ADDITIONS TO NFPA 61, STANDARD FOR THE PREVENTION OF FIRES AND DUST EXPLOSIONS IN THE AGRICULTURAL AND FOOD PROCESSING INDUSTRIES David E. Kaelin, Sr., Senior Process Safety Specialist ABSTRACT Facilities that process grains, flour, sugar, starch and other agricultural commodities must consider the requirements of NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities as a part of good engineering practices. The most recent edition of NFPA 61 has been modified to include important risk management practices described in the recently issued NFPA 652, Standard on the Fundamentals of Combustible Dusts. Those wishing to apply NFPA 61 need to collect physical property data on the powders and dusts processed and analyze the dust explosion hazard for all operations and activities where an explosion exposure may occur. Documentation should be created of the property data, hazard analysis and those management systems in place to control dust fire and explosion risks.
INTRODUCTION In 1923 the National Fire Protection Association (NFPA) issued a standard intended to minimize the fire and explosion risks associated with grain and other agricultural commodities. This standard, NFPA 61, has been modified numerous times over the years and now covers the fire and explosion hazards associated with grains, starch and other food processing facilities. The 2017 edition of NFPA 61 (effective date June 2, 2016) has integrated some sections of NFPA 652 Standard on the Fundamentals of Combustible Dust in order to ensure consistent management practices in the processing and handling of combustible particulates. Some sections have been reorganized and four new materials added, taken from NFPA 652, including: Chapter 5 - Hazard Identification, Chapter 6 - Performance-Based Design Option, Chapter 7 - Dust Hazard Analysis, and Chapter 9 - Management Systems. The most important requirement of the new NFPA 61 is that covered sites that handle and process combustible agricultural commodities (such as grain, starch and flour) shall complete a Dust Hazard Analysis (DHA) within five years of the effective date of the standard, June 2, 2016 for those processes using bucket elevators, conveyors, grinding equipment, spray dryers and dust collection systems. New facilities shall complete the DHA as part of the facility design process. THE DUST HAZARD ANALYSIS (DHA) PROCESS The first step in the DHA process is described in the flowchart, Figure 1 below In order to determine the combustible solid s hazards, the first requirement is to verify if the powders/dusts handled are indeed combustible. Determination of combustibility or explosibility is permitted to be based on the following: Historical facility data or published data that are deemed to be representative of current materials & process conditions Laboratory analysis of representative samples o Permitted to test a sample sieved to <75μm o Permitted to test the as-received sample Permitted to assume a material is explosible, forgoing the laboratory analysis It must be noted that the absence of previous incidents shall not be used as basis for deeming a particulate noncombustible or non-explosible The purpose of testing is to answer several important safety questions [References 1, 2, and 3]. Materials that are determined to be combustible may need to be tested to establish their ignition sensitivity and explosion severity. Explosibility, ignition sensitivity, and explosion severity of dusts must be determined in accordance with applicable test standards such as American Society for Testing and Materials (ASTM). Typical tests that might be considered include: Go / No Go test Minimum Ignition Energy Minimum Ignition Temperature (Cloud and Layer) Self-Heating Minimum Explosible Concentration Limiting Oxygen Concentration Maximum Explosion Pressure (Pmax) and Kst Electrostatic Chargeability and Volume Resistivity Figure 1 Step 1 of the DHA Process. These tests will provide an understanding of combustibledust properties and how easily dust clouds may form and be ignited. The test to determine a dust s explosion severity (Kst) requires suspending the dust in a suitable chamber and igniting the dust cloud with a high energy source. This test provides basic information regarding the resulting explosion, including peak pressure and maximum rate of pressure rise. Explosion severity data are required to design explosion
protections such as relief venting. The next step in the process hazard analysis is to complete the Dust Hazard Analysis and identify items of process equipment and rooms or enclosures where materials could form ignitable dust suspensions or dust layers and access ignition sources. The logic path below (Figure 2) describes this effort safeguards that had been in the previous versions of NFPA 61 specific to certain equipment have been moved to chapter 8. However, chapter 6 provides a management option: Performance-Based Design for some cases where it can be demonstrated that alternate safeguards meet life safety goals. MANAGEMENT SYSTEMS The revised NFPA 61 also includes Chapter 9, Management Systems taken from NFPA 652 (with some adjustments). This chapter applies to both new and existing systems and operations and covers those systems that support safe risk management of combustible dusts. Each section provides specifics expected for that system. Systems included: Operating Procedures and Practices - Written standard operating procedures (SOPs) such that fires and explosions are avoided. Procedures must include startup, normal operation, shutdown, and emergency response. Include all safe work practices required to prevent fires and explosions. Figure 2 Final Steps of the DHA Process The DHA should classify potentially hazardous dust locations within the facility into one of three categories: Not a hazard Possible hazard Fire or explosion hazard The DHA answers the following key questions for all areas where powders and dusts are handled and processed: 1. Can particulate exist in a size that would allow flame propagation? 2. Is there a mechanism to initiate dust suspension? 3. Could the dust suspension concentration exceed the Minimum Explosible Concentration? 4. Could effective ignition sources exist during 1-3 above? The DHA report provides documentation of the properties of process-materials and the operating conditions and, for each potential hazard zone, answers the above four questions and establishes what hazard management methods exist or are appropriate. Hazard management are those safeguards that prevent or mitigate a combustible dust fire or explosion event. Prescriptive Hot Work to meet NFPA 51B and/or a permit system include the following conditions: o Removal of combustible materials (including dusts) for a 35 foot radius around the worksite, o Documentation of a permit system, o Shutdown of electrical equipment and systems if not properly classified (Class II), and o Maintenance of a suitable fire-watch during the hot work and for at least 60 minutes after the work is completed. Inspection, Testing and Maintenance - Identify safety-critical equipment and systems required to manage combustible dust fire and explosion risks. Devices such as explosion relief vents, dust extraction systems, and classified electrical devices are necessary to maintain a low risk operation and must be identified and managed to ensure reliability. Routine, scheduled inspection and testing is key to safeguard reliability and a program must be in place to manage this issue. Training and Hazard Awareness - All affected personnel (including contractors) must receive training for combustible dust hazards. The training program should be documented and include jobspecific as well as training about those safeguards required to manage fire and explosion risks. Routine re-training should occur annually.
Emergency Planning and Response - A written emergency action plan must be established that includes: o A means to notify personnel in the event of a fire or explosion, o A pre-planned evacuation route and assembly location, o Designated emergency response personnel assigned to notify appropriate community response personnel and direct co-ordinate efforts, and o Maps, layout drawings and other support information (such as Safety Data Sheets for hazardous materials) necessary for responders use. The Emergency Response Plan should be reviewed periodically to ensure that it is current and should be used in annual personnel training. Incident Investigation - Incidents that occur can be too easily forgotten and lessons-learned not learned. A management program plan must be in place to investigate fires and explosions that may occur in a timely fashion and incorporate recommendations in the sites activities and systems. These learnings must be shared with appropriate personnel. Management of Change - Without a rigorous Management-of-Change program it is easy for changes to be made to equipment, procedures, systems or personnel that negatively impact the risk of fires and explosions. Changes that could affect the risk of fires and explosions must be assessed to ensure that they can be applied safely and do not introduce un-assessed risk or increase residual risk. Document Retention - There should be a program to retain documentation of safety related information including: o Training records, o Equipment and system inspections and maintenance records, o Incident investigation reports, recommendations and issue closure reports, o Dust Hazard Analysis reports, recommendations and issue closure reports. o Management of Change documentation, o Contractor records, and o Process and material technology Management Systems Review - In order to keep management practices current it is important that all management practices be reviewed on a routine schedule. Employee Participation - All affected personnel involved in the handling and processing of combustible particulate materials shall be included in the control and mitigation of fire and explosion hazards and in the investigation of combustible dust incidents. Warning Signs - Wherever personnel could be exposed to fire or explosions of combustible particulate appropriate warning signs shall be provided at a safe distance such that danger is avoided. This is particularly important for those areas in proximity to explosion relief vent discharges. SUMMARY The handling, storage, and processing of agricultural commodity materials such as grain, starch and flour requires that appropriate safeguards are in place to prevent damaging fires or explosions that could be caused by the ignition of combustible dusts. The consensus standard, NFPA 61 is intended to provide the accumulated experience of the grain, starch, flour and associated industries on those practices needed to manage fire and explosion risks. The latest revision of NFPA 61 has added specific requirements to conduct a dust hazard analysis as is described in the 2015 issue of NFPA 652, Standard on the Fundamentals of Combustible Dusts. An understanding of the fire and explosion properties of the dusts that could be present in the operation is a critical first step in the hazard analysis process. The new NFPA 61 requires sites to complete a Dust Hazard Analysis (DHA) for those operations using bucket elevators, conveyors, grinding equipment, spray dryers and dust collection systems within a five year period from the standard s effective date (June 2, 2016). The DHA should include: Consideration of dust hazard properties; Appropriate hazard expertise and experience of the DHA leader; A rigorous review process; and Prompt actions to correct identified deficiencies.
HOW WE CAN HELP YOU DEKRA Insight has a team of highly skilled process safety specialists that provide independent consulting advice on Dust Hazard Analysis (DHA), Process Safety Management (PSM), fire and explosion prevention and protection measures, and safety engineering. We have worked extensively with many companies to identify, prevent, and or mitigate fire, explosion, and thermal instability hazards associated with their operations/ processes and other issues that were identified as a result of OSHA (Occupational Safety and Health Administration) inspections, including informal OSHA conferencing to resolve citations. If you have any questions or need assistance, please contact 609-799- 4449 or email us at safety-usa@chilworthglobal.com. For more information on DEKRA Insight services, log on to www.dekra-insight.com. REFERENCES 1. National Fire Protection Association, NFPA Guide to Combustible Dusts, Page 92 (2012). 2. National Fire Protection Association, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, NFPA 654, Paragraphs 3.3.10, 3,3,20, 3.3.21, 4.2, A.3.3.10.1, A.3.3.10.2, A.3.3.17, A.4.2.1, and A.4.2.2 (2017). 3. National Fire Protection Association, Standard on Explosion Protection by Deflagration Venting, NFPA 68, Paragraphs 3.3.5, 3.3.27.1, 6.1.1, A.6.1.1, and A.6.1.2 (2013). DAVID E. KAELIN David E. Kaelin, Sr., B.S.Ch.E. Mr. Kaelin has over 30 years experience in the specialty chemical manufacturing industry and 20 years specializing as a Process Safety Engineer. He has participated in the design and construction of numerous chemical processing facilities and provided support and training in all areas of PSM. As a Process Safety Engineer he has led process hazard analysis, risk assessments and facility siting reviews. At the corporate level he has created and taught courses in PSM and hazard recognition methods. Mr. Kaelin has led or provided technical assistance to many fire, explosion and runaway reaction incident investigations including incidents involving nitrations, chlorinations, hydrogenations, thermal heat transfer fluids, spontaneous combustion, dust explosions and thermal oxidizer and incinerator operations. Mr. Kaelin is an expert in the application of hazard recognition techniques including: HAZOP, FMEA. What-If, Fault Tree Analysis, Risk Screening and Checklist. He is an active member of AIChE, and NFPA.
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