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Description
| Duct Venting and Hazard Management | |
| John discussed the venting of ducts as part of hazard management, highlighting the potential risks of deflagration in ducts due to high particulate concentration. They emphasized the importance of managing this hazard by either reducing the concentration or increasing it so that it's not a hazard. John also pointed out the need for venting ducts at specific locations to prevent the accumulation of pressure and the potential transition to detonation. The locations were discussed based on NFPA 68 guidelines, with vents required along the length of the duct, close to known ignition sources, and within 2 duct diameters of any enclosure that could support a deflagration. | |
| Duct Venting Safety and Pressure Changes | |
| John detailed the method for determining the safe distance between vents in a duct system to prevent detonation, which is based on the diameter of the duct and the velocity of the airflow. They also outlined the process of selecting the distance between vents using a set of curves, taking into account different categories of dust and maximum distances allowed by standard. The discussion was interrupted by Travis, who asked about changes in pressure in the 2023 edition of the Nfpa 68. John mentioned the need for ducts to be within certain distances of vessels or elbows and the space in between must be filled with additional vents. They also discussed the issue of handling degradation hazards when prevention and venting methods are not feasible and emphasized the importance of using an active explosion suppression system in such cases. | |
| Deflagration Control Methods and Systems | |
| John discussed the various methods of controlling deflagrations in vessels, including active deflation, isolation systems, declaration pressure containment, and passive explosion suppression. They detailed the workings of deflagration suppression systems, which use a storage vessel, release mechanism, and pressure sensor to activate the release of a suppressing agent when pressure increases. These systems are evaluated by FM Global approvals and are designed according to chapter 10 of NFP 69. John also highlighted the importance of removing vents if a vessel is equipped with a deflagration suppression system, as opening the vent could prevent system actuation. They concluded by emphasizing that any changes in the vessel require reengineering the system. | |
| Explosion Hazards and Pressure Control in Enclosed Spaces | |
| John discussed the management of flames within an enclosed space, emphasizing the importance of preventing pressure from exceeding design levels. They highlighted the potential for flames to propagate upstream in a dust collector and into the work area, necessitating measures to prevent deflagration propagation such as declaration isolation. John explained various methods of isolation, the importance of fast acting valves in managing explosion hazards, and the use of extinguishing agent in ducts to prevent flame propagation. They also responded to questions about the use of different valves and the potential effects on pressure within the duct connecting two vessels. John introduced a passive isolation device and discussed the various types of passive isolation units suitable for combustible particulate solids. They stressed the importance of meeting the requirements set by NFPA 69 for effective design. John also discussed the use of passive float valves and rotary valves in deflagration scenarios, the importance of deflagration and isolation services in rotary valves, and the potential use of air pulse nozzles to break bridges of particulates. Finally, John touched upon the importance of pressure containment in designing vessels to withstand maximum attainable deflation pressure. | |
| Vendor Management, Dust Collector Fires, and Plant Maintenance | |
| John presented their approach to managing vendor relationships and equipment selection, emphasizing the importance of performance metrics and evaluating proposals. The discussion then shifted to managing dust collector fires, with John highlighting the need for proper management to prevent larger disasters. They explained the importance of locating air mature separators safely and having a strategy for diverting cleaned air. John also discussed the use of commercially available board gates to divert return air to prevent the transmission of dust and energy from a fire into the building. They also raised concerns about the potential risks of using return air, particularly in the event of a fire in the dust collector. John emphasized the importance of fire safety measures in dust collectors and the use of spark detectors to prevent secondary fires. They also discussed the strategy of divert flames outside the building through the use of an abort gate. Towards the end, John stressed the importance of plant maintenance and housekeeping, stating that dust accumulation is a significant issue. | |
| Managing Combustible Dust and Performance-Based Design | |
| John discussed the importance of managing change in handling combustible dust, emphasizing the need for thorough documentation of technical basis, safety considerations, and employee training. They then shifted the discussion to performance-based design methods, explaining their use as an alternative to prescriptive design criteria when certain assumptions are invalid. John demonstrated a calculation method for determining air suspension velocity and discussed the methodology for predicting particle suspension. They highlighted the need for experimentally measuring the terminal settling velocity and explained how this method can be applied to different types of conveyors and mixers to predict dust lift off and suspension concentrations. | |
| Substance Concentration and Deflagration Hazards | |
| John discussed the significance of questioning assumptions about substance concentration and its impact on deflagration hazards. They proposed that altering dust collector cleaning frequencies could reduce the risk, and explained the concept of concentration control, suggesting that absorbing heat from the air could prevent flame propagation. John shared their experience with a client facing high silo replacement costs, concluding that the silos did not pose a fire risk due to high concentration control. They emphasized the importance of eliminating ignition sources and ensuring reliability and mission effectiveness. Towards the end, John discussed the importance of testing dust to run concentration control equations and demonstrated an example of motor failure implications. | |
| Consulting Practice and Fire Safety Evolution | |
| John discussed the evolution of their consulting practice and the growth of the program over the past decade, emphasizing the importance of understanding deflations and managing explosion hazards. They stressed the need for participants to develop working knowledge of management methods, interpret test data, and question answers received. John, Travis, and other participants had a technical discussion about the calculation of a building vent's turbulence factor and the fireball dimension d. John clarified the calculation process and suggested using certain K values for different materials. John also addressed the grace period for sites not to have a Dj iff and the requirement for the Dha at existing facilities in the Ifc, clarifying that the grace period ended in the 2019 edition. John offered their assistance to attendees of the program to figure out what was enforceable at any particular point in time. Continuing education certificates were announced as available for those who completed the seminar evaluation. |