On January 24, 2020, an explosion at a spray-coating facility killed two workers and damaged hundreds of nearby buildings. Why did this happen? Investigators found that the workers didn’t receive proper safety training.
The U.S. Chemical Safety and Hazard Investigation Board (CSB) found that the company failed to provide safety training to its employees regarding hazardous chemicals and how to properly respond to emergencies.
This lack of training contributed to the severity of the incident, according to a CSB report.
Extremely flammable gas used in coating process
Watson Grinding and Manufacturing Company was a small specialty grinding shop in Houston, Texas, that also had an onsite spray-coating facility.
The company used propylene, an extremely flammable gas, in its spray-coating process. Propylene is colorless and has a petroleum-like odor. The safety data sheet (SDS) for propylene states that:
- accidental releases pose a serious fire or explosion hazard
- no action shall be taken involving any personal risk or without suitable training
- surrounding areas should be evacuated in the event of an accidental release
- unnecessary and unprotected personnel should be kept from entering areas where it’s in use, and
- valves should be closed after each use.
Propylene was supplied via an on-site storage tank that could hold up to 8,600 pounds of the chemical in its liquid state, with the gas being piped into the spray-coating facility. The flow of the gas was controlled through two manually operated valves and one remote shut-off valve.
Safety protocols in place, no formal training
Watson Grinding’s original spray-coating facility was destroyed in a previous propylene explosion and fire in 2008, so it did have some safety protocols in place, although there was no formal safety training for employees.
Those protocols included:
- daily leak checks in the coating booths
- detection of leaks through an employee’s sense of smell
- end-of-day shutoff of the storage tank’s valves
- manual or remote shutoff of the storage tank’s valves if a leak was detected
- use of coating booth ventilation systems, and
- use of a gas detection alarm system.
However, because of the lack of training and written procedures, supervisors and employees stopped shutting off the storage tank’s valves at the end of every work day. Instead, the practice changed to closing the valves only for extended periods when no work was occurring, such as weekends or holidays.
Further, by January 2020, the gas detection alarm system was no longer functional.
Hose disconnected from fitting overnight
On the day before the incident, the coating booth operators shut down their individual booths following a normal workday and the coating supervisor closed and locked the coating building. The supervisor did not close the propylene storage tank’s valves since work would commence again the next morning.
At some point overnight, a propylene hose in one of the booths disconnected from its fitting because it had been improperly crimped.
The flammable gas flowed through the open storage tank valves and escaped through the hose where it accumulated within the coating building.
Workers call management about possible leak
On Jan. 24, 2020, at 3:37 a.m., two employees arrived at the facility to exercise at the company gym. One of them noticed the odor of propylene outside the building. The other employee couldn’t detect the odor but agreed they should investigate the source of the smell.
They left the gym at 4 a.m. and walked toward the coating building. As they approached, they could smell a strong propylene odor and heard a loud hissing noise coming from inside. One of the workers sent a text message to the coating supervisor warning that there was a possible gas leak. Both employees then went back to the gym and resumed exercising. The other employee called the plant manager at 4:07 a.m. and warned him of the gas leak.
Neither of the management-level employees thought to tell the workers exercising in the gym to evacuate from the facility.
Gas vapor ignites when employee turns on the lights
Shortly after calling the plant manager, one of the employees in the gym went back to investigate the leak.
At 4:19 a.m., the coating supervisor sent a text to all coating booth operators telling them there was a potential propylene leak and that they shouldn’t “start up, yet.”
A third employee arrived at the facility at 4:23 a.m. and parked his car just outside of the door to the coating building. This employee was a coating booth operator who would open the building if the coating supervisor wasn’t onsite. He hadn’t seen the text message regarding the leak.
Another coating booth operator arrived one minute later and noticed the third employee’s vehicle parked outside of the coating building. He saw the third employee enter the building just before the flammable propylene vapor was ignited by the lights being turned on, causing the coating building to explode.
2 workers, 1 nearby resident killed by blast
One of the employees in the gym and the employee who turned on the lights were killed in the explosion. The other two were injured.
A resident who lived nearby was also killed in the blast and more than 450 homes and businesses were damaged in the explosion that resulted from the ignition of about 2,600 pounds of propylene that had been released inside the facility.
Watson Grinding filed for bankruptcy after the explosion and is no longer in business.
Safety training could’ve prevented incident in multiple ways
This incident could have been completely avoided with proper safety training.
Consider that if Watson Grinding had provided thorough training based on written procedures regarding closing the valves to the propylene storage tank at the end of every shift, the leak wouldn’t have occurred in the first place. Even with the poorly crimped fitting falling off, the leak wouldn’t have happened since the main valves would have been shut off.
Properly trained employees would have been more likely to act appropriately when they arrived on site to begin their shift. Had they received proper safety training, the two employees who initially detected the leak would have:
- recognized the hazard they were exposed to
- evacuated the area
- prevented others from entering the area, if possible, and
- called 9-1-1 for emergency response.
The same could be said for the management staff who were contacted and failed to respond appropriately.
Thorough safety training may have prevented the employee who entered the building from turning on the lights when he smelled the propylene or heard the hissing noise from the leaking hose. That training may have clued him in that he’d stumbled onto a propylene leak and shouldn’t turn on the lights, which would be an ignition source for the flammable gas. Learn more about how your organization can provide proper safety training for your workers to prevent at-risk behavior or situations before they lead to an incident with Vector Solutions.