Seven lessons to prevent worker deaths during hot-work in and around tanks

The US Chemical Safety and Hazard Investigation Board (CSB) has identified over 60 fatalities in the US since 1990, caused by explosions and fires from hot-work activities (burning, welding, cutting, brazing, grinding, or a similar operation capable of initiating fires or explosions) on tanks and containers.

Workers are potentially at risk not only in the oil and gas industry, where flammables are handled regularly, but also in many other sectors within general industry, such as food production, paper and wastewater treatment.

During the course of investigating major accidents from hot-work, the CSB identified seven key lessons that were found to be applicable to most incidents, especially the need for effective hazard assessment and proper monitoring of potentially flammable air concentrations in work areas.

The lessons emphasise recurring safety issues that deserve special attention during hot-work operations. While each accident has unique features, all resulted from a flammable vapour coming in contact with an ignition source created by welding or cutting that was performed in, on, or near tanks that contained flammables. In some cases, the presence of a flammable material was completely unknown to the workers; in all cases, the workers had no knowledge that an explosive amount of flammable vapour had accumulated.

1. Use alternatives - Whenever possible, avoid hot-work and consider alternative methods.
2. Analyse the hazards - Prior to the initiation of hot-work, perform a hazard assessment that identifies the scope of the work, potential hazards and methods of hazard control.
3. Monitor the atmosphere - Conduct effective gas monitoring in the work area using a properly calibrated combustible-gas detector prior to and during hot-work activities, even in areas where a flammable atmosphere is not anticipated.
4. Test the area - In work areas where flammable liquids and gases are stored or handled, drain and/or purge all equipment and piping before hot-work is conducted. When welding on or in the vicinity of storage tanks and other containers, properly test and, if necessary, continuously monitor all surrounding tanks or adjacent spaces (not just the container being worked on) for the presence of flammables and eliminate potential sources of flammables.
5. Use written permits - Ensure that qualified personnel familiar with the specific site hazards review and authorise all hot-work and issue permits specifically identifying the work to be conducted and the required precautions.
6. Train thoroughly - Train personnel on hot-work policies/procedures, proper use and calibration of combustible gas detectors, safety equipment and job-specific hazards and controls in a language understood by the workforce.
7. Supervise contractors - Provide safety supervision for outside contractors conducting hot-work. Inform contractors about site-specific hazards including the presence of flammable materials.

While each lesson will reduce the likelihood of a catastrophic hot-work accident, special attention should be paid to lessons 2 and 3 - the importance of analysing the hazards and utilising a combustible-gas detector to monitor for a potential flammable atmosphere.

CSB is confident that the specific lessons will have the greatest safety impact if implemented in the workplace. In the recent cases investigated by the CSB, an appropriate safety management system, including an analysis of the hazards and the proper use of a combustible-gas detector, would likely have alerted workers to the presence of a flammable atmosphere before the disasters occurred.