Understanding. Combustible Dust Hazards: Basic Measures to Ensure the Safety of Combustible Dust Handling Operations

Transcription

1 Understanding Combustible Dust Hazards: Basic Measures to Ensure the Safety of Combustible Dust Handling Operations Michigan Safety Conference April 11, 2017 Mike Snyder PE CSP CFPS Vice President Organizational Process Safety

2 Outline for Today s Discussion: Overview: Combustible Dust Hazards Dust Explosions Dust Flash Fires Understanding What Makes a Dust Combustible Identifying a Basis of Safety for Dust Operations Introduce the Table of References Summary & Conclusions Questions

3 Food Industry Combustible Dust: A Challenging Hazard January 10, 2017 Sugar Silo Explosion (Erlanger, KY) 3 rd Silo Explosion at Facility since 2003! Sugar Transfer at Time of Explosion (Static Electricity) Previous Events resulted in Injury & Significant Damage Application of Improved Dust Hazard Assessments & Controls Properly Designed & Maintained Relief System in Place No Injuries & Limited Property Damage from this Explosion

4 Combustible Dust Hazard Basics

5 Conditions for Dust Explosions 1. Dust must be explosible (flammable, combustible) 2. Dust must be airborne 3. Concentration must be within explosible range 4. Particle size distribution capable of propagating flame 5. The atmosphere must support combustion 6. An ignition source must be present Conditions 1-5 often exist at some point during the handling, processing, and packaging operations In the presence of an incendive ignition source a flash fire or explosion will occur

6 Conditions for a Combustible Dust Fire or Dust Explosion OXIDANT FUEL IGNITION SOURCE CONFINEMENT SUSPENSION

7 Secondary Explosions Present Additional Risks 1 PRIMARY EXPLOSION DUST LAYER 2 BLAST WAVE DUST CLOUD FORMED 3 SECONDARY EXPLOSION

8 Combustible Dust Fire or Dust Explosion? SUSPENSION Remove the CONFINEMENT Leg Flash Fire Remove any other Leg NO Explosion!

9 What Makes a Dust Combustible? Collecting Proper Data

10 Examples of Combustible Materials Focus is on particles < 500 microns (35 mesh)

11 Combustibility / Explosibility of Dusts Determination of combustibility or explosibility shall be 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 Permitted to test a sample sieved to <75μm Permitted to test the as-received sample Permitted to assume a material is explosible, forgoing the laboratory analysis Absence of previous incidents shall not be used as basis for deeming a particulate non-combustible or non-explosible Note: Test results are strongly influenced by particle size, moisture content, presence of contaminants Be sure test results are representative for your material!

12 Combustibility / Explosibility Characteristics of Dusts Explosibility, ignition sensitivity, and explosion severity of dusts shall be determined in accordance with applicable test standards (such as ASTM) Typical tests that might be considered include: Go / No Go test Minimum Ignition Energy Minimum Ignition Temperature (Cloud and Layer) Minimum Explosible Concentration Maximum Explosion Pressure (Pmax) and Kst Electrostatic Chargeability and Volume Resistivity Mixtures of Dusts in Flammable Vapors (Hybrids) Generally Present a Greater Flammability Risks May ignited below the individual LFL and MEC of the individual materials

13 Typical Combustible Dust Tests Test Go/No Go Test (ASTM E1226) Minimum Ignition Energy (MIE) Minimum Explosible Concentration (MEC) Maximum Pressure Rise (Pmax) and Max Rate of Pressure Rise (Kst) Minimum Ignition Temperature (MIT) for Clouds and Layer Limiting Oxygen Concentration Electrostatic Chargeability Hazard Evaluated Does the Dust Explode (with a High Energy Ignition Source)? The energy required to ignite a dust cloud under fairly ideal conditions. The minimum amount of dust (dispersed in air) for an explosion. Dust Explosion Pressure Factors for Design of Containment and Relief Systems Used for Electrical Area Classification and for Dust Analysis if handled at Elevated Temperatures Ignition prevention below what level of oxygen (used for inerting system design) Determines How Easily a Material Develops and Retains Charge

14 Conducting a Go/No Go Test (ASTM E1226) Uses Standardized Test Vessel to determine whether the dust cloud is Explosible at the dust handling & processing conditions. Dusts which ignite and propagate away from the Source are considered Explosible (Group A/Go) Dusts which do not propagate flame away from the Source are considered Non-Explosible (Group B/No Go) Group B (No Go) Powders are known to present a fire hazard. They may be Explosible at Elevated Temperatures (e.g. Dryers).

15 Conducting a Go/No Go Test (ASTM E1226)

16 Case Study: Hazards of Color Runs June 27, 2015 Flash Fire (Formosa Fun Coast, Taiwan) Colored Corn Starch Deployed using Air Blowers An Extremely Dense Dust Cloud over the Stage and its Immediate Vicinity People near the Stage were Ankle Deep in Corn Starch What Hazards Existed with Air Dispersed Corn Starch? 497 People Injured; 15 Fatalities

17 Establishing a Basis of Safety for Combustible Dust Operations

18 Hazard Management: Prevention & Mitigation Basis of Safety Avoidance of flammable atmospheres Elimination of ignition sources Provision against consequences of ignition NO FIRE IGNITION SOURCE REMOVE IGNITION SOURCE

19 Hazard Management: Prevent &/or Mitigate Control of flammable atmospheres: Proper plant design (containment / source reduction) Maintaining fuel below its minimum explosible concentration (dust cloud) or lower flammable limit (vapors & gases) Management of liquid spills and dust deposits (housekeeping) Exhaust ventilation Inert Gas Blanketing Elimination/Control of Potential Ignition Sources: Electrostatic discharges Electrical Arcs / Sparks Mechanical friction and sparks Thermal decomposition Application of Explosion Safeguards: Explosion protection (containment, relief venting, explosion suppression)

20 Control of Combustible Dust Atmospheres (Control of Fugitive Emissions) Equipment should be maintained and operated in a manner that minimizes the escape of dust Continuous local exhaust ventilation should be provided for processes where combustible dust is liberated in normal operation so as to minimize the escape of dust. The dust should be conveyed to dust collectors Regular cleaning frequencies should be established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the facility (1/32 inch; 0.8 mm with adjustments) Warning Indicators that your Dust Accumulations are too large: Can you tell the color of the surface below the dust? Can you write your name in the dust?

21 Controlling Electrostatic Ignition Sources Bonding & Grounding of Equipment Routine Preventative Maintenance is also Required Use of Static Dissipative Footwear & PPE in Workplace Equipment Configuration & Operating Procedures Use of Antistatic (versus Insulating) Materials of Construction

22 Control of Friction and Impact Spark Ignition Prevent overheating due to misalignment, loose objects, beltslip/rubbing etc. by regular inspection and maintenance of plant Prevent foreign material from entering the system when such foreign material presents an ignition hazard. Consider use of screens, electromagnets, pneumatic separators, etc. Floor sweepings should not be returned to any machine Hot work operations should be controlled by a hot work permit system in accordance with NFPA 51B, Standard for Fire Prevention During Welding, Cutting and Other Hot Work: During Hot Work, Formation of dust clouds should be prevented, and dust deposits should be removed Careful consideration of alternative methods or shutdown of equipment

23 Concerns with Electrical Equipment Ignition Arcs and sparks occur during normal operation of many electrical equipment Consumption of energy produces hot surfaces Malfunction creates (more) potential ignition sources Electrical apparatus must be selected and installed carefully to ensure there is no risk of ignition Hazardous Area Classification was developed as a means to optimize equipment selection Combustible Dust Management is Indicated by Class II Designation The Division (1-high or 2-incidental), represents the anticipated exposure to combustible dust exposures Group (E, F, or G) representing type of dust present T Rating Maximum Surface Temperatures

24 Application of Explosion Safeguards Provision against consequences of ignition Preventative measures may not ensure adequate level of safety. Protective measure should also be considered: These measures are: Containment by explosion resistant construction, Design based on ASME Boiler and Pressure Vessel Code, Section VIII, Division I Explosion suppression by injecting a suppressant (NFPA 69) Explosion venting to a safe place (NFPA 68)

25 Managing Combustible Dust Fire and Explosion Hazards Requires Detailed knowledge of: Combustible material properties Process equipment Operating conditions Maintenance practices Existing controls (safeguards) and More These are Generally Collected and Analyzed through a Dust Hazard Analysis (DHA)

26 Strategy for Dust Explosion Testing & Implications for Basis of Safety

27 References Sources of Recognized and Generally Accepted Good Engineering Practices (RAGAGEP)

28 References (with Free Access) National Fire Protection Association (NFPA) NFPA 652 (2016), Standard on the Fundamentals of Combustible Dust. NFPA 654 (2017), Standard for the Prevention of Fires and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. NFPA 499 (2017), Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemicals Process Areas. NFPA 68 (2013), Explosion Protection by Deflagration Venting NFPA 69 (2014), Standard on Explosion Prevention Systems NFPA 61 (2017), Dusts in Agricultural and Food Processing Facilities NFPA 484 (2015), Standard for Combustible Metals NFPA 655 (2017), Standard for Prevention of Sulfur Fires and Explosions NFPA 664 (2017), Dusts in Wood Processing and Woodworking Facilities

29 References (with Free Access) OSHA Dust Resources OSHA Combustible Dust National Emphasis Program Firefighting Precautions at Facilities with Combustible Dust FM Global FM Global, Data Sheet No. 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fire (2017 Edition). United Kingdom Health & Safety Executive Safe handling of combustible dusts: Precautions against explosions DEKRA Insight SAFETY GUIDE : A strategic guide to characterization and understanding Handling Dusts and Powders Safely

30 Codes & Standards - Combustible Solids EPA Risk Management Rule OSHA PSM Regulation ACC Responsible Care OSHA General Duty Clause RAGAGEP Building Codes IBC, NFPA 5000 Facility Design Life Safety Code NFPA 101 State Fire Protection Codes IFC, NFPA 1 National Electric Code NFPA 68 NFPA 70 NFPA 69 NFPA 77 NFPA 91 NFPA 499 Combustible Dusts NFPA 652 NFPA 654 Special Dusts NFPA 61 NFPA 484 NFPA 655 NFPA 664 Best Industry Practice

31 NFPA 652 Compliance Requirements Owner/operator of facility with potentially combustible dust shall be responsible for: Determining combustibility and explosibility hazards of materials (Chapter 5) Conducting a Dust Hazard Analysis (DHA) - Identifying and assessing fire, flash fire, and explosion hazards (Chapter 7) Managing identified fire, flash fire, and explosion hazards Prescriptive Approach (Chapters 5, 7, 8, 9) It shall be permitted to use performance-based alternative designs for a building, equipment, ignition source control, and explosion protection in lieu of prescriptive requirements in Chapter 8 (Chapter 6) Establishing Safety Management Systems (Chapter 9)

32 Concluding Remarks Safe Management of Combustible Dust Hazards Requires: Establishing a sound process safety-management system and competency within the organization, including: Having appropriate data for the understanding of the combustibility, ignition sensitivity, electrostatic properties, and explosion characteristics of the fuel(s) A thorough understanding of all operations and processes Identifying locations where explosible atmospheres could be present Identifying potential ignition sources that could be present under normal and foreseeable abnormal conditions Defining one or more Basis of Safety

33 Concluding Remarks Safe Management of Combustible Dust Hazards Requires: Establishing a safety culture that starts at the top, and is fully supported (and understood) through the whole organization. Regular review and maintenance of process data and information, process-control systems, processing equipment, and the facility to ensure the continued safety of people, the community, and the business. Relevant Combustible Dust Data is the starting point for assuring Combustible Dust Safety

34 Thank you for Participating in Today s Presentation Mike.Snyder@dekra.com (609) All trademarks are owned by DEKRA Insight, reg. U.S. Pat. & Tm. Off.; reg. OHIM and other countries as listed on our website. No modifications, reproduction or use for training or distribution outside of your organization without written permission from DEKRA Insight.

35 DEKRA Insight: Serving as a Trusted Safety Advisor Integrated Solutions Provider Process Safety Consulting, Engineering and Laboratory Testing Occupational Safety Data Management & Analytics Organizational Safety Organizational Reliability (Human Error & Fatigue) For more information: