Incident Investigation: Vacuum Truck Explosion Injures Worker | WorkSafeBC

Summary

A vacuum truck explosion during hazardous waste unloading highlights the critical need for proper safety measures. The incident occurred due to the absence of crucial documents like MSDS or a hazardous waste profile sheet, leading to a lack of awareness about the waste's flammability. The use of an open hopper system and the truck engine running contributed to the disaster. The summary underscores the importance of understanding waste hazards, using proper documentation, engineering controls, and eliminating ignition sources to prevent such incidents.

Takeaways

• ⚠️ A vacuum truck transporting toxic and flammable liquid waste from a natural gas production plant to a hazardous waste facility resulted in an explosion and fire due to improper handling.
• 📄 The hazardous waste generator failed to provide essential documents like an MSDS or a hazardous waste profile sheet, which are crucial for understanding the waste's chemical composition and safe handling procedures.
• 🚫 The waste facility and the driver were not informed about the waste's flammability, leading to a lack of proper safety precautions during unloading.
• 🔍 A hazardous waste manifest was provided but it is not a substitute for an MSDS or hazardous waste profile sheet and does not detail the safe work procedures.
• ⛔ The waste facility routinely used an open hopper system for unloading, which increased the risk of exposure to flammable gases and vapors, instead of a safer closed hopper system.
• 🚨 The waste operator's gas detector and the facility's LEL alarm indicated the presence of flammable vapors, but the situation escalated before appropriate actions could be taken.
• 🔥 The truck's engine, left running to raise the pup tank, became an ignition source when flammable gases were drawn into the air intake, leading to the explosion.
• 🏥 The driver suffered serious burns in the incident, highlighting the severe consequences of not adhering to proper hazardous waste handling procedures.
• 🛠️ Engineering controls, such as pump-equipped closed hoppers, should be used to minimize workers' exposure to hazardous substances and control the release of flammable gases during waste offloading.
• 📋 It is imperative for waste generators, transporters, and receivers to review and adhere to documentation that identifies fire or explosion hazards and to conduct risk assessments to prevent similar incidents.

Q & A

What was the incident involving the vacuum truck?

An explosion and fire occurred during the unloading of liquid waste from a vacuum truck at a hazardous waste facility, which resulted in serious injuries to the driver.

What type of waste was being transported by the vacuum truck?

The vacuum truck was transporting liquid waste containing hydrocarbons and other toxic and flammable substances from a natural gas production plant.

Why is it important to provide an MSDS or hazardous waste profile sheet?

An MSDS or hazardous waste profile sheet is crucial as it provides information about the chemical composition of the waste and safe work procedures, which helps in preventing accidents.

What document was provided by the worker at the production plant instead of an MSDS?

A hazardous waste manifest stating that the waste was 'Petroleum crude oil NOS' was provided, which is not a substitute for an MSDS or hazardous waste profile sheet.

What are the two offloading options at the waste facility mentioned in the script?

The two offloading options are a closed hopper system, where the discharge hose is connected to a riser, and an open hopper system, where the waste flows directly into an open hopper.

Why was the open hopper system routinely used at the waste facility?

The open hopper system was used to eliminate the blockage problem that sometimes occurred with the closed system when solid waste blocked the discharge hose.

What happened when the driver activated the engine's positive air shut-off valve?

An explosion followed with a fireball coming out of the cab after the driver activated the engine's positive air shut-off valve in an attempt to stop the flow of air and flammable gases to the engine.

What is the significance of the 20% lower explosive limit (LEL) in waste offloading procedures?

The 20% LEL is the maximum concentration allowed for airborne flammable gas or vapor if it's not practicable to maintain the concentration below the applicable exposure limit during offloading or in an emergency.

What was the likely ignition source of the explosion according to the investigation?

The truck's engine, which was left running to enable the raising of the pup tank, was identified as the most likely ignition source of the explosion.

What are some preventive measures suggested in the script to avoid similar incidents?

The script suggests knowing the flammability and other hazards of waste, ensuring proper documentation like MSDS or hazardous waste profile sheets, conducting risk assessments, using engineering controls, minimizing workers' exposure, and controlling ignition sources.

Why were the workers not aware of the flammability hazard of the waste?

The workers were not aware of the flammability hazard because neither an MSDS nor a hazardous waste profile sheet was provided to them, and they lacked clear knowledge of the waste's properties.