injured.”

The CSB’s report chronicles how, in the days leading up to the incident, an operations technician discovered a small leak on methanol piping upstream of the unit’s acetic acid reactor. Soon after the leak was discovered, the shutdown of an adjacent unit required the acetic acid unit to also shut down.

LyondellBasell decided to use the shutdown opportunity to repair the leak and have contractors at the facility perform the work. To isolate the piping, company personnel chose to use the plug valve located between the leaking pipe and the nearby acetic acid reactor. A plan was developed to remove the actuator which was connected to the plug valve.

The contractor work crew began removing bolts that they believed were necessary to take off the actuator. The crew was not aware, however, that the bolts they removed actually secured the pressure-retaining valve cover in place. The plug ejected from the valve, releasing 74 tonnes of an extremely hot acetic acid mixture which was 114°C.

The two fatally injured contractors were sprayed by the hot acetic acid and inhaled its toxic fumes. In addition, two other workers were seriously injured, and 29 employees working in an adjacent unit were transported to medical facilities for further evaluation and treatment.

The CSB’s report discusses two key safety issues.

- Valve design to prevent human error: Over the course of its investigation the CSB identified four similar incidents where pressure retaining components of a plug valve were removed while attempting to remove equipment. The recurrence of these types of incidents points to the need to further re-design plug valves so that it is more difficult to remove pressure-retaining components while attempting to remove actuating equipment.

- Providing workers with conditions, procedures, and training to safely conduct work. The CSB found that both the company and the contractor considered the removal of the actuator a simple task and did not provide the work crew with any sort of procedure or training and did not adequately assess the potential risk of the operation prior to commencing work.

CSB Investigator-in-Charge Harold Griffin said: “This was a tragic accident. The CSB’s recommendations seek to address current safety gaps and make sure that a similar incident does not occur. With the understanding of the changes that need to be made, this type of incident is very preventable.”

The CSB’s report issues recommendations to LyondellBasell, the contractor – Turn2 Specialty Companies, the American Society of Mechanical Engineers, the American Petroleum Institute, and the Valve Manufacturers Association of America.

The recommendations seek to address gaps in equipment design and labelling, procedures, communication of past incidents, and worker training.

Read the CSB’s report in full by clicking here.