Aluminum Dust Management in a Metallizing Facility Safety and Regulatory Concerns

Transcription

1 Aluminum Dust Management in a Metallizing Facility Safety and Regulatry Cncerns William James Barlw, Jr., Prduct Develpment Engineer, Natinal Accunts Divisin Printpack, Inc., Villa Rica, GA Abstract: Accrding t the Occupatinal Safety and Health Administratin (OSHA), a cmbustible dust is a particulate slid f rganic, unxided metal particles, r ther xidizible material that presents a fire r deflagratin hazard when suspended in air r sme ther xidizing medium ver a range f cncentratins regardless f size r shape. Due t the deadly histry regarding related cmbustible dust explsins within multiple industrial peratins, federal regulatins are nw being enfrced at a much higher level t ensure the prtectin f every emplyer and emplyee within the wrkplace. There are plenty f safety regulatins and guidelines available frm OSHA, NFPA, etc. t ensure prper implementatin and cntinual best practices, especially in the area f industrial dust cntrl. This fllwing dcument summarizes the latest infrmatin available regarding the regulatins and guidelines currently being enfrced by OSHA, NFPA, etc. specifically in the area f aluminum/metal dust, with a fcus n the metallizing industry. Briefings will include details n the fllwing subjects: industry cdes, standards, classificatins, types f hazards, mnitring, measurements and assessments, apprved prcedures and devices fr implementing and maintaining gd huse keeping practices, apprved equipment and electrical peratin, prper ventilatin and exhaust systems, and strage, within an aluminum dust generating envirnment. Intrductin: Whether yu are aware f the facts r nt, accumulated fine particulates, dust, derived frm any cmbustible material and frm sme materials generally nt cnsidered cmbustible, can rapidly ignite and burn, causing injury and even death amng ur fellw clleagues in industry. As accumulated dust is disrupted, which frequently ccurs in a nrmal rutine wrk envirnment, it becmes suspended in air, and if in just the right cncentratin in air, it is cnsidered and has prven t be an explsive material. These dusts include: aluminum, magnesium, wd, cal (carbn dusts), plastics and additives, bi-slids, certain textiles, and even rganics such as sugar, flur, paper, sap, and dried bld. There is n dubt that gd husekeeping practices need t be implemented by emplyers t reduce physical injury and minimize emplyee expsure t health hazards. The gal f this paper is t prvide facts and resurces s that the prper decisins are being made that invlve the valuable wrkfrce and resurces that make the business what it is tday. Ultimately, it is the emplyers respnsibility t determine their wn risk regarding their envirnment and t ensure the prper regulatins and guidelines are fllwed that accmpany the emplyers assessment(s). If unapprved items r devices are used within the hazardus dust envirnment, cmpanies are at risk f vilating current established prvisins. Backgrund: Accrding t the U.S. Chemical Safety and Hazard Investigatin Bard (CSB), there have been 281 cmbustible dust incidents between 1980 and 2005 that have killed 119 and injured 718 wrkers, extensively damaging the industrial facilities that cntained the explsins. These cmbustible dust incidents have ccurred in frty-fur states, cvering a variety f industries, invlving many different materials. Figure 1 belw is a pie chart utlining data frm the CSB shwing the wide range f materials - 1 -

2 causing cmbustible dust incidents; wd, fd-related prducts and metals each accunting fr ver 20 percent f explsins, with plastics accunting fr 14 percent. Cal 8% Plastic 14% Inrganic 4% Metal 20% Other 7% Fd 23% Wd 24% Figure 1: Pie chart shwing the wide range f materials causing cmbustible dust incidents. Data taken frm CSB findings. Expnent Engineering and Scientific Cnsulting explains the tw types f explsins, deflagratin and detnatin, quite nicely. In a deflagratin, cmbustin r reactin waves prpagate at velcities less than the speed f sund. Expnent states that all cmbustin can be defined as a deflagratin, where the ignitin f a fuelxidizer mixture, r in ur case, a suspended clud f cmbustible dust in a cnfined envirnment, such as a building, causes rapid increases in pressure, causing explsins with extensive damage. Additinally, Expnent states that these explsins are typically assciated with gas, vaprs, r finely divided fuels, dust, and certain reactive chemicals. In a detnatin, cmbustin r reactin waves prpagate at velcities faster than the speed f sund. Due t the extremely fast reactins assciated with detnatin, these explsins create high-pressure shck waves that can cause damage at distances far frm the rigin f the blast. The familiar fire triangle, seen in Figure 2, shws that fr a fire t ccur, three cmpnents, fuel, ignitin and xygen must be present simultaneusly. The fuel can be a gas, a vapr r a cmbustible dust (e.g. aluminum frm metallizing prcess). The xidant is typically xygen in the surrunding ambient air; hwever ther xidants such as chlrine r nitric xide are effective in supprting cmbustin as well. Ignitin surces encmpass heat surces such as sparks, naked flames, r elevated temperatures. The fuel and the xidant are separate in a fire and need t be present at just the right cncentratins; the ignitin surce must have enugh energy t ignite the fuel-xidant mixture. Like all fires, a dust fire ccurs when fuel, the cmbustible dust, is expsed t heat, r ignitin surce in the presence f xygen. Remving any ne f these elements f the classic fire triangle eliminates the pssibility f a fire. Cmbustible dusts are typically explsible if the dust has a particle size less than 420 micrns (passing thru a U.S. N. 40 standard sieve), r a particle with a surface area t vlume rati greater than a 420 micrn diameter sphere. Sme flaky and fibrus materials may als be a hazard even thugh they will nt pass thru a #40 sieve. Even with this stated, a dust explsin still requires the simultaneus presence f tw additinal elements dust suspensin and cnfinement, seen in Figure 3 belw. Suspended dust burns mre rapidly, and cnfinement allws fr pressure buildup. Remval f either the suspensin r the cnfinement elements prevents an explsin, althugh a fire may still ccur. Fuel Oxygen Ignitin Figure 2: Typical fire triangle

3 Dispersin Cmbustible Dust Ignitin Cnfinement Oxygen Figure 3: Cmbustible dust pentagram. A Cmbustible Dust Incident: As reprted by the Chemical Safety and Hazard Investigatin Bard (CSB), n Octber 29, 2003, aluminum dust explded at the Hayes Lemmerz Internatinal facility in Huntingtn, Indiana, subsequently killing ne wrker and injuring several thers. The Hayes Lemmerz plant manufactures cast aluminum autmtive wheels. The explsins were fueled by the accumulatin f aluminum dust, a byprduct f the wheel prductin prcess. Belw in Figure 4 is a picture f the Hayes Lemmerz Internatinal facility after the explsin frm aggravated aluminum metal dust accumulatin. Figure 4: A picture f the Hayes Lemmerz Internatinal facility after the explsin frm aggravated aluminum metal dust accumulatin. As scrap aluminum frm the wheel manufacturing prcess was chpped int small chips, it was pneumatically cnveyed t a scrap prcessing area where it was dried and then fed int a melt furnace. The prcess f transprting and drying the aluminum scraps subsequently generated aluminum dust in the ambient atmsphere, which was then pulled int a dust cllectr. It was reprted that the dust cllectin system installed was nt specifically designed t handle r maintain the dust, preventing an explsin, r preventing a subsequent explsin frm spreading thrugh ducting. As all 5 requirements fr cmbustin were present, an explsin ccurred. Classificatins and Standards: Accrding t the Occupatinal Safety and Health Administratin (OSHA), the presence f cmbustible materials in sufficient amunts r cncentratins in any lcatin, r in a lcatin where sufficient cncentratins culd exist t prduce an ignitable mixture, it is cnsidered a hazardus lcatin. The lcatin becmes classified as a Class II hazardus lcatin when the cmbustible material is a cmbustible dust. The fact is that the metallizing prcess des prduce aluminum dust as a byprduct and aluminum dust can be cnsidered a cmbustible dust. A Class II, Divisin 1 hazardus lcatin, accrding t the Natinal Fire Prtectin Assciatin (NFPA) guidelines, is identified as any lcatin in which (1) cmbustible dust is in the air under nrmal perating cnditin is present in sufficient quantities t prduce explsive r ignitable mixtures, (2) cmbustible dust accumulates n hrizntal surfaces greater than 1/8, making the surface clr undeterminable, (3) mechanical failure r abnrmal peratin f equipment might cause such explsive r ignitable mixtures t be prduced, prviding a surce f ignitin thrugh simultaneus failure f electric equipment, (4) cmbustible dusts f an electrically cnductive nature may be present in hazardus r sufficient quantities. NFPA guidelines identify a Class II, Divisin 2 area as a lcatin where dust has accumulated n hrizntal surfaces less than 1/8 and the surface clr is undeterminable

4 Cmbustible dusts are further divided int grups E, F, and G based n the type f cmbustible material. Mst plastics, chemicals, wd, flurs, and starches fall int categry G. Hwever, dust frm aluminum and aluminum allys and variatins theref, fall int categry E with mst metals. Mnitring, Measuring and Management: Listed belw are sme references frm the NFPA and thers fr the management f cmbustible dust, in particular metal dusts in NFPA 484. In additin t utlining classificatins and divisins fr hazardus lcatins, these standards detail safe practices fr handling f dusts, fire prtectin, venting, electricity, equipment, machinery, etc. NFPA 61, Standard fr the Preventin f Fires and Dust Explsins in Agricultural and Fd Prducts Facilities NFPA 68, Guide fr Venting f Deflagratins NFPA 69, Standard n Explsin Preventin Systems NFPA 77, Recmmended Practice n Static Electricity. NFPA 484, Standard fr Cmbustible Metals, Metal Pwders, and Metal Dusts NFPA 499, Recmmended Practice fr the Classificatin f Cmbustible Dusts and f Hazardus (Classified) Lcatins fr Electrical Installatins in Chemical Prcess Areas. NFPA 654, Standard fr the Preventin f Fire and Dust Explsins frm the Manufacturing, Prcessing and Handling f Cmbustible Particulate Slids OSHA Directive Number: CPL Cmbustible Dust Natinal Emphasis Prgram FM Glbal 7-76 Cmbustible Dust Explsin and Fire Recently, OSHA has established a Natinal Emphasis Prgram t increase enfrcement activities fcusing n specific industry grups that have experienced frequent cmbustible dust incidents. OSHA initiated the Cmbustible Dust Natinal Emphasis Prgram n Octber 18, Because f sme recent accidents invlving dust explsins, OSHA has decided t intensify its fcus n this hazard. OSHA has begun t establish activities in the areas f utreach and training, specifically fcused n prviding emplyers with prper dcumentatin, infrmatin, prcedures, and resurces needed t educate emplyers, while establishing cperative ventures t enhance enfrcement, prtecting valued emplyees and assets. Accrding t OSHA, the purpse f the NEP is t inspect facilities that generate r handle these cmbustible dusts that culd have ptential fr a deflagratin r ther fire hazards when suspended in air. Additinally, the initiative is intended t examine lcatins fr the presence f any ther xidizing medium ver a range f cncentratins, regardless f particle size r shape, which can cntribute t deflagratins, leading t explsins. As stated by OSHA, situatins where the facility that is being inspected is nt a grain handling facility, citatins under 29 CFR r 29 CFR can be issued if: (1) the lab results indicate that the dust is cmbustible, (2) the cmbustible dust accumulatins are nt cntained within dust cntrl systems r ther cntainers, such as strage bins, that are adequate enugh t prevent a deflagratin, explsin, r ther fire hazard. Additinally, fr nn-grain handling wrkplaces where cmbustible dust hazards exist within dust cntrl systems r ther cntainers, citatins under sectin 5(a) (1) f the OSH Act can be issued fr deflagratin r explsin hazards. The NFPA standards listed in this sectin shuld be cnsulted t determine hw t btain evidence f a hazard(s) alng with directin fr establishing prtectin and preventin f dust explsins. OSHA states that if the wrkplace has a Class II lcatin, then - 4 -

5 citatins under 29 CFR may be issued t emplyers having electrical equipment that d nt meet standard requirements. Gd Husekeeping: Prcedures and Devices Accrding t Chilwrth Technlgy, Inc., the safe prcessing f flammable materials (dusts, gases r vaprs) is facilitated by either preventing the cnditins required fr an explsin t ccur, r prtecting the plant and persnnel frm the effects f any such explsin. The cmbinatin f measures required t achieve such safe cnditins is referred t as the Basis f Safety. A Basis f Safety is the effective safeguards in place t manage explsin risks. Just as in any industry, a frmulatin f a Basis f Safety can be established fr the metallizing industry by adpting sme gd husekeeping initiatives. A few suggestins are listed belw. Hwever, the NFPA standards and OSHA regulatins shuld be fllwed accrdingly t ensure prper handling and husekeeping f cmbustible dusts. By n means is the list belw a recmmended rule f thumb t fllw. Clean aluminum dust accumulatins n a regular basis, making sure t dcument regular scheduled maintenance, while frequently checking the accumulatins fr explsibility Prevent the accumulatin f the cmbustible aluminum dust frm exceeding the thickness established by a rati f the bulk density f the accumulatin sample dust t wd dust Clean light aluminum dust accumulatins by hand ften t prevent suspensin r the frmatin f an explsible dust clud Utilizatin f apprved vacuums is preferred ver cmpressed air cleaning t reduce the chance f generating a dust clud Cleaning prcedures shuld be carried ut in a manner that ultimately minimizes the dispersin f the explsive aluminum cmbustible dust int the air by ding this, the element f suspensin is remved frm the explsin pentagram fllw NFPA standards The apprved equipment fr cleaning, such as vacuum cleaners, shuld be prperly rated fr the classificatin f the lcatin Vacuums are typically industrial grade fr typical wet/dry shp vacuums are nt acceptable Vacuums utilized fr cleaning used near machinery, equipment, r flammable substances shuld be rated fr Class I, Divisin 1 r 2 Vacuum cleaners utilized in lcatins classified as Class II, Divisin 1 r 2 areas like a metallizing facility, shuld be listed fr use nly in thse designated areas Use prper dust cllectin systems and filters fr aluminum dust, minimizing the escape f dust frm prcess equipment r ventilatin systems Ultimately, fllw NFPA standards fr further recmmendatins n additinal cleaning devices such as vacuums, building/lcatin exhausters and indr/utdr dust cllectrs As prvided by the CSB, OSHA recmmends the fllwing as a plan f actin fr the industry, which culd be clsely fllwed r mdeled by emplyers t prtect their emplyees frm fire hazards and reduce the chances fr explsible dust incidents: Issue a standard prcedure t implement a hazardus dust inspectin, husekeeping, testing, - 5 -

6 and cntrl prgram t prevent cmbustible dust fires and explsins in general Base the standard prcedure n current Natinal Fire Prtectin Assciatin (NFPA) dust explsin standards (including NFPA 654 and NFPA 484), and include at least: hazard assessment engineering cntrls husekeeping building design explsin prtectin perating prcedures wrker training Revise the internal standards and MSDS t include clarificatin n aluminum cmbustible dusts generated during the metallizing prcess, including thse materials that may reasnably be anticipated t generate cmbustible dusts thrugh dwnstream prcessing r handling Establish and prvide a training prgram making all emplyees aware f hazards present Identity internal risks and establish an actin plan t minimize risks Ultimately, it is the respnsibility f plant managers, engineers, maintenance assciates, safety crdinatrs, and all assciates t see that a plicy is established fr managing a hazardus envirnment and see that it is carried ut n a daily basis t ensure the safety f all emplyees. References: U.S. Chemical Safety and Hazard Inspectin Bard (CSB). Investigatin Reprt: Cmbustible Dust Hazard Study, Reprt NO H-1, Nvember Occupatinal Safety and Health Administratin (OSHA). Cmbustible Dust Natinal Emphasis Prgram (NEP), Directive Number: CPL , 3/11/ ES&p_id=3830 Natinal Fire Prtectin Agency (NFPA) Standards and Regulatins NFPA 61, Standard fr the Preventin f Fires and Dust Explsins in Agricultural and Fd Prducts Facilities - 6 -

7 NFPA 68, Guide fr Venting f Deflagratins NFPA 69, Standard n Explsin Preventin Systems NFPA 77, Recmmended Practice n Static Electricity. NFPA 484, Standard fr Cmbustible Metals, Metal Pwders, and Metal Dusts NFPA 499, Recmmended Practice fr the Classificatin f Cmbustible Dusts and f Hazardus (Classified) Lcatins fr Electrical Installatins in Chemical Prcess Areas. NFPA 654, Standard fr the Preventin f Fire and Dust Explsins frm the Manufacturing, Prcessing and Handling f Cmbustible Particulate Slids Expnent Engineering and Scientific Cnsulting Chilwrth Technlgy, Inc.: A Prfessinal Prcess Safety Firm. Handling Dusts & Pwders Safely: A Strategic Guide t Hazard Characterizatin & Understanding. Chilwrth Technlgy Inc. 250 Plainsbr Rd., Bldg. #7 Plainsbr, NJ Tel: