40 CFR 92.115 - Calibrations; frequency and overview.
(b) At least monthly or after any maintenance which could alter calibration, perform the periodic calibrations required by § 92.118(a)(2) (certain analyzers may require more frequent calibration depending on the equipment and use). Exception: the water rejection ratio and the CO2 rejection ratio on all NDIR analyzers is only required to be performed quarterly.
(e) At least weekly or after any maintenance which could alter calibration, check the dynamometer (if used) shaft torque feedback signal at steady-state conditions by comparing:
(1) Shaft torque feedback to dynamometer beam load; or
(2) By comparing in-line torque to armature current; or
(3) By checking the in-line torque meter with a dead weight per § 92.116(b)(1).
(g) At least annually or after any maintenance which could alter calibration, calibrate the electrical output measurement system for the electrical load bank used for locomotive testing.
(h) Sample conditioning columns, if used in the CO analyzer train, should be checked at a frequency consistent with observed column life or when the indicator of the column packing begins to show deterioration.
(i) For equipment not addressed in §§ 92.116 through 92.122 calibrations shall be performed at least as often as required by the equipment manufacturer or as necessary according to good practices. The calibrations shall be performed in accordance with procedures specified by the equipment manufacturer.
(j) Where testing is conducted intermittently, calibrations are not required during period in which no testing is conducted, provided that times between the most recent calibrations and the date of any test does not exceed the calibration period. For example, if it has been more than one month since the analyzers have been calibrated (as specified in paragraph (c) of this section) then they must be calibrated prior to the start of testing.