US CSB release update on Texas chemicals plant explosion

THE US Chemical Safety Board (CSB) has released a factual update on the explosion and fire which occurred at a chemicals facility in Texas, US earlier this year, caused by an isobutylene leak.

The incident killed one worker and seriously injured two others.

On 2 April at about 10:50 local time, an explosion occurred at the facility of specialty chemicals company KMCO, located in Crosby, Texas, which is about 40 km northeast of Houston, Texas. More than 200 KMCO employees, contract workers, and visitors were onsite on the day of the explosion. At least 30 workers were injured – seven KMCO workers and 23 contract workers. Following the incident, a shelter-in-place was issued to community members within a one-mile radius of the facility.

KMCO manufactures specialty chemicals and operates tolling services, an arrangement in which a company with specialised equipment processes raw materials or semi-finished goods for another company.

According to the CSB’s update, the explosion was caused when an isobutylene vapour cloud ignited. KMCO used isobutylene as a raw material in the manufacture of sulfurised isobutylene lubrication additive products. The company received, stored, and used isobutylene as a liquid, but at standard temperature and pressure the hydrocarbon is a highly flammable, colourless gas.  

The leak was identified prior to the explosion and an evacuation was ordered. The explosion occurred despite the efforts of operators and supervisors, which included turning off equipment.

The source of the isobutylene leak was found to be the y-strainer on the inlet (suction) piping to the isobutylene charge pump which feeds isobutylene into the sulfurised isobutylene reactor at the proper step in the procedure. Typically, y-strainers are used to remove solid particles from a liquid stream.

The y-strainer responsible for the leak was found with a hole roughly 3 x 5.5 inches (7.62 x 13.97 cm) on one side. A metal fragment that appeared consistent with the hole was found on the ground nearby. A KMCO operator confirmed that the location of the hole was consistent with where he saw the leak originating.

According to the CSB, the incident interrupted normal business operations at the KMCO facility resulting in two rounds of layoffs which took the employee count from more than 180 to less than 50.

The CSB investigation is ongoing, and a final report is to come.