What is viscosity?
Viscosity is an important characteristic of a liquid which helps predict its flow behavior. It quantifies a liquid’s internal friction, determining its resistance to flow. The higher the viscosity, the slower the flow.
Why is it important for coatings?
Coating companies use viscosity as a means to measure and control the percent solids in coatings, establishing their coat weight thickness. Standard practice has been to maintain a constant cup viscosity target, day and night, summer and winter. Viscosity is directly related to temperature, so to measure one without taking into account the effects of the other is inadequate. For example, 70 secs @ 70°F, vs. 70 secs @ 100°F are dramatically different and produce significantly different coat weights. The first example yields very light coat weights, the second, very heavy coat weights. A temperature spread this large would probably yield out of spec product.
How is viscosity measured?
In the past, the cup method was a popular method of viscosity measurement in the coating industry. Using this method, an operator dips a cup into the can coating material, and then uses a stopwatch to measure the time it takes for the fluid to flow through a hole in the bottom of the cup. The longer it takes, the higher the viscosity. It is a simple approach. However, in a situation with many operators, there are many different variations on the basic method of measurement, and therefore there are many different measurements.
Results obtained with the cup method are inaccurate and are not repeatable even if the same person makes measurements all the time. Cups are just not accurate or reliable for today’s coatings, and that is why most professionals in the coating industry are installing process viscometers.
How do I know if I need a viscometer?
If you don’t have any problems with your coating process, and if you are completely satisfied with your finished quality and costs, then you don’t need a viscometer. If, however, you would like to improve your process, improve your quality and save money, then a viscometer can help dramatically.
What should I look for in a viscometer?
Process viscometers can be excellent additions to the coating process. However, not all viscometers are created equal. Traditional process viscometers have been used in many coating applications, and although they are better than cups, there are still significant problems with accuracy, reliability, and repeatability.
The main problem with traditional process viscometers is the wet/dry interface. Process viscometers are usually mounted in a coating tank with a constantly changing coating level. Every time the level goes low, the coating dries, promoting a buildup on the traditional rotating spindle or a piston rod. This is especially true for today’s water-based coatings which do not go back into solution after they have dried. As the coating builds up on the viscometer, the drag on the viscometer is higher and the viscosity number goes up artificially. The unit makes an adjustment to thin out the coating when it shouldn’t, resulting in bad product and lost production.
What’s different about viscometers from Cambridge Viscosity?
Viscometers from CVI provide a unique solution to the problem. Based on a patented piston sensor design, Cambridge viscometers are accurate, reliable, and require little or no maintenance for most can applications. For example, the ViscoPro 2100 accurately measures viscosity and temperature and calculates TCV (temperature compensated viscosity), the calculated value of viscosity at another temperature. TCV is an important tool that accurately indicates if percent solids have changed, allowing plant personnel to eliminate the effects of process temperature variations on viscosity readings.
What does the systems consist of, and how is it installed?
The CVI viscometer system consists of a sensor, piston, cable, and electronics. The sensor is rugged and simple in design, and the electronics are easy to use. Also included are 4-20mA outputs for both temperature and viscosity which can be connected to a monitoring and control system.
Installation is simple and inexpensive. Simply add a “tee” fitting into the existing coating line going to the applicator. Install the sensor and run the cable back to the electronics. The electronics come in an explosion-proof rated NEMA4 enclosure for protection or DIN-rail-mounted housing, which can be mounted hundreds of feet away if necessary. Install the valves for your water addition and wire the solenoid back to the electronics. It’s that simple.
What about maintenance?
Cambridge Viscosity viscometers are designed to be maintenance free. A simple field calibration is recommended for most applications.
How do I know it will work?
CVI systems are currently operating well in coating applications across many industries, including optical lenses, medical applications, automobile headlights, telescopes and cameras, and many others. Additionally, Cambridge Viscosity systems are guaranteed to perform to your satisfaction, or the system can be returned within 30 days for a full refund.
To ensure your success, CVI personnel will provided continued consultation after installation and make certain that it is installed correctly, and that its operation is understood by line personnel.
How do I order a system from CVI?
Cambridge Viscosity application engineers are available to discuss your specific needs. First, you can build your viscometer by clicking the Build your own viscometer button below.
A member of our customer support team will contact you to discuss and clarify any areas as necessary, and a quotation will be generated.
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