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January/February 2009

The Essence of Distillation and
Vapor Pressure Measurement

Manual Details Petroleum Tests

As gasoline, diesel and jet fuel, and petroleum solvents travel from refinery to vehicle, their properties come under scrutiny from buyer and seller, state government and federal regulators. The properties measured along the way include distillation and vapor pressure, which affect the starting, warm-up and vapor lock tendencies of automotive and aviation fuels as well as vehicle safety and performance, and which must be checked to meet both company and legislative requirements.

Comprehensive coverage of such measurements and the ASTM International standards that describe these tests can be found in a new manual now available from ASTM International. The work, Distillation and Vapor Pressure Measurement in Petroleum Products, complements many of the ASTM standards used in this field.

The manual (Manual 51) is a practical reference for anyone wanting a greater understanding of routine testing procedures. “Anyone” includes lab workers and research workers, technicians and technologists. Editor Rey G. Montemayor, Ph.D., chief chemist in the Products and Chemical Division Quality Assurance Laboratory at Imperial Oil Ltd. in Sarnia, Ontario, Canada, notes that “anyone” could be either experienced or inexperienced professionals.

For those new to or less familiar with the ASTM methods, the manual’s procedural discussions expand on the individual steps in the methods. For example, in the distillation measurement chapter, Montemayor notes, “a sample calculation is given on how the observed distillation temperature is corrected to atmospheric pressure if the ambient atmospheric pressure is different from the standard pressure.” In addition, sample calculations are given for both the arithmetical and graphical methods of determining temperature readings at prescribed percent evaporated temperature as well as how certain temperature readings are obtained from the distillation data.

For the more experienced technologist, the manual can increase an understanding of how results are calculated by the automated instruments and processes that measure distillation and vapor pressure measurement. The descriptions should increase their understanding of the calculated results and what could happen to the results if test method parameters were to change.

While the entire manual comprises a valuable reference, Montemayor points out three particularly significant chapters:

  • Chapter 2, Distillation Measurement at Atmospheric Pressure, gives example calculations to show how distillation results are obtained, a comparison of three standards in this area plus a brief description of a fourth, two new small-scale distillation methods and a troubleshooting guide for abnormal results;
  • Chapter 3, Distillation Measurement at Reduced Pressure, focuses on the details of such tests, their application, important parameters and how test standards provide a framework for laboratory distillation of crude oils; and
  • Chapter 5, Vapor Pressure Measurement, discusses and compares the time-honored Reid method for vapor pressure measurement with several related standards and a cross reference with other international methods.

The manual will complement a work currently under way about the flash point measurement of petroleum products. And, as researchers develop new distillation and vapor pressure measurement methods and newer precision studies are completed that could impact published information, the manual will be revised.