The ASTM D4052 standard is published by ASTM International (formerly American Society for Testing and Materials, as of 2001 “ASTM International”). The standard defines the test method used for determining the density, relative density, and API Gravity of petroleum distillates and viscous oils.
The procedure defined by ASTM D4052 is used to test, for example:
The density and related values such as relative density and API Gravity are fundamental physical properties which are used in industry to characterize petroleum and petroleum products.
It is essential to know the density or relative density of petroleum and petroleum products in order to convert the measured volumes to volumes at the standard temperature of 15 °C, for example when trading and transporting fuels.
For the determination of density in crude oil samples, the test method described in ASTM D5002 should be used.
The standard requires that the tested materials “can be handled in a normal fashion as liquids at the temperature of test, utilizing either manual or automated sample injection equipment.”[1]
Manual sample injection means filling using syringes. Syringe filling requires knowledge and patience.
Automated sample injection requires a sample changer. Sample changers range from single-sample devices to sample changers with magazines holding up to 96 samples at once.
Due to their high viscosity, waxes and other highly viscous samples require a density device with a temperature cell operated at elevated temperatures to keep the sample in a liquid state for measurement. Filling requires one of these options:
The ASTM D4052 procedure may only be applied to liquids with a total vapor pressure typically below 100 kPa. However, this limitation can be extended to >100 kPa if the density meter uses technology which ensures that there are no bubbles in the sample in the measuring cell (U-tube). This includes use of a density meter and sample changer setup which fills and measures under pressurized conditions. Bubbles in the sample have a negative effect on the density measurement.
The ASTM D4052 procedure may only be applied to liquids with viscosities typically below approx. 15,000 mm2/s at the temperature of test. To check the viscosity, a standard kinematic viscometer provides results according to both ASTM D445 and ASTM D7042.
Filling high-viscosity samples such as waxes requires a syringe or a sample changer which is heated to a temperature at which the sample becomes liquid. Read more about sample changers which operate at elevated temperatures.
When testing opaque samples ASTM D4052 stipulates either use of automatic bubble detection or that a “proper procedure shall be established so that the absence of air bubbles in the U-tube can be established with certainty.”[2] This “proper procedure” includes use of a density meter and sample changer setup which fills and measures under pressurized conditions.
The accepted units of measurement for density according to ASTM are kilograms per cubic meter (kg/m3, SI unit) or grams per milliliter (g/mL).
Before digital density measurement was invented in the 1960s, the density, relative density, and API Gravity of crude and petroleum products were determined using either pycnometers or hydrometers. These methods persist today and are described in the following ASTM standards:
ASTM D1298 Standard Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method
ASTM D1217 Standard Test Method for Density and Relative Density (Specific Gravity) of Liquids by Bingham Pycnometer
ASTM D287 Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method)
Portable density meters/digital hydrometers: D7777 Measuring the Density, Relative Density, or API Gravity of Liquid Petroleum using a Portable Digital Density Meter in field applications
For crude oil: D5002 Test Method for Density, Relative Density, and API Gravity of Crude Oils by Digital Density Analyzer