2009-05-19_REVISION - M1978039HR (28)

Home Browse Search

r? U • Pt. 60, App. A,4, Alt. Meth. 1 the photocell diameter+the diameter of the limiting aperture; and L=the distance from the photocell to the limiting aperture. The limiting aperture is the point in the path be- tween the photocell and the smoke plume where the angle of view is most restricted. In smoke generator smoke meters this is nor- mally an orifice plate. 3.3.2.4 Angle of Projection. Check construc- tion geometry to ensure that the total angle of projection of the lamp on the smoke plume does not exceed 15°. The total angle of projection may be calculated from: 0=2 tan-Id/2L, where 0=total angle of projection; d=the sum of the length of the lamp filament + the diameter of the limiting aperture; and L=the distance from the lamp to the limiting aperture. 3.3.2.5 Calibration Error. Using neutral- density filters of known opacity, check the error between the actual response and the theoretical linear response of the smoke meter. This check is accomplished by first calibrating the smoke meter according to 3.3.1 and then inserting a series of three neu- tral-density filters of nominal opacity of 20, 50, and 75 percent in the smoke meter pathlength. Filters calibrated within t2 per- cent shall be used. Care should be taken when inserting the filters to prevent stray light from affecting the meter. Make a total of five nonconsecutive readings for each fil- ter. The maximum error on any one reading shall be 3 percent opacity. 3.3.2.6 Zero and Span Drift. Determine the zero and span drift by calibrating and oper- ating the smoke generator in a normal man- ner over a 1-hour period. The drift is meas- ured by checking the zero and span at the end of this period. 3.3.2.7 Response Time. Determine the re- sponse time by producing the series of five simulated 0 percent and 100 percent opacity values and observing the time required to reach stable response. Opacity values of 0 percent and 100 percent may be simulated by alternately switching the power to the light source off and on while the smoke generator is not operating. 4. Bibliography 1. Air Pollution Control District Rules and Regulations, Los Angeles County Air Pollu- tion Control District, Regulation IV, Prohi- bitions, Rule 50. 2. Weisburd, Melvin I., Field Operations and Enforcement Manual for Air, U.S. Envi- ronmental Protection Agency, Research Tri- angle Park, NC. APTD-1100, August 1972, pp. 4.11!.36. 3. Condon, E.U., and Odishaw, H., Hand- book of Physics, McGraw-Hill Co., New York, NY, 1958, Table 3.1, p. 6-52. 40 CFR Ch. 1 (7-1-07 Edition) ALTERNATE METHOD 1-DETERMINATION OF THE OPACITY OF EMISSIONS FROM STA- TIONARY SOURCES REMOTELY BY LIDAR This alternate method provides the quan- titative determination of the opacity of an emissions plume remotely by a mobile lidar system (laser radar; Light Detection and Ranging). The method includes procedures for the calibration of the lidar and proce- dures to be used in the field for the lidar de- termination of plume opacity. The lidar is used to measure plume opacity during either day or nighttime hours because it contains its own pulsed light source or transmitter. The operation of the lidar is not dependent upon ambient lighting conditions (light, dark, sunny or cloudy). The lidar mechanism or technique is appli- cable to measuring plume opacity at numer- ous wavelengths of laser radiation. However, the performance evaluation and calibration test results given in support of this method apply only to a lidar that employs a ruby (red light) laser [Reference 5.1]. 1. Principle and Applicability 1.1 Principle. The opacity of visible emis- sions from stationary sources (stacks, roof vents, etc.) is measured remotely by a mo- bile lidar (laser radar). 1.2 Applicability. This method is applica- ble for the remote measurement of the opac- ity of visible emissions from stationary sources during both nighttime and daylight conditions, pursuant to 40 CFR §60.11(b). It is also applicable for the calibration and per- formance verification of the mobile lidar for the measurement of the opacity of emis- sions. A performance/design specification for a basic lidar system is also incorporated into this method. 1.3 Definitions. Azimuth angle: The angle in the horizontal plane that designates where the laser beam is pointed. It is measured from an arbitrary fixed reference line in that plane. Backscatter: The scattering of laser light in a direction opposite to that of the inci- dent laser beam due to reflection from par- ticulates along the beam's atmospheric path which may include a smoke plume. Backscatter signal: The general term for the lidar return signal which results from laser light being backscattered by atmos- pheric and smoke plume particulates. Convergence distance: The distance from the lidar to the point of overlap of the lidar receiver's field-of-view and the laser beam. Elevation angle: The angle of inclination of the laser beam referenced to the hori- zontal plane. Far region: The region of the atmosphere's path along the lidar line-of-sight beyond or behind the plume being measured. Lidar: Acronym for Light Detection and Ranging. 318