Viscosity refers to the resistance of a fluid to flow. It is defined as the shear stress required on each 1cm2 plane when the liquid flows at a speed of 1cm/s, which is called dynamic viscosity and is measured in Pa·s. Viscosity is a property of a fluid. When a fluid flows in a pipeline, there are three states: laminar flow, transitional flow, and turbulent flow. These three flow states also exist in the stirring equipment, and one of the main parameters that determines these states is the viscosity of the fluid. During the stirring process, it is generally believed that fluids with a viscosity less than 5Pa/s are low-viscosity fluids, such as water, castor oil, maltose, jam, honey, lubricating oil, heavy oil, low-viscosity emulsions, etc.; 5-50Pa/s are medium-viscosity fluids, such as ink, toothpaste, etc.; 50-500Pa/s are high-viscosity fluids, such as chewing gum, plastisol, solid fuel, etc.; and those greater than 500Pa/s are extra-high-viscosity fluids, such as rubber mixtures, plastic melts, silicones, etc. For low-viscosity media, a small-diameter, high-speed agitator can drive the surrounding fluid to circulate and reach a distant place. However, this is not the case with high-viscosity fluids, which need to be directly driven by a stirrer. Impellers suitable for low-viscosity and medium-viscosity fluids include paddle type, open turbine type, propeller type, long thin blade propeller type, disc turbine type, Brumakin type, plate-frame paddle type, three-blade backward curved type, MIG type, etc. Impellers suitable for high-viscosity and extra-high-viscosity fluids include spiral ribbon impeller, screw type, anchor type, frame type, propeller type, etc. The viscosity of some fluids changes as the reaction proceeds, so it is necessary to use an impeller that can adapt to a wide viscosity range, such as a pan-energy impeller.
Introduction to the shaft seal device of common chemical agitators
1. Mechanical seal refers to two annular sealing elements. On the smooth and straight end face of the chemical agitator, they rotate relative to each other under the action of medium pressure or spring force, thus forming a sealing structure.
2. When the shaft rotates, it drives the spring seat, spring, spring pressure plate, dynamic ring and other parts to rotate together. Due to the action of the spring force, the dynamic ring is tightly pressed on the static ring. When the shaft rotates, the dynamic ring rotates with the shaft, while the static ring is fixed on the seat frame and remains stationary. The annular sealing end face where the dynamic ring of the chemical agitator contacts the static ring prevents the leakage of the medium. Therefore, from a structural point of view, the mechanical seal mainly changes the axial seal that is more prone to leakage to the end face seal that is not easy to leak. It can be seen that the reason why the chemical agitator chooses mechanical seal as its shaft sealing device is mainly because the sealing structure of the mechanical seal is better and not easy to leak. At the same time, it can promote use and give full play to its performance.
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