How to choose the right inline viscometer in petrochemical processes

In refineries and petrochemical processes, on-site control is of primary importance with regard to product quality. Viscosity is an important parameter of many petroleum products. It affects storage, handling, operating conditions or makes quality control more efficient, depending on the instrument. In the manufacture of petroleum products, great importance is placed on testing standards, especially the ASTM. When a test standard only describes the lab measurement and not the process measurement, confusion can arise about what is the best choice for an inline measurement. This also appears to apply to inline viscosity measurements in refineries and petrochemical processes.

Dynamic and kinematic viscosity in the petrochemical industry

The dynamic viscosity and the kinematic viscosity are two important units in the petrochemical industry. Kinematic viscosity expresses the time it takes for a certain amount of fluid to flow at a certain temperature. The ASTM D445 test standard describes how the kinematic viscosity of liquid petroleum products is measured using a capillary tube with gravity as the driving force. Since gravity acts as the drive, density also plays a role in the outcome. The capillary technique described in ASTM D445 for obtaining kinematic viscosity is a lab measurement using mm2 / s (cSt or centiStokes) as the unit. Although new and more efficient lab and process techniques have been introduced, it is still the most important standard for the petrochemical industry. These new techniques all use a different drive than gravity and often require an external density meter to calculate kinematic viscosity. This means that all process viscometers (including the capillary process viscometers) are correlated or directly correlated with the ASTM D445.

More information on temperature compensation when measuring viscosity in pertoleum products

Disadvantage of a capillary process measurement

As a process measurement, the capillary technique has a major drawback. Highly viscous liquids in the capillary tube can quickly cause fouling or blockage. In addition, the inline viscometer at reference temperature has a number of important advantages over capillary process technology. Below we describe the benefits of Sofraser's Thermoset series analyzers that measure viscosity at reference temperature.

Measure in-line viscosity at reference temperature

Sofraser's Thermoset series analyzers measure real-time and continuous viscosity at reference temperature, eliminating both variations in process temperature and changes in product behavior. The Thermoset uses a MIVI sensor based on the vibration technology. This technique measures the resistance of a liquid to vibrations with a vibration amplitude. A resonator is immersed in a liquid and the amount of damping from the liquid is measured to determine the viscosity. This measurement is not only much faster and very accurate, but also maintenance-free.

Measuring viscosity in this way has a number of important advantages in different processes.

High viscous liquids

Where the capillary tube is prone to plugging and fouling, the in-line viscosity at reference temperature does not have this weakness. This is particularly advantageous when using highly viscous liquids such as heavy fuel oils, bitumen, etc. It also has no parts subject to wear and tear, making it an extremely suitable measurement for heavy processes and demanding environments. In a visbreaking process, where heavy or highly viscous petroleum stocks or residues are converted to lower viscosity fractions, Sofraser's in-line viscosity measurement can be used in several steps to avoid contamination and increase yield.

Calculating the viscosity index

In the oil production process, measuring and calculating the viscosity index is a real challenge as it is necessary to measure the viscosity of the oil at two reference temperatures 37.8 ° C (100 ° F) and 98.9 ° C (210 ° F) ), while the manufacturing process can take place at a different temperature. For example, with the capillary process viscometer, it is then necessary to install two different analyzers, one for each reference temperature. Sofraser's Thermoset CF and LT mean that only one analyzer is needed to measure both, even when the process temperature is higher. The Thermoset KV does not even require an external density meter. It is the only process analyzer that can measure kinematic viscosity directly with a single probe and provide measurements in cSt. The measurement is therefore directly correlated with the ASTM D445 and completely in accordance with the ASTM D2270.

Inexpensive and accurate process viscometers for the petrochemical industry

The different analyzers in the Thermoset series are very accurate, can be used for different process conditions and they have a wide range in terms of temperature and pressure. Because it is possible to work with one instead of several analyzers for different process conditions, it quickly becomes a very economical solution.

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