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Making Sense of Combustible Dust PHAs

Process hazard analyses (PHAs) have been conducted for decades in many industries. First conceived at ICI in the 1960s (Kletz, 2009), they have been refined and adapted for various applications, now finding their way into combustible dust hazard management. No matter the industry, the premise is the same, identify hazards, understand their causes and consequences, implement safeguards, and risks will be managed. The CCPS Guidelines for Hazard Evaluation Procedures, Third Edition, states: “A hazard evaluation is an organized effort to identify and analyze the significance of hazardous situations associated with a process or activity.” (Center for Chemical Process Safety, 2008) Keeping these in mind, a simple inclusive approach can be developed and applied. Several NFPA standards on combustible dust contain provisions for conducting process hazard analyses. The newest standard, NFPA 652, Standard on the Fundamentals of Combustible Dust, 2016 Edition, (NFPA, 2016) became effective on September 7, 2015. It requires that dust hazards analyses (DHAs) be completed on existing facilities and large modifications. The legacy standard, NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, 2013 Edition, (NFPA, 2013) contains requirements for process hazard analysis that includes hazard assessments. If the facility falls under an industry- or commodity-specific (dust specific) NFPA standard (e.g., metals, agricultural and food, wood processing and woodworking, and sulfur) different hazard analysis requirements may apply. All of these competing recommendations and requirements can make it difficult to know where to start and what approach to use. This article will summarize the specific requirements in the standards and present some guidance to meet them. The result is a basic, easy to apply approach that will guide implementation of this critical technique. Read more

Quickly Develop Chemical Interaction Matrices with SuperChems™

The development of accurate chemical interaction matrices can provide valuable information for the management of potential chemical reactivity hazards. SuperChems™, a component of Process Safety Office®, provides intuitive and easy to use utilities for the rapid development of chemical interaction matrices. These utilities were developed based on known heuristics and rules for the interaction of certain chemical groupings. SuperChems™ also provides additional utilities for the calculation of energy release and stoichiometry of one or more chemical reactions using detailed multiphase chemical equilibrium algorithms and reacting flow dynamics. In addition to thermo-physical and transport properties databanks, SuperChems™ provides hazards databanks where chemical groupings and other reactivity and toxicity data are available for approximately three thousand chemicals. Of particular interest is version 8.5 of the hazards databanks, released in March of 2018. Read more

Reactive Chemical Storage

It is a common practice to insulate storage tanks containing reactive chemicals to protect against fire exposure. While this mitigation technique is appropriate for vessels handling non-reactive chemicals, reactive chemicals storage represents a special challenge and must be examined on a case-by-case basis. For certain classes of reactive chemicals, given a sufficiently long hold time, the insulation will always lead to a runaway reaction. If insulation is to be used, special handling is required in order to insure that after the fire is extinguished, the vessel contents do not reach a temperature that causes a runaway within 48 hours. The 48 hours time limit is selected arbitrarily and should be long enough for most installations to empty the tank contents, inject and circulate additional inhibitor into the tank, cool the tank contents, and/or use the vessel contents in the process. Read more

Reactivity Screening Made Easy

During the past decade, large efforts were made by the US chemical and petrochemical industries to implement and maintain effective process safety management (PSM) and responsible care programs. Despite these large investments, incidents continue to occur at an alarming frequency. Many executives of leading companies are trying to understand why. A recent survey conducted by the US Chemical and Safety Hazard Investigation Board (CSB) concluded that reactive chemicals present a significant safety problem for the chemical process industries. Key root causes identified by the CSB survey included technical and management systems failures. This underscores the importance of the need to understand and manage chemical reaction hazards more effectively. We also believe that the “quality” of implementation, change management, and auditing of corporate PSM programs is the culprit. We focus in this short paper on incidents caused by runaway reactions and provide guidance on how to improve the “Quality” of managing chemical reactions hazards through a combination of screening and experimental tools. Read more

SADT Determination of Styrene System Using ARC

The United States Department of Transportation (US DOT) and United Nations (UN) have developed a transport systemization based on a classification of certain types of dangerous goods and descriptions of tests and procedures. Dangerous goods are chemical substances, or articles containing chemical substances, which pose a threat to public safety or the environment during transportation if not properly identified or packaged. If they are accidently released, outcomes such as fires or explosions can occur. The purpose of the various tests is to provide adequate protection against the risk to life and property inherent in the transportation of hazardous materials in commerce. Read more

Strategy for Managing Reactivity Hazards

The last few months have witnessed a high degree of focus on understanding and managing chemical reactivity to improve safety in process plants. These efforts have reinforced an important aspect of chemical reactivity, i.e. it is extremely complicated to try and list properties characterizing reactivity hazards. As an example, commercial explosives contain 2000 cal/g or more of energy; however, most of the chemicals involved in incidents in the process industries have energies between 500 and 1500 cal/g. There are therefore a variety of aspects, besides the energy content, that can pose reactivity hazards and recognizing such scenarios is an area of considerable research. The principle objective of this document is to assist readers in understanding, evaluating, and managing reactivity hazards for a particular situation by directing them to appropriate sources and utilizing a tiered evaluation protocol. Read more