Document 377wr1LM5DqYyGkearjbLRb90

FILE NAME: Z< DATE: DOC#: Z< DOCUMENT DESCRIPTION :ZZ&ZZ WZK/ Applied Occupational and Environmental HygIene Volume 14: 397-M.l2. 1999 CojiYTlilhl l~ Applied [nduslnaj HygIene I 1047-322X.199 $12.00 +.00 Ashestos Fihpr R.lllease from the Brak~ Pads of Overhead Industrial Cranes John W. Spencer, Marc J. Plisko, and J. LeRoy Baize.. Environmental Profiles, Inc., Baltimore. Maryland . The purpose of this evaluation was to determine the actual contribution of airborne asbestos fibers to the work environment from the operation of overhead cranes and hoist... that use asbestos composition brake pads. The evaluation was conducted in a working manufacturing facility. Other potential sources of asbestos were accounted for by visual inspection and background air monitoring. An overhead crane assembly comprised of a troUey and two hoists was employed for this study. The crane was oper ated for two consecutive-eighthour shifts representa~ive of a heavy-duty cycle. Forty-four personal and area air samples were collected during the assessment. Asbestos fibers were analyzed for by phase contrast (NIOSH 7400), and tramsmission electron (NIOSH 7402) microscopy methods. Eighthour time~weighted average (TWA) asbestos fiber concentrations ranged from <0.005 to 0.011 fibers/cc (PCM), and <0.0026 to <:0.0094 flce (TEM). There Were no asbestos fibers detected by the TEM method from air sam pies collected during the operation of the cranes. Keywords Asbestos, Brake Pads, Cranes. Hoists <reM Asbestos has been used in thenna] insulation, building ma- terials, gaskets und packings, friction products, and many other end-user goods for decades. Several asbestos-containing products such as gaskets. packing materials. and equipment brake pads remain in use as integral pans of industrial machinery systems. Previous studies have reported that asbestos fibers released from brake linings lend to be In the electron-microscope size range.(I) The purpose of this study was to detellTIine the actual contribution of optically (phase contrast microscopy visible airborne asbestos fibers 10 the work environment from the operation of overhead cranes and hoists which use asbestoscomposition brake pads. The tenn asbestos refers to fibrous, naturally occurring siliClU@ minernl.ll that ~xhihjt properties rend~nng th~m !.I1l(;fui in commerce.(2) Such properties include resistance to heat, chemical corrosion. and frictional wear; high tensile strength: and flexibility. A~bestos-composition friction products have been utilized for many years in brake/friction applications, including auro- mobile and truck brakes. elevator brakes. and clutch assemblies. Traditionally, friction products have contained blends ~f asbestos. ce;llulose, synthetic fibers, and non-fibrous binding materials. In July 1989. the Erivironmental Protection Agency (EPA) issued a final rule under the Toxic Substances Control Act (TSCA) to prohibit the manufacture. importation, processing, and distribution of asbestos in almost all products. This final rule sought to eliminate the use of asbestos in most commercial products in three stages over seven years beginning in 1990. In October 1991, the Fifth Circuit Court of Appeals vacated and remanded most of the ban and phase-out rule. As a reSUlt. asbestos-composition brake pads are still manufactured on a limited basis. BACKGROVND Ovcmead'cnlI1es are utilized for a variety of material han- dling needs and other industrial applications. They are available in a range of capacities, typically from 1 to 250 tons, and may be found in thousands of plants and facilities nationwide. industrial uses include shipbuilding. automotive and heavy equipment assembly, and other industrial operations where heavy material loads have to be moved. Overhead, or bridge cranes, are supportedabove the working surface by a. movabl~ bridge. The bridge travels horizontally along parailel girders which may be either ,elf-supported or supported by the structure housing the crane. The bridge contains the essential working elements of the crane induding the bridge motor and bridge drive systems, dectrical controls. an operator's cab, and Ihe trolley supporting the hoist(s). The trolley is supponed by wheels which move along a track perpendicular to the directional movement of the bridge. The trolley comams a motor and drive machinery that allow it5 movement to be comrolled independently from the bridge. The movement of the bridge, and perpendicular movement of the trolley 397 39R J. w. SPENCER ET AL. enable operation of the crane in all directions with respect to an x-y (Carresian) coordinate system. The trolley also cOntains the hoists. the hoist motors, and the hoist gear assemblies. Many overhead --cranes operate with t\V() hOjft<;~ mcfl'...ai.- !:-:ia~. 'I.:ir..:~. ;l':.:~.::....:Hhe majority of the '>'>'Ofk, and the auxiliary hoist which often has a lift capacity less than that of the main hoist. The operation of overhead crane~ is usually controlled in onc of three ways-an operator's control cab anached to the crane, a pendant push-button control operated from the floor. or a wireless radio control. The inertia generated during the movement of the bridge, trolley, and hoists is controlled usrng friction brake products. The typical overhead industrial crane may contain four sets, or pairs. of brake shoes. One pair each may be found attached to the bridge drive gearing, the trolley drive gearing, the main hoist drive system, and the auxiliary hoist drive system. The brake shoes consist of friction materials bonded or riveted to metal brake shoes, whi\,;h arc in turn attached to brake calipers. GENERAL PROCESS DESCRIPTION This evaluation was performed in a building utilized forflroduct subassembly and light welding at a mining equipment manufacturing plant. No manufacturing activities were in progress during the evaluation. The building size was approximately' 1071 x 270' x 30'. TIle building contained a total of six overhead cranes and two light-duty jib cranes. The main runway, situated along the cemer ofthe building. contained two overhead cranes, each with a 15-ron main hoist and a 5-ton auxiliary hoist. Two additional runways, each situated on either side of the main runway, contained two 540n overhead cranes. One of the two 15-ton cranes which plant personnel reported as being manufactured and installed in 1941, was used for this evaluation. As reported by the plant's test engineer,. the brake shoes on the bridge, trolley. and auxiliary hoist were original (i.e. installed in 194 J). The brake shoes on [he main hoist were replaced in the mid- to late 1960s. Prior to our amval at the site, the unused 15-Ion crane was parked-at one end of the mair. relJ""_Y opp(;~E,~ t:.~<;..,i~'J!,c<'c ,l..... work was perfonncd. Wirh only a few exceptions. an 80-foot portIOn of the approx- imate 270-foot-Iong runway was used during the study; See Figure 1. The evaluation was performed over lWO consecutive eight- hour shifts. Based on normal plant operations, a test duty cycle was prepared by a Crane engineer. TIle duty cycle analysis was prepared to reflect a representative worst-case scenario of a duty cycle for cranes in manufacturing facilities operating at a Crane Manufacturer's Association ofAmerica (CMAA) Gass "C" rating. The test loads included a 6.75-ton weight for the main hoist and a 1.98-ton weight for the auxiliary hoist. The first shift dUly cycle included eight steps, with a total cycle time of approximately six minutes per cycle. This resulted in a frequency of 10 duty cycles per hour. The first shift duty cycle included the following steps: 1. main hoist lowering 15 feet unloaded 2. mam hoist raising 15 feet under load with 2 "jogs" (i.e., engage brakes) 3.. troiley motion! span (20 feet) 4. bridge motion of 80 feet 5. trolley motion ~ span (20 feet) 6. main hoist lowering 15 feet under load with 2-3 jogs 7. reverse above 5 steps unloaded 8. crane remained stationary for 3 minutes During the first shift duty cycle, the auxiliary hoist was in- tennittently raised and lowered, though no load was attached. The second shift duty cycle was similar to the first shift duty cycle; however, operation of the auxiliary hoist with a weighted load attached was added dunng the second shift Operation of 270' 1107' ~~_l Locations ofArea Air Samples I FIGURE 1 Facility layout. ASBESTOS ABER RELEASE fROM OVERHEAD CRANES BRAKES 399 tl.le auxiliary hoist with its attached load was perfonncd during the reverse steps of the main hoist duty cycle. The performance of repetitive duty cycles during the nrst and .,.:......,J ~.;;i..:. .E1lW .......; in\he brakes 'being appiied. on aveJ ..gc, 39 times per 6-minute cycle. This resulted in approximately 390 applications of the brakes per hour. In terms of average brake ' usage per duty cycle, the brakes on the bridge were applied 9 times, on the trolley 11 times. on the main hoist 9 times, and on the auxiliary hoist 10 times. Prior to initiating the process evaluation, all heating and ventilation within the building was deactivated. All doors and winiows were closed in an effort to minimize air currents in the )uilding. Air tlow ~ithin the building was qualitatively assessed 'y observing smoke flow pauems in the air current. Air currents lIere determined to be relatively stable with no significant air low detected. Temperature measurements averaged 75.YF at ~ound level and RS.5F at crane level (approximately 25 feet lhove the finished floor). The outdoor temperature averaged ~9F. Step 1. Abnospheric Screening Test The atmospheric screening test was conducted [0 determine whether ambient atmospheric contaminanls- would adversely affect the analyst's ability to evaluate sample filters at low fiber concentrations. The screening was performed using different sampling collection durations and air flow rates. The infonna- tion obtained from the analysis of the screening samples (e.g., t)Stimated dust loading, fiber densHy, fiber concentration) was used to develop the final sampling strategy for the baseline and process evaluation samples. Sampling parameters and sample rl:sults for [he atmospheric screening test may be found in the Results section in Table I. Step 2. Baseline Samples Baseline air samples were coJlected indoors and outside the building. The purpose of the baseline sampling was to detennine the existing backgr-ound or'ambient asbestos fiber level. absent the crane/hoisting operations. ~ total offive indoor samples and five outdoor samples were collected. Two sample blanks were also obtained. The results from the baseline samples were com- ~ETHOD pared to me results of the exposure samples obtained during the study to detennine the actual contribution of airborne asbestos NIOSH Method 740O-Issue 2 (Fibers by Phase Contrast fibers from the activities monitored. ,ficroscopy [peM] August 15. 1994)(3) was selected for this (ork, given its use by the Occupational Safety and Health Ad- Step 3. Monitoring of the Subject Process Unistration (OSHA) as the srandard for evaluating personal Bulk samp1t<S of the brake pad material were obtained and xposure to asbestos and oilier fibers.(4) NIOSH Method 7402 , <\sbestos by Transmission Electron Microscopy [TEM))(5) was analyzed prior to initiating the dUty cycle evaluation. One bulk i~ ~lected as a backup/verification if interference were experi- sample each was obtained from the bridge, trolley. and the main and auxiliary hoist brake pads. Samples were extracted from " thr need during sample analysis. The 7402 method is prescribedby existing brake pads using a knife to scrape material from [OSH for confinnation of results obtained by NlOSH method the surface of the pads. The selected pad surfaces consisted of WO.(6) Accordingly, the 7402 method specifies that only as- ~tos fibers meeting the size requirement specified in the 7400 . an exposed edge where the brake pad ~e shoe. an are~ material fits into [he Iethod be counted. This means that onJy asbestos fibers greater 'that does not come into conmct with the brake wheel during brake use. The objective was to collect i8ll 5 J.Lm in length and 0.25 IJ.m wide were measured and Jantified.(7) a sample without altering the existing contact surface or the perfonnance specification of the brake pads. Analysis was per- Following the review and selection of sampling and analytal methods. a standard operating procedure was developed. fonned using Polarized Light Microscopy (PLM) with disper- sion staining. The results of laboratory analysis indicated that !le procedure included an atmospheric screening test, baseline mple collection. and the sampling protocol for the process each brake shoe material CQntaIDed 12 percent chrysolile asbestos by weight. The laboratory which perfonned the analy- 'aluation. sis was accredited by the National Institute for Standards and TABLE I Air sample results summary table for atmospheric screening test Sample no. SS-l SS-2 SS-3 SS-4 S5-5 Description/location Center of crane bay Crane working area Crane working area Blank Blank Flow rate CL/min) 4.0 4.0 3.0 n/a n/a Duration (min) 482 242 247 nla nla Volume (liters) 1928 968 741 nja n/a peM result (fIcc) <0.005 <0.010 o <0.010 o fi bers/100 fields fiOOrs/JOO fields ,I 400 J. W. SPENCER ET At. TABLE JI Sample distribution for first shift and second shift sampling Location No. of first shift samples No. of second shift sampJes Total Floor level 8 Crane control 0 Crane level 2 Outdoors 1 Personal (operator) I Personal (bystanders) 0 Blank 2 Total 14 8 16 I 1 2 4 I 2 0 2 3 2 3 5 18 32 Technology (NIST), and the American Industrial Hygiene As~ociation (AIHA) for PLM analysis. Visual inspection of the installed brake shoes indicated mod- erate wear. Plant personnel reported that the brake shoes on the bridge, trolley, and auxiliary hoist were installed when the crane was mapufactured. The brake shoes on the main hoist were re- portedly replaced in the mid- to late 1960s. Air sample collection focused on two levels within the build- ing--tbe bridge/trolley level. and the main floor. Sample col- lection at the bridge/trolley level was conducted using portable, battery-operated air sampling pumps. 'The portable pumps were used to collect air samples on and around the trolley, and in the area formerly occupied by the operator's cab. The sample col- lected from the operator cab area was intended to represent fiber concentrations to which an operator may have been exposed. were the cab still present. Sampling locations at the main floor level were evenly distributed wifhin, and adjacent to, the crane areaway (also referred to as the hOisting area) and were obtained using high-flow air sampling pumps. The collection of samples wirhin and adjacent tt) tr.", rf"lDP "r';;"way (hoisting area) was intended to represent fiber cpncentrntions to which both floor-level crane operators and bystanders may be exposed. Representative personal samples were also collected using portable air sampling pumps. Thirty-two air samples were collected during the process evaluation. The sample distribution for the first and second shifts is described in Table IT. Four locations were selected for the collection ofthe tIoor-level (five to six feet above the floor) samples. The sample filter cassettes were changed halfway through each shift, resulting in eight floor-level samples per shift. The floorlevel sample locations remained constant from the first to the second shift. During the second shift, a personal sampling pump was attached to the crane's pendant control to represent the operator's exposuTC. Three personal samples were also collected during the second shift. The personal samples were obtained. from the breathing zones of the investigators, who were evaluating the duty cycles while observing from me hoisting and adjacent areas. . RESULTS AND DISCUSSION The results of air sampling and analysis are presented in the following tables. Each table gives the sample location/description, flow rate duration. volume, and r.esult. Table I lists sample datll and test results for the Atmo$pheric Screening Test. The sample data and test results for the Baseline Samples are presented in Table ID. The sample data and test results for the Process Evaluation are presented in Table rv. All sample results reported in Table I are based On sample analysis by PCM using NIOSH Method 7400. Sample results reponed in Tables ill and IV are based on analysis by PCM using NIOSH Method 7400 and con6nnatory analysis by TEM using NIOSH Method 7402. Sample no. 11 1596-MPl 111596-MP2 1115%-MP3 I 11596-MP4 11I596-MP5 1115%-MP6 111596-MP7 11 1596-MP8 I11596-MP9 IllS9f.>-MPlO I I 1596-MPI 1 11l596-MP12 TABLE III Air sample results sut:J1l11ary table for baseline sample collection Flow rate Duration Volume Descriptlon/location (L/min) (min) (liters) PCM result (f/ce) Baseline: Outdoors Baseline: Outdoors Baseline; Outdoors Baseline: Outdoors Baseline: Outdoors Baseline: Indoors Baseline: Indoors Baseline: Indoors Baseline: Indoors Baseline: Im.loors Blank Blank 2.7 2.~ 2.75 2.6 2.45 12.0 12.0 12.0 12.0 12.0 n/a nla 240 648 <O.OID 240 696 <O.OlD 240 660 <0.010 240 624 <0.010 240 58~ <0.010 180 2160 <0.005 180 2160 <0.005 180 2160 0.006 180 2160 IgO 2160 <O.fXl5 ..;:0.005 n/a nla I fiher/lOO fields n/a n/a 1 fiberilOO fields TEM result (flee) <0.0054 ..;:0.0050 <0.0053 <0.0056 <0.0060 <0.0016 <0.0016 <0.0016 ~O_OOIi) <0.0016 / ASBESTOS FIBER RELEASE FROM OVE.RHEAD CRANES BRAKES 401 PCM ResuJts All PCM results reported in Table I were below the limit of quantitation (LOQ). Wtth one eXl."eprion, all Baseline S~ pie results (Tab1" ~) were "'so UClUW 11lci, IcSpective LOQs. The one exception was marginally above its respective LOQ. peM analysis indicated one fiber each on the blank samples. A total of 27 samples were collected during the Process Evalua- tion (Table IV). Fifteen of the 27 samples were reported by the laboratory as being below the respective LOQs. n:MR~I."ts TEM analysis was petformed on the baseline and process evaluation samples to determine whether fibers detected by PCM analysis were asbestos fibers. The analysis was perfol1l1ed using TABLE IV Air sample results summary table for Process Evaluation Samples Sample location No. of samples Sample period (min.) PCM result (f/ce) 8-Hr. TWA (peM flee) TEM result (f/Cc) . NE corner of hoisting 2 225 0.006 <0.006 <0.0026 area-1st shift 225 <0.005 <0.0026 NE corner of hoisting 2 225 <0.005 <0.006 <0.0026 area-2nd shift 225 0.006 <0.0026 NW corner of hoisting 2 225 <0.005 <0.005 <0.0026' area-l st shift 225 <0.005 <0.0026 NW corner of hoisting 2 225 0.011 <0.008 <0.0026 .I ' area-2nd shift 225 <0.005 <0.0026 SE corner of hoisting 2 225 0.005 <0.005 <0.0026 area-lsl shift 225 <0.005 <0.0026 SE corner of hoisting 2 225 <0.005 <0.006 <0.0026 area-2nd shift 225 0.006 i <0.0026 > SW corner of hoisting 2 225 0.005 0.006 <0.0026 r area-I sI shift 225 0.006 -' <0.0026 SW corner of hoisting 2 225 <0.005 <0.005 <0.0026 area-2nd shift 225 '<0.005 <0.0026 Center of crane bridge 435 <0.005 <0.005 <0.0031 on guard rail-1st shift Center of crane bridge on guard rail-2nd shift 401 <0.005 <0.004 <0.0036 Beneath bridge at former operator cab-lst shift 435 <0.005 <0.005 <0.0031 Beneath bridge at fonner operator cab-2nd shift 470 <0.005 <0.005 <0.0030 Beneath crane on pendant control-2nd shift 435 0.006 0.005 <0.0032 Personal (bystander)1st shift 4;17 0.00& 0.007 <0.0034 Personal {bystander}2nd shift 149 0.035 O.OIl <0.0094 Personal (bystander)- 1 225 2nd shift 0.011 0.005'" <0.0066 Personal (bystander)2nd shift 206 0.010 0.004* <0.0069 Outdoors-I st shift 465 <0.005 <0.005 <0.0025 Outdoors-2nd shift 435 <0.005 <0.005 <0.0027 Blanks 5 0.2 fibers/IOO ftds (average) 'Pibers were detennmed by TEM 10 be non-asbcstifonn.  402 J. W SPENCER ET AL. / TEM in conjunction withNIOSH Method 7402., which is recommended by NIOSH as a backup/verification for PCM analysis. the NIOSH 7402 method during the operation of the crane and hoists. The operation of cranes and hoists fitted with asbestos- The samples generated during the atmospheric screening test o were l'If'!t 9";lly'7J".~ ..~ ~~.( IJl'X:ause the peM results rlid not in- comaming brakes did not c.!)ntribute measurable (optically vis.i"'e) airbll~?,!.~b~1~.~1! <;ber.{,':l1Ce!ltrations to the crane operators dicate interference due to particu1ate matter or other obstr.Jctive or bystanders. material. 0 The TEM analysis indicated the presence of asbrlstos fibers on only two ofthe 44 samples analyzed; one asbestos fiber each was reported on two ofthe baseline samples. No asbestos tibers were reported on any of the process evaluation samples, including the personal samples and the blanks. All samples collected during this evaluation yielded analytical results below the OSHA eight-hour time-weighted average (TWA) pennissible exposure limit (PEL) for aSbestos of 0.1 f/cc.(8) With the exception of the personal air samples, all but one ofthe axea samples were reported to be less than 0.0 I ffcc, 10 times below the OSHA PEL as measured by PCM. The sample reported to be greater than 0.01 flee was only marginally above this value. The sample was further evaluated by NIOSH method 7402, which revealed that the fibers were non-asbestifonn. CONCLUSIONS The pwpose of this evaluation was to determine the con- tribution of airborne asbestos fibers to the work environment from the operation of overlJead cranes with asbestos-containing brake shoes. The air monitoring results revealed that airborne asbestos fiber concentrations were in all cases below the OSHA eight-houT TWA exposure limit of 0.1 f/ce. Further analysis of air samples by the TEM method determined' that no asbestos tibers were detected in the size range detennined by REFERENCES 1. Nicholson, W.l.; Pundsack, EL.: Asbestos in the Environment. lARC Sci Pub 8: 126-132 (1973). 2. Asbestos in Public and Commercial BuiIdings-A Literature Re view and Sy()thesis ofCurrent Knowledge, pp. 1-2. HealthEffects Institute-Asbestos Research. Cambridge, MA (1991 ). 3. National Institute for Occupational Safety and Health: Method #7400-1-7400-14. In NIOSH Manual of Analytical Methods, 4th ell. (DHHS/NIOSH Pub!. No. 84-100). Government Printing Office, Washington, DC. (1995). . 4. Occupational Exposure to Asbestos. Code ufFederal Regulations TItle 29, Pt. 19IO.lOOI-Appendix A (1994). . 5. National Institute for Occupational Safety and Health: Method 7402. In NIOSH Manual of Analytical Methods. 4tlJ ed. National Institute for Occupational Safety and Health, Cincmnati, OH (1995). .1 6. National Institute for Occupational Safety and Health: Method 7402. In NIOSH Manual of Analytical Methods, 4th ed. National Institute for Occupational Safety and Health. Cincinnati, OH-(l995). 7. National Institute for Occupational Safety and Health: Method 7402. In NIOSH Manual of Analytical Methods, 4th ed. National Institute for Occupational Safety and Health, Cincinnati, OH (1995). 8. U.S. Department of Labor, Occupational Safety and Health Ad- o ministration: Federal Register. 59FR 40964 (August 10, 1994).