The U.S. Chemical Safety and Hazard Investigation Board (CSB) issued a bulletin about the incident at the Acetylene Service Co. (ASCO), the company where the explosion occurred.
The agency found that a combination of factors, including a misaligned rubber plug due to a valve design flaw, allowed acetylene to flow backwards from ASCO's acetylene generator through water pipes and out of an open drain valve into a shed, causing the inflammable gas to build up and ignite once reaching the shed's propane space heater.
CSB lead investigator Stephen Selk said that other factors such as the unsafe location of the pipe drain as well as the lack of procedures allowing the recycled-water valve to be opened without water running through it also played a part in causing the tragedy.
The blast could have been avoided, according to Selk.
Three workers Ynio Perez, 35, Pablo Morillo, 30, and German Gonzalez Vasquez, 46 died from the explosion's shock waves while shoveling snow near the shed. Another worker, Jiovani Peña Gomez, was severely injured.
The bulletin offers safe handling guidelines showing acetylene gas producers how to properly take special precautions when handling the flammable gas. The bulletin makes the following recommendations:
- Maintain up-to-date operating procedures.
- Use checklists.
- Train on the procedures.
- Relocate vents to safe, outside locations.
- Test critical valves and ensure that enclosures such as sheds containing hazardous materials meet national fire code standards.
Gary Visscher, a CSB board member who accompanied the investigation team to the scene when the accident occurred, urged acetylene producers and handlers to review the bulletin to prevent further calamities.
"The tragic accident at ASCO pointes to how important it is to have comprehensive operating procedures, to train workers in these procedures and to have effective measures in place to prevent the back flow of flammable gases," he said.
