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Welding Gas Explosion

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Michael Fox, PhD.



Welding Gas Explosion

A truck with a driver and a helper stopped at loading dock to pick some equipment. The driver went inside to let the appropriate person know they were there while the helper opened the back sliding door of the truck. When the helper opened the back door of the truck, he smelled gas. Shortly after the building sliding door was opened, there was an explosion. The photo below shows the truck at the loading dock after the explosion.

welding gas explosion

The fire fighters, who were quick to respond, found a propylene welding gas cylinder lying on the floor of the truck as shown below.

propylene welding gas cylinder lying on the floor of the truck

Further timely inspection by the firefighters revealed that the welding gas cylinder had ice that formed between the cylinder and the floor of the truck, indicating that the cylinder valve had been leaking. The ice is formed by the evaporative cooling that takes place as the welding gas changes from liquid to gas inside the cylinder, thereby chilling the cylinder which then allows humidity to form ice on the outside of the cylinder. The driver and helper had just finished a welding assembly job prior to this pickup and had evidently failed to completely close the valve.

ice on the outside of the cylinder

It was believed that the welding gas (propylene) had found its way to a gas furnace that was not too far inside the dock once the building sliding door was opened. There were personal injuries and property damage. Once the cylinder valve was closed, the cylinder no longer leaked, hence there were no defects in the valve itself. It simply had not been turned off properly.

A lawsuit was filed against the company that owned the truck and the case settled a few weeks before trial. The main technical issues were compliance with the Department of Transportation and OSHA Regulations, which included the OSHA Hazard Communication Standard and the training it requires.

Dr. Fox has his Ph.D. in Physical Chemistry and specializes in the reconstruction of complex industrial chemical accidents, fires and explosions as well as chemical-related consumer product accidents. He is also OSHA Certified as a Process Hazard Analysis (PHA) Team Leader and a Certified Fire & Explosion Investigator (CFEI). In addition, Dr. Fox began developing a Chemical Risk Assessment and Prevention Program, known as CHEMRAP, in the mid-1980's when the OSHA Hazard Communication Standard was initially enacted and expanded. As a result, Dr. Fox is intimately familiar with this OSHA standard.