ASTM D5482 Standard Test Method for Vapor Pressure of Petroleum Products (Mini Method - Atmospheric)
12. Procedure
12.1 Remove the sample from the cooling bath or refrigerator, dry the exterior of the container with absorbent material, uncap, and insert a chilled syringe. Draw a bubble-free aliquot of sample into the gas tight syringe, and deliver this test specimen to the test chamber as rapidly as possible. The total time between opening the chilled sample container and securing the syringe into the test chamber shall not exceed 1 min.
12.2 Follow the manufacturer's instructions for injection of the test specimen into the test chamber and for operation of the instrument to obtain a vapor pressure result for the test specimen.
12.3 If the instrument is capable of calculating the dry vapor pressure equivalent automatically, ensure that the equation in 13.2 is used.
13. Calculation
13.1 Record the vapor pressure reading from the instrument to the nearest 0.1 kPa (0.01 psi). For instruments that do not automatically record a stable pressure value, manually record the pressure indicator reading every minute to the nearest 0.1 kPa. When three successive readings agree to within 0.1 kPa, record the result to the nearest 0.1 kPa (0.01 psi).
13.2 Calculate the DVPE using Eq 1. Ensure that the instrument reading used in this equation corresponds to the total pressure and has not been corrected by an automatically programmed correction factor. Use the variable pertaining to the type of equipment utilized.
DVPE, kPa (psi) = (0.965 X) + A
where:
X = measured total vapor pressure in kPa (psi),
A = 0.538 kPa (0.078 psi) for HERZOG Model SC 970, and
A = 1.937 kPa (0.281 psi) for ABB Model 4100.
NOTE 5 - The correlation equations were derived from data obtained in a 1991 interlaboratory cooperative test program. The equations correct for the relative bias between the measured vapor pressure and the dry vapor pressure obtained in accordance with Test Method D4953, Procedure A.
13.3 The calculation described in Eq 1 can be accomplished automatically by the instrument, if so equipped, and in such cases the user shall not apply any further correction.
