Document nm4pzeJ9QZ8dVqEdjg9aZL2dR

FEB-02-2005 08=38 6 SfiE CUSTOMER SALES 724 776 0002 P.08 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. Con* sequently, the supply air duct was removed and sealed. To re duce the background asbestos level to a minimum, the dyna mometer 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 Pig. 1. Hie 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 rectang ular collector no2zle to the exhaust air duct, about 2 ft down stream 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, com pared 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 0.4S jun pores were se lected 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 canes 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 in stalled in 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 pg. Filters 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 lo cated where the upstream air velocity equalled the average over the test grid. In this way the sampling was isokinetic with es sentially equal volume flows through both filters. TEST PROCEDURE All brake stops were conducted from the same speed equiv alent (40 mph, or 18 m/s) to maintain fixed airflow condi- turns. Burnish and "normal use" brake applications were at 0.25 *`g" (2.45 m/s2) deceleration and with a 2 min time in terval. This provided a peak rotor temperature of 180C (350F). The number of brake applications was selected to provide about 1 g of lining wear per test. Break-in wear was monitored for the first 82 stops. No sampling was performed for about 200 more brake applica tions,'while the linings and rotor developed essentially steadystate 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 ve locity was adjusted to match the grid velocity at each reloca tion. Pour grids were used to monitor exhaust velocity. Slight Test Brake speed, rpm Brake decei,*`g" Wheel load, kg Brake applications Total energy, kw-h Maximum apply temperature, C Total lining wear, g Lining wear rate, g/kW-h Table A-l - Test Data Break-in 535 (40 mph) 0.25 (2.45 m/s2) 257 (567 lb) 82 0.938 (1.25 hp-h) 115 (24QF) Normal Use 535 (40 mph) 0.25 (2.45 m/s2) 257(56710) 560 6.405 (8.54 hp-h) 11S (240F) Hqh Temperature Use S35 (40 mph) 0.50 (4.9 m/s2) 257 (567 lb) 41 0.469 (0.625 hp-h) 410 (770F)