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Physical and chemical characteristics

Cedre performs various physical and chemical characterisation tests in its laboratory: flash point, density, viscosity, asphaltene and paraffin contents, etc.

Flash point

The flash point is measured according to ISO standard 13736:2008 "Determination of Flash Point - Abel Closed Cup method" (standard equivalent to IP 170) on samples of oil topped at 150, 200 and 250°C, as well as on the photo-oxidised residue.

This parameter is measured up to a maximum temperature of 100°C determined by the method (or by the samples in the case of a high water content), a threshold value which appears sufficient in terms of the risk of ignition of oil slicks during response operations.

 

Density

The density of oil samples, whether emulsified or not, is measured using ASTM method D70-09e1 "Standard Test Method for Specific Gravity and Density of Semi-Solid Bituminous Materials (Pycnometer Method)".

 

Viscosity

The density of oil samples, whether emulsified or not, is measured at 25°C using a Haake VT 550 viscometer, at given shear rates (10, 20, 50 and 100 s-1). The viscometer is calibrated using a reference oil prior to each series of measurements.

 

Asphaltenes and paraffins

The asphaltene content is determined according to the standard IP-143/90 "Asphaltenes (Heptane Insolubles) in Crude Oil and Petroleum Products".

This gravimetric method should be applied to samples which do not contain light fractions. For samples containing light fractions, the measurement is taken after distillation at 250°C (or simply by evaporation) then compared to the initial sample, taking into account the evaporation rate.

Paraffins are measured on the same residue following precipitation of the asphaltenes (measurements performed directly on the residue are liable to cause co-precipitation of asphaltenes and paraffins).

The protocol, described by Bridié et al. in 1980 [1], consists in precipitating a mixture of MEK (methly ethyl ketone) and DCM (dichloromethane) with a ratio of 1:1 at -10°C.

 

[1]  Bridié A.L., T.H. Wanders and W.V. Zegweld, H.B. den Heijde. 1980. Formation, Prevention and Breaking of Seawater in Crude Oil Emulsions, Chocolate Mousse. Marine Poll. Bull., vol 11, pp. 343-348.