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Industrial Safety

CSB completes 2 more stalled accident reports

Runaway chemical reaction, huge Texas tank fire investigated in latest safety board reports

by Jeff Johnson, special to C&EN
July 11, 2023 | A version of this story appeared in Volume 101, Issue 23

A chemical and fuel storage tank on fire.
Credit: US Chemical Safety and Hazard Investigation Board
The fire at Intercontinental Terminals Company burned for three days.

The US Chemical Safety and Hazard Investigation Board (CSB) has completed two more incident investigations, cutting the number of incomplete, outstanding reports to six, one of its lowest backlogs in years. Altogether, the board has issued a dozen reports over the past year.

The new two reports present the root causes of a 2020 explosion at the Optima Chemical facility in Belle, West Virginia, and a 2019 tank farm fire at the Intercontinental Terminals Company (ITC) facility in Deer Park, Texas.

The Optima explosion occurred during production of a sanitizing compound on behalf of the pool chemical firm Clearon. A dryer at the facility was removing water from the compound and exploded, resulting in the death of an employee, $33 million in property damage, and a shelter-in-place order for the nearby community.

The CSB found the cause to be a runaway chemical reaction and overpressurization of the dryer. Optima did not adequately understand the potential for, or detect and mitigate, the self-accelerating reaction, the board says. Also contributing to the incident was the fact that Clearon, Optima’s customer, did not transmit sufficient process safety information to Optima. Both companies also had ineffective process safety management systems, according to the report.

Optima was dehydrating sodium dichloroisocyanurate dihydrate, an isocyanurate, when the compound underwent a decomposition reaction, releasing gases that increased the dryer’s internal pressure. The dryer exploded, the CSB says, releasing toxic chlorine gas and metal debris. Dryer fragments struck a pipe containing methanol that caught fire.

In a statement accompanying the report, CSB Chairperson Steve Owens notes that the failure to control reactive chemicals has been a concern of the board for more than 20 years. The CSB has urged that reactive chemicals be included in Occupational Safety and Health Administration (OSHA) process safety management (PSM) programs and Environmental Protection Agency risk management program (RMP) rules, which neither agency has done.

Most recently, the CSB identified an incident involving another reactive isocyanurate, trichloroisocyanuric acid, in an incident at a Bio-Lab facility in Louisiana.

The second report investigates the cause of a massive fire at ITC, a bulk liquid storage terminal. The fire burned for three days and caused $150 million in property damage, significantly impacting the environment and leading to several shelter-in-place orders.

More than 240 tanks at the site store petrochemical liquids and gases, fuel oil, bunker oil, and distillates. An accidental release of butane-enriched naphtha ignited near a large storage tank. The CSB found that a circulation pump connected to the tank failed, allowing the naphtha to escape for 30 min. The flammable vapors caught fire and spread to 14 other tanks and burned for days.

Among recommendations, the CSB urges ITC to establish a formal mechanical integrity oversight program and a flammable gas detection system as well as other means to recognize and mitigate releases. The board also recommended that OSHA and the EPA begin a formal process to determine if PSM and RMP provisions should apply to tank farms.


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