Viscosity
The viscosity of an oil is a measure of its resistance to internal flow and is an
indication of its lubricating qualities. In the oil industry it is usual to quote
viscosities either in centistokes (which is the unit for kinematic viscosity), Saybolt
universal seconds, Saybolt Furol seconds, or Redwood seconds. These units have
been correlated and such correlations can be found in most data books. In the
laboratory, test data on viscosities is usually determined at temperatures of 100
F,
130
F, or 210
F. In the case of fuel oils, temperatures of 122
F and 210
F
are used.
Cloud and Pour Points
Cloud and pour points are tests that indicate the relative coagulation of wax in the
oil. They do not measure the actual wax content of the oil. In these tests, the oil is
reduced in temperature under strict control using an ice bath initially and then a
frozen brine bath and finally a bath of dry ice (solid CO 2 ). The temperature at which
the oil becomes hazy or cloudy is taken as its cloud point. The temperature at which
the oil ceases to flow altogether is its pour point.
Sulfur Content
This is self-explanatory and is usually quoted as %wt or wt ppm (wppm) for the
total sulfur in the oil.
Assays change in the data they provide as the oils from the various fields change
with age. Some of these changes may be quite significant and users usually request
updated data for definitive work, such as process design or evaluation. The larger
producers of crude oils provide laboratory test services on an “ongoing” basis for
these users.
The next few sections of this chapter illustrate how the assay data and basic
petroleum refining processes are used to develop a process configuration for an oil
refining complex.
Other Basic Definitions and Correlations
As described earlier, the compositions of crude oil and its fractions are not
expressed in terms of pure components, but as “cuts” expressed between a range
of boiling points. These “cuts” are further defined by splitting them into smaller
sections and treating those sections as though they were pure components. As such,
each of these components will have precise properties such as specific gravity,
viscosity, mole weight, pour point, etc. These components are referred to as pseudo
components and are defined in terms of their mid-boiling point.
12
D.S.J. Jones
The viscosity of an oil is a measure of its resistance to internal flow and is an
indication of its lubricating qualities. In the oil industry it is usual to quote
viscosities either in centistokes (which is the unit for kinematic viscosity), Saybolt
universal seconds, Saybolt Furol seconds, or Redwood seconds. These units have
been correlated and such correlations can be found in most data books. In the
laboratory, test data on viscosities is usually determined at temperatures of 100
F,
130
F, or 210
F. In the case of fuel oils, temperatures of 122
F and 210
F
are used.
Cloud and Pour Points
Cloud and pour points are tests that indicate the relative coagulation of wax in the
oil. They do not measure the actual wax content of the oil. In these tests, the oil is
reduced in temperature under strict control using an ice bath initially and then a
frozen brine bath and finally a bath of dry ice (solid CO 2 ). The temperature at which
the oil becomes hazy or cloudy is taken as its cloud point. The temperature at which
the oil ceases to flow altogether is its pour point.
Sulfur Content
This is self-explanatory and is usually quoted as %wt or wt ppm (wppm) for the
total sulfur in the oil.
Assays change in the data they provide as the oils from the various fields change
with age. Some of these changes may be quite significant and users usually request
updated data for definitive work, such as process design or evaluation. The larger
producers of crude oils provide laboratory test services on an “ongoing” basis for
these users.
The next few sections of this chapter illustrate how the assay data and basic
petroleum refining processes are used to develop a process configuration for an oil
refining complex.
Other Basic Definitions and Correlations
As described earlier, the compositions of crude oil and its fractions are not
expressed in terms of pure components, but as “cuts” expressed between a range
of boiling points. These “cuts” are further defined by splitting them into smaller
sections and treating those sections as though they were pure components. As such,
each of these components will have precise properties such as specific gravity,
viscosity, mole weight, pour point, etc. These components are referred to as pseudo
components and are defined in terms of their mid-boiling point.
12
D.S.J. Jones