Document RnMvk2BoZeb51pNoJ6dKkJdX

I PLAINTIFF'S | i EXHIBIT I II Brake and Clutch Emissions Generated During * Vehicle Operation Michael G. Jacko Research UBcratcnes, 3endix Cor?. Robert T. DuCharme Automotive Control Systems Group, Sendix Corp. Joseph R. Somers Office of Air and Water Programs, environmental Protection Agency SOCtEHTVT OF AUTOMOTIVE ENSEM EERfS^U Automobile Engineering Meeting Detroit, Mich, May 14-13,1973 C&5 ' 3Efrr CCHiBnvyo.. t DATE WITNESS OUNtte JONCS, ** 730548 he brake system plus more a the clutch mechanism. it be comes apparent dut an ur pollution problem may exist. Con* sidered us another light, the.e are perhaps 1 billion pieces of faction material us vehicles in die United States gradually _ being pyroiyzed and ground to dust. The brake systems in the vehicles utdizmg these friction matenais can thus oe consid ered as chemical reactors, each emitting organic and inorganic compounds including asoestos and its decomposition products to the atmosphere. The compositions of the gaseous ana solid emissions are not well-known nor art the particle sues and shapes of the solid emissions well-known. has never, to the authors' knowledge, been reported m the lit erature. To define the extern of these emissions. a collection system was devised which combined me functions of separa tion and storage. Unique emissions collectors for noth disc and drum brakes and for a dutch were conceived, designed, and built as the mam emoodiment of this instrumentation. The collectors separated the wear deorts into three different fraeaons: a sump sample which jiciuded the wear leans on the lining surfaces, m the rivet hoiea. and on the craxe drum; a surface sample which included the wear leans on -.ne craxe and collector shroud surfaces, and an airborne sample col lected on membrane filters. OBJECTIVES Because of the possible damage which asbestos emissions can produce in the human respiratory system, it is destraele to identify and quantify these emissions. Thus the objectives of dua paper are to: 1. Descr.be the methodology 'used to generate, collect, and analyze brake and dutch emissions. 2. Report the asbestos contents in emissions from a test ve hicle. 3. Estimate the total asbestos emissions for all vehicles in the country. TECHNICAL APPROACH 'Dae major requirements for the emissions sample collection system may be summed up a* follows: l. Collect all particulate and gaseous emissions. L Store collected emissions unchanged. 3. Prevent intrusion of contaminants. . Maintain ordinary braking and clutching conditions. 5. Be operable at high temperatures. . Permit easy separation and analysis of emissions. MATERIAL SELECTIONS For the results to be represen tative of average consumer-type vehicle usage, a vehicle inter mediate between compact and luxury was selected. The vehide was equipped with front disc brakes, rear drum brakes, and a dry clutch. All friction material used contained asoestos. Three vefcide tests were run. The detailed technical approach may be summarized as follows: 1. Select a suitable vehicle and linings representative of the marketplace. 2. Conceive, design, and build brake and clutch emissions collectors. 3. Teat and check out a typical collector on an inertial dyna mometer and install instrumentation on the ten vehicle. . Select and run suiubie driving teat schedules representa tive of consumer-type driving. S. Collect and analyze emissions to obtain the asbestos con tent and the panicle so* distribution. . Estimate the asbestos emission for ail passenger vehicles and extend Ac dau to trucks to obtain a result for all vehicles operating in 'die United States. A passenger car was selected for testing because of the fol lowing factors: 1. Vehicle braking cannot be simulated realistically on smallscale friction test machines with the present stace-or-che art 2. Full-scale brake and dutch dynamometers provide fairly good simulation and can be used for checking out the emi> sons collection system: however, separate tests for brakes and dutches would be required thus increasing program costa. On die vehicle, disc and drum brakes and dutches can be tested simultaneously. INSTRUMENTATION METHODOLOGY AND CRITERIA - The collection of par ticulate and gaseous emiasons from any vehicle friction couple The Urn vehicle test was run with the original equipment friction matenais. The second vehicle test simulated a partial feline--fronts only .flitted--while the rears were repeated to give a replicate test and an indication of emissions trends for friction materials with continued use. The third vehicle test simulated a complete brake relint and Included dimed discs and drums. The friction materials selected for the program were representative of those supplied by die industry-five different manufacturers (Abex. Bendix, Raybestos-Manhatun, Thiokoi, and Wortdbestos) produced the ongmal equipment and aftermarket disc pads and drum liunp which were se lected in part because of their high-vottnsn uBge. VEHICLE INSTRUMENTATION A passenger car of mediua weight (4850 lb test weight) produced in high volume was elected. It was equipped with a three-speed manual transmission, ventilated cast-iron disc brakes on the front, and cast-iron drum brakes on die rear. This vehicle *u selected in order that the emissions from clutches and from disc and drum brakes could be tested simultaneously on a vehicle size representing a large percentage of the present vehicle popula tion. The vehicle was equipped with standard brake test instru mentation. A front disc brake collector and a rear drum brake collector were installed on the right side of die vehicle. The clutch was scaled by closing die few holes tn its casing. The left wheel brakes were left is their normal configuration and were used to monitor die operation of the shrouded brakes. Wear debris u takes from the left brakes as w*u as from those os the right. The amounts of debris formed and die? compositions were used to demonstrate that die brake shroud* jig did not significantly affect the operation of me craxes on me r.gnt s;ae. EMISSIONS COLLECTION systems OVERALL SYSTEM DESIGN The base design concept of each iraxe emissoiu coilecucn system * shown .a rig. Air from inside me vehicle was puiied mrough a ced wnccn removed water ana caroon dioxide from me ur. The nr men passed through i filter to remove ail panacea larger man 0.2 am (8 x 10'6 m). The filtered nr was men routed to me sealed oraxe usemQiy through clean Teflon ruerng. The airstream. along with weir particles and gases, men passed out :f me oraxe througn Tetlon tuotng wtuca was rteated to avoid condensation. Thu stream passed through two filters to re move the airborne particles and preserve mem for analysis. The stream then passed through three cold traps a orser to condense and trap me gases evolved during braking and pre serve mem for analysis. The remaining unmeant men passed through a flowmeter, the vacuum manifold, and finally through an air pump run by me vehicle engine where it was expelled to me atmosphere. Fig. 2 shows., mounted in the front seat of me test vehicle, the front brake inlet air filter and gas collection system, e clutch gas colltenon system, and me 12 position thermo couple switch and pyrometer used to monitor gas and filter trap temperatures. Fig. 3 shows, as mounted in me rear seat of the test vehicle, me rear brake air filter and gas coilecucn system, the dutch air filter, and me electrical system (bat- ? 6 loaded graphite-filled Teflon seal of commercial manufacture. A view of major components of the collector :s shown m Fig. 5; the system, as mounted on the vehicle. is shown in Figs. 5 and ?. The mam portion of the shroud u coated, vtth biack oxide; a water-cooling system was added and an open "mag'* wneet was used to aid m cooling the enclosed brake. DRUM 3RAX2 CCHECTOR Fig. 3 shows a crosssectional view of the collector along with the detail of the rubbtng seal. The seal was of the same type as for the disc brake collector. The axle hub used to align the drum was modified 'with a piece that was concentre to the axle bear ings within 0.001 in (0.0Q25 cm). A tapered lead was used to facilitate mounting of the drum. The dose toterances on die concentnciues were necessary in order to obtain reason able seal life. Figs. 9 and 10 show outboard and inboard views of the system as mounted on the test vehicle. CLUTCH COLLECTOR The dutch system consisted mainly of a filtered air inlet and as outlet to the sample storage system with all other external holes sealed. INERTIA DYNAMOMETER TESTS The front disc brak.' emission collector was tested on an in ertia dynamometer to check out its opentioo and its most Fig. 9 Awabiid me dram bake imirtnn collector cr.ticai part, the rotating sail. Thermal response tests were made with the results indicating tnat for normal operation me shrouded disc brute would operate sc s uigatiy rugher tempera ture this the normal braxe configuration. A method was de vised :o detemune me ieak rate of the collector. The rotating seal was lately responsible for me residue leak: me ieax rate was reduced significantly oy use of i very smail amount of high* temperature grease. The rotating seal underwent duraouity test ing and survived h at SO mph. A second senes of dyna mometer tests gave reproducible emissons and temperatures. Finally, a test was made m which the collector and especially the routing seal were shown to be relatively leak-tight to ex ternal liquid and paniculate contaminants. VEHICLE TESTS RATIONALE - For a jtvtn vohide brake system, friction material wear is primarily a function of the duty cycle. For light-duty cydes. where pad and lining temperatures remain under 350*F, low wear results and is primarily due to the abrasvt and adhesive wear mechanisms. Heavier duty cycles at higher temperatures give some combination of thermal, abrasive, and adhesive wear. Under severe heavy duty where the use borders on abusveness, brake fade may occur, the inability of the brakes co hold the friction level resuits in part from the formation of gases (and wear debris) at the interface. Although there are many acceptable original equipment manufacturers' friction matenal tests to measure a specific condition or combination of conditions, there is no one test which adequately matches normal dnvuig conditions which would be representative of all vehicles. Consequently, u oecaste necessary to devise a rational and meaningful vehicle test driving schedule. SELECTED VEHICLE-DRIVING SCHEDULES * A total of seven rest schedules were chosen and each was followed by a measurements procedure (take emissions samples, measure wear, inspect systems, and replace worn parts). The first three tests-- Burnish, After-Burnish (.A3.) Baseline, and Detroit TrafSe-rtprestac the low-temperature teats. The final four tests--10 Stop Fade. .After-Fade (A.5.) 3aaeiine. v ft|. 10 -tapoaid *iew o( d me dran brace enusiem set- 3 ceduxe 'ji iHc prewired for the sampling, handling, md analysis of the ubeitoi emissions. ANALYTICAL PROBLEM DEFINITION Toe tiersoi ind mechanical forces which act at the meaon^saMpie inter face produce a complex chenacaily sdatiycaijr cnuad~ micrcstruaturt vaao samor a* sccuncery deaesshtd ec present. Table 5 pves an est^nate of the *-*<! H campoa* non of wear aeons. Asbestos a a cnmpiex isorgmc merenal via the as> promnaie compasnon /oriraia: . M|3 (S0<) (0K)4 or JMgO ao, 2H-0 The baste unit has a fibnl form (1. 2)*. Asbestos is readily identified when none or m stmpie mixtures at high con* centntions by these analytical methods: x-ray diffraction, thermal methods, microscopy, and infrared analysis. How. ever m complex mixtures or at very low concentrations the analysis for asbestos is very difficult. In brake wear deoha, the problem is compounded because the reaction products of asbestos, forsterite and olivine have similar elemental ratios and similar x-ray diffraction patterns. The only sensitive method which can be used is microscopy, la extremely low concentrations, asbestos is identifiable in the electron microscope by its physical shape (tubular fibril) which is distinguishable from that of other fibers and particles. At the begmning of the program, one optical (3) and three transmission electron microscopy (d-o) methods had been developed by others. Two of the electron microscopy methods were aot suitable because they changed the fiber size dis* tnbution of die asbestos. ANALYTICAL METHOD SELECTED* From the available analytical methods and the problems associated with brake wear debris analysis, die following considerations were necessary. Chora and Flow Ovrr Three important criteria had to be met by the analytical method used: The very small portion of brake debris used had to be representative of the much '.spec aspic collected: the analytical steps could not decide :'sit pemuie se aismbution of the asbestos fibers ootainei; rhe vaults obramed must be mdicacve of me actual asoestos coorent of die sample. These erttena were met by -it analytical scheme outlined ;n Fig. 11. Rcpmentar** Simotmf snd Lo h*Ttmpmr^rr Ajjung 'L TA) The aaayss of bcus iasns laaaauo me pctamceof 2^SO% by wcaui -** praiy-aecc md curraacsous matenal. vrschm are produces a cluifr -perg;v>ce *bas :fx material was ccaacea is the scancmg elector) micrcscoce. The organic pomon wea therefore removed by LT.A. Two representative samplings were used: die first in samoit selection for LTA and the second m santpte setecaoo for at tribution on a filter membrane for subsequent maims. Stitcttd Microscopy Methods In the very eariy tests, wear debns from a sample dynamometer was collected on the filter tram of the 3.0 a and 0.2 a Nudeport filters. 3oui filters were examined by a combination of optical md transmission electron microscopy. The following oosemuona were made: 1. Asbestos fibers lonju than 20 a were obtained. 2. Very Sat fibrils were extremely difSeuit to detect u less thaa $000 diameters magnification. Based on the above jnid.es, it was deemed necessary to employ two magnifications. To detect fibers greater taa 2 u, a magnification in the range 10.000-*0,QOG diameters 4Ja**r* uaMbftH t UiffMUIMM 4lbTM `Numbers in parentheses designate References at end of paper. Table 3 Esosated Cbeaieal Coopowbon Oaraeeniea of vwoea Cweipcoq Percent Low eteleeulsc iipt itgndauea products Poiyraenc components Carbonaceous fRetenai inorganic*: Minanl OUvtse Oadaa (from limng) F^03 (from rotor) Atoeetot 2*101 12*20 ' i*i j 30*30 > M0*30 ^;o-*o 0*10 ^ Mi 'o-ao <b T mmif >t**uar<wrt I wnamw uimuwm wTa 1 CBWXV MiwiMswniin t f Fig. 11 Flow cbait af psraeulatas saaiysee r 10 T*Mc 4 k u k c iiM f c n lH iu I)u iIr ItufMtoli m J Ik lio M T iillk r u u tlli| 150 110 0 10 I Mi 110 100 MU 150 210 210 MO 3 9*1 9-* 39 99 a 9 9~ 3 e3% 90* 933 9a 3 35 9 v* a 3 9933 99 9 9* 3a 9 9 SS<* < a oM 39 S;:2S ^ 22322 3222s 3 ^3 2 39933 39999 S23 r 55? 5 23322 22522 i?5*f mm a 22321 * 22222 2222 222 * 9F> 9 4* 94 9>1 ? 3 2 a 9 5* 9 1 1 tiii*f!l!f ail * * 3 3a<< 11 1m111il1 | f V S V tf S !<<<<< 2lg 1 * J2? iiUiilriii n 111ii?i|* I5 IIJt 12 ii 3> -> < (Uwgc / V/ only three wtrt in it range 0.50-0.96%; ill others were less haw 0.50%. The overall average was 0.15%. For vehicle 3, it range of asbestos content in brake emissions rants from s high of 0-51 % down :o a low of 0.C03%. Of it analyse* reported, iree were m the range 0.10-0.51%; all oien were -ess ian 0.10%. The overall average was 0.0'%. For ail iree vehicle tests, it overall average of asbestos content is ie brake emissions -was 0.13%. Indtpmdtat Asbtttot Anaiyui To provide a systematic independent check os ie asbestos analyses, it Environmental Protection Agency (E?A) arranged for BaneUe Columbus Laboratones :o analyte 14 samples generated iunng ie Program. The Jchns-Manviiie Research and Engineering Center also provided iree analyses ('). In 19 of ie 14 analyses, ie Program results were slightly higher than ie corresponding Satteile results (Table 10). The Program Table I - DUmbuuen of Emmons4, % Vtnieia Test l 2 3 Collector Sump Surfaces Airborne Sump Surfseta Airborne Sump Surfaces Airborne Front Brakes Rif&t Left (Shrouded) (Normal) 6-31 63-39 2-iS 2-20 71*93 2-22 :-3s **36 7-19 41-13 17-39 - 43-13 17-37 - - - - Rear Brakes Right Left 'Shrouded) (Normal) 8-22 ::i$ >4 12-22 4*44 1- 2 9-34 61-17 Ml 36-43 33-43 3943 37-41 - - -- Table 9 Summary st Asbestos analytical R*uit*-Vtnie:e Teat :. WtifBt "irctnt Schedule Front Brutss Rev Bruces Right Lett-- Right Let Collector Shrouded) Normu) Shrcucedi Nomail Burusa Sump Surfaces Airoome A.3. Saacufte Sump Surfaces Airborne Detroit Tra/Sc Sump Surfaces Aireoma 10 Step Fade Sump Surfaces Airborne AJr Baseline Sump Surfaces Airborne IS Stop Fade Sump Surfaces Airborne Final Basetine Sump Surfaces Airborne Average 0.313 3.291 0.1*4 (0.4S2)4 1.430 0.*?: 0.290 (0.SO4) 0.2*? 0.13? 0.032 (0.1 *3) 0.*43 0.142 3.13* (0^60) 0.436 0J0? 0.134 (0.432) 0.602 U4g 0.1 ?s (0.773) 0.433 0.390 0.16? (0.29?) 0.432 Average _ 0.363 0.2*9 0.60?' 0.1*9 0.*12 2.490 0.242) 0.129 0.2?0 0.092 i0.l9f) 0.230 0.071 0.132 (0.161) 0.419 0.2*2 0.079 (0.2*7) 0.0? \ 1 0.23? 0.222 (0.183) 0JS3 0.J2* 0.1*5 (0.331) 0.201 V 0+ ;.?9 \ 0.265 -. - 0.2" 5 0.*16 . 0.429 0.4?2 - The ranges five tae loewst usd Highest percentage found for the area drnrtng tcnedulea as a vftott. Avenge value for wheel where coUeeooe root place. Not analysed--indicates that aaalyss wu not required Test Schedule Collector 1 Detroit TraflJe Samp Serfages Airborne 10 Stop Fade Sump Surfaces AtfbORM 2 Burnish Sump Surfaces Airborne Detroit Traffic Sump Surfaces .Airborne 3 Detroit Traffic Sump Surfaces Airborne Avenges Program avenge: 0.24? BetteUa avene: li?l Ratio; Batted* Frapem 0.49 TaMe 10 Comparison of Analytical* Results for Asbestos Froat Pise Brakes _____ Proven PA Sstttde 0.2*7 0.137 1032 a*43 0.234 0.402 ai84 aoo* _ 0224 aou - 0.023 a:o4 .a 003 . . - - 0.21 0.011 a 001 1.22 0.31 lit - no 162 a oo4 0.133 - 0.016 a:63 hear Dram Braces Program Batted* ai:9 i3?3 a092 0.230 an: a*** 1.414 - a:*9 am ai 12 0.0*4 aos? 0.289 m 1002 0.004 - - - -- - - 1025 1004 0.001 122 - 100? 110 138 - 1037 1041 1013 1010 1044 0.07? Cutcn Program 0.291 -- 3su*de . _ 3.00? - . _ _ _ _ - .i i. Asbestos emissions were higher for new friction surfaces and decreased with use. Z. The drum brake produced more iscestcs emissions than 'die disc brake uucuiiy with the difference decreasing as die fneaon materials concnued in use. 3. Heavy (abusive) Jury did not .necessarily jive a higher percent of ssoesios: die large amount of deons produced, however, gave a significant nse n asoestos emissions. . .Asbestos emissions from die boxes were found 10 decrease from fade or heavy-duty stops (highest) to burnish :o moderate boxing (.lowest). 5. For the disc pads only, there was an increase :n asoestos emissions -with increased asbestos content m die friction material. (There was no such trend for die arum oraxe ma cenais.) . 9oth die front disc pads and the drum linings of vemcie test 3 have wear comparable to that found m die other rwo vehicle testa, yet die asbestos emissions were significantly lower. (Both pads and secondary linings contained brass chips which may have been in part responsible for the more complete conversion of the asoestos m the brake emissions.) 7. For both disc and drum brakes the surfaces sample was the largest of the three (-91%). die sump sample was next (--?%), and the airborne sample was the smallest (--i^). ESTIMATE FOR .ASBESTOS EMISSIONS The purpose of the following discussion is to develop an estimate of total brake and dutch emission* from the United Sates population of motor vehicles in use on die roads asd highways. Inputs include ail of the test results described earlier together with a supplementary data oase on United Sates motor vehicle population asd usage asd on fricaoa material usage asd consumption obtained from other sources. Because of the uncertainties is all of the data available, emissions can only be considered aa a broad range, rather than as a single value, with the expectation that the true average emissions for both individual vehicles and the motor vehicle population in general will be within the range of values calculated below. DaTa BASE - To calculate the asbestos masons for afl vehicles it was necessary to asstmbie the following dau base. Sumter of Vthicles in Use Table 12 lists the total United Sates motor vehicle population as estimated by both De partment of Transportation (DOT), National Highway Traffic Safety and Federal Highway Administration (S), and by the R. L Folk Co. (9). The Polk census is said to be more prease because it eliminates multiple registrations of the same vehicle. Polk considers that DOT esumatts may be as much as 12% too high. Both Polk and DOT ormt military vehicles but include all other motor vehicles that art statelicensed including police can. school buses, and the like. Independently, the General Servicas Admimstntion reports that 190,000 Department of Defense vehicles are in use worldwide. In addition, there are 6.6 million braked trailers and 3B.4 million motor vehicles with dry dutches. Motor Vtktclt Usjfr The approximate total number of miles traveled by ail United Sates motor vehicles was l .149 trillion miies for '.9~7 according to a recant DCT esemate ($). The average annual mileage for passenger cars :s 99"S miles wrule for trucks ;t a 990" miles. An attempt was made to estimate the proportion of United Sates dnvmg that takes piacc m predominantly hilly or mountainous areas wnere long steep graces are common. Basic dau on miles drrren -ji each state were ootainec from DOT. The percentage of driving that taxes piece ui mountainous areas, where abusive brake use may be necessary, is estimated :o be i 1 .S*o of all invuig. The ssamate j suitecsve :c a large depse and .may be oiga. but no better dau have been located. Asbestos in ruction 'fertrais The data .a Tacie 13 jidicate that the total amount of asbestos contained .n id of the automonve brake friction materials soid each year s calculated to be about 103 million lb wnich corresponds to -US millioa lb 'used prior to grading. Two of the most iciowiedgeablt sources (10, 11) report that 90* 100 millioa lb per year are -used, A report from HT Research Institute suggests that 6? million lb are used annually m brake linings (12). A Bureau of Mines Report (13) based on 1969 data credits omy 50 million lb of asbestos to automotive use. a number tire authors find to be much too small. Ignoring the two latter values, the three estimates of asbestos contained .n brake friction materials range from 90-120 million lb. Using the calculated venicie of 113 million lb and assuming a ; 5*5 grinding and drilling loss, the maximum amount of asoestos incorporated in brake friction materials is oxen :o pe 103 million lb per year. A compilation of dau on clutch friction materials was aiso made (14). Based on these data, the total amount of asbestos contained in ail automotive clutch friction materials soid each year is calculated to be about 4.5 million lb. AMOUNT OF FRICTION MATERLAL ACTUALLY WORN - For several reasons the amount of brake lining (and asbestos) worn away during a year ts significantly less than me total amount installed on vehicles. Brake usings are seidom completely worn away. (Due to the geometry of brake TaWe ] a CampUsnon of Calculations for amount of 3nxe rr.cr.on Material Worn Away Aanuaily Ciimiaoon Total grace rnraon Minna*. million '.b Installed weignt easft year Discarded on teiuunf, * Discarded on venseies retired million can x L2t lb x S.T * 0.?j mulion litat truck* x 5 lb x *0* L.i * 0.10 million medium truces x U (b x u<W 0.6 0.15 million heavy truce* x *1 lb x *0% L* miscellaneous * 0.5) amount worn sway annually n.a : r.o t-ys ,, r 1 If nr 11!,, 1 ] ?1 3sf | 3*;s?:3? 25 s 393339333333333- *399S9aaSf 333339*3 -- 3933- ill! If*! a s lr SI 1" X SSeSsSSSSfsSIsS 339933333339399 --y* g-- --9^-- 9-- --9 *--9-- --9 9-- 9-- --9 9-- 9-- 999333333993399 35 *<51 9*9- *939 3-- 99 -- 93 -- 9# 9-- y>9 -- 3 9-- < i * 1I < i S3 X* 5 g 39 -- -- 9-- i-- -- '39'9 -- o*9 SS AZ S --9 --<N ---- -- *9 M f 1 M 33 9 ^<* ^* H 24 f Zw 4 *? 12 4i 12 is 1 f2 J 1^1^!^!?? ij ||2j|2i|2|i2||2 \6 /-// 13 ASBESTOS EMISSION ESTIMATE rOR .All VEHICLES The test vehicle results an be extended to ail passenger vehicles m the following manner. Pssunftr Csn The estimated total asbestos emission ' per year can be calculated from the following information: l. Total asoestos emission per vehicle is 23.51 ag/sule. Z. Nuraoer of sales per -vehicle is 99^3. 3. Number of passenger vemdes is 96.AOO.OOO. from the above, the estimated asbestos emission in pounds per year: :3.51 ug _ x *06 i * 9.973 x mile-vemcie ag x J___ 4*4 g X 96.4 x IQ* -vehicles * 60,400 '.b per year The distribution of the total asbestos emission calculated for the test vehicle can be determined by applying the percent distributions given earlier. The fata of the 60,400 lb cal* euiated above for the test vehidt is shown in Table 19. Trucja end Jum Truck brakes usually tend to operate at higher temperatures than passenger can. Thus a greeter proportion of high^emperacurt use in severity weighting can be obtained by uang a larger flection of the 10 3top fade asbestos amission, for trucks and buses, the test remits are arbitrarily weighted, as given in Tabic 30. In addition to the seventy factors, it is necessary to estimate the total average asbestos ermssioa for a light truck, a medium truck (or bus), and a heavy muck. The -value for the test car was 23.51 ug/tmle. Assuming that trucls have remits proportional to the raoos of the friction material weights, the asbestos emission for trucks art larger than for the test car by the factors shown in Table 21. A slightly larger factor is selected for the dutch a it is used more often in trucks man in passenger cars. The esureates for the total asbestos emission per light truck, medium truck (or bus), and heavy truck were calculated using the severity and emuaons factors given m Tables 20 and 21. These results are shown in Tabie 22. The total asbestos emission per year for light trucks can be calculated from the following information: I. Total asoestos emission per vehide a 3T.S1 ayrniie. 2. Number of miles per vehicle is 9807. 3. Number of light trucks is :7.:CQ,2C0. Estimated asoestos emission in pounds per year: 87.51 X ;06 -S- x 9.307 x I03 SiS * JL_ mu* ug year 454 j X 17.1 X iO4 vehicles 3U0Q lb per year The estimated value for the total asbestos emission from trucks and buses a shown in Tabie 25. The distribution-weighting factors for trucks were cal culated based on the following considerations. The truck drum brake is designed to be more open than the car dram brake and in many instances no splash shields are used. 3ased on the estimates. 'Jut only about 25ft as much aeons re mains in a truek dram brake as compared with a passenger car drum brake, disuibunon-wtighanf factors for tracks -were estimated. The distribution of the total asbestos emis sion estimate a shown in Table 24. SUMMARY AND CONCLUSIONS The purpose of this program was to obtain asbestos emis sion data from brakes and dutches for 2 vehicle dunag actual operation. Unique emissions collectors for a disc brake, drum brake, and dutch were concerned, designed, built, and in stalled on a vtfaide. The vehicle was driven through various test cycles to determine Jie extent and type of brake emis sions generated at both low and high temperatures. Typical original equipment and aftermarket friction materials for both disc and drum brakes were used in the testa. Brake relines were made to simulate consumer-cype practices. The partieuiates -were processed and analyzed by j combination of optical and electron microscopy. ? Table 25 Summary of.Ml Sake aa* Cutca Sourness, pounds per reen Vbida No. of Vthsdes teas AsPenes Emaaons Stooout Dtambutiou Airborne Sake Rerencer Puamor an lilbt seeks Medium trucks see buses Heavy sucks Miscellaneous* 96.400.000 17.100.000 1600.000 60,400 32.200 16.300 1.200.000 32,900 6.6U.000 16.300* Teals 138.200 Piroent of teal 49.470 28,420 14,330 21920 14.330 133,470 15.6 2,230 940 470 930 470 3.060 3.2 8.700 1940 UOO 3.030 UOO 17.670 U.2 'Eso&aad equal to medium nudes u wtttnts of friction material used for been atefoces are almost quai liable 12). lade dee aetoceyeies. aiders, <t& /-/?