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The top photo is the instrument cabin housing the dual viscometer system featured on the previous page.

The use of such cabins is primarily to provide operators with a suitable environment... Not just to access the system but to collect sample for laboratory evaluation.

A heavy fuel oil blending facility in Southern Siberia. (Photos right : bottom and middle:).

The dual viscometer system is again installed in a cabin to allow the operators all-weather access for maintenance (if required) and to take samples for laboratory evaluation.

Steam jacketed lines travel only a short distance from the pipeline to the hut delivering a continuous sample stream.

The second photo shows the system arranged inside the cabin.

In this system, two heat exchangers are used; systems are not standardised but custom designed to meet the application objectives and reflect the process conditions.

At the bottom right hand side is a steam flow control valve to the first heat exchanger controlling the temperature of the fluid as it reaches the first viscometer (middle left).

Above is another control valve, this one for coolant for the second heat exchanger controlling the sample temperature at the second viscometer above the first.

Application Objectives:

As is the case in many refineries, heavy fuel oil is a critical operation requiring process measurement of viscosity. In the original arrangement residual oil is mixed in the pipeline with cutter stock to produce a blend with the required properties.

The blended oil is then delivered to an intermediate storage tank.

From this tank top, middle and bottom samples would be taken for analysis in the laboratory. Adjustments would then be made to the blend while still in the tank.

Despite an exacting laboratory procedure using 8 parallel capillary viscometers in temperature baths to find the statistical averaged value they would still have major problems with quality control. Incidentally, this type of statistical measurement in the laboratory, along with suitable sampling methods, is recommended in standards such as API 554 and API 555, but rarely implemented with conventional blending systems.

With the installation of this dual viscometer system and especially because of its accuracy and speed of response, very precise control of the blend quality becomes a reality. This allows the blend to be delivered direct to the tank car loading area.

This illustrates one of the major benefits of the modern digital viscometer in whatever system or method employed; the ability to blend on demand straight to use or distribution. Without having to have storage facilities for final adjustment far greater flexibility is available and less capital investment in plant and equipment.

A  second major advantage of these systems is cost efficiency.

Improved quality control can pay dividends. In heavy fuel oil blending conservative estimates suggest savings of around $7 a ton. For the plant operator, the very low maintenance and very high on stream factor means that the operator does not have to invest in special skills for service and maintenance and the maintenance costs are dramatically reduced.

In the blending of heavy crude oils with distillate for pipeline pumping the cost benefits can be even more dramatic. Again, it is the reduction in the “give-away” that pays dividends and in this case also, the avoidance of financial penalties for incorrect blends in the pipe line.

Viscosity: Dual Viscometer Systems examples: Back