Product Focus: Viscometers
The ease of adding ketchup from a squeeze bottle to an order of French fries, the trouble that it takes to press toothpaste out of a tube, and many other common needs depend on viscosity.
The range of measurement conditions keeps expanding up and down
If toothpaste, for example, is not viscous enough it would just pour out of control from the tube; if it’s too viscous, you might need a steamroller to get something on your brush. In discussing the measurement of viscosity overall, Bob McGregor, manager of global marketing and high-end instrument sales at Brookfield Engineering (Middleboro, MA), says, “It’s a huge area. In any industry with materials that physically flow, you can be sure they’ve been tested for viscosity.”
The options for measuring viscosity are just as numerous as the applications, and growing. When asked about exciting trends in viscosity measurement, Eric Swertfeger, director for viscosity products at Anton Paar (Graz, Austria), turns immediately to temperature. “They want to see how far they can push it—high and low—and still get reliable data,” he says. For now, the desirable range starts higher than 100 degrees Celsius and goes down below –20, with some people looking to drop that even more. In addition, says Swertfeger, “People want to take traditional methods and make them faster.”
At Core Laboratories Canada in Calgary, Ken Chong, general manager and vice president, uses a viscometer for hydrocarbon samples of from light to very heavy oils. When asked about the most important features of a viscometer, he says, “Density and viscosity over a range of temperatures on a single charge, and the minimal volume it requires to accomplish this.” He adds, “The former makes it very efficient, and the latter is very important for heavy oil where sample volumes can be limiting.”
The features that matter most, though, depend fundamentally on the materials being tested. So setting up the best viscosity measuring system will vary from lab to lab.
Reasons to be unreliable
“With older technology,” says Swertfeger, “sample handling and maintenance are huge factors in getting repeatable results.” He adds that newer, more automated devices usually just need to be kept clean. “If you make measurements in a dirty environment, you tend to have more problems,” he says. For any viscometer, though, he recommends regular maintenance. He says, “For anything that requires a specific temperature, you need a reference to check it against. That way you can verify the operation of your instrument.”
Newer technology can also be more accurate. For example, Anton Paar offers a frictionless technology that provides more accurate results.
Today’s viscometers can also be easier to use. As an example, McGregor points out the touchscreen interface. “You can use it like a handheld device,” he says. “It also provides the ability to see live graphical information in terms of what’s being measured.”
In many cases, companies can save money by placing a viscometer in a production line, making measurements in real time. “This way,” says McGregor, “they can monitor viscosity continuously and make process changes if they see deviations.”
When shopping for a viscometer, McGregor encourages customers to “try to do what others are already doing, because they’ve established test procedures on known parameters.” That way, you can find the right instrument and figure out how to use it without starting from scratch.
For additional resources on viscometers, including useful articles and a list of manufacturers, visit www.labmanager.com/viscometers