DENSITY TEST EQUIPMENT
HYDROMETERS
Hydrometers shall meet the requirements set forth in API Manual of Petroleum Measurement Standards, Chapter 9.1,“Standard Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid
Petroleum Products by Hydrometer Method” (ASTM D1298) and American Society of Testing and Materials, Standard
E100, “Standard Specification for ASTM Hydrometers”:
The accuracy of each hydrometer shall be verified by a Saudi Aramco Laboratory or a recognized independent
inspection agency before initial use in accordance with API Manual of Petroleum Measurement Standards (MPMS),
Chapter 9.1:
The verification shall be conducted by comparing readings covering the entire range of the thermohydrometer to
readings from a reference hydrometer.
The uncertainty of the reference hydrometer shall have been established against a national weights and
measures standard.
Long Plain Hydrometer
THERMOHYDROMETERS (COMBINED FORM HYDROMETERS)
Thermohydrometers shall meet the requirements set forth in API Manual of Petroleum Measurement Standards,
Chapter 9.3, “Standard Test Method for Density, Relative Density and API Gravity of Crude Petroleum and Liquid
Petroleum Products by Thermohydrometer Method” (ASTM D6822) and American Society of Testing and Materials,
Standard E100, “Standard Specification for ASTM Hydrometers”:
The accuracy of each hydrometer shall be verified by a Saudi Aramco Laboratory or a recognized independent
inspection agency before initial use in accordance with API Manual of Petroleum Measurement Standards (MPMS),
Chapter 9.3:
The verification shall be conducted by comparing readings covering the entire range of the thermohydrometer to
readings from a reference hydrometer.
The uncertainty of the reference hydrometer shall have been established against a national weights and
measures standard.
The accuracy of the thermometer shall be verified before initial use and at least once every six months thereafter by a
Saudi Aramco laboratory or a recognized independent inspection agency.
The verification shall be conducted by comparing readings at three or more temperatures over the range of the
working thermometer to readings from a reference thermometer. All readings shall meet or exceed the
specification for the thermometer.
The uncertainty of the reference thermometer shall be traceable to a national weights and measures standard.
DENSITY THERMOMETERS
The thermometer used to measure the temperature of density test samples shall conform to the requirements of API
Manual of Petroleum Measurement Standards, Chapter 9.1, “Standard Test Method for Density, Relative Density
(Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method” (ASTM
D1298) and American Society of Testing & Materials Standard E1, “Standard Specification for ASTM Liquid-in-Glass
Thermometers”:
The accuracy of the thermometer shall be verified by a Saudi Aramco laboratory or a recognized independent inspection
company before initial use and at least once every 6 months thereafter in accordance with API Manual API Manual of
Petroleum Measurement Standards, Chapter 9.1:
The verification shall be conducted by comparing readings at three or more temperatures over the range of the
working thermometer to readings from a reference thermometer.
The uncertainty of the reference thermometer shall have been established using a thermometer certified against
national weights and measures standard.
HYDROMETER CYLINDERS
The hydrometer cylinder shall have a minimum length of 15 inches (38 centimeters) and a minimum inside diameter of 2
inches (5 centimeters). The length of the hydrometer cylinder shall be sufficient to ensure that a clearance of at least 1
inch (25 millimeters) is provided between the tip of the thermohydrometer or hydrometer at the uppermost scale
graduation. The diameter of the hydrometer cylinder shall be at least 1 inch (25 millimeters) greater than the diameter of
the thermohydrometer or hydrometer. The hydrometer cylinder shall be constructed of clear glass, plastic or metal. If
constructed of plastic, it shall be resistant to discoloration and chemical degradation, and not become opaque under
prolonged exposure to sunlight.
CONSTANT TEMPERATURE BATH
The constant temperature bath shall have sufficient depth to permit the surface of the test sample in the hydrometer
cylinder to be immersed below the surface of the bath liquid. The bath shall be capable of controlling the bath
temperature to within ±0.5 ºF (+.25 ºC) of the density test temperature. The bath shall be suitable for use in a Zone 1
hazardous area.
STIRRING ROD
The stirring rod shall be constructed of glass or plastic and shall have a length of approximately 16 inches (400
millimeters).