Document dY0byGxmrQ4z8Ky0O1rLDGoV0

tr 1, Disc brak* emission* collector (left) from back, showing Instrumentation; (right) showing thermal control aids. HOW MUCH ASBESTOS DO VEHICLES EMIT? Most of asbestos emitted from vehicle brakes and clutches cation of emissions trends for frlci is converted to other products, with only 3.2% of total asbestos emitted entering the atmosphere, according tion materials with continued use. The third vehicle test simulated a complete brake reline, including to Bendix researchers. turned discs and drums. All friction materials contained asbestos, and were representative of those supplied by the industry. Ma A comprehensive investigation of gas Surfaces samples, including wear terials from Ahex, Bendix, KaybextiiH. jiiwl particulate emissions from auto, debris on brake, and collector shroud Munbatten, Thiokol, and Worhlheslos motive brakes-mid clutches during surfaces. ' t were used for original equipment und actual vehicle operation shows that, Airborne samples, collected on aftermarket disc pads and drum ! on the overage, moru than 99.7% membrane filters. linings, selected in part because of of the asbestos emitted is converted The clutch was sealed by closing i their high-volume usage. to other products, The contribution tiie remaining few holes in its-casing. to the atmosphere is estimated to be The left wheel brakes were kept in Collecting the emissions 5060 lb per year for the whole, coun their normal configuration. They were Fig. 3 shows a cross-seclinnul view try -- or 3.2% of the total asbestos used to monitor the operation of the of the disc brake emissions collector, emitted. shrouded brakes. Wear debris was The rubbing sen) is located ut the I These figures were obtained with taken from the left brakes as well Os ' hut or hub section of the rotor. The a medium, weight (1850.11> test weight I, high-volume passenger car with a 3-speed manual transmission, ventilated east-iri>i\ disc brakes in front, cast-iron drum brakes in the from those on the right. The gmounts of debris formed and the composi tions were used to demonstrate that the brake shrouding did not signi ficantly affect operation of the right- seal is a spring-loaded, graphite-filled Teflon seal of commercial manufac ture. The main portion of the shroud was coated with black oxide. A water cooling system was added, and an ! I i rear, and a dry cl (itch, A front disc hand brakes. Open "mag" wheel was used to aid brake collector (Fig, 1) and a rear drum brake collector (Fig, 2) in How the teat* yuere run in cooling the enclosed brake. A cross-sectional view of the drum i stalled on (lie right side of the vc. Three vehicle tests were run: tho liruke emissions collector is shown in Iiiele collected the weur debris and first with original equipment fric Fig. 4, along with details of (lie rub separated it into three fractions) tion materials; the second simulating bing seal, which is the same type as Sump samples, including the wear a partial reline -- fronts only were that on the disc brake emissions col debris on lining surfaces, in rivet relined, with the rears 'retained as is lector. The axle hub used to align boles, and on the brake drum. to give a replicate test, and an indi |he drum was mod>fi"J 'th a > ' rr FMSl 06667 4 I ! \ t\ I 1 ( I l file- rd n ding aim'd i n of Mil- eslos- ll'KlDK t mill drum .op of view prior, il 1 In' . Tim -filli'd infrtrliroud water id an 0 aid drum mi ill c mb1 nr no l pl> align niiM'C (hat ivas ro|ierntric lu the nxlo lirarings within t).(X)l in;' (0.0025 ein). A taprred lead facilitated ' drum mounting. Close tolerances were necessary on the concentricitjes to ohlain reasonable seal life. Seven lest vehicle driving schedules t were used. Each was followed by a measurement procedure that included Inking emissions samples, measuring imir, inspecting systems, und replac ing worn purls, if necessary. First, three low-temperature tesla were rim Burnish, Afterhurnish Baseline, and Detroit Traffic. These were followed hy the high-tempera ture tests -- 10-stop Fade, Afterfade Baseline, 15-stop Fade, and Final Baseline. Measuring asbestos content Kuril of the samples was analyzed lor asbestos content hy optienl and electron inlrroscopy. For vehicle test 1, asbestos content uf brake emissions ranged from l ,65ft down to 0.5ft). Of |he 47 analyses reported, only two were iiliovc 1.00ft, For test 1, the overall airragp was 0..HBft>, For lest 2, the usheslos content ranged from 1.12ft down to O.OHft, Of tlie Id analyses reported, only nne was above 1.09ft, and only three were between 0.50 and 0.96ft:) all others were less than 0.50ft., The merall average was 0.25ft, For vehicle te6( H, the range of asbestos content in brake emissions inried (mm 0.51 ft down to O.OOHft, Of the imnlyses reported, three were iM'lweyn 0.20 jind 0.51ft; all others were less than 0.20ft. The overall average wus 0.07ft, For all three vehicle tests, the over,. all average of asbestos content in the brake emissions was 0.2.'1ft. As a check on Bendix results, in dependent asbestos analyses were ulso mude*, which gave slightly different results. For example, Battellc Colum bus Laboratories, which analyzed 24 samples generated during the pro gram, obtained mi average of 0.17] ft, which is 69ft, of the Bendix average of 0.21ft. for the same 2i analyses. Tlie explanation for the higher Bendix values is as follows; all lurger fibers (bundles of fibrils) found were assumed to be cylinders of projected diameter and length, and a fiber with an elliptical cross-section was actually smuller in volume than reported. In addition, all fibers were assumed to lie 100ft asbestos (partially de graded asheslof) or olivine fibers were weak and niechunieally reduced In nonfihroiis material by the other analytical technique used, hence, only the remaining asbestos fibrils:`were counted). r To compare emissions properly, it was necessary to calculate the asbestos emissions factors for each sample in micrograins/mile, Values of these fur. tors were obtained by multiplying tlie weights of brake debris generated by the appropriate usheslos percents, then dividing hy miles per lest schedule. Thus, either a high usheslos content or a large sample gave a high fuctor. The trends in asbestos emissions can be summarized as follows: Asbestos emissions are higher for iicw friction surfaces and dec.reuse with list'. The drum |iruke produces mure ashrstos emissions Ilum the disc brake initially, hut the difference decreases us the friction muteriuls continue in use. Heavy (abusive) duly do not nepcssurily give a higher per cent "asbestos; the large amount of debris produced, however, give a signific,|pt rise is asbestos emissions, Asbestos emissions from |>rnkes de crease from fade or iieavy.duly slops (highest) to burnish to moderate braking (lowest). For the disc pads only, (here is an incrouse in usheslos emissions w itli increased asbestos content in the fric tion material. (There was no such trend for the drum brake materials.) Both front disc pads and drum linings of vehicle lest 5 had wear rales comparable In those found in l|ie oilier two vehicle tests, yet tlie asbestos emissions were sigiiificunliy lower. (Both pads and secondary linings contained brass chips, which may have been in part responsible for the more complete conversion of (he asbestos in liruke emissions.) Fur both disc and drum brakes, the surfaces sample was the largest of tlie three (iilioul 92ft), the sump sample was next (about 7ft ), and the airborne sumplv was smallest (about 1ft I. How asbestos emissions add up An estimate of the total emissions from brakes und elutrhes is given in Table 1. Values for llio number of vehicleill use are based on estimates from the National Highway Traffic Safely Adiniitjstraliun, the Federal Highway Administration, and other sources. FMSI 06668 wa* driven |>i>r year ami ilia number of vehicle* in use, Fur example, for passenger curs, the following estimates ware nscdl miles 1 X 90.1 X 10" vehicles year 451 g *= 60.400 lli per year emissions per light truck urc cal culated ut 87.51 pg/mile. Distribution factors had to he modified because the truck drum Total 'asbestos amission* par va, hic'la; 28.51 pg/mllr, which was oh* luluad hy averaging ilia vnliias from ilia lliraa valilala lasts, ! The usheslos from lha test vehicle brake is more open than the cur drum friction materials' was calculated to brake and, in many instances, has no end up as follows: 81.9% deposited splash shields. It was estimated, there on the ground, 11.1% retained in fore, that only about 25% as much the brake and/or disposed of during .; debris remains in a truck drum brake \vcrage animal mileage for |iassai|* gcr cars was asliiniilai) at 0078 inila*, sen ire, anil 8.7% emitted to ' Ilia atmosphere, These percentages were used to determine the distribution of as in a passenger-ear drum brake. The distribution of emissions for trucks, was, therefore, calculated to he: \umliar of passenger valilrlasi emissions for passenger ears. 87.9% road dropout, 2.9% airborne, 06, 100.000, Truck brakes usually are heavier and 9.2% retained in the brakes. Substituting lliasa values in ilia than passenger-ear hrakgs und tend (This work was performed with the support of the Environmental Protec Tabl* 1 Summary ol All Braka and Clutch Emissions (lb par year) tion Agency, through contract No, 68-01-0020.1 A Distribution Peasenger Cara Light Truck* Medium Truck! and Buses Heavy Truckt Miscellaneous' Number of Vehicles 96.400.000 17,100,000 Asbestos Emission* 60,400 32,300 2.600.000 1,200.000 6,615.000 Totals % ol Total 16,300 32,600 16,300' 158,200 Dropout 49,470 26,420 14,330 28,920 14,330 135,470 (85.6) Airborne 2,230 940 Brake Retention 8,700 2,940 470 950 470 5,060 (3.2) ' 1,500 3,030 1,500 17,670 (11-2) 'Estimated equal to medium trucks at weights of Irlction material peed for both cate gories are almost equal, tnoludee motoroyoles, trailers, and the like. Michael G. Jocko, physical chemist, Bcndix Research Laboratories; Robert T. DuCharme, supervisor. Brake Kngineering Laboratory, Automotive Control Sys tems Group, Bendlx Corp-i nd Joseph H. Somers, Office of Air & Water Pro group, Knvirnnmental Protection Agency. Based on SAK paper No. 73054H, "Brake and Clutch Emission* Genera led during Vehicle Operations," presented at the SAE Automobile Engineering Meeting, May 1973. Detroit. FMSI 06669