Section 1065.247 - Diesel exhaust fluid flow rate(a)Application. Determine diesel exhaust fluid (DEF) flow rate over a test interval for batch or continuous emission sampling using one of the three methods described in this section.(b)ECM. Use the ECM signal directly to determine DEF flow rate. You may combine this with a gravimetric scale if that improves measurement quality. Prior to testing, you may characterize the ECM signal using a laboratory measurement and adjust the ECM signal, consistent with good engineering judgment.(c)Flow meter. Measure DEF flow rate with a flow meter. We recommend that the flow meter that meets the specifications in Table 1 of § 1065.205 . Note that your overall system for measuring DEF flow must meet the linearity verification in § 1065.307 . Measure using the following procedure:(1) Condition the flow of DEF as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, straightening fins, or pneumatic pulsation dampeners to establish a steady and predictable velocity profile upstream of the meter. Condition the flow as needed to prevent any gas bubbles in the fluid from affecting the flow meter.(2) Account for any fluid that bypasses the DEF dosing unit or returns from the dosing unit to the fluid storage tank.(d)Gravimetric scale. Use a gravimetric scale to determine the mass of DEF the engine uses over a discrete-mode test interval and divide by the time of the test interval. 86 FR 34536 , June 29, 2021 81 FR 74163, 12/27/2016; 86 FR 34536, 6/29/2021