ASTM D5190 Vapor Pressure of Petroleum Products (Automatic Method)
ASTM D5190 Standard Test Method for Vapor Pressure of Petroleum Products (Automatic Method)
8. Sampling
8.1 General Procedures:
8.1.1 The extreme sensitivity of vapor pressure measurements to losses through evaporation and the resulting change in composition is such as to require the utmost precaution and the most meticulous care in the drawing and handling of samples.
8.1.2 Obtain a sample and test specimen in accordance with Practice D4057, except do not use "Sampling by Water Displacement" for fuels containing oxygenates. Use a 1-L (1-qt) size container filled between 70 and 80 % with the sample.
NOTE 2 - The present precision statement was derived using the samples in 1-L (1-qt) containers. However, the samples in containers of other sizes, as prescribed in Practice D4057 can be used, with the same ullage requirement, if it is recognized that the precision can be affected.
8.1.3 In the case of referee testing, the 1-L (1-qt) sample container is mandatory.
8.1.4 Perform the vapor pressure determination on the first test specimen withdrawn from a sample container. Do not use the remaining sample in the container for a second vapor pressure determination. If a second determination is necessary, obtain a new sample.
8.1.5 Protect the samples from excessive temperatures prior to testing. This can be accomplished by storage in an appropriate ice bath or refrigerator.
8.1.6 Do not test samples stored in leaky containers. If leaks are detected, discard and obtain a new sample.
8.2 Sampling Handling Temperature - Cool the sample container and contents in an ice bath or refrigerator to betweem 0 and 1°C (32 and 34°F) prior to opening the sample container. Allow sufficient time to reach this temperature. Verify the sample temperature by direct measurement of the temperature of a similar liquid in a similar container placed in the cooling bath or refrigerator at the same time as the sample.
8.3 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 3). If the sample is contained in a transparent glass container, verify that the container is 70 to 80 % full by suitable means (see Note 3).
NOTE 3 - 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 comparing the sample container to a like container that has the 70 and 80 % levels clearly marked, has been found suitable.
8.3.1 Discard the sample if the container is filled to less than 70 volume % of the container capacity.
8.3.2 If the container is more than 80 volume % full, pour out enough sample to bring the container contents within 70 to 80 volume % range. Do not return any sample to the container once it has been withdrawn.
8.3.3 Reseal the container, if necessary, and return the sample container to the cooling bath or refrigerator.
8.4 Air Saturation of the Sample in the Sample Container:
8.4.1 Transparent Containers Only - Since 8.3 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-transparent containers.
8.4.2 With the sample again at a temperature of 0 to 1°C, take the container from the cooling bath or refrigerator, 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 bath or refrigerator for a minimum of 2 min.
8.4.3 Repeat 8.4.2 twice more. Return the sample to the bath or refrigerator until the beginning of the procedure.
8.5 Verification of Single Phase Samples - After drawing a test specimen into the sample cup and coupling the cup to the instrument for analysis, check the remaining sample for phase separation. If the sample is contained in a glass container, this observation can be made prior to sample transfer. If the sample is contained in a non-transparent container, mix the sample thoroughly and immediately pour a portion of the remaining sample into a clear glass container and observe for evidence of phase separation. A hazy appearance is to be carefully distinguished from separation into two distinct phases. The hazy appearance shall not be considered grounds for rejection of the fuel. If a second phase is observed, discard the test and the sample. Hazy samples may be analyzed (see Report section).
9. Preparation of Apparatus
9.1 Prepare the automatic vapor pressure instrument for operation in accordance with the manufacturer's instructions.
9.2 Clean and dry the sample cup prior to use. (Warning - Do not analyze a water saturated sample. If water is accidentally introduced into the instrument, analyze a dry sample six to ten times until all the water has been flushed from the instrument and a repeatability of +/-1.4 kPa (0.20 psi) is obtained for duplicate runs.)
9.3 Chill the stoppered, dry sample cup to between 0 and l°C (32 and 34°F) in a refrigerator or ice bath before transferring the sample into the cup. Avoid water contamination of the sample cup by sealing the sample cup during the cooling process.
9.4 Prior to starting the measurement, check that the temperature of the test chamber is within the required range specified by the manufacturer of the instrument.
