Appendix E to Part 80 - Test for Determining Reid Vapor Pressure (RVP) of Gasoline and Gasoline-Oxygenate Blends

Method 3—Evacuated Chamber Method 1. Scope.

1.1This method covers the determination of the absolute pressure, measured against a vacuum of a gasoline or gasoline-oxygenate blend sample saturated with air at 32-40 °F (0-4.5 °C). The absolute (measured) pressure is observed with a system volume ratio of 1 part sample and 4 parts evacuated space at 100 °F (37.8 °C).

1.2The values stated in pounds per square inch absolute are standard.

2. Summary of method.

2.1A known volume of air-saturated fuel at 32-40 °F is introduced into an evacuated, thermostatically controlled test chamber, the internal volume of which is or becomes five times that of the total test specimen introduced into the test chamber. After the injection the test specimen is allowed to reach thermal equilibrium at the test temperature, 100 °F (37.8 °C). The resulting pressure increase is measured with an absolute pressure measuring device whose volume is included in the total of the test chamber volume. The measured pressure is the sum of the partial pressures of the sample and the dissolved air.

2.2The total measured pressure is converted to Reid vapor pressure by use of a correlation equation (see Section 9).

3. Apparatus.

3.1The apparatus shall employ a thermostatically controlled test chamber which is capable of maintaining a vapor-to-liquid ratio between 3.95 and 4.05 to 1.00.

3.2The pressure measurement device shall have a minimum operation range from 0 to 15 psia (0 to 103 kPa) with a minimum resolution of 0.05 psia (0.34 kPa). The pressure measurement device shall include any necessary electronic and readout devices to display the resulting reading.

3.3The test chamber shall be maintained at 100±0.2 °F (37.8±0.1 °C) for the duration of the test except for the time period after sample injection when the sample is coming to equilibrium with test temperature of 100±0.2 °F (37.8±0.1 °C).

3.4A thermometer that meets the specification ASTM 18 F (18 C) or a platinum resistance thermometer shall be used for measuring the temperature of the test chamber. The minimum resolution for the temperature measurement device is 0.2 °F (0.1 °C) and an accuracy of ±0.2 °F (±0.1 °C).

3.5The vapor pressure apparatus shall have a provision for the introduction of the test specimen into the evacuated or to be evacuated test chamber and for the cleaning or purging of the chamber following the test.

3.6If a vacuum pump is used, it must be capable of reducing the pressure in the test chamber to less than 0.01 psia (0.07 kPa). If the apparatus uses a piston to induce a vacuum in the sample chamber the residual pressure shall be no greater than 0.01 psia (0.07 kPa) upon full expansion of the test chamber devoid of any material at 100±0.2 °F (37.8±0.1 °C).

3.7Ice water or air bath for chilling the sample to a temperature between 32-40 °F (0-4.5 °C).

3.8Mercury barometer, 0 to 17.4 psia (0 to 120 kPa) range.

3.9McLeod vacuum gauge, to cover at least the range of 0 to 5 mm Hg (0 to 0.67 kPa). Calibration of the McLeod gauge is checked as in accordance with Annex A6 of ASTM test Method D 2892-84, (Standard test method for distillation of Crude Petroleum (15-Theoretical Plate Column)). ASTM D-2892-84 is incorporated by reference. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C 552(a) and 1 CFR part 51. Copies may be obtained from the American Society for Testing and Materials, 1916 Race St., Philadelphia, PA 19103. Copies may be inspected at the U.S. Environmental Protection Agency, Air Docket Section, room M-1500, 401 M Street, SW., Washington, DC 20460 or at the Office of the Federal Register, 800 North Capitol Street, NW., Washington, DC.

4. Reagents and materials.

4.1Quality control standards. Use chemicals of at least 99% purity for quality control standards. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the committee on Analytical Reagents of the American Chemical Society where such specifications are available (see section 7.3). Specifications for analytical reagents may be obtained from the American Chemical Society, 1155 16th Street, NW., Washington, DC 20036.

4.1.12,2,4-trimethylpentane

4.1.22,2-dimethylbutane

4.1.33-methylpentane

4.1.4n-pentane

4.1.5acetone

4.2n-pentane(commercial grade-95% pure)

5. Handling of samples.

5.1The sensitivity of vapor pressure measurements to losses through evaporation and the resulting change in composition is such as to require the utmost precaution in the handling of samples. The provisions of this section apply to all samples for vapor pressure determinations.

5.2Sample in accordance with 40 CFR part 80, appendix D.

5.3Sample container size. The minimum size of the sample container from which the vapor pressure sample is taken is 4 ounces (118 ml). It will be 70 to 85% filled with sample.

5.4Precautions.

5.4.1Determine vapor pressure as the first test on a sample. Multiple analyses may be performed, but must be evaluated given the stated precision for the size of the sample container, and the order in which they were run in relation to the initial analysis.

5.4.2Protect samples from excessive heat prior to testing.

5.4.3Leaking samples should be replaced if possible. Analysis results from leaking sample containers must be marked as such.

5.4.4Samples that have separated into two phases should be replaced if possible. Analysis results from samples that have phase separated must be marked as such.

5.4.5Sample handling temperature. In all cases, cool the sample to a temperature of 32-40 °F (0-4.5 °C) before the container is opened. To ensure sufficient time to reach this temperature, directly measure the temperature of a similar liquid at a similar initial temperature in a like container placed in the cooling bath at the same time as the sample.

6. Preparation for test.

6.1Verification of sample container filling. With the sample at a temperature of 32-40 °F (0-4.5 °C), take the container from the cooling bath, wipe dry with an absorbent material, unseal it, and examine its ullage. The sample content, as determined by use of a suitable gauge, should be equal to 70 to 85 volume % of the container capacity.

6.1.1Analysis results from samples that contain less than 70 volume % of the container capacity must be marked as such.

6.1.2If the container is more than 85 volume % full, pour out enough sample to bring the container contents within the 70 to 85 volume % range. Under no circumstance may any sample poured out be returned to the container.

6.2Air saturation of the sample in the sample container. With the sample at a temperature of 32-40 °F (0-4.5 °C), take the container from the cooling bath, wipe dry with an absorbent material, unseal it momentarily, taking care to prevent water entry, re-seal it, and shake it vigorously. Return it to the bath for a minimum of 2 minutes. Repeat the air introduction procedure twice, for a total of three air introductions to completely saturate the sample.

6.3Prepare the instrument for operation in accordance with the manufacturer's instructions.

6.3.1Instruments with vacuum pumps. Clean and dry the test chamber as required to obtain a sealed test chamber pressure of less than 0.01 psi (0.07 kPa) for 1 minute. If the pressure exceeds this value check for and resolve in the following order; residual sample or cleaning solvent, sample chamber leaks, and transducer calibration.

6.3.2Instruments without vacuum pumps. The sample purges the sample chamber through a series of rinses before the analysis occurs. Errors due to leaks in the plunger, piston seals, or carryover from previous samples or standards may give erratic results (see Note of section 6.3.2). The operator must run a quality control standard for at least one in twenty analyses or once a day to determine if there is carryover from previous analyses or if leaks are occurring.

Note:

When using a self cleaning apparatus some residual product may be carried over into subsequent analyses. Carryover effect should be investigated when conducting sequential analyses of dissimilar materials, especially calibration standards. Inaccuracies caused by carryover effect should be resolved using testing procedures designed to minimize such interferences.

6.4If a syringe is used for the physical introduction of the sample specimen, it must be either clean and dry before it is used or it may be rinsed out at least three times with the sample. When cleaning the syringe, the rinse may not be returned to the sample container. The syringe must be capable of obtaining, upon filling with the sample charge, a quantity of sample that has an entrained gas volume of less than 3% of the necessary sample volume.

7. Calibration.

7.1Pressure measurement device.

7.1.1Check the calibration of the pressure measurement device daily or until the stability of the device is documented as having less than or equal to 0.03 psi (0.2 kPa) drift per unit of the appropriate calibration period. When calibration is necessary, follow the procedures in sections 7.1.2 through 7.1.4.

7.1.2Connect a properly calibrated McLeod gauge to the vacuum source line to the test chamber. Apply vacuum to the test chamber. When the McLeod gauge registers a pressure less than 0.8 mm Hg (0.1 kPa) adjust the pressure measurement device's zero control to match to within ±0.01 psi (0.07 kPa) of the McLeod Gauge.

7.1.3Open the test chamber to the atmosphere and observe the pressure measurement device's reading. Adjust the pressure measurement devices span control to within ±0.01 psi (0.07 kPa) of a temperature and latitude adjusted mercury barometer.

7.1.4Repeat steps 7.1.2 and 7.1.3 until the instrument zero and barometer readings read correctly without further adjustments.

7.2Thermometer. Check the calibration of the ASTM 18 F (18 C) thermometer or the platinum resistance thermometer used to monitor the test chamber at least every six months in accordance ASTM E1-86, (Standard Specification for ASTM Thermometers). ASTM E1-86 is incorporated by reference. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from the American Society for Testing and Materials, 1916 Race St., Philadelphia, PA 19103. Copies may be inspected at the U.S. Environmental Protection Agency, Air Docket Section, room M-1500, 401 M Street, SW., Washington, DC 20460 or at the Office of the Federal Register, 800 North Capitol Street, NW., Washington, DC. Check the reading of the thermometer against a National Institute of Standards and Technology traceable thermometer.

7.3Quality assurance. The instrument's performance must be checked at least once per day using a quality control standard listed in section 4.1. In the case of the non-vacuum pump instruments the frequency is stated in section 6.3.2. The standards must be chilled to the same temperature, have the same ullage, and saturated with air in the same manner as the samples. Record total measured pressure and compare against the following reference values:

CompoundLower control limitUpper control limit2,2,4-trimethylpentane2.39 psia (16.5 kpa)3.03 psi (20.9 kpa)3-methylpentane6.86 psia (47.3 kpa)7.26 psi (50.1 kpa)acetone7.97 psia (55.0 kpa)8.12 psi (56.0 kpa)2,2-dimethylbutane10.64 psia (73.4 kpa)10.93 psi (75.4 kpa)n-pentane16.20 psia (111.7 kpa)16.40 psi (113.1 kpa)

If the observed pressure does not fall between the reference values, check the instrument for leaks and its calibration (Section 7).

7.3.1Other compounds, gasolines, and gasoline blends may be used as control standards as long as these materials have been statistically evaluated for their mean total measured pressure using an instrument that conforms to this procedure.

7.3.2The control limits can be calculated with the following formula:

Mean Measured Pressure $EC01SE92.148$ Standard Deviation $EC01SE92.149$ Upper Control Limit (UCL) UCL=X+(tn−1,0.975) * (Sx) Lower Control Limit (LCL) LCL=X−(tn−1,0.975) * (Sx) where: xi is the individual analyses of the control standard, n is the number of analyses (for a new instrument or a new control standard this should be at least ten analyses); (tn−1,0.975) is the two-tailed student t statistic for n-1 degrees of freedom for 95% of the expected data from the analysis of the standard. 8. Procedure.

8.1Remove the sample from the cooling bath or refrigerator, dry the exterior of the container with absorbent material, unseal, and insert the transfer tube, syringe, or transfer connection (see section 6). Draw an aliquot (minimize gas bubbles) of sample into a gas tight syringe or transfer the sample using tubing or transfer connection and deliver this test specimen to the test chamber as rapidly as possible. The total time between opening the chilled sample container and inserting/securing the syringe or transfer connection into the sealed test chamber shall not exceed one minute.

8.2Follow the manufacturer's instructions for injection of the test specimen into the test chamber, and for the operation of the instrument to obtain a total measured vapor pressure result for the test specimen.

8.3Set the instrument to read the test results in terms of total measured pressure. If the instrument is capable of calculating a Reid Vapor Pressure equivalent value ensure that only the parameters in section 9.2 are used.

9. Calculation and record of result.

9.1Note the total measured vapor pressure reading for the instrument to the nearest 0.01 psi (0.07 kPa). For instruments which do not automatically display a stable pressure value, manually note the pressure indicator reading every minute to the nearest 0.01 psi (0.07 kPa). When three successive readings agree to within 0.01 psia (0.07 kPa) note the final result to the nearest 0.01 psia (0.07 kPa).

9.2Using the following correlation equation, calculate the Reid Vapor Pressure (RVP) that is equivalent to the total measured vapor pressure obtained from the instrument, in order to compare the vapor pressure standards set out in 40 CFR 80.27. Ensure that the instrument reading in this equation corresponds to the total measured pressure and has not been corrected by an automatically programmed correction factor.

RVP psi = (0.956 * X)−0.347 RVP kPa = (0.956 * X)−2.39 where: X = total measured vapor pressure in psi or kPa

9.3Record the RVP to the nearest 0.01 psi (0.07 kPa) as the official test result.

9.4EPA will use the above method as the official vapor pressure test method. EPA will recognize correlations from regulated parties if the correlations are established directly with EPA's test laboratory. Any test method may be used for defense as long as adequate correlation is demonstrated to this method (i.e., any vapor pressure defense test method could be used if adequate correlation exists directly to this method, which can then be converted to Reid Vapor Pressure by use of the EPA Grabner correlation equation in section 9.2 of this method).