CCPS Beacon Addresses Vapor Cloud Explosions

The January, 2011 edition of the Process Safety Beacon, published by the Center for Chemical Process Safety (CCPS), addresses the issue of vapor cloud explosions. It briefly describes both the potential causes and actions that people in the chemical process industry can take to prevent such explosions.

In my opinion, the most important information comes in the final bullet point under ‘What can you do?’:

“If your plant contains flammable or combustible materials, you should have written emergency procedures for a leak [emphasis added]. Review and understand these procedures, participate in drills, and know what you must do to protect yourself and others in case of a leak. Know when and how to use appropriate personal protective equipment (for example, flame resistant clothing) and leak detection equipment such as portable flammable material detectors.”

This should be of particular interest to CFATS covered facilities that have release flammable COI. Such COI have the potential for forming the vapor clouds that could lead to these catastrophic explosions. That being the case, at CFATS covered facilities at least, the written emergency procedures should address both accidental releases and deliberate releases caused by terrorist attacks.

Chemical Storage Dikes

The Center for Chemical Process Safety has released their June 2010 Beacon. It deals with the issue of containment dikes and pads. The Beacon notes that while these dikes and pads have important environmental functions they also have a variety of safety functions as well. They provide three examples of safety functions:

“[L]imiting the spread of a fire and preventing exposure of other equipment if a flammable material spills and is ignited “[P]reventing contact of incompatible reactive materials in case of leak or spill “[L]imiting the spread of spilled corrosive material and preventing contact with equipment which could be damaged by contact with the corrosive material”

As with most safety devices, these safety features of dikes are frequently an overlooked yet important part of the facility security plan since they serve to mitigate the potential effects of a terrorist related release from the storage tanks within the diked area. As such the security plans for CFATS covered facilities need to address the protection of the integrity of these dikes. 

Containment dikes around critical COI storage tanks need to be able to withstand the force of the expected attacks on those COI. For example the dike wall between the storage tank and the expected location of a VBIED, must be able to withstand the force of the VBIED blast to remain a mitigating device in the facility protection scheme. Dikes around flammable chemical storage tanks need to be able to withstand the heat of a pool fire of those chemicals. 

Beyond protecting them against gross physical breaches, there needs to be provisions for verification of the status of drain valves, sump pumps and other controlled openings in the containment areas. While this is important for dikes around any COI storage areas, it is especially important for dikes separating incompatible materials that could violently react or produce toxic chemical vapors upon reaction. These dikes are a common feature at chemical facilities and are usually taken for granted. 

Security professionals need to take a second look at these structures when they are preparing site security plans that include bulk storage of COI. They could perform a vital security function in the mitigation of potential releases in the event of a successful terrorist attack.