Industrial Explosion Suppression Technology

Transcription

1 88 th Annual Michigan Safety Conference 2018 Tuesday April 17 th :45 AM Industrial Division Lansing Center, Lansing, MI Industrial Explosion Suppression Technology Presenter: Rob Markle Phone: (309)

2 1 2 3 (Fundamentals) (OSHA, NFPA, AHJ) (Protection Methods)

3 Fundamentals of an Explosion

4 Combustion Materials Testing 20-Liter Test Vessel for Kst, Pmax Determination Go-No Go Test

5 Explosibility Calculation (identifying risk) Pressure P max R max dp K st = R max V 1/3 [bar-m/s] Where R max = The maximum rate of pressure rise [bar/s] dt R max = (dp/dt) max V = The volume of the test vessel [m 3 ] Time

6 Hazard Classes of Dust Deflagrations relative explosibility hazard Hazard Class ST - 1 ST - 2 ST - 3 K st Value and above Example Pittsburgh seam coal has a Kst of 129 bar-m/sec, making it an ST-1 dust

7 Deflagration Propagation Interconnected Equipment NFPA recognizes the need to isolate explosion hazards Pressure piling in duct Elevated pressures and ignition source

8 Secondary Explosions Dust Accumulation in plant leads to more severe explosion NFPA recognizes 1/32 accumulation over 5% surface area a severe hazard Initial explosion creates vibration and a plant wide dust cloud Flame ruptures from vessel and ignites secondary explosion

9 Secondary Explosions SECONDARY EXPLOSIONS ARE THE MAIN THREAT TO PERSONNEL AND PROPERTY! Plastics Mfg. in NC Polyethylene Powder 6 fatalities Hundreds of injuries Plant destroyed Was major employer Acoustic Board Mfg. Kentucky 7 fatalities 37 injured Use phenolic resin powder as binder for fiberglass mats Sugar Refinery Georgia 14 fatalities 38 injuries Milling and Packaging destroyed

10 Regulation NFPA Standards - Enforceable when incorporated into state, local law - Most have strengthened EP requirements due to NFPA 652 OSHA Responsible for enforcing workplace safety OSHA Combustible Dust Directive driving explosion mitigation OSHA Combustible Dust Standard now tabled

11 National Emphasis Program on Combustible Dusts General Duty Clause requiring safe and healthful workplace Issued , Revised March 2008 Testing samples for combustibility Explosion mitigation requirements per NFPA 654 Deflagration isolation required per NFPA 654 Reviewing housekeeping (1/32 ) Emphasis on dust collection Citations and Fines

12 New NFPA Standard on the Fundamentals of Combustible Dust First released as a standard in 2016 Intended to simplify OSHA compliance and enforcement Will provide the basic principles of and requirements for identifying and managing the fire and explosion hazards of combustible dusts and particulate solids NFPA 652 committee members advise the other industry standards during cycle meetings

13 NFPA Edition Will co-exist with industry-specific standards NFPA 61 Agricultural and Food Facilities NFPA 654 Combustible Particulate Solids NFPA 664 Wood Processing/Woodworking NFPA 484 Combustible Metals Conflicts - The more stringent requirement between NFPA 652 and the industry-specific standard will apply

14 NFPA Edition

15 NFPA Edition Defines Responsibility 4.1 General. The owner/operator of a facility with potentially combustible dust shall be responsible for the following activities: 1. Determining the combustibility and explosibility hazards of materials in accordance with Chapter 5 2. Identifying and assessing any fire, flash fire, and explosion hazards in accordance with Chapter 7 (DHA) 3. Managing the identified fire, flash fire, and explosion hazards in accordance with Communicating the hazards to affected personnel in accordance with Section 9.5

16 NFPA Edition Defines Responsibility Chapter 7 Dust Hazards Analysis (DHA) Responsibility. The owner/operator of a facility where materials that have been determined to be combustible or explosible in accordance with Chapter 5 are present in an enclosure shall be responsible to ensure a DHA is completed in accordance with the requirements of this chapter For existing processes and facility compartments that are not undergoing material modification, the owner/operator shall schedule and complete DHAs of existing processes and facility compartments within a 3-year period from the effective date of the standard. The owner/operator shall demonstrate reasonable progress in each of the 3 years.

17 DHA for Process Equipment Identifying Risk

18 Explosion Prevention Measures Process Hazard Evaluation Ignition Control Bonding/Grounding Electrical Equipment/Classification Control of Friction, Impact Spark Potential Hot Work Procedures Housekeeping Hazard Training and Awareness Management of Change

19 Explosion Protection Methods Containment Inerting Deflagration Suppression Deflagration Relief Venting Deflagration Isolation

20 Deflagration Relief Venting Relieve internal pressure in vessel Prevent flame escalation from deflagration to detonation Must not become projectile

21 Deflagration Relief Vents Rupture-style flat or domed Square or rectangular Optional burst sensors Optional Insulated Models Shear pins Magnetic latched or spring-loaded doors Gravity panels

22 Venting Considerations Fireball 7x volume of vessel Flame ejection >50 Must vent to safe area Combustible must be safe to vent outside Potential for Explosion Propagation? Post Explosion Fires? Reaction Forces?

23 Explosion Vent Sizing NFPA 68 for Sizing INSIDE VESSELS: Vent ducts require additional vent area Vessel overpressure strength needed Will not stop flame propagation through inlet or exhaust

24 Flameless Explosion Vents Passive protection means Inside venting performed without ducts Temperatures cooled to approx C

25 Flameless Explosion Vents - Considerations Does not suppress deflagration, fire could remain in vessel. Fire protection must be considered Flame propagation issue still exists. Deflagration isolation must be considered Safe zone needed around unit (hot gases, toxicity)

26 Maintenance Requirements - Vents NFPA * Inspection Vent closures shall be inspected at least annually * The frequency of the inspection described in shall be permitted to be increased or decreased based on documented operating experience A record shall be maintained that indicates the date and the results of each inspection and the date and description of each maintenance activity The records of inspections shall be retained for a minimum of 3 years.

27 Explosion Suppression Pressure sensor located on dirty volume Dry Chemical agent discharges into vessel Fireball is extinguished and process is shut down Agent quantity based on dirty volume, Kst, Pmax Agent is discharged into interconnected ducts to prevent propagation

28 Suppression Sequence - Starch in 1 m 3 Vessel Extinguisher Detector Time 0 ms 20 ms 30 ms 40 ms 80 ms

29 Explosion Suppression Components Control Unit Explosion Pressure Detectors Explosion Suppression Extinguisher

30 Dynamic Pressure Detector Programmable Rate of Rise CIP Compatible Event Memory Flange installed by fab shop

31 Dynamic Pressure Detector History can show evidence of a successful suppression event FAB Module

32 IR Flame Detector Infrared Flame detector desensitized to look for flame only (not for spark detection) Used on ducts to shorten the required isolation distance for low Kst dust (~50) or lazy deflagrations

33 Explosion System Control Unit User interface for alarm and trouble conditions Key switch for arming/disarming Provisions for OSHA LOTO Relays to interface with process PLC for shutdown upon alarm

34 Dry Chemical Extinguisher Sizes: PF II-1000, 4 Kg PF II-2000, 10 Kg PF II-3000, 20 Kg - Actuates in milliseconds - Sodium-bicarbonate agent - Used for suppression and chemical explosion isolation

35 Suppression Discharge Nozzle Disperses suppressant Pipe cap for inspection of discharge nozzle per NFPA requirement End sealed with silicone cap, to prevent plugging in discharge pipe Spreader cap blows off during discharge

36 Maintenance Requirements - Systems NFPA Inspection Systems shall be inspected and tested at 3-month intervals * The frequency of inspection described in shall be permitted to be increased or decreased based on documented operating experience or a documented hazard analysis, and only with approval of both the explosion prevention system designer and the AHJ Maximum inspection and test interval shall not exceed 2 years System inspection reports shall be kept or accessible at the site for at least 3 years.

37 Extinguisher - Lockout Plate Storage for plate Process Maintenance OSHA lockout plate provides a mechanical barrier for safer access inside vessel Agent cannot discharge through the nozzle to the inside of the vessel Protection system cannot be armed when OSHA plate is installed Normal operation

38 Explosion Propagation NFPA 652 NFPA 654 Active Explosion Isolation Passive Explosion Isolation

39 Chemical Isolation Barrier Activated by pressure (or flame detection for Kst<50) Location on duct is based on vessel volume, Kst, Pmax and detection time

40 Explosion Isolation Valve High speed valve closes in milliseconds. Rated for 150 psig deflagrations. Available 2 up to 24 sizes Requires detection and controller to activate

41 Passive Explosion Isolation Passive Explosion Isolation for Collector Inlet Ducts Lower Cost Alternative to High- Speed Valves or Chemical Isolation Sensors improve reliability, reduce inspection frequency Third-Party Performance-Based Approvals per NFPA requirements

42 Rotary Valves NFPA Rotary Valve Design Criteria Rotary valves intended for deflagration isolation systems shall be designed according to one of the following isolation concepts: (1) Deflagration isolation by flame quenching (close-clearance valves) (2) Deflagration isolation by material blocking (product layer above the valve)

43 Passive Isolation Valve Clean air Considerations DN100 DN600 ~ 4 in 24 in sizes Suitability: light dust concentrations Dust collector exhaust ducts Mill air intake ducts Collectors with light dust loading

44 IEP Applications Dust Collectors, Receivers Cyclones, Classifiers Dryers (Spray, Fluid Bed, Flash) Bucket Elevators Mixers, Blenders Mills, Grinders, Pulverizers Bins, Hoppers, Silos Conveying ducts

45 Vented - Passive Isolation (inlet)

46 Vented - Passive Isolation (outlet)

47 Vented - Chemical Isolation (inlet)

48 Vented Inlet / Outlet Isolation

49 Suppressed - Inlet Isolation only

50 Suppressed - Outlet Isolation too

51 Thank You! Questions?