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A Summary of the Reissued OSHA Combustible Dust NEP

The OSHA directive for the inspection of workplaces that create or handle combustible dusts increased activities in outreach, training, the creation and dissemination of guidance and educational materials and cooperative ventures, as well as enhancing its enforcement activities. Read more

Analysis of PRV Stability In Relief Systems Part IV

An independent and accurate estimation of the speed of sound can provide an important quality check for a multitude of single and multi-phase flow applications. More recently, proposed screening methods for the calculation of PRV stability require an accurate estimate of the speed of sound for the fluid/piping system. This paper outlines proper methods for the calculation of thermodynamic properties and speed of sound for single and multi-phase systems. Comparisons with actual measurements indicate that credible values can be obtained for single and multi-phase systems. Read more

Changes to the 2013 Edition of NFPA 654

After much anticipation, the new 2013 Edition of NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids, has finally been issued. This is one of the key standards utilized for safe handling of combustible solids. Several important updates and additions were incorporated into this edition of the standard, including: Updated definition of a combustible dust, added determination method for a dust flash fire or explosion hazard area, added housekeeping frequency specification and cleaning methods, updated recommendations for separation, segregation, or detachment, updated usage specifics for flexible and rigid intermediate bulk containers, strengthening of included safety management systems (SMSs), and added contractor and subcontractor management system. Read more

Chemical Interaction Matrices

Despite the promulgation of the “PSM Standard” by OSHA in 1992, chemical accidents continue to occur at an alarming rate. As part of the process safety information element of the standard, OSHA requires reactivity data on the chemicals in the process. Part of this reactivity data is a chemical interaction matrix. Several software programs provide simple approaches to generating these interaction charts for common materials using assigned reactive groups. If your process involves materials not included, you are left to determine the reactivity and incompatibilities on your own. This presentation will explain a process for assigning reactive groups using chemical classification and structural analysis. This process can be used for less commonly understood materials such as additives, lubricants, etc. that may come into contact with process chemicals. Read more

Determination of SADTs Using Accelerating Rate Calorimeter

Safe storage, proper handling, and dependable transport of self-reactive substances are fundamental operations required in the chemical process industries. One of the key parameters used to assess the extent of a substance’s reactivity is its self-accelerating decomposition temperature (SADT). Various methods for estimating the SADTs have been well documented, including the “Recommendations on the Transport of Dangerous Goods: Manual of Tests and Criteria” by the United Nations. In this paper, using the Accelerating Rate Calorimeter (ARC) to assess SADT is the primary focus. Styrene polymerization and its applicable inhibitor effectiveness, including loss of inhibitor, are evaluated. Presented as a case study, a detailed kinetic model is developed illustrating the ability and flexibility to calculate the SADTs for any package sizes, shape and configurations. Complete simulations of time to reactions thermal runaway for selected DOT storage and transport vehicle are also included. Read more

Forget Direct Scaleup Vent Sizing and Master Kinetic Modeling Instead

Direct scale-up methods have been used to develop relief requirements and vent sizing for runaway reactions since the early 1990s. Direct scale-up methods have been popular because one is able to measure in a laboratory test the required relief size in equivalent vent area per unit mass of a reacting mixture, in 2/kg, and then scale it up to plant scale equipment sizes. Read more