Views:4 Author:Site Editor Publish Time: 2020-06-12 Origin:Site
Whether a kinematic viscometer is clean or even directly affects the accuracy of the liquid viscosity measurement, which is why it is necessary to perform subsequent cleaning after using the Kinematic viscosity meter. So how do we clean the kinematic viscosity measuring instrument is correct?
The role of a kinematic viscometer
Why is it important to clean the kinematic viscometer?
How to clean the kinematic viscometer?
A kinematic viscometer measures the viscosity (thickness or viscosity) of a liquid due to internal friction. kinematic viscometers typically measure the resistance of a moving liquid between the entire surface, indicating the properties of many industrially relevant properties, such as the lubricity of the oil, the protein concentration in the biomanufacturing process, or the wetting characteristics of the liquid.
Many types of viscometers are used in the R&D environment. The most common varieties are orifices, descending/moving pistons, rotating, falling balls, vibrations and capillaries, which work by measuring vibration, fluid pressure and Coriolis force. The Capillary viscometer uses a U-shaped glass tube with bulbs at both ends - one end higher than the other. The viscosity of a fluid is determined by the time it takes for a certain amount of fluid to pass through the tube at a distance (through a certain diameter).
Unlike most analytical modes that use a capillary Kinematic viscosity meter to isolate the sample from the inside of the instrument, the sample chamber is the instrument. Therefore, cleaning is critical to achieving reproducible and accurate results. Joseph T. Mastro Pietro, Technical Director of the Associate Laboratory at Cannon Instruments (Pennsylvania State University) stressed the need for thorough, careful cleaning. “Excluding as much of the test material as possible from the kinematic viscometer before cleaning is critical to speeding up the cleaning process,” he said. “When the viscosity of the test material is high, this can be tricky because drainage can cost some Time." Increasing the temperature reduces the viscosity of the test material and helps it drain more efficiently.
“The second key step is to choose a cleaning solvent that will dissolve the material being tested. After adding the solvent to the Kinematic viscosity meter, leave enough soaking time to ensure complete dissolution and removal of the test substance. Low-viscosity solvents help ensure cleanliness. After cleaning the solvent, leave the proper time for air drying to help ensure that the residual solvent is removed." Insufficient cleaning can seriously affect the quality of subsequent viscosity tests. Mastropierro added: "Based on the difference in viscosity between the previously tested sample and the current test sample or the cleaning solvent used, higher or lower results may be incorrectly derived."
Capillary viscometers are reliable and time-tested, but users should only select this instrument type after considering their test fluid and conditions for measuring viscosity. Walsh warned: "Not only the analysis but also the sample preparation and any interference that may occur or develop over time."
The test sample was taken from the kinematic viscometer. The first step in cleaning is to remove most of the test sample. For low viscosity liquids, the kinematic viscometer can be inverted and suspended while the test sample is discharged into the tank. For highly viscous liquids, it may be necessary to draw the sample under vacuum. The material remaining in the viscometer must then be rinsed off with a suitable solvent. Distilled water is an obvious choice for aqueous solutions. Petroleum based lubricants and bitumen can generally be dissolved with light naphtha, heptane, octane, highly aromatic solvents and many other petroleum derived solvents. Hydrocarbon solvents are commercial solvents that are very suitable for this purpose. For some types of samples, it may be difficult to find a suitable solvent.
High viscosity samples are not easily pour out of the instrument and do not respond well even under vacuum. The best way to do this is to lower the viscosity by heating the instrument in an open oven or with a hot air stream. Simply flip the instrument upside down and hang it over the container in an open oven to capture the sample, which usually works well. Another method is to take a large amount of sample when the instrument is placed at a high temperature in a constant temperature bath. The kinematic viscosity measuring instrument is typically placed in an open aluminum oven (2 inches x 7 inches by 5 inches deep) and maintained at a high temperature. Even if most of the viscous sample is taken out of the instrument, dissolving the remaining sample can cause significant problems. We have found that a mixture of octane isomers is particularly effective for removing the last traces of high viscosity standards from a kinematic viscometer.
Dry the kinematic viscometer after cleaning. The kinematic viscometer must be completely dry before loading another sample. Cleaning with a highly volatile solvent is recommended because all residual solvent evaporates quickly after the sample is rinsed from the Kinematic viscosity meter. However, the optimum solvent choice for materials in a viscometer is generally not particularly volatile. In this case, the second highly volatile solvent that will dissolve the first solvent can be used in the final step of cleaning. Acetone is commonly used as a second solvent due to its high volatility and ability to dissolve traces of petroleum solvents and water. The low-speed clean air stream is sufficient to evaporate residual volatile solvents, but note that the rapid evaporation of these solvents cools the glass surface to a degree that allows the humid air to fall below the dew point, resulting in the inner surface of the kinematic viscometer A water film is formed. Heating the air that is drawn into the instrument or heating the glass itself can often overcome this problem.
Clean insolubles. Capillary viscometers are commonly used to measure materials that are strained or significantly deposited by materials that are insoluble in common cleaning solvents. The most common method of removing this material is to fill the instrument with a chromic acid cleaning solution and allow the instrument to soak in acid for 24 hours. The chromic acid solution oxidizes strongly and converts many substances into a soluble form. Chromic acid does not erode the borosilicate glass of the viscometer and therefore does not change the calibration constant. Since chromic acid is a hazardous substance, the correct procedure must be followed when using and discarding chromic acid. Commercially produced oxidizers (Nochromix) contain no chromium and can replace chromic acid solutions. Nochromix is available from Cannon Instrument Company. Beware of high pH glass cleaners. Due to the long-term use of alkaline cleaning solutions, the viscometer calibration changes by up to 20%. If the viscometer calibration has been performed with an alkaline cleaning solution with a pH greater than 10, make sure there are no significant changes. Insoluble particles sticking to the Capillary viscometer can sometimes be removed by using an ultrasonic cleaner.
A clean kinematic viscosity measuring instrument is essential if accurate and accurate measurements are to be made. If you are looking for a reasonably priced high quality kinematic viscometer, NANJING T-BOTA SCIETECH INSTRUMENTS&EQUIPMENT CO.,LTD can provide you with the best products.