40 CFR § 1065.543 - Carbon balance error verification.
(a) Carbon balance error verification compares independently calculated quantities of carbon flowing into and out of an engine system. The engine system includes aftertreatment devices as applicable. Calculating carbon intake considers carbon-carrying streams flowing into the system, including intake air, fuel, and optionally DEF or other fluids. Carbon flow out of the system comes from exhaust emission calculations. Note that this verification is not valid if you calculate exhaust molar flow rate using fuel rate and chemical balance as described in § 1065.655(f)(3) because carbon flows into and out of the system are not independent. Use good engineering judgment to ensure that carbon mass in and carbon mass out data signals align.
(b) Perform the carbon balance error verification after emission sampling is complete for a test interval or duty cycle as described in § 1065.530(g). Testing must include measured values as needed to determine intake air, fuel flow, and carbon-related gaseous exhaust emissions. You may optionally account for the flow of carbon-carrying fluids other than intake air and fuel into the system. Perform carbon balance error verification as follows:
(1) Calculate carbon balance error quantities as described in § 1065.643. The three quantities for individual test intervals are carbon mass absolute error, εaC, carbon mass rate absolute error, εaCrate, and carbon mass relative error, εrC. Determine εaC, εaCrate, and εrC for all test intervals. You may determine composite carbon mass relative error, εrCcomp, as a fourth quantity that optionally applies for duty cycles with multiple test intervals.
(i) Calculate the carbon mass absolute error limit, LεaC, in grams to three decimal places for comparision to the absolute value of ε;aC, using the following equation:
(ii) Calculate the carbon mass rate absolute error limit, LεaCrate, in grams per hour to three decimal places for comparison to the absolute value of εaCrate, using the following equation:
(iii) The carbon mass relative error limit, LεrC, is 0.020 for comparision to the absolute value of εrC, and optionally the absolute value of εrCcomp.
(c) A failed carbon balance error verification might indicate one or more problems requiring corrective action, as follows:
Table 1 of § 1065.543 - Troubleshooting Guide for Carbon Balance Error Verification
|Area of concern||Problem||Recommended corrective action|
|Gas analyzer system||Incorrect analyzer calibration||Calibrate NDIR and THC analyzers.|
|Incorrect time alignment between flow and concentration data||Determine transformation time,
|Problems with the sample system||Inspect sample system components such as sample lines, filters, chillers, and pumps for leaks, operating temperature, and contamination.|
|Fuel flow measurement||Zero shift of fuel flow rate meter||Perform an in-situ zero adjustment.|
|Change in fuel flow meter calibration||Calibrate the fuel flow meter as described in § 1065.320.|
|Incorrect time alignment of fuel flow data||Verify alignment of carbon mass in and carbon mass out data streams.|
|Short sampling periods||For test intervals with varying duration, such as discrete-mode steady-state duty cycles, make the test intervals longer to improve accuracy when measuring low fuel flow rates.|
|Fluctuations in the fuel conditioning system||Improve stability of the fuel temperature and pressure conditioning system to improve accuracy when measuring low fuel flow rates.|
|Dilute testing using a CVS system||Leaks||Inspect exhaust system and CVS tunnel, connections, and fasteners. Repair or replace components as needed. A leak in the exhaust transfer tube to the CVS may result in negative values for carbon balance error.|
|Poor mixing||Perform the verification related to mixing in § 1065.341(f).|
|Change in CVS calibration||Calibrate the CVS flow meter as described in § 1065.340.|
|Flow meter entrance effects||Inspect the CVS tunnel to determine whether entrance effects from the piping configuration upstream of the flow meter adversely affect flow measurement.|
|Other problems with the CVS or sampling verification hardware or software||Inspect hardware and software for the CVS system and CVS verification system for discrepancies.|
|Raw testing using intake air flow measurement or direct exhaust flow measurement||Leaks||Inspect intake air and exhaust systems, connections, fasteners. Repair or replace components as needed.|
|Zero shift of intake air flow rate meter||Perform an in-situ zero adjustment.|
|Change in intake air flow meter calibration||Calibrate the intake air flow meter as described in § 1065.325.|
|Zero shift of exhaust flow rate meter||Perform an in-situ zero adjustment.|
|Change in exhaust flow meter calibration||Calibrate the exhaust flow meter as described in § 1065.330.|
|Flow meter entrance effects||Inspect intake air and exhaust systems to determine whether entrance effects from the piping configuration upstream and downstream of the intake air flow meter or the exhaust flow meter adversely affect flow measurement.|
|Other problems with the intake air flow and exhaust flow measurement hardware or software||Look for discrepancies in the hardware and software for measuring intake air flow and exhaust flow.|
|Poor mixing||Ensure that all streams are well mixed.|
|Accuracy of fluid properties||Inaccurate fluid properties||If defaults are used, use measured values. If measured values are used, verify fluid property determination.|