EN ISO 3104 Petroleum Products - Clear and Opaque Liquids - Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity

Many petroleum products and some non-petroleum materials are used as lubricants. The proper operation of equipment depends on the appropriate viscosity of the fluid used. Furthermore, the viscosity of many petroleum fuels is important for predicting optimum storage, handling, and operating conditions. Therefore, accurate viscosity measurement is essential for many product specifications.

The standard “EN ISO 3104 Petroleum products - Clear and opaque liquids - Determination of kinematic viscosity and calculation of dynamic viscosity”, which is based on a European standard and was later published by the International Organization for Standardization (ISO), describes two test methods:

• Procedure A (manual): The kinematic viscosity of both transparent and opaque products is determined using manual glass viscometers in an automated setup.
• Procedure B (automatic). Performed using glass capillary viscometers.

Procedure A is an arbitration testing method (or reference testing method) for resolving doubts or disputes.

For the purposes of this standard, the following definitions apply:

• Kinematic viscosity: This refers to the resistance of a fluid to flow under gravity. In gravitational flow under a given hydrostatic load, the pressure load of a fluid is proportional to its density. For any viscometer, the flow time of a fluid at constant volume is directly proportional to its kinematic viscosity.
• Dynamic viscosity: This refers to the ratio between the applied shear stress and the shear rate of a fluid. It is a measure of a fluid's resistance to flow or deformation. The term dynamic viscosity is also used in a different context to denote a frequency-dependent quantity where shear stress and shear rate have a sinusoidal time dependence. Dynamic viscosity may also be referred to as the dynamic viscosity coefficient or absolute viscosity.

The EN ISO 3104 standard covers liquid petroleum products, fatty acid methyl esters, paraffinic diesel, hydrogenated vegetable oil, gas-to-liquid blends, and biofuel diesel blends containing up to 50% fatty acid methyl ester. Kinematic viscosity is determined by measuring the flow time of a volume of liquid under gravity using a calibrated glass capillary viscometer. Dynamic viscosity is obtained by multiplying the measured kinematic viscosity by the density of the liquid. The kinematic viscosity range covered by this test method is between 0,2 mm²/s and 300.000 mm²/s at temperatures ranging from -20 degrees to +150 degrees Celsius.

The results obtained from these procedures depend on the behavior of the sample and are primarily designed to be applied to fluids where shear stress and shear rates are proportional (Newtonian flow behavior). However, if the viscosity changes significantly with shear rate, different results may be obtained from viscometers with different capillary diameters.

In the world of petroleum and chemical engineering, viscosity is a critical property affecting everything from fuel performance to lubricant efficiency. The EN ISO 3104 standard provides a precise method for determining the kinematic viscosity of liquid petroleum products. This standard guarantees consistency and reliability in tests that are essential for industries relying on accurate fluid dynamics data.

The EN ISO 3104 standard applies to a wide range of petroleum-based liquids, including:

• Fuels (e.g., gasoline, diesel)
• lubricating oils
• Bitumen and asphalt
• Crude oil derivatives

This standard covers both transparent (clear) and opaque (cloudy or dark) samples and addresses challenges in measurements such as suspended particles or color interference.

Procedure A (manual) and Procedure B (automatic), defined in the EN ISO 3104 standard, are both based on the principle of timing how long it takes for a fixed volume of liquid to flow under gravity through a calibrated glass capillary tube:

• Procedure A - Manual glass viscometers: This traditional method uses counterflow viscometers:
• Sample preparation: The liquid is filtered if necessary and preheated to the test temperature (typically 20, 40, or 100 degrees).
• Filling the viscometer: Exactly 10-20 mL of sample is drawn into the viscometer chamber using vacuum.
• Flow timing: The liquid is released, and a stopwatch records the flow time from the top mark to the bottom mark; this usually requires multiple runs to take the average.
• Calculation: Kinematic viscosity and dynamic viscosity are calculated according to the formulas given in the standard.

Accuracy is ensured by maintaining the ambient temperature within a range of plus/minus 0,01 degrees and by ensuring the viscometer is suspended vertically in a bath at a constant temperature.

• Procedure B - Automated glass capillary viscometers: Designed for high-throughput laboratories, this method uses robotic setups with integrated sensors.
• Automation performs filling, timing, and cleaning processes.
• Optical or pressure sensors detect meniscus passage, eliminating stopwatch errors.
• It is ideal for opaque liquids because it minimizes visual parallax problems.

Both procedures specify viscometer dimensions according to expected viscosity ranges.

Viscosity directly affects the following:

• Fuel efficiency: In engines, unsuitable viscosity leads to poor atomization and increased emissions.
• Lubrication: Oils must have sufficient fluidity at low temperatures but maintain their thickness under heat.
• Pipeline transportation: Accurate data prevents blockages in crude oil pipelines.
• Quality assurance: In Europe, compliance with the EN ISO 3104 standard is mandatory for certifications such as ISO 9001 or REACH.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "EN ISO 3104 Petroleum products - Clear and opaque liquids - Determination of kinematic viscosity and calculation of dynamic viscosity" standard.