Source: https://www.law.cornell.edu/cfr/text/40/91.424
Timestamp: 2017-05-28 20:27:42
Document Index: 158987530

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40 CFR 91.424 - Dilute sampling procedure - CVS calibration. | US Law | LII / Legal Information Institute
CFR › Title 40 › Chapter I › Subchapter C › Part 91 › Subpart E › Section 91.424 40 CFR 91.424 - Dilute sampling procedure - CVS calibration.
§ 91.424 Dilute sampling procedure - CVS calibration.
(a) The CVS is calibrated using an accurate flowmeter and restrictor valve. (1) The flowmeter calibration shall be traceable to the National Institute for Standards and Testing (NIST), and will serve as the reference value (NIST “true” value) for the CVS calibration.)
In no case should an upstream screen or other restriction which can affect the flow be used ahead of the flowmeter unless calibrated throughout the flow range with such a device.)
(2) The CVS calibration procedures are designed for use of a “metering venturi” type flowmeter. Large radius or American Society of Mechanical Engineers (ASME) flow nozzles are considered equivalent if traceable to NIST measurements. Other measurement systems may be used if shown to be equivalent under the test conditions in this section and traceable to NIST measurements. (3) Measurements of the various flowmeter parameters are recorded and related to flow through the CVS. (4) Procedures used by EPA for both PDP-CVS and CFV-CVS are outlined below. Other procedures yielding equivalent results may be used if approved in advance by the Administrator. (b) After the calibration curve has been obtained, verification of the entire system may be performed by injecting a known mass of gas into the system and comparing the mass indicated by the system to the true mass injected. An indicated error does not necessarily mean that the calibration is wrong, since other factors can influence the accuracy of the system (e.g., analyzer calibration, leaks, or HC hangup). A verification procedure is found in paragraph (e) of this section. (c)PDP-CVS calibration.
(1) The following calibration procedure outlines the equipment, the test configuration, and the various parameters which must be measured to establish the flow rate of the CVS pump. (i) All the parameters related to the pump are simultaneously measured with the parameters related to a flowmeter which is connected in series with the pump. (ii) The calculated flow rate, in cm
3/s, (at pump inlet absolute pressure and temperature) can then be plotted versus a correlation function which is the value of a specific combination of pump parameters. (iii) The linear equation which relates the pump flow and the correlation function is then determined. (iv) In the event that a CVS has a multiple speed drive, a calibration for each range used must be performed. (2) This calibration procedure is based on the measurement of the absolute values of the pump and flowmeter parameters that relate the flow rate at each point. Two conditions must be maintained to assure the accuracy and integrity of the calibration curve: (i) The temperature stability must be maintained during calibration. (Flowmeters are sensitive to inlet temperature oscillations; this can cause the data points to be scattered. Gradual changes in temperature are acceptable as long as they occur over a period of several minutes.) (ii) All connections and ducting between the flowmeter and the CVS pump must be absolutely void of leakage. (3) During an exhaust emission test the measurement of these same pump parameters enables the user to calculate the flow rate from the calibration equation. (4) Connect a system as shown in Figure 5 in appendix B of this subpart. Although particular types of equipment are shown, other configurations that yield equivalent results may be used if approved in advance by the Administrator. For the system indicated, the following measurements and accuracies are required: Calibration Data Measurements
Parameter Symbol Units Sensor-readout tolerances Barometric pressure (corrected)
±0.34 kPa Ambient temperature
±0.28 °C Air temperature into metering venturi
±1.11 °C Pressure drop between the inlet and throat of metering venturi
±0.012 kPa Air flow
±0.5 percent of NIST value Air temperature at CVS pump inlet
±1.11 °C Pressure depression at CVS pump inlet
±0.055 kPa Pressure head at CVS pump outlet
±0.055 kPa Air temperature at CVS pump outlet (optional)
1.11 °C Pump revolutions during test period
(5) After the system has been connected as shown in Figure 5 of appendix B of this subpart, set the variable restrictor in the wide open position and run the CVS pump for 20 minutes. Record the calibration data. (6) Reset the restrictor valve to a more restricted condition in an increment of pump inlet depression that will yield a minimum of six data points for the total calibration. Allow the system to stabilize for 3 minutes and repeat the data acquisition. (7) Data analysis: (i) The air flow rate, Qs, at each test point is calculated in standard cubic feet per minute 20 °C, 101.3 kPa from the flowmeter data using the manufacturer's prescribed method. (ii) The air flow rate is then converted to pump flow, Vo, in cubic meter per revolution at absolute pump inlet temperature and pressure: Where: VO = Pump flow, m
3/rev at TP, PP,
QS = Meter air flow rate in standard cubic meters per minute, standard conditions are 20 °C, 101.3 kPa. n = Pump speed in revolutions per minute. Tp = Pump inlet temperature in Kelvin, = PTI 273 [°K]. PP = Absolute pump inlet pressure, kPa. = PP−PPI
Where: PP = barometric pressure, kPa. PPI = Pump inlet depression, kPa.
(iii) The correlation function at each test point is then calculated from the calibration data: Where: XO = correlation function. Δ
p = The pressure differential from pump inlet to pump outlet, kPa. = PE−PP. PE = Absolute pump outlet pressure, [kPa] = PB PPO
Where: PPO = Pressure head at pump outlet, kPa (inches fluid).
(iv) A linear least squares fit is performed to generate the calibration equation which has the form: VO = DO − M(XO)
(8) A CVS system that has multiple speeds should be calibrated on each speed used. The calibration curves generated for the ranges will be approximately parallel and the intercept values, DO, will increase as the pump flow range decreases. (9) If the calibration has been performed carefully, the calculated values from the equation will be within ±0.50 percent of the measured value of VO. Values of M will vary from one pump to another, but values of DO for pumps of the same make, model and range should agree within ±three percent of each other. Calibrations should be performed at pump start-up and after major maintenance to assure the stability of the pump slip rate. Analysis of mass injection data will also reflect pump slip stability. (d) CFV-CVS calibration. (1) Calibration of the CFV is based upon the flow equation for a critical venturi. (i) Gas flow is a function of inlet pressure and temperature: QS = flow rate [m
3/min.]. KV = calibration coefficient. P = absolute pressure [kPa]. TK = absolute temperature [°K].
(ii) The calibration procedure described in paragraph (d)(3) of this section establishes the value of the calibration coefficient at measured values of pressure, temperature and air flow. (2) The manufacturer's recommended procedure shall be followed for calibrating electronic portions of the CFV. (3) Measurements necessary for flow calibration are as follows: Calibration Data Measurements
±0.34 kPa
Air Temperature into flow meter
±0.28 °C
±0.012 kPa
±0.5 percent of NIST value
CVS inlet depression
±0.055 kPa
(4) Set up equipment as shown in Figure 6 in appendix B of this subpart and eliminate leaks. (Leaks between the flow measuring devices and the critical flow venturi will seriously affect the accuracy of the calibration.) (5) Set the variable flow restrictor to the open position, start the blower, and allow the system to stabilize. Record data from all instruments. (6) Vary the flow restrictor and make at least eight readings across the critical flow range of the venturi. (7) Data analysis. The data recorded during the calibration are to be used in the following calculations: (i) The air flow rate (designated as Qs) at each test point is calculated in standard cubic feet per minute from the flow meter data using the manufacturer's prescribed method. (ii) Calculate values of the calibration coefficient for each test point: QS = Flow rate in standard cubic meter per minute, at the standard conditions of 20 °C, 101.3 kPa. TV = Temperature at venturi inlet, °K. PV = Pressure at venturi inlet, kPA = PB−PPI
Where: PPI = Venturi inlet pressure depression, kPa.
(iii) Plot KV as a function of venturi inlet pressure. For choked flow, KV will have a relatively constant value. As pressure decreases (vacuum increases), the venturi becomes unchoked and KV decreases. (See Figure 7 in appendix B of this subpart) (iv) For a minimum of eight points in the critical region calculate an average KV and the standard deviation. (v) If the standard deviation exceeds 0.3 percent of the average KV, take corrective action. (e) CVS system verification. The following “gravimetric” technique can be used to verify that the CVS and analytical instruments can accurately measure a mass of gas that has been injected into the system. (Verification can also be accomplished by constant flow metering using critical flow orifice devices.) (1) Obtain a small cylinder that has been charged with 99.5 percent or greater propane or carbon monoxide gas (CAUTION - carbon monoxide is poisonous). (2) Determine a reference cylinder weight to the nearest 0.01 grams. (3) Operate the CVS in the normal manner and release a quantity of pure propane into the system during the sampling period (approximately five minutes). (4) The calculations are performed in the normal way except in the case of propane. The density of propane (0.6109 kg/m
3carbon atom is used in place of the density of exhaust hydrocarbons. (5) The gravimetric mass is subtracted from the CVS measured mass and then divided by the gravimetric mass to determine the percent accuracy of the system. (6) Good engineering practice requires that the cause for any discrepancy greater than ±2 percent must be found and corrected. This is a list of United States Code sections, Statutes at Large, Public Laws, and Presidential Documents, which provide rulemaking authority for this CFR Part.This list is taken from the Parallel Table of Authorities and Rules provided by GPO [Government Printing Office].It is not guaranteed to be accurate or up-to-date, though we do refresh the database weekly. More limitations on accuracy are described at the GPO site.United States CodeU.S. Code: Title 42 - THE PUBLIC HEALTH AND WELFARE§ 7401 - Congressional findings and declaration of purpose§ 7402 - Cooperative activities§ 7403 - Research, investigation, training, and other activities§ 7404 - Research relating to fuels and vehicles§ 7405 - Grants for support of air pollution planning and control programs§ 7406 - Interstate air quality agencies; program cost limitations§ 7407 - Air quality control regions§ 7408 - Air quality criteria and control techniques§ 7409 - National primary and secondary ambient air quality standards§ 7410 - State implementation plans for national primary and secondary ambient air quality standards§ 7411 - Standards of performance for new stationary sources§ 7412 - Hazardous air pollutants§ 7413 - Federal enforcement§ 7414 - Recordkeeping, inspections, monitoring, and entry§ 7415 - International air pollution§ 7416 - Retention of State authority§ 7417 - Advisory committees§ 7418 - Control of pollution from Federal facilities§ 7419 - Primary nonferrous smelter orders§ 7420 - Noncompliance penalty§ 7421 - Consultation§ 7422 - Listing of certain unregulated pollutants§ 7423 - Stack heights§ 7424 - Assurance of adequacy of State plans§ 7425 - Measures to prevent economic disruption or unemployment§ 7426 - Interstate pollution abatement§ 7427 - Public notification§ 7428 - State boards§ 7429 - Solid waste combustion§ 7430 - Emission factors§ 7431 - Land use authority§ 7450 to 7459 - Repealed. Pub. L. 101–549, title VI, § 601, Nov. 15, 1990, 104 Stat. 2648§ 7470 - Congressional declaration of purpose§ 7471 - Plan requirements§ 7472 - Initial classifications§ 7473 - Increments and ceilings§ 7474 - Area redesignation§ 7475 - Preconstruction requirements§ 7476 - Other pollutants§ 7477 - Enforcement§ 7478 - Period before plan approval§ 7479 - Definitions§ 7491 - Visibility protection for Federal class I areas§ 7492 - Visibility§ 7501 - Definitions§ 7502 - Nonattainment plan provisions in general§ 7503 - Permit requirements§ 7504 - Planning procedures§ 7505 - Environmental Protection Agency grants§ 7505a - Maintenance plans§ 7506 - Limitations on certain Federal assistance§ 7506a - Interstate transport commissions§ 7507 - New motor vehicle emission standards in nonattainment areas§ 7508 - Guidance documents§ 7509 - Sanctions and consequences of failure to attain§ 7509a - International border areas§ 7511 - Classifications and attainment dates§ 7511a - Plan submissions and requirements§ 7511b - Federal ozone measures§ 7511c - Control of interstate ozone air pollution§ 7511d - Enforcement for Severe and Extreme ozone nonattainment areas for failure to attain§ 7511e - Transitional areas§ 7511f - NOx and VOC study§ 7512 - Classification and attainment dates§ 7512a - Plan submissions and requirements§ 7513 - Classifications and attainment dates§ 7513a - Plan provisions and schedules for plan submissions§ 7513b - Issuance of RACM and BACM guidance§ 7514 - Plan submission deadlines§ 7514a - Attainment dates§ 7515 - General savings clause§ 7521 - Emission standards for new motor vehicles or new motor vehicle engines§ 7522 - Prohibited acts§ 7523 - Actions to restrain violations§ 7524 - Civil penalties§ 7525 - Motor vehicle and motor vehicle engine compliance testing and certification§ 7541 - Compliance by vehicles and engines in actual use§ 7542 - Information collection§ 7543 - State standards§ 7544 - State grants§ 7545 - Regulation of fuels§ 7546 - Renewable fuel§ 7547 - Nonroad engines and vehicles§ 7548 - Study of particulate emissions from motor vehicles§ 7549 - High altitude performance adjustments§ 7550 - Definitions§ 7551 - Omitted§ 7552 - Motor vehicle compliance program fees§ 7553 - Prohibition on production of engines requiring leaded gasoline§ 7554 - Urban bus standards§ 7571 - Establishment of standards§ 7572 - Enforcement of standards§ 7573 - State standards and controls§ 7574 - Definitions§ 7581 - Definitions§ 7582 - Requirements applicable to clean-fuel vehicles§ 7583 - Standards for light-duty clean-fuel vehicles§ 7584 - Administration and enforcement as per California standards§ 7585 - Standards for heavy-duty clean-fuel vehicles (GVWR above 8,500 up to 26,000 lbs.)§ 7586 - Centrally fueled fleets§ 7587 - Vehicle conversions§ 7588 - Federal agency fleets§ 7589 - California pilot test program§ 7590 - General provisions§ 7601 - Administration§ 7602 - Definitions§ 7603 - Emergency powers§ 7604 - Citizen suits§ 7605 - Representation in litigation§ 7606 - Federal procurement§ 7607 - Administrative proceedings and judicial review§ 7608 - Mandatory licensing§ 7609 - Policy review§ 7610 - Other authority§ 7611 - Records and audit§ 7612 - Economic impact analyses§ 7613 - Repealed. Pub. L. 101–549, title VIII, § 803, Nov. 15, 1990, 104 Stat. 2689§ 7614 - Labor standards§ 7615 - Separability§ 7616 - Sewage treatment grants§ 7617 - Economic impact assessment§ 7618 - Repealed. Pub. L. 101–549, title I, § 108(q), Nov. 15, 1990, 104 Stat. 2469§ 7619 - Air quality monitoring§ 7620 - Standardized air quality modeling§ 7621 - Employment effects§ 7622 - Employee protection§ 7623 - Repealed. Pub. L. 96–300, § 1(c), July 2, 1980, 94 Stat. 831§ 7624 - Cost of vapor recovery equipment§ 7625 - Vapor recovery for small business marketers of petroleum products§ 7625-1§ 7625a - Statutory construction§ 7626 - Authorization of appropriations§ 7627 - Air pollution from Outer Continental Shelf activities§ 7628 - Demonstration grant program for local governments§ 7641 - Noise abatement§ 7642 - Authorization of appropriations§ 7651 - Findings and purposes§ 7651a - Definitions§ 7651b - Sulfur dioxide allowance program for existing and new units§ 7651c - Phase I sulfur dioxide requirements§ 7651d - Phase II sulfur dioxide requirements§ 7651e - Allowances for States with emissions rates at or below 0.80 lbs/mmBtu§ 7651f - Nitrogen oxides emission reduction program§ 7651g - Permits and compliance plans§ 7651h - Repowered sources§ 7651i - Election for additional sources§ 7651j - Excess emissions penalty§ 7651k - Monitoring, reporting, and recordkeeping requirements§ 7651l - General compliance with other provisions§ 7651m - Enforcement§ 7651n - Clean coal technology regulatory incentives§ 7651o - Contingency guarantee, auctions, reserve§ 7661 - Definitions§ 7661a - Permit programs§ 7661b - Permit applications§ 7661c - Permit requirements and conditions§ 7661d - Notification to Administrator and contiguous States§ 7661e - Other authorities§ 7661f - Small business stationary source technical and environmental compliance assistance program§ 7671 - Definitions§ 7671a - Listing of class I and class II substances§ 7671b - Monitoring and reporting requirements§ 7671c - Phase-out of production and consumption of class I substances§ 7671d - Phase-out of production and consumption of class II substances§ 7671e - Accelerated schedule§ 7671f - Exchange authority§ 7671g - National recycling and emission reduction program§ 7671h - Servicing of motor vehicle air conditioners§ 7671i - Nonessential products containing chlorofluorocarbons§ 7671j - Labeling§ 7671k - Safe alternatives policy§ 7671l - Federal procurement§ 7671m - Relationship to other laws§ 7671n - Authority of Administrator§ 7671o - Transfers among Parties to Montreal Protocol§ 7671p - International cooperation§ 7671q - Miscellaneous provisions
40 CFR 91.425 — CVS Calibration Frequency.