Powder and Bulk Engineering


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34 / July 2020 powderbulk.com step is to develop an action plan. In this coal handling and milling system DHA, the personnel at the facility realized they knew very little about the actual dust collection system, including the system's operation, condition, design, flaws, and other system details. The personnel's action plan included seeking expertise from outside sources to conduct an audit and make recommendations to convert this high-risk situation into an acceptable low- to very low-risk situation. A timetable was established as to when these steps would be accomplished and monthly follow-ups would occur until the situation was resolved. The basics covered in this article are applicable to all DHAs. Although it's common sense to do an assess- ment of the hazards created in a facility that handles combustible dusts, there's been significant resistance to this concept. Considering the risks involved, ignoring or avoiding the necessity of assessing and analyzing these hazards goes against common sense. Please don't procrastinate any longer on completing your DHA. And for those in the agricultural and food industries who have about a year and a half until the deadline, please don't procrastinate either. The time will pass quickly, and the consequences of ignoring the require- ment are significant. PBE For further reading Find more information on this topic in articles listed under "Dust collection and dust control" in Powder and Bulk Engineering 's article index in the December 2019 issue or the article archive on PBE's website, www.powderbulk.com. Jack Osborn (josborn@airdusco.com, 901-362-6610) is an engineer at Airdusco. He has over 45 years of expe- rience in dust collection and bulk handling systems and is a member of all six NFPA combustible dust com- mittees (NFPA Standards 61, 484, 652, 654, 664, and Correlating Committee). Airdusco Memphis, TN 901-362-6610 www.airdusco.com and what-if questions. While not a complete list, the previous questions do represent the type of questions and information that must be provided to make intelli- gent and viable decisions. Risk assessment. A risk assessment was done on node P (dust collector) using the risk assessment matrix in Figure 1 as a guide. The group consensus for the coal DHA example was that the risk level was 4A, Occasional and Catastrophic, due to the combus- tible dust type, lack of deflagration protection, system history, and presence of credible ignition sources. To move the risk level from the red (high-risk) zone to the green (low-risk) zone, which is an acceptable level, the required action includes a dust collection system audit to ascertain the level of performance and condition; obtaining proposals for deflagration and isolation pro- tection; and taking into account system performance monitoring methods. This same checklist–what-if process was done for nodes Q (rotary valve), R (fan package), and S (ducting and hoods), and in applying this method, you can imagine the review of each node. Action plan. After the zone determination, or mul- tiple zones if need be, is completed, the next necessary

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