Risks associated with “simple tasks” can often be overlooked by employees and management despite the fact that those risks are very real and could lead to injury or death.
An investigation report issued by the U.S. Chemical Safety and Hazard Investigation Board (CSB) illustrates just how deadly underestimating the risks of a simple task can be.
The accidental removal of certain pressure retaining components of a plug valve caused the release of 164,000 pounds of an acetic acid mixture, killing two contract workers in a July 2021 incident in La Porte, Texas.
The report states that the unintentional dismantling of plug valves has led to similar incidents in the past.
Removing equipment connected to the plug valves is typically considered a simple task, according to the CSB. However, it can turn deadly when a plug valve is inadvertently taken apart while removing the other 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,” said CSB Chairperson Steve Owens.
Accidental removal of bolts releases 164K pounds of acid
The incident occurred on July 27, 2021, at the LyondellBasell La Porte Complex in La Porte, Texas. In the days leading up to the incident, a small leak was found on methanol piping upstream of the acetic acid reactor. A short time later, an adjacent unit was shut down that also required the shutdown of the reactor.
LyondellBasell used the shutdown opportunity to have contractors repair the leak. The company decided to isolate the piping using the plug valve located between the leaking pipe and the acetic acid reactor. This involved removing an actuator connected to the plug valve.
The contractors began removing bolts they thought were necessary to take off the actuator unaware that they were actually removing bolts that secured the pressure-retaining valve cover. The plug ejected from the valve, releasing 164,000 pounds of an extremely hot acetic acid mixture.
Two of the contract workers were killed after being sprayed by the hot acid. Two other workers were seriously injured and 29 more employees were transported to medical facilities for evaluation and treatment after inhaling toxic fumes.
The facility’s property damage, including loss of use from the incident, was estimated to be $40 million.
To avoid repeating this incident, the CSB brought up two things that need to be addressed:
1. Simple tasks still require training, procedures
Investigators found that both the company and the contractor considered the removal of the actuator a simple task that didn’t require any training or procedures. They both failed to adequately assess the potential risk of the operation before work began.
These simple tasks aren’t unique to chemical processing. They exist in every job and in every industry. Simple tasks could be what workers consider easy jobs that they do every day or they could seem like relatively mundane assignments that “anyone with a brain” could do.
Despite how simple or easy such tasks actually are, they can still carry unseen risks, as the La Porte incident illustrates. That means:
- risk assessments must be performed on them
- procedures must be created covering the proper way to perform the task, and
- workers need to be trained on how to safely accomplish the job.
2. Use engineering to remove potential for human error
The CSB identified four similar incidents involving the accidental removal of pressure retaining components of a plug valve while employees were attempting to remove other equipment.
This points to a need to re-design plug valves to make it more difficult to remove pressure-retaining components while attempting to remove actuating equipment.
Human beings, even well-trained ones, can make mistakes. They can be fatigued, distracted or complacent.
If engineering out the risk of human error is possible to make a piece of equipment or process safer, then it’s probably a good idea to do so.