[Code of Federal Regulations]

[Title 40, Volume 31]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR1065.245]



[Page 707]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents

 

                    Subpart C_Measurement Instruments

 

Sec.  1065.245  Sample flow meter for batch sampling.



    (a) Application. Use a sample flow meter to determine sample flow 

rates or total flow sampled into a batch sampling system over a test 

interval. You may use the difference between a diluted exhaust sample 

flow meter and a dilution air meter to calculate raw exhaust flow rates 

or total raw exhaust flow over a test interval.

    (b) Component requirements. We recommend that you use a sample flow 

meter that meets the specifications in Table 1 of Sec.  1065.205. This 

may involve a laminar flow element, an ultrasonic flow meter, a subsonic 

venturi, a critical-flow venturi or multiple critical-flow venturis 

arranged in parallel, a positive-displacement meter, a thermal-mass 

meter, an averaging Pitot tube, or a hot-wire anemometer. Note that your 

overall system for measuring sample flow must meet the linearity 

verification in Sec.  1065.307. For the special case where CFVs are used 

for both the diluted exhaust and sample-flow measurements and their 

upstream pressures and temperatures remain similar during testing, you 

do not have to quantify the flow rate of the sample-flow CFV. In this 

special case, the sample-flow CFV inherently flow-weights the batch 

sample relative to the diluted exhaust CFV.

    (c) Flow conditioning. For any type of sample flow meter, condition 

the flow as needed to prevent wakes, eddies, circulating flows, or flow 

pulsations from affecting the accuracy or repeatability of the meter. 

For some meters, 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, orifice plates or 

straightening fins to establish a predictable velocity profile upstream 

of the meter.