Visual Dust Hazard Analysis - Understanding Threats and Assuring Controls

The potential harm and asset damage from a dust explosion have been known for many centuries. A wide variety of materials that can be explosive in dust form exist in many industries, however knowing about an issue is not the same as properly understanding and adequately addressing the challenges.

Since the US Occupational Health and Safety Administration (OSHA) does not have a comprehensive combustible dust standard, they rely on existing related regulations and recognized and generally accepted good engineering practice (RAGAGEP) standards. In this manner, the deadline for most facilities to complete a dust hazard analysis (DHA) is 7^th September 2020 (later for agricultural and food manufacturers) in accordance with National Fire Protection Agency (NFPA) Standard 652 on the Fundamentals of Combustible Dust and the associated industry-specific standards.

The NFPA does not specify a DHA technique to be adopted however one example is provided and several commonly applied hazard analysis techniques are listed in the appendix.

The authors draw on their complementary experience in DHA application and BowTie implementation to present a novel approach to scenario visualisation and asset management using bowties. (Their experience is demonstrated in recent papers by Michelle Murphy of Mica (https://www.aiche.org/resources/publications/cep/2016/april/making-sense...) and David Hatch of Process Safety Integrity (https://www.aiche.org/resources/publications/cep/2019/february/enhancing...).

Just as a conventional HAZOP or PHA subdivides the process into nodes, the DHA breaks the plant into systems which are systematically challenged to determine if explosion or fire hazards exist. For dusts, this includes identification of competent ignition threats. Subsequent evaluation is conducted to determine which are prevented and/or mitigated by safeguards specific to each threat and consequence.

Risks are assigned and actions issued as per a normal hazard analysis, however the graphical presentation of the ignition scenarios and safeguards and the illustration of potential ignited particles which can travel and ignite within downstream equipment offers significant communication benefits. This can be particularly helpful in facilities or countries where English and/or Risk are not the primary language or familiar terminology. This paper will show how BowTies are an effective tool to engage less technical stakeholders and offer a robust framework to assure the health (presence and performance) of the assumed or planned human and hardware controls which must be sustained to provide the necessary risk reduction.

The Visual Dust Hazard Analysis technique can be applied to all jurisdictions where the management of dust hazards is scrutinised. It is consistent with the objectives of US RAGAGEP, the EU ATEX directive, and UK DSEAR regulations. The design of the technique can also help to apply the principles of EN 60079-10-2: "Explosive atmospheres. Classification of areas. Explosive dust atmospheres".

In summary, this novel approach evolves analysis into an operational framework to ensure that the ignition risks are better understood and the controls are properly implemented, operated and maintained.