Document k6L5ejEL8YQBabXjgnqpGmD9y

FILE NAME: Railroads (RR) DATE: 1978 July DOC#: RR062 DOCUMENT DESCRIPTION: Report Prepared for the US Dept of Transportation - Asbestos Emissions From Railroad Brake Shoes Report on Research Work F R A Purchase Order 810-4351 Asbestos Emissions From Railroad Brake Shoes by J. F. Queciy and J. M. Wandrisco U. S. Steel Corporation Research Laboratory Monroeville, Pa. 15146 July 1978 Final Report Prepared for U. S. D E P A R T M E N T OF T R A N S P O R T A T IO N 'FEDERAL R A ILR O A D ADM INISTRATION Office of Rail Safety Research Washington, DC 20590 1, R p Ot i No. 9 C o v K o m in l / .C C M tiO " No. T.tu Asbestos Emissions From Railroad Composition Brake Shoes A u , h o ' ' ' - j . f . Queal y and J . H. Wandrlsco ? . P u r i o r m i n ; ) O / g o n i j o t i o n N o .t >o ch>d A d d ' * i U. S. Steel Corporation Research Laboratory M o nr o e v i ll e , Pa. 15146 1 2. S p o m o t i n j A g n c y K o m i a n d A d d ' : U. S. Department of Transportation Federal Railroad Administration O f f i c e of Rail S a f e t y Research Washington, D. C. 15. S v p I o m n t o' y N o t e * T e c h n i c a l R ep o rt D o c u m o n ia iio n P a g o 3. j Coiolog N o. i i !). R e p o n O o ' J u l y , 1978 . P ( i o i m i n r i 0 1c o n 1 x o 11 o n C o d 8. P ( l o t T m n j O ' p o o i j o t i o n R * p c r i N o . 76-H-045(0 1 8 ) ` 10. Urr.i N o . ( T S A I S ) 11. C o n n o c i . e i C ' O 't 1 K o . P. 0. 810-4361 13- o p e p o ' i e n d P /i o d C o v r o d c ; na i Report 1^. S p o n s o r i n g A g e n c y C o d * Samples of airborne emissions from three brands o f composition r a i l r o a d brake shoes were c o l l e c t e d during tests on a ful 1- s e a l e - r a i 1road-wheel-testing dynamometer under con trolled conditions simulating a high-energy-dissipation braking. A sb est os -fi ber concentrations, as measured by i nd iv id ua l samples, ranged from zero to 0.067 f i b e r longer t h a n '5 mi crons/cm^ -- f a r less than the c u rr e n t permissible occupational ex pos ur e l i m i t s of 2 f i b e r s longer than 5 microns/cm^ of a i r sp ecified on the OSHA Asbestos Standards. 1 7 .K y W o rd i Asbestos * Brake Shoes Composite M a t e r i a l s 19. S e c u r i t y C l o i v i f . ( o t h i i r p o rl) Form DOT F 1700.7 (8- 72) 1 8 . D i 1 t r i l >u l i o n S ' o l o m n t 2 0 . S * c u f i y C l o i . ( o ih p o g l 2 1 N o . o P 0 7 1 22. P > ' < r * Roproduclion o conplolnd pogc outl^ori tnd Conversion Factors 1 mph = 0.447 ni/s 1 hp = 0.746 kW i rpm = 0.105 rad/ 1 inch = 25.4 rrun 1 foot = 0.3043 m 1 ib = 4.45 N 1 ton 0.907 tonne Table of Contents 1. Introduction 2. Materials and Experimental Work 2.1 Wheel-Testing Dynamometer 2.2 Tests Conducted 2.3 Air Sampling and Analysis 3. Discussion and Summary Page ' 2 3 3 3 4 4 Tables Table I - Asbes.tos Emissions From Composition Brake 5 Shoes During Drag Braking List of Figures Figure 1 - View of Wheel-Testing Dynamometer 6 U. S. Steel Research Laboratory, Monroeville, Pa. Figure 2 - View Showing 33-Inch-Diameter Wheel in 7 Dynamometer Figure 3 - Portable Air-Sampling Pump and Filter 8 Cassette Figure 4 - View Showing Sampling Pumps Located 9 6 Inches and 6 Feet From Brake Shoe Figure 5 - View Showing Sampling Pump Located 10 17 Feet From Brake Shoe Introduction In recent years, the use o f compo sition brake shoe. instead of cast-iron brake shoes has been generall y accepted by the railroad industry, and prac tically a 11 cars being constructed have brake-system comp on ents designed for the us of composition shoes. Also, the bra ke-sys tem compo nents in many of the older cars in service ar e being modif i0 d so that composition- shoes can be used. Mo d ifica tio n of ol der cars i necessary because with composition shoes on 1y half the brake shoe pressure needed with cast-iro shoes is requi red to produce the same retardation. The averag e coef fic ier.t of friction of composition shoes is abo ut 0.30 , where s chat of cast-iron shoes is about 0.15. Co r.sequen tly , the raiIroad favors the use of composition shoe because of the r greater braking efficiency. There are three principal suppliers of composition brake shoes to the domestic railroad industry. Each manufacturer has developed a brake shoe containing various components that are bonded together by resin compounds. Their- compositions are considered proprietary, but the service performance of all types has been similar. Inasmuch as one of the components of composition brake shoes was reported to be asbestos, the subject study was proposed by the Federal Railroad Administration, Office of Rail Safety Research, because of concern that the airborne emissions that result from decomposition of the brake shoes during braking might contain sufficient asbestos fibers to create a health hazard. The criterion for -determining .whether a health hazard exists is the present OSHA.Asbestos Standard which establishes a permissible occupational exposure limit of 2 fibers longer.!than `5 microns per cubic centimetre of. air, based on an-8-hour time-weighted average exposure. The Standard also states that exposures shall not exceed 10 fibers/cubic centimetre for any period during the workday. OSKA has proposed to reduce the 8-hour exposure limit to 0.'5 fiber/cm^, with a ceiling 'limit of 5 fibers/cm^, as determined over a period of up to 15. minutes. -2 - Materials and Experimental Work Wheel-Testing Dynamometer .The railroad wheel-testing dynamometer at the U. S. Steel Research Laboratory ir. Monroeville, Pennsylvania was used to perform controlled rests of simulated railroad braking conditions with composition brake shoes. Samples of airborne emissions were obtained both under confined atmospheric condi tions and under conditions simulating the actual turbulentair-mixing effects resulting from train operations.*15 The whee 1- te sting :nachine , Figur e 1, is lairge inertia dynamomete r dr iven b/ a mill- type el ec tr lc mo::or W1 a power output up to 450 hp ;and speed s up to 1500 rpm.. Standard full-seal e railroad wheels froiti 30 to 48 incrres in diameter can be te sted , Figu:re 2., und er co nd it ion s or loadi and braking that simul ate no::na;L exis ting ra il roa d se:"V 1ce , under exaggerated cond itions of load! ng an a br ak ing far in exces's of those encoun tered :rn servie e. Tests Conducted For the tests used in this study, a high-energydissipation braking conditio n known as drag braking was simulated so that a sustained heat bui Idup would occur and the brake shoe would decompose at a re latively.high rate. This drag . braking is similar to that wh.ich would occur in normal railroad service when a loaded 70-ton car with 33-inch-diameter wheels is retarded in descending a grade. The dynamometer was fitted with a 33-inch-diameter v.'hee1 and a single composition brake shoe. A braking force of 13 00 pounds was exerted by the shoe onto the wheel tread for 50 seconds of each minute for a duration of 9 minutes, with, she equivalent translatory speed . of the wheel maintained at 45 miles per hour. " The energydissipation rate for these conditions was 50 hp. During the tests/ air samples were simu Itaneously collected for analysis, as will be described in a la ter section, at locations 5 inches, 6 feet, and 17 feet from the brake shoe, Figures 3 , 4 , and 5. Similar tests were conducted with brake shoes of the compositions produced by the three principal manufacturers, which are designated in this report as A, B, and C. Each type of br~ake shoe was also tested under two different aircirculation conditions, the first with the wheel rotating in nonturbulent air, and the second in a turbulent-air condition produced by an exhaust fan to sim u l a t e brak i n g of a train in motion. -3- Air Sampling and Analysis Air samples were collected and analyzed in accordance with, the USPHS/NIOSH membrane-fi1ter method for evaluating airborne asbestos fibers. Samples were collected by drawing air at a rate of 2.0 litres per minute through a cellulose ester membrane filter (Millipore Type AA, O.C micron pore size) by means of a battery-powered personal sampling pump. During sampling, the top cover of the plastic filter cassette was removed to provide an even particle distribution over the entire filter. Sampling pumps were calibrated immediately prior to, and after, the survey. After collection, a wedge-shaped section was taken from each filter, rendered transparent in a one-to-one solution of dimethyl phthalate and ethyl oxalate, and examined for asbestos count and characteristics under phase-contrast microscopy at 450.X magnification. The asbestos-fiber-count procedure consists of comparing fiber length with calibrated circles, and counting all fibers greater than 5 micrometres in length within a given counting field area. The Porton reticle,' a glass plate inscribed with a series of circles and rectangles, is used for this purpose; The reticle, placed in the eyepiece of the microscope, is calibrated with a stage micrometer. The square on the left side of the reticle, divided into six rectangles, is defined as the counting field. Discussion and Summary As is shown in Table I, the airborne asbestos concentra tions emitted during simulated severe railroad drag braking by each of -.the brake-shoe compositions tested were negligible. The measured'concentrations were in the range zero to 0.067 fiber/cm^, far lower than the permissible limits of both the present and proposed OSHA Asbestos Standard. One hundred counting fields were examined on each sample filter, and at most, only one fiber was observed per 100-field area. These extremely low fiber counts may possibly be attributed to background levels alone. -4- Table I Asbestos Emissions From Composition Brake Shoes During Drag Braking Energy Dissipation Rate, 50 hp Sampling Duration, 9 minutes Air Circulation Past Wheel None None None Turbulent Turbulent Turbulent Sample Collection Distance From Brake Shoe 6 inches 6 feet 17 feet 6 inches 6 feet 17 feet Asbestos Concentration for Different Brake Shoes, fibers/cm J A B C 0.000 0.000 0.000 0.000 0.000 0.000 0-000 0.067 0.067 0.000 0 '. 0 0 0 0.000 0.000 0 .067 0.067 0.067 0.000 0.000 -5 \ 'T 6 w 1EW OF W H E E L - T ES T IN G D Y N A M O M ET ER ' ' . S. S T E E L R E S E A R C H L A B O R A T O R Y , M O N R O E V I L L E 76-H-045(018| c< V IE W SHOWING 33-INCH-DIAM ETER W H E E L IN D YN AM OM ETER. 76-H-045(018) Figure 2 PO RTABLE AIR-SAMPLING PUMP AND FILTER CASSETTE. 76-H-O45(0l8) Figure 3 VIEW SHOWING SAMPLING PUMPS LOCATED G INCHES AND 6 FEET FROM BR A K E SHOE. 76-H-045(018) Figure 4 V I E W SH O W ING S A M P L IN G PUM P LO CATED 17 F E E T FROM BR A K E SHOE. 76-H-045013) Figure 5