The critical speed is related to the centrifuge and the rotor used. A centrifuge can be equipped with several kinds of rotors. Therefore, when designing a centrifuge, the vibration damping design of the centrifuge should be considered to be inclusive of various rotors. The working range of the centrifuge is very wide, from a few thousand revolutions per minute to tens of thousands of revolutions per minute. The higher the rotational speed of the centrifuge vibration, the greater the danger.
Once the vibration occurs at a high speed, the centrifuge should be stopped immediately with the fastest downshift speed. All personnel should leave the site quickly to avoid injury when a shaft breakage or other accident occurs. It must not be powered off. When the power is turned off, the brake (quickly decelerating) is gone and the rotor stalls slowly. The accident is generally caused by improper operation of the centrifuge. For example, if the rotor is not placed on the spindle, the cover of the rotor is not covered, and the basket that flies off the rotor is not placed. The structure of this accident was accompanied by a huge sound, 300-400kg of Shanghai centrifuge suddenly rotated 270 degrees. Open the lid section and see the rotor lying in the cavity. Take out the rotor branch and observe that the outer edge surface of the rotor is severely scratched and discolored, and the inner wall of the centrifugal cavity of the centrifuge is damaged, even the refrigerant leaks. Sometimes the rotor and rotor cover are separated, the liquid in the test tube is spilled in the chamber, and the spindle of the centrifuge is broken or severely bent. Due to the frequent occurrence of such accidents caused by improper operation of users, modern centrifuges generally have unbalanced protection functions. That is, once the centrifuge is started, once the vibration of the rotor is greater than a certain size, the centrifuge will automatically stop at a reduced speed. Centrifuges with this type of performance will sometimes fail to report, and failure to ensure accidents will not occur.
Both the centrifuge rotor machining error and the centrifuge mounting error will cause the rotor center of mass to deviate from the centrifuge spindle to varying degrees. Therefore, vibrations may occur when the centrifuge rotor rotates. These vibrations may interact with the centrifuge drive system at certain rotational speeds. The natural frequency resonates, causing the entire system to vibrate strongly. The speed at which this phenomenon occurs is called the critical speed.
Centrifugal rotors can cause vibrations when they rotate at high speeds, but the flexible shafts have "self-aligning action." Its principle of action is that the rotor produces a disk effect when it rotates at high speed, so that the elastic reaction force when the flexible shaft is bent pulls the rotor, which deviates from the geometric centerline of the spindle, back to the geometric centerline of the spindle, and the vibration disappears. Of course, there must be a certain limit to the amount of imbalance present in the rotor. Exceeding its limit, the vibration will not disappear.
Chromium carbide thermal spray powder is a type of coating material used in thermal spray processes. It is composed of chromium and carbon, with the chemical formula Cr3C2.
This powder is commonly used in applications where high wear resistance and hardness are required. It is often applied as a protective coating on surfaces that are subjected to abrasive or erosive environments, such as industrial equipment, cutting tools, and engine components.
The thermal spray process involves heating the powder to its melting point and then propelling it onto the surface to be coated using a high-velocity gas or plasma stream. Upon impact, the molten particles solidify and bond with the substrate, forming a dense and durable coating.
The chromium carbide coating provides excellent resistance against wear, corrosion, and oxidation. It also exhibits good adhesion to various substrates, including metals, ceramics, and composites. Additionally, it has a low coefficient of friction, making it suitable for applications where reduced friction and improved sliding properties are desired.
Overall, chromium carbide thermal spray powder is a versatile and effective coating material that offers superior protection and performance in demanding industrial applications.
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