Download - Combustible Wood Dust Safety 2015 nfpa 644

Combustible Dust Safety

John NewquistDraft 8 2 2015

History of Dust Explosions• First recorded dust explosion

occurred in Turin, Italy back in 1785

• 281 combustible dust incidents in the US from 1980-2005

• Resulted in 119 deaths and 718 injuries

Introduction Accidents in Industry caused by Combustible Dusts

For example, combustible sugar dust was the fuel for a massive explosion and fire that occurred Feb. 7, 2008, at the Imperial Sugar Co. plant in Port Wentworth, GA., resulting in 13 deaths and hospitalization of 40 more workers, some of whom received severe burns.

Below is an illustration of the facility after the explosion.

Introduction• Accidents in North Carolina caused by Combustible Dusts

Above: Courtesy U.S. Chemical Safety Investigation BoardAbove: Aerial View of explosion and fire that occurred on Jan 29, 2003, at

West Pharmaceutical Services plant in Kinston, N.C

Introduction

What Materials Can Form a Combustible Dust? A combustible dust explosion hazard may exist in a variety of

industries, including: food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation.

Above: Courtesy U.S. Chemical Safety Investigation Board, November 2003, fatal accident at an automotive parts plant explosion in the U.S. that involved aluminum dust that originated near an aluminum chip melting furnace.

Combustible Dust Events in US: 1980-2005

Food Products24%

Lumber & Wood15%

Chemical Manufacturing12%Primary Metal Industries

8%

Rubber & Plastic

Products8%

Electric Services

8%

Other7%

Fabricated Metal

Products7%

Equipment Manufactur-

ing7%

Furniture & Fixtures4%

Distribution of Dust Events by Industry

Food23%

Wood24%Metal

20%

Plastic14%

Coal8%

Inorganic4%

Other7%

Distribution of Dust Events by Material Type

Note: Coal mines & grain handling facilities excluded from study(Ref. U.S. Chemical Safety Board Report No. 2006-H-1)

Dust Explosion by Equipment Type

Equipment Type % of Incidents

Dust Collector 52

Impact Equipment 17

Silos & Bins 13

Dryers & Ovens 9

Processing Equipment 6

Conveyor 3

Source: FM Global Property Loss Prevention Data Sheet 7-76, “Prevention andMitigation of Combustible Dust Explosion and Fire”, May 2008

NFPA Dust Standards

• Keyway Documents

Standard Industry Edition

NFPA 652 All New

NFPA 654 All – General Industry Document 2013

NFPA 61 Food/Agricultural 2013

NFPA 664 Wood 2012

NFPA 484 Metal 2012

NFPA 655 Sulfur 2012

NFPA Dust Standards

• How-to Documents

Standard Purpose Edition

NFPA 68 Explosion Venting 2013

NFPA 69 Suppression/Isolation/Containment/Inerting 2014

NFPA 77 Static Hazards 2014

NFPA 70 National Electric Code 2014

NFPA 499 Practical Electric Classification 2013

April 2014

• Corrigan TX• Four people remain hospitalized, three in critical condition, after an

explosion and fire at a Polk County plywood mill • a) dust collector bags impeded the venting area of the dust collector

deflagration vents. • b) explosion vents releasing in the dust collector without taking measure

to protect employees from the fireball path• c) dust collector vented and the deflagration traveled upstream to the

sander. • d) responding to a fire within the sander dust collection system without

the main blower remaining in operation. • e) responding to a fire within the sander dust collection system without a

choke between the sander dust collector and silo leading to the briquetter.

Chemical Safety Board

• From 2008 to 2012, The CSB board documented, 50 combustible dust accidents that led to 29 fatalities and 161 injuries.

Objectives)

• Identify the NFPA 654/664 Standards applicable to your dust issues.

• Identify three OSHA Standards cited in COMDUST NEP

• Identify three questions that a plant would be asked in an OSHA COMDUST NEP inspection.

OSHA• OSHA has regularly stated that NFPA standards that have not

been specifically incorporated into OSHA standards or adopted by state or local jurisdictions should be considered by companies as guidance.

• At the same time, however, the NEP Compliance Directive instructs OSHA inspectors to consult the NFPA standards to “obtain evidence of hazard recognition and feasible abatement methods” to support a citation under the GDC.

• Consequently, companies should consult NFPAs when evaluating and mitigating potential combustible dust hazards at their facilities.

The Long and Winding Road

• History of Hazards• OSHA Inspections• Issues• Citations• Trends

Trend 1 – Rare Events but Still Occurring

• Two British Columbia sawmills - 2012

• Four dead and 52 injured

• Fines of up to $652,000• These were wood dust

explosions

Trend 2 – OSHA NEP continues

• Combustible Dust National Emphasis Program (NEP) – revised March 2008

• CSB issues recommendations in 2005

• Advanced Notice of Proposed Rulemaking (ANPRM) – published October 2009

• Expert panel met May 2011

Possible Ignition Sources

• Possible ignition sources include:– Open flames and sparks (welding, industrial grinding and

cutting, matches, etc.)– Hot Surfaces (dryers, bearings, heaters, etc.)– Heat from Mechanical Impacts– Electrical Discharges (switch and outlet activation)– Electrostatic Discharges (static electricity)– Smoldering or burning dust– Smoking materials (cigarettes, lighters, cigars, etc.)

http://images.google.com/imgres?imgurl=http://www.nasa.gov/centers/glenn/images/content/270043main_2008_01300%20_welding_sparks_946-710.jpg&imgrefurl=http://www.nasa.gov/centers/glenn/multimedia/imagegallery/if036_weld_sparks.html&usg=__JddlZEnzMNVlqk2bZPYI0qRgAvY=&h=710&w=946&sz=155&hl=en&start=99&um=1&itbs=1&tbnid=yf6RnNHy0cRZVM:&tbnh=111&tbnw=148&prev=/images?q=welding+pictures&start=80&um=1&hl=en&sa=N&ndsp=20&tbs=isch:1

OSHA Inspections• Over 1000 COMDUST NEP

inspections since 2008• High Violations per

inspections (Over 6.0/inspection)

Triggers are: • Complaint or referral • Media reports of fires and

explosions• Inspection Targeting List

~150-300 inspections in 2014

Sample Accident Jan 2009• The laminate panels pass on

a conveyor underneath a curing UV light.

• A panel jammed up underneath the UV light.

• The panel heated up to the point where it charred, smoldered and eventually caught fire.

• The charred pieces were sucked up into the local exhaust system, where they ignited the dust collector located outside the plant.

• The dust collector blew up, sending a shock wave back into/through the plant.

Several overhead doors were blown off, and one of these struck 4 employees, injuring them.

COMDUST NEP • Plant history of fires• Employer’s Dust

Management System• MSDS’s• Dust Accumulation• Dust Collectors• Ventilation Specifications• One liter of dust sampled• Photos• Interviews – Employees,

Employers

Sample OSHA Questions• What is the Plant’s

Housekeeping program? • Is there dust accumulation

of 1/32 inch thick?• Dust collectors located

inside of buildings? • Explosion relief venting

distributed over the exterior walls of buildings and enclosures?

NFPA 654 Layer Depth Criterion Method 6.1.3

Hazard is present if dust 1/32 inches thick covers

• 5% of room or building area up to 20,000 ft2 • Up to 1000 ft2 in a building 20,000 ft2 or larger

100 feet

200 feet

20,000 sq. ft. Building

5% or 1000 sq. ft.

40 feet

50 ft

1000 sq. ft. Building or Room

5% or 50 sq. ft.

200feet

200 feet

40,000 sq. ft. Building

1000sq. ft.

22

How much dust is too much?Fugitive dust outside equipment – Permitted thickness NFPA 654 Particulate

Solids1/32 inch at 75 lbs/ft3 , adjusted for other bulk densities

NFPA 664 Wood 1/8 inch assumes 20 lbs/ft3 bulk density

NFPA 484 Metals No accumulation – clean dailyNFPA 61 Food +

AgricultureRemove along with operations – references NFPA 654

OSHA Grain

Grain Handling

1/8 inch – program and priority areas listed

OSHA NEP

General Industry

1/32 inch – Refers to NFPA 654 and FM Data Sheet 7-76

Adapted from: Application of NFPA 654 . . . Samuel A. Rogers, Process Safety, 3 - 2012 23

Sample OSHA Questions• Does the facility have

isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork?

• Does the facility have an ignition control program, such as grounding and bonding?

Fire through a duct is bad

Sample OSHA Questions• Are Vacuum cleaners

used in dusty areas and approved for the hazard classification?

• Are separator devices to remove foreign materials used?

• Can tramp metal ignite combustible dusts in the dust collection systems? Check the label for Class II

Sample OSHA Questions

• Is the exhaust from the dust collectors recycled?

• Does the dust collector system have spark detection and explosion/deflagration suppression systems?

Sample OSHA Questions• Are ducts designed to maintain

sufficient velocity to ensure the transport of both coarse and fine particles?

• What is the design basis for the ventilation?

• Are duct systems, dust collectors, and dust-producing machinery bonded and grounded to minimize accumulation of static electrical charge?

Sample OSHA Questions• Is metal ductwork used? • Are bulk storage containers

constructed of noncombustible materials?

• Are employees trained in the hazards of the combustible dust?

• Are MSDSs for the chemicals which could become combustible dust under normal operations available to employees?

NEP Citations• 1910.22, Housekeeping • 1910.38, Emergency action plans • 1910.94, Ventilation• 1910.132, PPE Hazard Analysis• 1910.146, Permit-required confined

spaces • 1910.307, Hazardous (classified)

locations • 1910.1000 Z table, Toxic and

hazardous substances • 1910.1200, Hazard communication • General duty clause

5/16/2002 Vicksburg, MS5 fatalities, 7 injured23 serious, 2 unclassified $210,000Fire in the baghouse, then rubber dust explosionNo explosion venting or suppression in baghouse Poor housekeeping88 fire reports in 13 years

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9714






http://www.osha.gov/pls/oshaweb/owastand.display_standard_group?p_toc_level=1&p_part_number=1910


Trend 3 – OSHA will continue to use the General Clause Violation

• Dust collectors (Air Material Separator) inside

• No proper explosion protection systems such as explosion venting or explosion suppression systems

NFPA 654 – 2013 7.13.1.1.1 Where an explosion hazard exists, air-material separators with a dirty-side volume of 8 ft3 (0.2 m3) or greater shall be located outside of buildings.There are exceptions.

Typical 5(a)(1) Violations

• Systems were not provided to prevent deflagration propagation from dust collectors to other parts of the plant.

October 29, 2003 - Hayes Lemmerz Manufacturing Plant, INShawn Boone, 33, died in the Aluminum Dust explosion


• No explosion relief venting distributed over the exterior walls and roofs of the buildings.

CTA Acoustics 2003 – 7 deadFiberglass fibers and excess phenolic resin powder probably went to the oven while workers were using compressed air and lance to break up a cogged bag house filter


• Dust Collector and ducts do not prevent propagation to other parts of the plant

From BS&B


• Ducts and system were not grounded


• Airborne fugitive dust


• A means of tramp metal protection was not provided to keep any unwanted metal fragments out of the air-material separators

From Duramag


• Excessive dust• Not cleaning per the

appropriate NFPA Standard


• Compressed Air was used for cleaning

• Tip: Clean fugitive dust• Regular program• Access to hidden areas• Safe cleaning methods• Maintain dust free as possible• No blow down unless All

electrical power and processes have been shutdown and other means cannot work.

• See NFPA


• No PVC or nonconductive ducts


• Not maintaining duct velocity

• While conditions can vary, 4000 ft/min is generally accepted as a minimum conveying velocity for wood particulate.

• Sec 8.2.2.1.5

Strategy for Employers• Test for Combustible

Dust • Find Applicable NFPA

standards• Implement a Safety

Management System• Housekeeping• Electrical Classification• Conduct Process Hazard

Analysis for Dust Generation Processes

• Control Ignition sources

• Develop safety procedures for working on dust collectors

• Investigate leaks, hot spots, near misses

• Train Employees in hazards of combustible dust

• Plan for fires and emergencies

Hazard Assessment & Mitigation

• Below Illustrations: Examples of Woodworking Shop area that is kept clean, uses engineering controls (dust collection systems), and is kept free of dust accumulation.


• Below Illustration: An example of another Woodworking Shop area that is kept clean and free of dust accumulation.


• Below Illustration: An example of an overhead exhaust ducting at Woodworking Shop area that is kept clean and free of dust accumulation.

Where are Dust Sources?

• Bag Openers (Slitters)• Blenders/Mixers• Dryers• Dust Collectors• Pneumatic Conveyors• Size Reduction Equipment (Grinders)• Silos and Hoppers• Hoses, Loading Spouts, Flexible Boots

Ignition Source ControlElectrical equipmentHot WorksStatic electricity controlMechanical sparks & frictionOpen flame controlDesign of heating systems & heated surfacesUse of tools, & vehiclesMaintenance

Mitigation - VentingVenting:• Rupture panels to relieve

pressure preventing a vessel failure

• Amount of vent area needed is determined using NFPA 68 equations

• Explosion vent need to exhaust into a safe area or a quenching device

Mitigation – Suppression

Suppression:• Detect a deflagration at early stage

and quench the event with chemical suppressant

• Cannon/bottle consist of pressurized gas and suppressant chemical

• System triggers by pressure or optical sensor

• Higher maintenance requirements

Mitigation – Suppression

Factors that Impact Suppression

• Vessel Volume • Vessel Strength

– Reduced Pressure (Pred)

• Vessel Geometry – (L/D Ratio)– Filter Bag/Cartridges

Factors that Impact Suppression

• Initial Pressure (+/-)• Material (Kst)

• Activation Pressure (Pstat)

Isolation

Isolation

Isolation:• Must be used to prevent

propagation of an event in one vessel to interconnected equipment

• Usually always needed in conjunction with venting or suppression

Hierarchy of Equipment Use

6.) Containment

7.) Inerting

1.) Free venting a vessel outdoors

2.) Free venting a vessel indoors next to an exterior wall using a duct

3.) Free venting a vessel indoors next to an exterior roof using a duct

4.) Flameless venting

5.) Active Suppression

Prevention

Maintenance

– It is also important to ensure that all dust-collection systems are operating properly and collected dust is recycled and/or disposed according to the manufacture specifications for the equipment.

Maintenance Check dust collection

systems to make sure all leaks are sealed and dust is not accumulating in the ductwork. Check bonding and ground of all components in accordance with the manufacturer instructions.


• Below Illustrations: An example of an industrial dust collection system connected to a woodworking shop exhaust ventilation system to capture generated dust.

NFPA 654 - 2013• Chapters 1 – 3

Administrative • Chapter 4 General

Requirements • Chapter 5 Performance-

based Design Option • Chapter 6 Facility and

Systems Design • Chapter 7 Process

Equipment

• Chapter 8 Fugitive Dust Control and Housekeeping

• Chapter 9 Ignition Sources

• Chapter 10 Fire Protection

• Chapter 11 Training and Procedures

• Chapter 12 Inspection and Maintenance

Seven Key NFPA 654 Changes

• 4.2 Process Hazard Analysis (PHA)

• TREND 5 – PHA are conducted in less than 10% of companies, but increasing rapidly

• OSHA VPP facilities have conducted numerous PHAs

• 4.2.1* The design of the fire and explosion safety provisions shall be based on a process hazard analysis of the facility, the process, and the associated fire or explosion hazards.

NFPA 654 PHA

• Examine the facility, process, and fire and explosion hazards

• Actual test data required to support analysis

• Which materials are combustible?

• If not known, but suspected, then data are needed

• Closed or open processes? • Rate of generation or

release of solids to an environment?

• Any collection methods in place?

• Conclusion: processes generates or handles solids and dusts are formed in process, potential exists


• 4.3 Management of Change. Written procedures to manage change to process materials, technology, equipment, procedures, and facilities shall be established and implemented.


• 4.4.1* Incidents that result in a fire or explosion of a magnitude that causes property damage, production shutdown time, or injury shall be investigated.

• 4.4.3* A written report …

• 4.4.4* A summary of the incident investigation report shall be shared with affected personnel…

Seven Key NFPA 654 Changes• 6.1.1.1 Those portions of

the process and facility interior where dust accumulations exist external to equipment in sufficient depth to prevent discerning the underlying surface color shall be evaluated to determine if a dust explosion hazard or flash fire hazard exists.

Seven Key NFPA 654 Changes• 6.1.1.3* Dust flash fire or

dust explosion hazard areas shall additionally be determined in accordance with any one of the following four methods:

Layer depth criterion method in 6.1.3

Mass method A in 6.1.4 Mass method B in 6.1.5 Risk evaluation method in

6.1.6

The NFPA 2 day course on combustible dust covers these assessment.

Seven Key NFPA 654 Changes• 6.2 Segregation, Separation, or

Detachment of Combustible Dust Handling and Processing Areas.

• 6.2.1 General. Areas in which combustible dusts are produced, processed, handled, or collected such that combustible dust accumulation on exposed or concealed surfaces, external to equipment or containers, exceeds the threshold as determined in Section 6.1, shall be detached, segregated, or separated from other occupancies to minimize damage from a fire or explosion.

Seven Key NFPA 654 Changes• 7.3.2* Pneumatic Conveying, Dust

Collection, and Centralized Vacuum Cleaning Systems.

• 7.3.2.1 The design of the system shall be documented, and the documentation shall include the following information:

Data on the range of particulate size Concentration of combustible dust

in the conveyance air stream Potential for reaction between the

transported particulates and the extinguishing media used to protect process equipment

Conductivity of the particulates Other physical and chemical

properties that could affect the fire protection of the process

Mitigation Ignition source control• Electrical equipment

• Class II, Division 1 and 2• Consider equipment both inside dust handling equipment and outside

• Static electricity control• Grounding and bonding are key• Inspection of ground and bonding means• Vibrating equipment (e.g., sifters) may cause fatigue failure in straps

• Mechanical sparks & friction• Rotating equipment bearing failure can lead to very hot surfaces (above the MIT)• Sliding surfaces can develop charges• Steel tools dropping onto concrete or steel• Mechanical integrity management system/vibration analysis system

• Hot work program• Open flames

• Design of heating systems & heated surfaces• Use of tools & vehicles• Maintenance

• Comfort heating equipment shall obtain combustion air from clean outside source

http://images.google.com/imgres?imgurl=http://publicsafety.tufts.edu/firemarshal/images/pubsafe_fm__47.bmp&imgrefurl=http://publicsafety.tufts.edu/firemarshal/?pid=39&usg=__vjyIp53guIqrUK_O5faKK91dxwA=&h=502&w=640&sz=942&hl=en&start=2&um=1&tbnid=__pWu1AZoeFZuM:&tbnh=107&tbnw=137&prev=/images?q=hot+work+permit&hl=en&sa=N&um=1

Damage Control• Detachment (outside or other bldg.)• Separation (distance within same room)• Segregation (barrier)• Pressure resistant construction• Pressure relieving construction• Pressure Venting• Relief valves• Maintenance• Specialized detection systems• Specialized suppression systems• Explosion prevention systems• Maintenance

Dust Collectors


6.) Containment

7.) Inerting






Prevention

Dust Collectors


6.) Containment

7.) Inerting






Prevention

Dust Collectors


6.) Containment

7.) Inerting






Prevention

Dust Collectors

Dust Collectors

Milton Hershey School

Location: Hershey, PA

Application: Woodworking

Model: CYLK4440

Air Flow: 8,500 CFM

Dust Collectors

Lincoln Middle School

Location: Passaic, NJ


Model: DKLD48015

Air Flow: 4,800 CFM

Dust Collectors

William Patterson University

Location: Wayne, NJ


Model: DKPD72015

Air Flow: 5,700 CFM

Dust Collectors

Gloucester HS

Location: Gloucester, MA


Model: CYLK4450

Air Flow: 10,000 CFM

Dust Collectors

New Oxford Middle School

Location: New Oxford, PA


Model: DKLD48015

Air Flow: 8,500 CFM


6.) Containment

7.) Inerting






Prevention

Multiple tasks involving exposures may involve use of FR as normal work wear.

NFPA 2113 (2012) Recommends FR use for combustible dust A.5.2

• Work where dust is present on equipment or structure

• Changing dust collector bags

For example, FR garments should be required for the following:

Per OSHA NEP

84

Dust depth Frequency Hsk’pg Req. Classification

Negligible dust (color discernable)

N/A N/A Unclassified – general purpose

Negligible dust to < 1/32 inch (paper clip)

Infrequent – Episodic release, not > 2-3 times yearly

Clean up during same shift

Unclassified – general purpose

Negligible dust to < 1/32 inch

Continuous to frequent – Continuous with < 1/32 inch per 24 hours or Episodic release, > 3 times yearly

Clean as needed – maintain average < 1/64 inch (puffy little cloud with each step)

Unclassified – NEMA 12 dust entry resisting enclosures and /sealed non- heat producing equip. (For existing plants – New to be Class II, Div. 2)Groups F and G Dusts 85

1/32 to 1/8 inch(Two Quarters stacked)

Infrequent Clean up during same shift

Unclassified – NEMA 12 dust entry resisting enclosures and /sealed non- heat producing equip. (For existing plants – New to be Class II, Div. 2)

1/32 to 1/8 inch

Continuous to frequent

Clean as needed – maintain average < 1/16 inch

Class II, Division 2

>1/8 inch Infrequent Immediately shut down and clean


> 1/8 inch Continuous to frequent

Clean frequently – minimize accumulation


Groups F and G Dusts 86

NFPA 654 – Housekeeping 8.1,2

Fugitive dust control is to be provided by continuous suction wherever dust is liberated in normal operations

The dust is to be conveyed to air-material separators

Cleaning frequency, methods and portable vacuum cleaner requirements are RETROACTIVE for all facilities

Continuous Suction ?

87

Cleaning Frequency 8.2.1

At facilities operated with LESS than the chosen threshold dust mass/accumulation per 6.1, cleaning frequency must ensure:

• Accumulated dust levels do not exceed the chosen amount of dust

• There is a planned inspection process that maintains cleaning at the correct rate

89

Cleaning Frequency 8.2

For facilities operated with LESS than the chosen threshold dust mass/accumulation

• Set specific time requirements for cleaning local and short term spills

• The intent is to remove the excess materials quickly so that such spills do not need to be included in the mass calculations of 6.1

90

Timing of Unscheduled Cleaning Longest Time to Complete

Unscheduled Local Cleaning

Accumulation on the worst single square meter of surface

Accessible Surface

Remote Surface

1 to 2 times threshold dust mass/accumulation limit (TDM/AL)

8 Hours 24 Hours

2 to 4 times TDM/AL 4 Hours 12 Hours>4 times TDM/AL 1 Hour 3 Hours

Adapted from NFPA 654 Table A.8.2.1.3(a)91

Cleaning Frequency 8.2.1

For facilities operated with MORE THAN the chosen criterion for threshold dust mass/ accumulation per 6.1:

DUST• FR clothing and properly installed explosion venting would be included

• Chapter 4 identifies some general safety requirements

92

• Additional protective measures are necessary per A.8.2.1.4.

• It is permitted to prepare a documented risk assessment to determine the level of housekeeping consistent with protection requirements

Cleaning Methods 8.2.2

Surfaces shall be cleaned in a manner that minimizes the risk of generating a fire or explosion hazard.Vacuuming shall be the preferred method of cleaning.Where vacuuming is impractical, permitted cleaning

methods shall include sweeping and water wash-down.

93


Blow-downs are permitted for cleaning inaccessible surfaces or surfaces where personal safety risk is less than other methods. Use the following precautions:

Vacuuming, sweeping, or water wash-down methods are to be used first

Dust accumulations in the area after vacuuming, sweeping or water wash-down are not to exceed the threshold dust accumulation.

94


NEMA 12 (resists ingress dust of particles)

• All ignition sources and hot surfaces capable of igniting a dust cloud or dust layer must be shut down or removed from the area

Additional requirements for dust blow-down• Compressed air hose nozzles must be limited to 30

psi discharge pressure as per OSHA• All electrical equipment potentially exposed to

airborne dust in the area is to meet

95

Housekeeping Procedures 8.2.2.5

Housekeeping program is BIG

Must be documented (and addressed) in the dust process hazard analysis and management of change proceduresHousekeeping procedures should include:

• Risk analysis of the dust• Particle size• Moisture content• MEC and MIE• Other safety risks introduced

by cleaning methods• Personal safety procedures and fall

protection• Flame-resistant garments per NFPA

2113 96

Housekeeping Procedures 8.2.2.5

Procedures should also include:• Cleaning sequence and

methods to be used• Equipment including:

• lifts, • vacuum systems, • attachments, etc.

Safety Note: Large and high velocity fans may be used to prevent dust accumulations. Use of such fans to blow down significant dust accumulations present the same risks as compressed air blow-downs.

97

Portable Vacuum cleaners 8.2.3.1

• Hoses are to be conductive or static-dissipative – both suction and air delivery hoses

• All conductive components including wands and attachments must be bonded and grounded

• Dust-laden air must not pass through the fan or blower

Conductive or Static-dissipative Hose

They are to meet the following:• Generally non-combustible construction and meet

requirements for construction and static electrical hazard controls per 9.3.2 and 7.13.2

98

Portable Vacuum cleaners 8.2.3.1

Additional requirements• Electrical motors must not be in the

dust laden air stream unless listed for Class II, Division 1 locations

• No paper filter elements for liquid or wet pick-up

• Metal dust vacuums are to be listed for Class II, Division 1, Group E and meet other NFPA 484 requirements for specific metal used

99

Vacuum Cleaners for Use in Hazardous Locations 8.2.3.2 And .3

• Use vacuums listed for the location or

• Provide a fixed-pipe suction system with appropriate remotely located exhauster and dust collector.

• Where flammable vapors are present, units are to be listed for both Class I and Class II locations

HAZ LOC 100

Spills of Large quantities of dust A.8.2.3.1

In UNCLASSIFIED areas• Bulk material should be collected by sweeping, or

shoveling•Listed Class II vacuums may also be used

• Vacuum cleaners per 8.3.2.1 (e.g.: compliant air driven units) may be used afterwards for residue

Vacuum Truck See also OSHA Fact SheetDSG FS-358910 2012

Vacuum trucks are similar to vacuum cleaners. They require analysis with management of change (MOC) to remove large quantity spills or releases of dust per 4.3

101

Concluding Remarks

• No two dust explosions are the same. – No uniform dust laws like there are for gases

• Standards are evolving

• The dust explosion hazard exists– Be aware of the “I’ve never had a dust explosion

before”

Questions?

Safety and Health Information Bulletin

PurposeBackgroundElements of a Dust ExplosionFacility Dust Hazard AssessmentDust ControlIgnition ControlDamage ControlTrainingReferences

Resources and Questions?

• NFPA 2-day Combustible Dust Seminar

• Combustible Dust Guidebook - NFPA

• OSHA SHIB• www.csb.gov

• LinkedIn Combustible Dust Forums

• Facebook Grain Mill Accident page

Download - Combustible Wood Dust Safety 2015 nfpa 644

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