FIG. E-2 EXHAUST GAS SAMPLING AND ANALYTICAL TRAIN-CATAGORY B ENGINES SAMPLE PROBE SAMPLE VI R3 WTI FI VI2 LEGEND PARTICULATE FILTER FLOWMETER V6 RI HEATED AREA BACKPRESSURE REGULATOR WITH LINE PRESSURE REGULATOR WITH BALL VALVE OR EQUIVALENT (DARKENED LEG INDICATES COMMON PORT) FLOW CONTROL OR NEEDLE VALVE (6) Calibration or span gases for the NOx measurement system shall pass through the NO2 to NO converter. (7) A stainless steel sample probe shall be straight, closed-end, multiholed, and shall be placed inside the exhaust pipe. (i) The probe length shall be at least 80 percent of the diameter of the exhaust pipe. (ii) The inside diameter of the sample probe shall not be greater than the inside diameter of the sample line. (iii) The heated sample line shall have a 0.197 inch (5 mm) minimum and a 0.53 inch (13.5 mm) maximum inside diameter. (iv) The wall thickness of the probe shall not be greater than 0.040 inch (1 mm). (v) There shall be a minimum of 3 holes in 3 different radial planes sized to sample approximately the same flow. (8) The sample probe shall be located in the exhaust pipe at a minimum distance of 1.6 feet (0.5 meters) or 3 times the diameter of the exhaust pipe, whichever is the larger, from the exhaust manifold outlet flange or the outlet of the turbocharger. The exhaust gas temperature at the sample probe shall be a minimum of 158 °F (70 °C). (9) The maximum allowable leakage rate on the vacuum side of the analyzer pump shall be 0.5 percent of the in-use flow rate for the portion of the system being checked. (10) General analyzer specifications. (i) The total measurement error, including the cross sensitivity to other gases, (paragraphs (b)(11)(ii), (b)(12)(iii), (b)(13)(iii), and (b)(13)(iv) of this section), shall not exceed ±5 percent of the reading or 13.5 percent of full scale, whichever is smaller. For concentrations of less than 100 ppm the measurement error shall not exceed +4 ppm. (ii) The repeatability, defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than +1 percent of full scale concentration for each range used above 155 parts per million (ppm) or parts per million equivalent carbon (ppmC) or ±2 percent of each range used below 155 ppm (or ppmC). (iii) The analyzer peak to peak response to zero and calibration or span gases over any 10 second period shall not exceed 2 percent of full scale on all ranges used. (iv) The analyzer zero drift during a 1-hour period shall be less than 2 percent of full scale on the lowest range used. The zero-response is the mean response, including noise, to a zero gas during a 30-second time interval. (v) The analyzer span drift during a 1-hour period shall be less than 2 percent of full scale on the lowest range used. The analyzer span is defined as the difference between the span response and the zero response. The span response is the mean response, including noise, to a span gas during a 30-second time interval. (11) CO and CO2 analyzer specifications. (i) Measurements shall be made with nondispersive infrared (NDIR) analyzers. (ii) For the CO analyzer, the water and CO2 interference shall be less than 1 percent of full scale for ranges equal to or greater than 300 ppm (3 ppm for ranges below 300 ppm) when a CO2 span gas concentration of 80 percent to 100 percent of full scale of the maximum operating range used during testing is bubbled through water at room temperature. (12) For NOx analysis using a chemiluminescence (CL) analyzer the following parameters shall apply: (i) From the sample point to the NO2 to NO converter, the NOx sample shall be maintained between 131 °F (55 °C) and 392 °F (200 °C). (ii) The NO2 to NO converter efficiency shall be at least 90 percent. (iii) The quench interference from CO2 and water vapor must be less than 3.0 percent. (13) For NOx analysis using an NDIR analyzer system the following parameters shall apply: (i) The system shall include a NO2 to NO converter, a water trap, and a NDIR analyzer. (ii) From the sample point to the NO2 to NO converter, the NOx sample shall be maintained between 131 °F (55 °C) and 392 °F (200 °C). (iii) The minimum water rejection ratio (maximum water interference) for the NOx NDIR analyzer shall be 5,000:1. (iv) The minimum CO2 rejection ratio (maximum CO2 interference) for the NOX NDIR analyzer shall be 30,000:1. (14) When CH is measured using a heated flame ionization detector (HFID) the following shall apply: (i) The analyzer shall be equipped with a constant temperature oven that houses the detector and sample-handling components. (ii) The detector, oven, and samplehandling components shall be suitable for continuous operation at temperatures of 374 °F (190 °C) ± 18 °F (10 °C). (iii) The analyzer fuel shall contain 402 percent hydrogen. The balance shall be helium. The mixture shall contain ≤1 part per million equivalent carbon (ppmC), and ≤ 400 ppm CO. (iv) The burner air shall contain < 2 ppmC hydrocarbon. (v) The percent of oxygen interference shall be less than 5 percent. (15) An NDIR analyzer for measuring CH4 may be used in place of the HFID specified in paragraph (b)(14) of this section and shall conform to the requirements of paragraph (b)(10) of this section. Methane measurements shall be made on a dry basis. (16) Calibration gas values shall be traceable to the National Institute for Standards and Testing (NIST), "Standard Reference Materials" (SRM's). The analytical accuracy of the calibration gas values shall be within 2.0 percent of NIST gas standards. (17) Span gas values shall be traceable to NIST SRM's. The analytical accuracy of the span gas values shall be within 2.0 percent of NIST gas standards. (18) Calibration or span gases for the CO and CO2 analyzers shall have purified nitrogen as a diluent. Calibration or span gases for the CH, analyzer shall be CH with purified synthetic air or purified nitrogen as diluent. (19) Calibration or span gases for the NOx analyzer shall be NO with a maximum NO2 concentration of 5 percent of the NO content. Purified nitrogen shall be the diluent. (20) Zero-grade gases for the CO, CO2, CH, and NOx analyzers shall be either purified synthetic air or purified nitrogen. (21) The allowable zero-grade gas (purified synthetic air or purified nitrogen) impurity concentrations shall not exceed ≤ 1ppm C, ≤1 ppm CO, ≤ 400 ppm CO2, and ≤0.1 ppm NO. (22) The calibration and span gases may also be obtained by means of a gas divider. The accuracy of the mixing device must be such that the concentration of the diluted calibration gases are within 2 percent. (c) Particulate sampling system shall be used in determining the particulate index. A schematic of a full flow (single dilution) particulate sampling system for testing under this subpart is shown in Figures E-3 and E-4. (1) The dilution system shall meet the following parameters: (i) Either a positive displacement pump (PDP) or a critical flow venturi (CFV) shall be used as the pump/mass measurement device shown in Figure E-3. (ii) The total volume of the mixture of exhaust and dilution air shall be measured. (iii) All parts of the system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, shall be designed to minimize deposition or alteration of the particulate. (iv) All parts shall be made of electrically conductive materials that do not react with exhaust gas components. (v) All parts shall be electrically grounded to prevent electrostatic effects. (vi) Systems other than full flow systems may also be used provided they yield equivalent results where: (A) A seven sample pair (or larger) correlation study between the system under consideration and a full flow dilution system shall be run concurrently. (B) Correlation testing is to be performed at the same laboratory, test cell, and on the same engine. (C) The equivalency criterion is defined as a ± 5 percent agreement of the sample pair averages. (2) The mass of particulate in the exhaust shall be collected by filtration. The exhaust temperature immediately before the primary particulate filter shall not exceed 125 °F (52.0 °C). (3) Exhaust system backpressure shall not be artificially lowered by the PDP, CFV systems or dilution air inlet system. Static exhaust backpressure measured with the PDP or CFV system operating shall remain within ± 0.44 inches Hg (1.5 kPa) of the static pressure measured without being connected to the PDP or CFV at identical engine speed and load. (4) The gas mixture temperature shall be measured at a point immediately ahead of the pump or mass measurement device. (i) Using PDP, the gas mixture temperature shall be maintained within ± 10 °F (6.0 °C) of the average operating temperature observed during the test, when no flow compensation is used. (ii) Flow compensation can be used provided that the temperature at the inlet to the PDP does not exceed 122 °F (50 °C). (iii) Using CFV, the gas mixture temperature shall be maintained within ± 20 °F (11°C) of the average operating temperature observed during the test, when no flow compensation is used. (5) The heat exchanger shall be of sufficient capacity to maintain the temperature within the limits required above and is optional if electronic flow compensation is used. (6) When the temperature at the inlet of either the PDP or CFV exceeds the limits stated in either paragraphs (c)(4)(i) or (c)(4)(iii) of this section, an electronic flow compensation system shall be required for continuous measurement of the flow rate and control of the proportional sampling in the particulate sampling system. (7) The flow capacity of the system shall be large enough to eliminate water condensation. |