Benchtop low speed centrifuge controls vibration range
2019-04-03 08:23:14 Click: 238
Low-speed centrifuges are one of the most common laboratory instruments in the laboratory. How do you control the vibration range when using them? As we all know, only when the working speed of the centrifuge is not at the critical speed, the rotor can move smoothly. For low-speed centrifuges with low operating speeds, the critical speed is generally increased as much as possible to allow the centrifuge to operate below the critical speed. The centrifuge has a very thick shaft and a high stiffness, called a rigid shaft. When the speed requirement is high, the critical speed is reduced as much as possible. The shaft is made thinner and the rigidity is small. It is called a flexible shaft. Modern ultracentrifuges use flexible shafts.
The critical speed is related to the centrifuge and the associated rotor. A centrifuge can be equipped with several kinds of rotors, so the design of the centrifuge should consider the containment of the various vibrations of the centrifuge. Centrifuges have a wide operating range, from a few thousand revolutions per minute to tens of thousands of revolutions per minute. The higher the rotational speed of the centrifuge, the greater the risk.
Once the vibration occurs at high speed, the centrifuge should be stopped immediately with the fastest speed reduction gear. All personnel should leave the scene quickly to avoid personal injury in the event of a broken shaft. Never power off, once the power is off, the brakes (fast speed reduction) are gone, and the rotor stops very slowly. The accident is usually caused by improper operation of the centrifuge. For example, if the rotor is not placed on the main shaft, the cover of the rotor is not covered, and the basket of the rotor is not placed. The structure of this accident is accompanied by a huge sound, and the 300-400kg Shanghai centrifuge suddenly rotates 270 degrees. Open the cover section and see that the rotor is lying in the cavity. When the rotor is removed, the outer surface of the rotor is severely scratched and the inner wall of the centrifugal cavity is damaged, and even the refrigerant leaks. Sometimes the rotor and rotor cover are separated, the liquid in the test tube is sprinkled inside the cavity, and the spindle is broken or severely bent. Due to the frequent occurrence of such accidents caused by improper operation of the user, modern centrifuges generally have an imbalance protection function. That is, once the vibration of the rotor is greater than a certain size when the centrifuge is started, the centrifuge will automatically stop and stop. The centrifuge with this performance sometimes misses the report and cannot ensure that there is no accident.
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