Document LpDN4wgRm96Ry7q4Gq1Qv8DOz

FILE NAME Brakes BRK DATE 1973 May DOC BRK041 DOCUMENT DESCRIPTION Report - Meeting of The Society of Automotive Engineers - Asbestos Emissions from Brake Dynamometer Tests TOEH Code No 3915 2 ' 74 80 SOCIETY OF AUTOMOTIVE ENGINEERS INC ~ _. Two Pennsylvania Plaza New York N.Y. 10001 . ew ow? 2 Asbestos Emissions from Brake | Dynamometer Tests A. E. Anderson R. L. Gealer R. C. McCune and J. W. Sprys Scientific Research Staff Ford Motor Co. Automobile Engineering Meeting Detroit Mich May 14 118973 730549 Copyright Society of Automotive Engineers Inc. 1973 All rights reserved 730549 Asbestos Emissions from Brake Dynamometer Tests A. E. Anderson R. L. Gealer R. C. McCune and J. W. Sprys Scientific Research Staff Ford Motor Co. ASBESTOS HAS BEEN A MAJOR constituent of automotive friction materials for more than 50 years It is used to impart strength flexibility and heat resistance to a brake lining and to enhance friction and wear properties Most present brake linings use resin or rubber binders and chrysotile asbestos together with organic and inorganic friction modifiers and fil- lers The asbestos content varies with formulation from a low of 25 to about 65 by weight Minimum asbestos levels are found in some high performance European disc brake lin- ings which are highly filled with metals and inorganic constituents Brake linings in the United States average about 50 asbestos content Of a total United States annual asbestos consumption of 800,000 tons 730 Mkg about 28,000 tons 25 Mkg of chrysotile asbestos are purchased annually for friction materi- als of all types * Ref 9 suggests 59,000 tons 53 Mkg is more correct Of this it has been calculated that brake lining wear consumes about 12,000 tons 11 Mkg of asbestos per year Roughly an equal amount remains on brake shoes at the time of replacement or is manufacturing wastage Numbers in parentheses designate References at end of paper Recent tests have shown that densely populated urban at- mospheres often contain significantly higher asbestos concentrations than surrounding areas 2 Background asbestos levels in the atmosphere result from the natural weathering of asbestos rock and soil as well as from mining farming and excavating The generally higher urban concentrations suggest commercial and industrial sources Brake lining and clutch facing wear was suggested by Thomson 3 as a possible source for higher asbestos levels in the urban atmosphere Lynch 4 in a study undertaken by the Public Health Service reported the findings of several brake dynamometer and friction machine tests in which wear debris was trapped on a filter and subsequently examined by means of a transmission electron microscope TEM He concluded that free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution Lynch detected no free fiber from an automobile clutch and a bus drum brake but some free fibers were found in one test of an experimental disc brake With mounting concern over air quality in general and asbestos pollution in particular this study was initiated in 1970 to provide additional data on the asbestos emissions from disc brakes ABSTRACT Dynamometer tests of a production disc brake provided new information on asbestos fiber emissions during break normal use and high temperature use conditions Both ambient air and brake cooling air were sampled isokinetically using 0.45 ...mfilters Examination of test and background filters required a clarification process to maximize fiber detectability the use of transmission electron microscopy at 40,000X for detection and electron diffraction for positive identification of asbestos fibers Most of the lining asbestos was found to be converted to a nonfibrous material by the high flash temperatures of the braking surface Less than 0.02 of the lining wear was released as asbestos fibers The concentration of as- bestos fibers in the urban atmosphere due to brake usage m was conservatively estimated at less than 0.07 ^ 10fl ,, . Based on this upper bound the use of brakes was judged to be not significant as a source of atmospheric asbestos 2 OBSERVATIONS OF LINING WEAR The near absence of free asbestos fiber from lining wear has been reported by Luxon 5 using ray diffraction and by Lynch 4 using the TEM Several authors have suggested that interfacial temperatures during braking could be high enough to decompose the chrysotile asbestos into nonfibrous thermal degradation products Analytical relationships exist which permit calculation of interfacial temperatures 6 However several of the significant parameters are difficult to determine accurately for heterogeneous materials such as brake linings The asbestos crudes larger fiber bundles were calculated to reach their rapid decomposition temperature during normal braking at speeds above 56 mph 25 m as an upper bound value and above 18 mph 8 m as a lower bound value An experimental approach was undertaken to provide closer bounds Added insight into the thermal decomposition of asbestos fibers in brake lining wear was attempted by direct visualization of the frictional process A small laboratory friction test machine was constructed using a thermal shock resistant Vycor glass rubbing surface replacing the conventional cast iron in which the friction interface was directly viewed with a low power 7-50X binocular microscope 7 Scaled rubbing velocities were used to compensate for the thermophysical property differences between the glass and cast iron Moderate scaled velocities roughly equivalent to 12 mph 5 m provided a view of intermittently incandescent asbestos crudes During the initial burnishing operation resinous material surrounding these asbestos crudes was observed to pyrolize producing microbeads of condensation products around the crude These organic products of resin degradation and the apparently powdered asbestos decomposition products were seen to smear into platelets often of such size as to be discernible to the unaided eye At higher rubbing velocities over 30 mph or 13 m the platelets formed a surface char layer under the action of more severe thermal and mechanical action The larger asbestos crudes then could be seen to glow with apparent depth and for greater time durations often several seconds The actual brake lining contact area was only a few percent of the total available surface with contact spots moving in a random manner with time From these friction visualization studies it appeared that local flash temperatures and severe mechanical action could be major factors in the breakdown of asbestos fibers for most brake usage Examination of the lining surfaces revealed the presence of nonfibrous magnesium silicate in both crystalline Forsterite and amorphous phases Magnesium silicate is a thermal degradation product of chrysotile asbestos Forsterite transformations have been reported to occur at 600 over a period of hours Differential thermal analysis DTA studies in our laboratory indicated this transformation occurs within seconds at 820 Special brake lining formulations were then prepared and tested on the glass visualization apparatus and a Friction Assessment and Screening Test FAST machine 8 Chemical reactions were found to take place at the friction interface which would require a flash temperature rise of 740 to initiate when an equivalent of 35 mph 16 m rubbing speed was used on the FAST machine At this same speed melting of inorganic lining additives and metal particles confirmed brake flash temperatures up to 980 Based on these findings it would not appear surprising for few asbestos fibers to be emitted from brakes in normal usage However some mechanical removal of fiber appeared possible during the first several brake applications with new linings Also high brake temperatures possibly could weaken the organic binders and cause increased fiber emissions TEST PROCEDURES Complete sample collection and examination procedures along with sample data calculations are included as Appendixes D Briefly the tests were performed as follows a new Pinto disc brake assembly was installed on a single station brake dynamometer in a room which was cleaned of extran- eous asbestos sources Air from within the room was blown through a diffuser screen to provide a velocity distribution over the brake which approximated that of vehicle usage The air stream in front of and behind the brake was sampled isokinetically using matched 0.45 ...mfilters holders and air pumps The system schematic is shown in Fig 1 and the ac- DRIVE MOTOR Fig 1 " Dynamometer test schematic TEST GRID TEST FILTER EXHAUST 4ra > TEST PUMP AND FLOWMETER TEST INERTIA SCREEN DIFFUSER DYNO TAILSTOCK BACKGROUND FILTER BACKGROUND PUMP AND FLOWMETER 3 tual test setup in Fig 2. The brake exhaust air was discharged out of the building The first pair of filters was used during the first 82 burnish stops to represent break conditions After further burnishing a second pair of filters collected samples during 560 normal use brake applications A third set of filters was then utilized in a high temperature use test of 41 brake stops All brake applications were made from a 40 mph 18 m equivalent speed Break and normal use tests employed brake torques corresponding to 1/4 g 2.45 sdecelera- tion This torque level was doubled for the high temperature tests During the normal use procedure the test filter was located for 20 brake applications at each of 28 grid locations in the exhaust duct throat to insure a representative sampling of the airflow over the brake This test grid and filter are shown in Fig 3. A central collection site in the test grid was used for the break test and the final high temperature test Samples of the three pairs of filters break normal use and high temperature use were subjected to a clarification process involving low temperature ashing to oxidize all organic material and mechanical action to separate the particles This assures maximum detectability of asbestos filter 2 RESULTS AND DISCUSSION Transmission electron microscopy at 40,000X was used in the search for fibers At this magnification the ultimate fibrils appear to be above 1 mm 0.040 in in diameter Quantity length and apparent diameter measurements provided data for calculation of asbestos fiber mass per unit of filter area Coupled with dimension mass and flow determinations from the dynamometer tests these data were used to calculate the emitted asbestos fiber concentration in the collected wear dust in the cooling air stream and from the brake lining worn The size distribution of collected fibers was not determined by this method since the clarification process involved suf- ficient mechanical action to reduce most fiber bundles to the ultimate fibril size Additional samples of the normal use test filters were ex- amined on the TEM without recourse to the clarification process in an effort to determine the asbestos fiber size distribu- tion Roughly 10 of the asbestos fiber was visible on the background sample based on the results from corresponding samples after clarification The largest observed fiber bundle was 0.20 min diameter and over 1.1...mlong A similar direct TEM search of the normal use test filter revealed about % of the asbestos fibers observed after clarification This reduced percentage of visible fiber was attributed to the greater con- centration of obscuring matter in the test filter However the mS) RNY MA Ale FindOs <3 x > m eS ASTABS tede ye . SONSf re . te SVU Fig 3 - View of brake assembly and test grid Test Grid and Filter Test Broke Assembly Hot Wire Anemo- meter Infrared Pyrometer we ; Background Filter Fig 2 - Dynamometer test setup 4 largest observed asbestos fiber in the test filter 0.13 min diameter and over 1.2 mlong was about the same size as was found on the background sample The similar low fiber content of both background and test filters precluded a fiber size distribution estimate However it appeared that the quantity of the larger asbestos fibers on the test filter was no greater than that of the background filter This supports the observation from the lining wear visualization tests that normal brake wear degrades most of the asbestos fibers A brake lining grade of asbestos appears on the TEM as in Fig 4. The fiber bundles are composed of strong but weakly adhering fibrils of about 0.03 mroughly 1 in diameter Mechanical action causes the larger fibers to open into smaller fibers or even fibrils as illustrated in Fig 5. Contrast these raw material fibers with one of the larger fibers Fig 6 and one of the more typical fibrils Fig 7 from the normal use test filter The similar low fiber content of both background and test filters required clarification to permit an asbestos fiber count thus providing more accurate fiber mass determination but obscuring the actual fiber size distribution Therefore the calculations of fiber concentration Table 1 were expressed as asbestos mass per unit mass of lining wear dust and asbestos mass per unit mass of lining worn Asbestos fiber concentration in the ambient air background and in the brake exhaust air test was calculated in units of nanograms ng = 10-9 grams per cubic meter of air However the actual asbestos emissions from brake usage would be diluted substantially through mixing The asbestos concentration in urban air due to brake usage was estimated based upon existing automotive exhaust lead dilution data These calculations appear in Appendix C. All the test results in Table 1 have been reported as ten times the calculated test values to allow for possible losses in Fig 4 - TEM image of chrysotile asbestos fibers Fig 5 - TEM image of partially opened fiber bundles 2 a ry pekases SRA he = BS ee He Wt ST aS, ay . pn Fig 7 - TEM image of fibril on normal use filter S Table 1 - Asbestos Emissions from Normal Use Braking Dynamometer Data for Production Disc Brake Background asbestos in ambient air Asbestos fiber from brake in exhaust air Total asbestos fiber in exhaust air Estimated brake asbestos fiber in urban air Asbestos fiber from brake in airborn wear dust Asbestos fiber released from lining wear 19 X 10 m 13 ^ 109 m 32 ^ 10 m 0.07 ^ 10-9 m 0.05 0.02 and tire Accurate measurement of this material was not possible due to the added retention of dust from the ambient air More precise values of brake lining asbestos emissions or the determination of their particle size distributions appear possible for these low fiber concentrations only by testing brakes in an asbestos atmosphere This approach was used in an EPA sponsored study 9 where prefiltered air was flowed through sealed brakes at a flow rate greatly reduced from normal CONCLUSIONS Reported values are 10 times the observed test values to provide upper bounds collection processing and counting These values therefore should provide upper bounds for asbestos emissions from brake uage For example the local Detroit atmospheric asbestos concentration ranges 0.5-13.4 mThe observed background asbestos value was 1.9 ng m, for the normal use test but is reported in Table 1 as 19 m. The low asbestos emis- sions from the test disc brake under normal use conditions is underscored by the addition of only 13 m1.3 m observed in the undiluted exhaust air stream The lining wear rate during the first 82 break stops was found to be about five times above the normal use rate As- bestos fiber release during break was also higher an average sevenfold increase However since the break wear is less than % of the total lining wear the increase of emitted asbestos fiber resulting from this temporary sevenfold increase would be about % when averaged over the life of the linings High temperature brake usage also increased lining wear rates in this case by a factor of 11. Asbestos fiber emissions increased by less than a factor of three Frequent vehicle operation under such high temperature conditions would lower lining life to levels far below present averages However even if all brake wear provided the same fiber emission rate as found in the high temperature use test the percentage fiber release to the atmosphere would still be under 0.06 of the lining wear The remaining brake wear was a mixture of nonfibrous organic and inorganic matter Of the estimated 62-77 collectable wear debris 47 were accounted for by the test filter on the normal use test The remaining 15-30 presumably were retained on the lining edges the caliper spindle rotor wheel 1. Automotive brake usage provides a very small emission of asbestos fiber less than 0.02 of the lining worn 2. Automotive brake usage provides a very small asbestos fiber input to urban atmospheres estimated to be below 0.07 m 3. Intense local heating and severe local mechanical action causes the decomposition of most asbestos fiber in brake linings during typical usage REFERENCES 1. R. J. Sullivan et al Preliminary Air Pollution Survey of Asbestos NAPCA Publication APTD 69-27 1969 2. E. J. Selikoff et al Asbestos Air Pollution Arch Environ Health Vol 25 July 1972 3. J. G. Thomson Asbestos and the Urban Dweller Ann Y. Acad Sci Vol 132 No. 196 1965 4. J. R. Lynch Brake Lining Decomposition Products J. Air Pollution Control Assoc Vol 18 No. 12 1968 5. S. Luxon Technical Implementation of the New Asbestos Regulations Ann Occup Hyg Brit Vol 13 1970 6. E. Rabinowicz Friction and Wear of Materials New York John Wiley and Sons Inc. 1965 7. A. Anderson Wear in Brake Materials ASME Wear Conference 1969 8. A. E. Anderson et al A New Laboratory Friction and Wear Test for the Characterization of Brake Linings SAE Transactions Vol 76 paper 670079 9. M. G. Jacko et al Brake and Clutch Emissions Generated During Vehicle Operation Paper 730548 presented at SAE Automobile Engineering Meeting Detroit May 1973 10. K. Yada Study of the Microstructure of Chrysotile Asbestos by High Resolution Electron Microscopy Acta Crystal Vol A No. 27 1971 APPENDIX A SAMPLE COLLECTION DYNAMOMETER ROOM PREPARATION The normal brake cooling air was found to be more variant and higher in dust concentration than was the room air Consequently the supply air duct was removed and sealed To reduce the background asbestos level to a minimum the dynamometer room was thoroughly cleaned and vacuumed while maximum exhaust airflow was maintained All potential sources of fiber emissions were removed from the room and asbestos handling was curtailed in adjacent rooms A production Pinto disc brake assembly was installed on the single station brake dynamometer as shown on the schematic of Fig 1. The major elements of the test setup may be seen in the photograph of Fig 2. Cooling air was supplied from the room by means of a fan and diffuser screen Containment of all possible airborn wear dust was assured by fitting a rectangular collector nozzle to the exhaust air duct about 2 ft downstream of the brake Metal panels were installed below and beside the brake to contain the cooling airflow further and to help provide a representative airflow over the brake compared with vehicle service System parameters were adjusted until the air velocity distribution matched closely with actual usage and the air flowing over the brake assembly was fully captured by the exhaust duct This was confirmed using a smoke generator The exhaust duct throat was partitioned into a 4 X 7 array of roughly 3 in square grids Fig 3 The velocity profile within this grid was measured to provide mean values for each grid square SAMPLE FILTER PREPARATION Microporous membrane filters with 0.45 ...mpores were selected to assure high retention of asbestos fibrils and most of the wear dust powders A matched pair of Gelman sampling pumps and 35 mm diameter holders were used Thin metal cones of 12 deg included angle were fabricated and sealed to the filter entrance These cones increased the tip entrance velocity to that of the exhaust air duct so isokinetic sampling could be achieved The cone tips were carefully matched in size Flowmeters and differential pressure indicators were installed the system to monitor the filter airflow during each test and to set the tip entrance velocity before each test Tests were performed on the unused filters to determine their weight change with variation of humidity Filter weights were measured on a microbalance to the nearest 10 gFilters were placed in the center of the designated exhaust duct grid and at a fixed position upstream of the brake but downstream of the diffuser screen This latter background filter was located where the upstream air velocity equalled the average over the test grid In this way the sampling was isokinetic with essentially equal volume flows through both filters TEST PROCEDURE All brake stops were conducted from the same speed equivalent 40 mph or 18 m to maintain fixed airflow conditions Burnish and normal use brake applications were at 0.25 g 2.45 s m deceleration and with a 2 min time in- terval This provided a peak rotor temperature of 180 350 The number of brake applications was selected to provide about 1 g of lining wear per test Break wear was monitored for the first 82 stops No sampling was performed for about 200 more brake applications while the linings and rotor developed essentially steady- state conditions The normal use test was then performed on this burnished brake assembly Twenty brake applications were made under the same conditions with the test filter located sequentially at each of the 28 grid locations The filter cone entrance velocity was adjusted to match the grid velocity at each relocation Four grids were used to monitor exhaust velocity Slight Table A - Test Data Test Break Normal Use High Temperature Use Brake speed rpm 535 40 mph 535 40 mph 535 40 mph Brake decel g 0.25 2.45 s 0.25 2.45 s 0.50 4.9 s Wheel load kg 257 567 lb 257 567 lb 257 567 lb Brake applications 82 560 41 8.54 0.625 Total energy kW 0.938 1.25 hp 6.405 hp 0.469 hp sg Maximum apply temperature C 115 240 115 240 410 770 2 Total lining wear g 1.10 1.60 1.07 in Lining wear rate kW 0.051 in in 17 0.250.25 0.011 0.011 hp 2.282.28 0.1h0p0 7 adjustments were sometimes required to compensate for drift which appeared to be external wind initiated A third test was performed to provide an estimate of the fiber emissions from a hot brake assembly As in the break test the test filter was positioned in a central location for this procedure Thirty stops were made at 0.5 g 4.9 s and minimal time interval until the rotor attained 410 770 This temperature was then maintained by adjusting the application time interval Ten additional stops were made as the brake was allowed to cool the filters were individually stored in covered glass containers Lining weights were taken after removal of wear debris but before they had cooled completely to minimize weight changes from water absorption Between tests the linings were stored in a dry jar The relevant test data are included in the Table A A slight pad drag caused the outboard lining to wear above expectations on the normal use test Since this added work was not included in the lining wear rate calculations the specific wear is above the usual range for this lining No adverse effect on the test results would be expected to have resulted All filter weight determinations were performed at equilib- from this drag Similar pad drag effects may occur on cars rium conditions and then corrected for humidity After use when smooth road conditions prevent pad knockback APPENDIX B . SAMPLE EXAMINATION ASBESTOS PREPARATION AND EXAMINATION OF CARRYING SAMPLES FROM TEST FILTERS 1. All slides dishes scalpels and other utensils used in the following preparations were cleaned in acetone followed by rinse in 200 proof ethanol 2. An area of measured dimension was selected at random from the test filter cut and placed particle side down on clean glass slide 3. Several drops of acetone were placed on the filter segment to dissolve it partially and secure it to the plate 4. The samples were ashed for a period of 2 h by using a low temperature asher at a chamber pressure of 0.5 torr 70 Pa oxygen and power of 200 W. 5. Several drops of a % solution of cellulose in amyl acetate were placed on the residue and a clean watch glass was used to grind the mixture for a period of 5 min 6. A second clean glass slide was then placed over the mixture of cellulose and residue and a smear obtained by pressing the two slides together and then sliding them apart 7. The films thus formed were permitted to dry and then were removed by scoring the edge of the slide with a scalpel and floating the film free from the slide in a distilled water bath It was found that the film was most easily removed from the slide introduced in Step 6 8. Approximately 10 electron microscope grids 3 mm finder grids were placed at random on the floating film and the film was lifted by putting a clean slide on top of the film and drawing the slide down through the water so as to trap the grids between the slide and the film which should now cling , to the slide Sample preparation techniques outlined are similar to those reported by Selikoff et al in Ref 2 9. carbon layer of approximately 0.06 mwas deposited on the film to prevent charging during examination in the TEM Direct examination specimens were prepared by depositing a carbon layer on the dust side of the test filter and dissolving the filter in acetone Electron microscope grids were used both to support the sample and to provide grid location ref- erence marks TEM EXAMINATION AND COUNTING PROCEDURES Approximately 10 electron microscope grids were prepared for each of the five filter samples analyzed Four grids were arbitrarily selected from each sample and two grid squares on each grid were scanned for asbestos The individual grid squares are approximately 90 ...mon each side and were examined at a TEM magnification of about 40,000 For each grid area scanned photographs were taken where possible of the first last and one randomly chosen fibril for the purpose of determining an average fibril diameter accurately Measurements were then made visually that is each fibril fiber or asbestos bundle was compared to known calibration marks on the electron microscope screen to estimate the lengths The length could be estimated to within 20 as determined by the photographic measurements The marks on the screen are 0.5 cm apart corresponding to 0.125 ...mwhen a magnification of 40,000 is used This approach was taken because it was impractical to photograph all the fibrils and furthermore length measurements were not as critical as diameter measurements in determining fiber volume Where both measurement methods were used the values providing the greatest indicated brake asbestos levels were chosen The results are shown in Table B From photographic measurements of 120 chrysotile fibrils 8 the asbestos fibril average diameter was determined to be 0.0337 mwith distributions similar to that observed by other workers 10 From 45 fibrils of triple milled chryso- tile the average diameter was determined to be 0.0316 ...m with a standard deviation of 0.0063 m ; ASBESTOS IDENTIFICATION Asbestos can be identified in the transmission electron micro- scope in one of two ways The first and absolute method is by electron diffraction Such a diffraction pattern is presented as Fig B Measurement of diameters and correlation of these measurements with a known standard gives the interplanar spacings of the material Comparison of these spacings with the ASTM file identifies the material as chrysotile asbestos The second method of identification is by appearance Fig 2A represents an image of asbestos obtained in the TEM Fine lamellae are observed within the fibril which are parallel to the long axis This appearance is characteristic of chrysotile asbestos fibrils Because of the nature of the elec- tron beam radiation and heat damage can occur in the material markedly altering the appearance Such changes in asbestos are represented in Fig 2B The fine linear appearance of the fibril of Fig 2A has been changed to a mottled struc- ture Sample AACDE AACDE AACDE AACDE AACDE F I Table B Asbestos Concentration on Filters Concentration Sample Identification cmof filter normal stop brakes Background for A normal burnished brakes Background for C Test temperature burnished brakes Background for not used insufficient sample unused filter 15.32 1.06 7.98 4.64 5.37 0.33 Fig B - TEM image of fibril before after electron beam damage APPENDIX C DATA REDUCTION Table C contains the pertinent test data and calculated results from the brake dynamometer tests determination the asbestos concentration in urban atmospheres from brake wear should be less than ESTIMATION OF BRAKE LINING ASBESTOS DILUTION IN URBAN ATMOSPHERE lining The concentration of asbestos fiber from the brake wear debris is assumed to be the same as was found in the normal usage dynamometer test and to be dispersed and have the same residence times as the lead emitted from the engine Assume an average mileage of 15 mpg from cars which emit 75 of the lead to the atmosphere When gasoline averaged 2.52 g gal the typical Pb concen- m trations in urban atmospheres were about 2 JAPCA September 1969 Vol 19 p 684 Typical United States cars wear 202 g of lining and drive 10,000 miles The normal use dynamometer tests provided asbestos fiber amounting to 0.0023 2.3 ^ 10fl5) of the brake lining worn Allowing a factor of ten to provide an upper bound in this ^ 10,000 miles 2.3 10-5 202 10,000 \| ...gm15 mpg 8 Pb 2.52 gal 0.75 or 0.07 m Urban atmospheres vary in asbestos fiber concentration from city to city within a city and from one time to another This variation does not correlate with expected automobile brake usage The concentration has been reported to reach 100 m2 Thus it appears that the wear of brake lining pro- lining duces at most a small fraction of the asbestos fiber in urban air This is not surprising when one considers that brake wear involves only 1.5 of United States asbestos usage and that brake usage converts over 99.95 of this to nonfibrous dust Table C - Test Data and Calculated Results from Brake Dynamometer Tests Break Normal Use High Temp Use Test Sample Test 1. Filter airflow m 2. Filter pickup mg 3. Filter asbestos concentration 2.22 0.36 cm 4. Blank asbestos concentration cm 5. Filter area cm 6. Filter asbestos ng 7. Asbestos concentration in air m 8. Lining asbestos in exhaust air 15.32 0.33 9.62 144.2 64.95 ng 9. Lining asbestos on filter ng 10. Duct filter flow 11. Lining asbestos released mg 12. Lining wom mg 13. Asbestos released as % of wear 14. Lining dust on filter mg 15. Lining dust in air mg 16. % asbestos in wear dust 17. Lining dust as % of wear 61.8 137.2 1235 0.169 1100 0.015 0.26 321 0.053 29 Bkgrd 2.22 0.10 Test 23.00 1.56 1.06 7.98 0.33 9.62 7.02 3.16 0.33 9.62 73.59 3.19 1.29 29.7 1235 0.0367 1600 0.0023 0.61+ 754 0.0049 47 Value calculated based on normal use background due to insufficient sample Filter in one central location and thus possibly nonrepresentative Corrected for flow volume difference through test and background filters Bkgrd 21.80 0.90 Test 0.564 0.27 4.64 5.37 0.33 9.62 41.46 1.90 0.33 9.62 48.48 85.96 84.1 47.4 _ 1235 0.0586 1070 0.0055 0.27 333 0.018 31 Bkgrd 0.564 0.00 0.12 0.33 9.62 1.07 1.90 Calculation Basis Measured Measured Measured Measured Measured 3 4 X5 6+1 A 8X1 From measure 9 X 10 Measured 11 12 X 100 10 X 14 11 ^15 ^ 100 15 12 X 100 APPENDIX D CALCULATIONS OF COLLECTION EFFICIENCY Lining composition estimate from laboratory analysis % SiO2 MgO F-- 203 Al2O3 HO CaCO3 Zn Organic Total 16.3 17.8 2.5 0.3 5.5 15.4 3.9 38.3 100.0 Chrysotile asbestos 42.4 Wear debris estimate % Decomposed asbestos . Decomposed limestone Zinc metal Inorganic 36.9 8.6 3.9 49.4 Organic Volatile Uncertain Low volatility 10.5 15.7 12.1 Organic collectable Total collectable 12.1-27.8 61.5-77.2 t Collected on filter 47 Collectable material not trapped by filter 14.5-30.2 This material presumably on shoe edges caliper rotor wheel and tire use pony Sal This paper is subject to revision Statements and opinions advanced in papers or discussion are the author's and are his responability not the Society's however the paper has been edited by SAE for uniform styling and format Dis cussion will be printed with the paper if it is published Society of Automotive Engineers Inc. 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