§ 85.2233Steady state test equipment calibrations, adjustments, and quality control—EPA 91.
(a)Special calendar and model year applicability. The requirements of § 85.2232 apply concurrently for tests conducted under Emission Performance Warranty on 1995 and earlier model year vehicles or engines until December 31, 1993, after which the requirements of this section are solely in effect. The following exceptions apply: in a state where the Administrator has approved a SIP revision providing for implementation of a basic centralized program meeting the requirements of part 51, subpart S of this chapter, according to the schedule specified in § 51.373 of this chapter, the requirements of § 85.2232 are concurrently in effect until June 30, 1994 for 1995 and earlier model year vehicles or engines; in a state where the Administrator has approved a SIP revision providing for implementation of an enhanced program meeting the requirements of part 51, subpart S of this chapter, according to the schedule specified in § 51.373 of this chapter, the requirements of § 85.2232 are concurrently in effect until December 31, 1995 for 1995 and earlier model year vehicles or engines.
(b) Equipment must be calibrated in accordance with the manufacturers' instructions.
(c)Prior to each test—
(1)Hydrocarbon hang-up check. Immediately prior to each test the analyzer automatically performs a hydrocarbon hang-up check. If the HC reading, when the probe is sampling ambient air, exceeds 20 ppm, the system must be purged with clean air or zero gas. The analyzer must be inhibited from continuing the test until HC levels drop below 20 ppm.
(2)Automatic zero and span. The analyzer conducts an automatic zero and span check prior to each test. The span check must include the HC, CO, and CO2 channels and, if present, the NO channel. If zero and/or span drift cause the signal levels to move beyond the adjustment range of the analyzer, it must lock out from testing.
(3)Low flow. The system locks out from testing if the sample flow is below the acceptable level as defined in § 85.2225(c)(6).
(d)Leak check. A system leak check is performed within 24 hours before the test in low volume stations (those performing less than 4,000 inspections per year) and within four hours in high-volume stations (4,000 or more inspections per year) and may be performed in conjunction with the gas calibration described in paragraph (e)(1) of this section. If a leak check is not performed within the preceding 24 hours in low volume stations and within four hours in high-volume stations or if the analyzer fails the leak check, the analyzer must lock out from testing. The leak check must be a procedure demonstrated to effectively check the sample hose and probe for leaks and is performed in accordance with good engineering practices. An error of more than ±2 percent of the reading using low range span gas must cause the analyzer to lock out from testing, and requires repair of leaks.
(1) On each operating day in high-volume stations, analyzers must automatically require and successfully pass a two-point gas calibration for HC, CO, and CO2 and must continually compensate for changes in barometric pressure. Calibration must be checked within four hours before the test and the analyzer adjusted if the reading is more than two percent different from the span gas value. In low-volume stations, analyzers must undergo a two-point calibration within 72 hours before each test, unless changes in barometric pressure are compensated for automatically and statistical process control demonstrates equal or better quality control using different frequencies. Gas calibration is accomplished by introducing span gas that meets the requirements of paragraph (e)(3) of this section into the analyzer through the calibration port. No adjustment of the analyzer is necessary if the analyzer reads the span gas within the allowable tolerance range; that is, the square root of sum of the squares of the span gas tolerance (described in paragraph (e)(3) of this section) and the calibration tolerance (which is equal to two percent). The gas calibration procedure corrects readings that exceed the allowable tolerance range to the center of the allowable tolerance range. The pressure in the sample cell must be the same with the calibration gas flowing during calibration as with the sample gas flowing during sampling. If the system is not calibrated, or the system fails the calibration check, the analyzer must lock out from testing.
(2)Span points. A two-point gas calibration procedure must be followed. The span is accomplished at one of the pairs of span points listed in paragraphs (e)(2)(i) and (ii) of this section.
(A) 300 ppm and 1200 ppm propane (HC).
(B) 1.0% and 4.0% carbon monoxide (CO).
(C) 6.0% and 12.0% carbon dioxide (CO2).
(D) (if equipped for nitric oxide) 1000 ppm and 3000 ppm nitric oxide (NO).
(A) 0 ppm and 600 ppm propane (HC).
(B) 0.0% and 1.6% carbon monoxide (CO).
(C) 0.0% and 11.0% carbon dioxide (CO2)
(D) (if equipped for nitric oxide) 0 ppm and 1200 ppm nitric oxide (NO).
(3)Span gases. The analyzed concentrations for the span gases used for calibration must be nominally within two percent of the span points specified in paragraph (d)(2) of this section and must be traceable to National Institute of Standards and Technology (NIST) standards within two percent. Zero gases must conform to the specifications given in § 86.114-79 (a)(5) of this chapter.
(1)Monthly check. Within one month preceding each loaded test, the accuracy of the roll speed indicator must be verified and the dynamometer must be checked for proper power absorber settings.
(2)Semi-annual check. Within six months preceding each loaded test as described in § 85.2217, the road-load response of the variable-curve dynamometer or the frictional power absorption of the dynamometer must be checked by a coast down procedure similar to that described in § 86.118-78 of this chapter. The check is done at 30 mph (48 kph), and a power absorption load setting to generate a power of 4.1 horsepower (or 3.057 kilowatts). The actual coast down time from 45 mph to 15 mph (72 kph to 24 kph) must be within 1 second of the time calculated by the equation in paragraph (f)(2)(i) of this section for English system units or paragraph (f)(2)(ii) of this section for SI units.
where W is the total inertia weight as represented by the weight of the rollers (excluding free rollers), and any inertia flywheels used, measured in pounds, and P is power, measured in horsepower. If the coast down time is not within the specified tolerance the dynamometer must be taken out of service and corrective action must be taken.
where W is the total inertia weight as represented by the weight of the rollers (excluding free rollers), and any inertia flywheels used, measured in kilograms, and P is power, measured in kilowatts. If the coast down time is not within the specified tolerance the dynamometer must be taken out of service and corrective action must be taken.
(g)Other checks. In addition to the other periodic checks described in this section, those described in paragraphs (g)(1) and (2) of this section are also used to verify system performance under the special circumstances described therein.
(i) Each time the analyzer electronic or optical systems are repaired or replaced, a gas calibration is performed prior to returning the unit to service.
(ii) In high-volume stations, monthly multi-point calibrations are performed. Low-volume stations must perform multi-point calibrations every six months. The calibration curve is checked at 20 percent, 40 percent, 60 percent, and 80 percent of full scale, and must be adjusted or repaired if the specifications in § 85.2225(c)(1) are not met.
(2)Leak checks. Each time the sample line integrity is broken, a leak check is performed prior to testing.