ASTM D323 for vapor pressure of petroleum products (Reid method)
PROCEDURE A FOR PETROLEUM PRODUCTS HAVING REID VAPOR PRESSURES BELOW 180 kPa (26 psi)
10. Preparation for Test
10.1 Verification of Sample Container Filling - With the sample at a temperature of 0 to 1°C, take the container from the cooling bath or refrigerator and wipe dry with absorbent material. If the container is not transparent, unseal it, and using a suitable gage, confirm that the sample volume equals 70 to 80 % of the container capacity (see Note 5). If the sample is contained in a transparent glass container, verify that the container is 70 to 80 % full by suitable means (see Note 5).
NOTE 5 - For non-transparent containers, one way to confirm that the sample volume equals 70 to 80 % of the container capacity is to use a dipstick that has been pre-marked to indicate the 70 and 80 % container capacities. The dipstick should be of such material that it shows wetting after being immersed and withdrawn from the sample. To confirm the sample volume, insert the dipstick into the sample container so that it touches the bottom of the container at a perpendicular angle, before removing the dipstick. For transparent containers, using a marked ruler or by comparing the sample container to a like container that has the 70 and 80 % levels clearly marked, has been found suitable.
10.1.1 Discard the sample if its volume is less than 70 % of the container capacity.
10.1.2 If the container is more than 80 % full, pour out enough sample to bring the container contents within the 70 to 80 % range. Under no circumstances shall any sample poured out be returned to the container.
10.1.3 Reseal the container, if necessary, and return the sample container to the cooling bath.
10.2 Air Saturation of Sample in Sample Container:
10.2.1 Non-transparent Containers - With the sample again at a temperature between 0 and 1°C, take the container from the cooling bath, wipe it dry with an absorbent material, remove the cap momentarily taking care that no water enters, reseal, and shake vigorously. Return it to the cooling bath for a minimum of 2 min.
10.2.2 Transparent Containers - Since 10.1 does not require that the sample container be opened to verify the sample capacity, it is necessary to unseal the cap momentarily before resealing it so that samples in transparent containers are treated the same as samples in non-transparnt containers. After performing this task, proceed with 10.2.1.
10.2.3 Repeat 10.2.1 twice more. Return the sample to the bath until the beginning of the procedure.
10.3 Preparation of Liquid Chamber - Completely immerse the open liquid chamber in an upright position and the sample transfer connection (see Fig. A1.2) in a bath at a temperature between 0 and 1°C (32 and 34°F) for at least 10 min.
10.4 Preparation of Vapor Chamber - After purging and rinsing the vapor chamber and pressure gage in accordance with 11.5, connect the gage to the vapor chamber. Immerse the vapor chamber to at least 25.4 mm (1 in.) above its top in the water bath maintained at 37.8 more or less 0.1°C (100 more or less 0.2°F) for not less than 10 min just prior to coupling it to the liquid chamber. Do not remove the vapor chamber from the bath until the liquid chamber has been filled with sample, as described in 11.1.
11. Procedure
11.1 Sample Transfer - Remove the sample from the cooling bath, uncap, and insert the chilled transfer tube (see Fig. 1). Remove the liquid chamber from the cooling bath, and place the chamber in an inverted position over the top of the transfer tube. Invert the entire system rapidly so that the liquid chamber is upright with the end of the transfer tube approximately 6 mm (0.25 in.) from the bottom of the liquid chamber. Fill the chamber to overflowing (see Note 6). Withdraw the transfer tube from the liquid chamber while allowing the sample to continue flowing up to complete withdrawal.
NOTE 6 - Precaution: In addition to other precautions, make provision for suitable containment and disposal of the overflowing sample to avoid fire hazard.
11.2 Assembly of Apparatus - Immediately remove the vapor chamber from the water bath and couple the filled liquid chamber to the vapor chamber as quickly as possible without spillage. When the vapor chamber is removed from the water bath, connect it to the liquid chamber without undue movement that could promote exchange of room temperature air with the 37.8°C (100°F) air in the chamber. Not more than 10 s shall elapse between removing the vapor chamber from the water bath and completion of the coupling of the two chambers.
11.3 Introduction of the Apparatus into Bath - Turn the assembled apparatus upside down and allow all the sample in the liquid chamber to drain into the vapor chamber. With the apparatus still inverted, shake it vigorously eight times up and down. With the gage end up, immerse the assembled apparatus in the bath, maintained at 37.8 more or less 0.1°C (100 more or less 0.2°F), in an inclined position so that the connection of the liquid and vapor chambers is below the water level and carefully examine for leaks (see Note 7). If no leaks are observed, further immerse the apparatus to at least 25 mm (1 in.) above the top of the vapor chamber. Observe the apparatus for leaks throughout the test and discard the test at anytime a leak is detected.
NOTE 7 - Liquid leaks are more difficult to detect than vapor leaks; and because the coupling between the chambers is normally in the liquid section of the apparatus, give it particular attention.
11.4 Measurement of Vapor Pressure - After the assembled apparatus has been in the water bath for at least 5 min, tap the pressure gage lightly and observe the reading. Withdraw the apparatus from the bath and repeat the instructions of 11.3. At intervals of not less than 2 min, tap the gage, observe the reading, and repeat 11.3 until a total of not less than five shakings and gage readings have been made. Continue this procedure, as necessary, until the last two consecutive gage readings are the same, indicating that equilibrium has been attained. Read the final gage pressure to the nearest 0.25 kPa (0.05 psi) and record this value as the uncorrected vapor pressure of the sample. Without undue delay, remove the pressure gage from the apparatus (see Note 8) without attempting to remove any liquid that may be trapped in the gage, check its reading against that of the pressure measuring device (see A1.6) while both are subjected to a common steady pressure that is within 1.0 kPa (0.2 psi) of the recorded uncorrected vapor pressure. If a difference is observed between the pressure measuring device and the pressure gage readings, the difference is added to the uncorrected vapor pressure when the pressure measuring device reading is higher, or subtracted from the uncorrected vapor pressure when the pressure measuring device reading is lower, and the resulting value recorded as the Reid vapor pressure of the sample.
NOTE 8 - Cooling the assembly prior to disconnecting the gage will facilitate disassembly and reduce the amount of hydrocarbon vapors released into the room.
11.5 Preparation of Apparatus for Next Test:
11.5.1 Thoroughly purge the vapor chamber of residual sample by filling it with warm water above 32°C (90°F) and allowing it to drain. Repeat this purging at least five times. Purge the liquid chamber in the same manner. Rinse both chambers and the transfer tube several times with petroleum naphtha, then several times with acetone, then blow dry using dried air. Place the liquid chamber in the cooling bath or refrigerator in preparation for the next test.
11.5.2 If the purging of the vapor chamber is done in a bath, be sure to avoid small films of floating sample by keeping the bottom and top openings of the chamber closed as they pass through the water surface.
11.5.3 Preparation of Gage - Disconnect the gage from its manifold connection with the pressure measuring device and remove trapped liquid in the Bourdon tube of the gage by repeated centrifugal thrusts. This is accomplished in the following manner: hold the gage between the palms of the hands with the right palm on the face of the gage and the threaded connection of the gage forward. Extend the arms forward and upward at an angle of 45°. Swing the arms rapidly downward through an arc of about 135° so that centrifugal force aids gravity in removing trapped liquid. Repeat this operation at least three times or until all liquid has been expelled from the gage. Connect the gage to the vapor chamber with the liquid connection closed and place in the 37.8°C (100°F) bath to condition for the next test. (see Note 9).
NOTE 9 - Caution: Do not leave the vapor chamber with the gage attached in the water bath for a longer period of time than necessary to condition for the next test. Water vapor can condense in the Bourdon tube and lead to erroneous results.
