(100b) Lessons Learned and Efficiencies Developed in Conducting Dust PHAs

Braskem America, with assistance from ABS Consulting, is performing dust hazard analyses (DHAs) and layer of protection analyses (LOPAs) on its solids handling, processing, and dust collection systems at its polypropylene manufacturing plants in the United States.  The objectives of these DHAs/LOPAs are to (1) systematically identify upset events/scenarios that present combustible dust fire or explosion hazards, (2) develop order-of-magnitude estimates of the consequences and frequencies of the scenarios, (3) identify independent protection layer (IPL) safeguards, and (4) if necessary to meet corporate risk tolerance criteria, make recommendations for additional safeguards or other modifications to reduce the risk of identified scenarios.

Braskem’s  standard risk management, process hazard analysis (PHA), and LOPA protocols provide the foundation for performing the DHAs/LOPAs, and the DHA/LOPA teams have supplemented the standard protocols with tools to improve the efficiency and consistency of the DHAs to a level comparable to the more traditional analysis of flammable liquid and gas processing hazards.  These tools include:

• A look-up table that establishes hazard zone radii for various levels of injury caused by dust fires and explosions that considers thermal radiation and overpressure effects
• A look-up table for ignition probabilities that defines probabilities as functions of the ignition sensitivity of individual dusts and the potential ignition mechanisms that arise from the specific operation and specific deviation
• Aids to collect pertinent dust-specific process safety information such as flow rates for various operations and normal and worst case dust concentrations

In addition, the DHA/LOPA teams specifically identify the primary and secondary protections in place for each operation or system to prevent dust fires/explosions (e.g., inerting, minimizing airborne dust concentration, preventing ignition) and have developed sets of HAZOP deviations or what-if questions that are directed to each different prevention strategy to help streamline and ensure completeness of the hazard identification process.

This paper presents the tools Braskem and ABS Consulting developed to aid in performing DHAs/LOPAs and provides examples and lessons learned from their application.