- Measurement and Testing 33 inconsistencies in the end product that the line was experiencing.


The plant engineers decided to test this concept by using the new in-line viscometer to automatically control the kinematic viscosity of the in-process material. The results are shown in Figure 2.


This figure displays process data for the two days prior to implementing in-line viscosity control with the Cambridge viscometer and three days afterward. Figure 2 illustrates that the viscosity results fluctuated a great deal prior to implementation of the in-line analyzer. The figure also shows that using the in-line viscometer enabled much tighter viscosity control in the process and a continuing close correlation between the results of the periodic laboratory tests with associated in-line results.


Consistent Data and Cost Savings


By using the new in-line viscosity management system, the refinery was able to achieve continuous sample measurement with no missed data points and spot-on correlation with lab results. While the control parameters for the Cambridge viscometer were not optimized for the characteristics of the specific plant process environment, the plant was able to:


• Reduce product variation by 90% • Realize significant cost savings by reducing diluent use to achieve targeted specifications • Reduce tankage requirements and associated capital and maintenance costs • Increase throughput with less investment in inventory and capital equipment


By reducing product variation, it allowed the refinery to attain the targeted product specs with minimal post-process blending. Reducing product variation also limited the amount of “excess tankage,” or extra material that previously was being inventoried in blending tanks. Less inventory in the blending tanks translated into less diluent that was required to be blended to achieve the targeted product specs; all of which ultimately results in a reduced operating cost and a higher throughput. “By producing the mixture to spec in the first batch, it prevents re-work, allowing a great cost and time savings by the refinery,” explains Cambridge Viscosity Regional Sales Manager, Jonathan Cole.


When a refinery delivers the final product to its end-user, the refinery supplies certified documentation proving that the asphalt meets proper specification. The documentation will state that the product has been tested, what the mixture breakdown is, what was used as a diluent (usually diesel), and ensure that the final product meets ASTM criteria.


“Customer specs are based on international standard test methods that utilize standard laboratory test equipment. These lab tests are done periodically throughout production, and the process is adjusted based on the test results. The material is then tested in the storage tank, and re-blended to meet the exact customer specifications. Unfortunately, the asphalt characteristics can vary significantly between lab tests. This can require significant post-process blending to meet customer specifications, ”states Mr. Cole.


Figure 4: A Schematic of a Cambridge sensor operating in-line Sensor Technology


Figure 3: ViscoPro2000, an In-line Cambridge Viscometer


Cambridge viscometers are fundamentally simple, rugged, accurate and repeatable, even when used in operating environments with significant vibration (See Figure 3). A key to the company’s technology is its use of a single, non-contact moving part both to clean and measure. The motion of the piston is


Resources


1. International Petroleum Encyclopedia 2004 . Tulsa, OK: PennWell Corporation, p. 286., Oil and Gas Production - Oil Refining. International Labour Organization. http://www.ilo.org/public/english/dialogue/sector/sectors/oilgas.htm


controlled so that it monitors the fluid viscosity and keeps the sensor’s measurement chamber clean, so that the sensor requires minimum operator attention. A temperature detector is also included in the measurement chamber so that both temperature and viscosity are known for every measurement. The company’s patented self-cleaning and self-recovery characteristic enable the sensors to operate trouble-free in-line.


Cambridge viscometers use proprietary electromagnetic technology to analyze the piston’s travel time to measure absolute viscosity and monitor temperature. With all wetted parts stainless steel, the constant motion of the piston keeps the measurement sample fresh while mechanically scrubbing the measurement chamber. Cambridge Viscosity, which is part of the PAC team, has more than 10,000 sensors installed worldwide in many applications where viscosity knowledge and management is critical. A schematic of the operating characteristics of a typical Cambridge viscometer sensor is shown in Figure 4.


Viscometers for Reproducable Inline Measurements


Marimex Industries (Germany) offers their VA- 300 model for reliable inline viscosity measurements, suitbale for use in pipes as well as in reactors. Individual installation scenarios demand tailor-made sensors. VA-300 series ViscoScope sensors can be used to realise any technically feasible design, therefore mostly no modifications on existing pipes or reactor nozzles are necessary.


Installations in bunker oil, bitumen and fuel oil are a small part of the manyfold applications. Of course the sensor is available with ATEX certificate to mount the probe in Zone 0.


With the integrated RTD the process temperature will be measured at the same place where the viscosity is measured, allowing an accurate temperature compensation to a reference temperature. All transmitters of the ViscoScope series are capable to calculate the kinematic viscosity in cSt.


User-selectable and configurable analogue outputs and serial interfaces render a connection to any process control system. If desired, a relay board option is also available.


Reader Reply Card No 74 Reader Reply Card No 75 April / May 2012 • www.petro-online.com


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