What Is a Viscometer?

Viscosimeter An instrument used to measure the viscosity of fluids (liquids and gases). Viscosity is a physical quantity that indicates that internal friction occurs within a fluid when it is flowing. It is the fluid's ability to resist deformation. Viscosity varies with fluid and changes with temperature. There are three types of capillary viscometer, rotational viscometer and falling ball viscometer. ^[1]

When a liquid flows, the nature of internal friction between its molecules is called the viscosity of the liquid. The viscosity is expressed by viscosity, which is a resistance factor used to characterize the properties of the liquid. The viscosity of the insulating oil is the same as the concept of the viscosity of the general liquid, that is, the internal friction of the liquid, which means that the insulating oil performs relative laminar flow under external force. The nature of the insulating oil molecules is responsible for the internal frictional resistance. The greater the internal friction of the insulating oil, the greater the viscosity, the more difficult it is to flow, and the poorer the heat dissipation performance.

There are many ways to express viscosity, which can be divided into two categories: The viscosity measured directly according to the definition of viscosity is called "absolute viscosity", such as

1.The machine must be kept horizontal

2. When the rotor is placed in the sample, avoid generating bubbles, otherwise the measured viscosity value will decrease. The method to avoid is to put the rotor into the sample at an angle, and then install the rotor. The rotor cannot touch the cup wall and the bottom of the cup. The sample to be measured must not pass the specified scale.

3. When measuring different samples, the rotor must be kept clean and dry. If there are other samples in the rotor or water remaining after cleaning, it will affect the accuracy of the measurement.

4. The maximum acidity (PH) cannot exceed 2. If the acidity is too high, a special rotor should be used. When using ULA, determine the sample size (only 16ml).

5. Select the viscosity standard solution according to the measured viscosity range, and verify the instrument before each use of the viscometer or rheometer, or periodically check to ensure the accuracy of the measurement. Newtonian fluids can be provided for each viscosity range Silicone oil or oil standard, with an accuracy of ± 1%. The recommended use period of the viscosity standard solution is one year from the opening.

6. When connecting the rotor, gently lift and hold the mandrel (on the host) with your left hand and rotate the rotor with your right hand. This operation is to protect the mandrel and hairspring in the fuselage, which can prolong the service life of the instrument.

7. The value should be set when the value is relatively stable, otherwise there will be a large error in the value obtained

8. When selecting a rotor, select the number of the rotor that depends on the viscosity of the sample being measured and the measurement range of the rotor.

1. Divided by operation mode: capillary, rotary and vibrating.

Capillary viscometer: Capillary viscometer is usually a Sai's viscometer, which is a common viscometer. The working principle is that the sample container (including the outflow capillary) is filled with the sample to be measured, is in a constant temperature bath, and the liquid column height is h . Open the cock, the sample begins to flow to the receiver, and the time is calculated at the same time, until the sample liquid level reaches the graduation line. The greater the sample viscosity, the longer this time. Therefore, this time directly reflects the viscosity of the sample.

Rotary viscometer: A common rotary viscometer is a cone-plate viscometer. It mainly consists of a flat plate and a cone plate. Motor Warp

In actual engineering and industrial production, it is often necessary to check the viscosity of the fluid online to ensure the best process operating environment and product quality, thereby improving production efficiency. By measuring the liquid viscosity in the process, the data of the liquid rheological behavior can be obtained. It has important guiding value for predicting the process control of the product process, the transportability and the operability of the product during use. The characteristics of the liquid are often related to other characteristics of the product such as color, density, stability, solid content and molecular weight changes, and the most convenient and sensitive way to detect these characteristics is to check the viscosity of the liquid online. Process viscosity requirements for online viscosity testing can minimize product scrap rates and production line downtime.

According to its measurement principle, in order to obtain accurate and reliable measurement data, the following points must be paid attention to:

First, the performance indicators of the instrument must meet the country

1. Handle the rotor carefully during loading and unloading. Lift up the connecting screw slightly during loading and unloading. Do not apply excessive force. Do not subject the rotor to lateral forces to prevent the rotor from bending.

2. Do not place the viscometer with the rotor on its side or upside down.

3. Keep the connecting screw and rotor connection end face and thread clean, otherwise it will affect the sway of the rotor.

4. When the viscometer is lifting, it should be held by hand to prevent the viscometer from falling due to its own weight.

5. After changing the rotor, please enter the new rotor number in time. After each use, the replaced rotor should be cleaned (wipe clean) in time and put back in the rotor frame. Do not leave the rotor on the instrument for cleaning.

6. When changing the liquid to be measured, please clean (wipe) the rotor and the rotor protection frame in time to avoid measurement errors caused by the confusion of the liquids to be measured.

7. The instrument and rotor are matched one-to-one, please do not confuse several instruments with the rotor.

8. Please do not disassemble and adjust instrument parts at will.

9. When moving and transporting the instrument, the yellow cap should be installed at the connecting screw, and the screw should be tightened and put into the packing box.

10. After installing the rotor, please do not rotate it for a long time without liquid, so as not to damage the shaft tip.

11. Many suspensions, emulsions, polymers, and other high-viscosity liquids are "non-Newtonian liquids." Their viscosity values change with conditions such as shear rate and time. Inconsistent results with time measurements are normal and not instrumental errors. The determination of non-Newtonian liquids should generally specify the rotor, speed and time.

12. Doing the following points will help to obtain more accurate values:

Precisely control the temperature of the liquid being measured.

Immerse the rotor in the liquid to be measured for a sufficient period of time so that the temperatures are the same.

Maintain liquid uniformity.

When measuring, place the rotor in the center of the container, and be sure to install the rotor protection frame.

Keep the rotor clean and sloshing.

When the high-speed measurement changes to a low-speed measurement immediately, it should be turned off or mastered a little longer at the low-speed measurement time to overcome the error caused by the liquid's rotational inertia.

When measuring low viscosity, use No. 1 rotor, and when measuring high viscosity, use No. 4 rotor.

When measuring viscosity at low speed, the measurement time is relatively long.

Due to the need to change the rotor and the measured liquid during the measurement process, after the position of the viscometer has been changed by turning the lifting chuck, the horizontal position of the viscometer should be checked and adjusted in time.