Video: Key Lessons from Deadly Propylene Explosion

The US Chemical Safety and Hazard Investigation Board (CSB, the Board) recently published a video accompanying its Final Report on a gas release and explosion incident that killed two workers, fatally injured a nearby resident, and damaged more than 450 structures including homes and businesses. After the incident, the company filed for bankruptcy and closed its doors.

In this article:

• CSB Video: No Detection
• Two Key Safety Issues
• Three Lessons for Industry
• Our Takeaway

Fatal Incident on January 24, 2020

Before the incident, the company performed grinding, machining, and high-performance coating services. High-Velocity Oxygen Fuel (HVOF) coating, a service performed at the facility, provides a longer service life to metal parts exposed to highly corrosive environments. Propylene gas is used in the HVOF coating process.

At around 3:30 AM on January 24, 2020, two employees entered the facility's gym to exercise before their shift, and thought they smelled a propylene leak. Less than an hour later, a third employee entered the coating facility and, according to the CSB, flicked on the light switch, igniting high concentrations of propylene gas. 

CSB Video: No Detection

In its report and new video, US CSB notes three circumstances that caused the release:

1. A degraded and poorly crimped rubber welding hose that disconnected from its fitting inside a coating booth.
2. Not closing the manual shutoff valve at the propylene storage tank at the conclusion of production operations the previous workday.
3. The inoperative automated gas detection alarm, exhaust fan startup, and gas shutoff system.

Two Key Safety Issues

Process Safety Management

The incident could have been prevented, US CSB said, if the company had an effective process safety management program to identify and control hazards. Specifically, the Board referred to these elements of such a program:

• Process safety information,
• Process hazard analysis,
• Management of change,
• Mechanical integrity, and
• Operating procedures.

Emergency Preparedness

The morning of the incident, employees suspected a propylene leak. The company's emergency response plan did not address responding to a propylene gas leak, and the company did not train its employees to respond appropriately. The employees that suspected the leak did not evacuate, did not prevent others from entering the area, and did not contact emergency responders.

Though the two employees that suspected the leak did inform a supervisor and a plant manager, the Board said the lack of an effective emergency response plan added to the incident's severity.

Three Lessons for Industry

With its Final Report, the Board issued three lessons for industry that it urges companies to review:

1. Companies have a duty of care to ensure the safety of workers at their facilities who handle flammable gases or other hazardous materials and protect surrounding communities and the environment regardless of whether the chemical(s) on-site meet the threshold quantity under OSHA’s PSM standard or EPA’s RMP rule.

To prevent catastrophic incidents, a company should apply a process safety management system such as CGA P-86 Guideline for Process Safety Management, CCPS’ Guidelines for Risk Based Process Safety, or CCPS’ Guidelines for Implementing Process Safety Management. The harm to Watson Grinding workers and to members of the surrounding community occurred because Watson Grinding did not develop and implement an effective process safety management program for its coating process.

2. At facilities that handle flammable gases or other hazardous materials, gas detection, alarm, exhaust, and shutdown systems must be adequately designed, maintained, inspected, and tested to ensure reliability. Inspection and testing frequencies must be established to ensure the system provides adequate warning of the presence of flammable chemicals. Inspections should identify disassembled or bypassed preventive measures as well as deterioration of equipment.

Testing should go beyond system maintenance, such as sensor calibration, and ensure the functional integrity of the system. Alarms should clearly alert to the hazard through visual and audible indications. Shutoff valves should effectively isolate the flammable material. Facilities should promptly and effectively respond to reports of non-functional safety systems.

3. Facilities that handle flammable gases or other hazardous materials should ensure that there is a comprehensive written emergency response plan that adequately addresses all actions to be taken in the event of a chemical release. Workers must be trained on the plan, and periodic drills should be conducted to ensure the plan can be effectively implemented.

US CSB, Fatal Propylene Release and Explosion at Watson Grinding. Investigation Report, June 29, 2023.

In addition to identifying key safety issues and providing lessons for the chemical industry, the Board asks the Compressed Gas Association to urge its member companies, such as the supplier of the facility this report is based on, to share the safety issues described in this report as well as the importance of effective process safety management systems. CSB also recommends that the company's gas supplier shares that information with its customers.

Key Takeaways

Like other incidents covered by the US Chemical Safety and Hazard Investigation Board, this one reminds us of the importance of two OSHA safety Standards: The Process Safety Management Standard (PSM), and the Hazard Communication (HazCom) Standard.

The PSM Standard exists to prevent or minimize the consequences of catastrophic releases of hazardous chemicals. Employees working at covered facilities must be trained “in an overview of the process and in the operating procedures” that emphasizes safety and health standards, emergency operations (including emergency shut down), and safe work practices. The OSHA HazCom Standard or "HCS" requires employers to provide training and information to employees about the hazardous chemicals in the workplace [29 CFR 1910.1200].