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Safe use of laboratory centrifuges and elimination of common faults

Apr 09, 2019

Safe use of laboratory centrifuges and elimination of common faults

Safe use of laboratory centrifuges

In the design and manufacture of the centrifuge, the imbalance caused by the machining error of the rotor has been remedied by the dynamic balance test, but all centrifuges have their allowable unbalanced load. Centrifuge manufacturers strive to give larger values in order to compete with other manufacturers on the maximum unbalance limit allowed by the centrifuge. At this larger value, the centrifuge can be operated, but the imbalance force generated at this time suddenly hits the bearing and the bracket at n times per minute, and the centrifuge is damaged. Therefore, the user is trying to find a good balance and centrifugation for those expensive centrifuges, which is good for the life of the centrifuge.

Clearing up stagnant water

The refrigerating centrifuge uses refrigeration when it is running. It is frosted in the centrifugal chamber due to the moisture of the air, and is frosted into water after the shutdown. Most foreign low-speed large-capacity centrifuges have no drainage holes, and the water in the centrifugal chamber is more and more accumulated. At this point, the user should remove the rotor and clean up the accumulated water. When reinstalling the rotor, be sure to install it to avoid accidents.

Free from corrosion

Centrifuge rotors are generally made of aluminum alloy, which, when corroded, have reduced strength and are prone to accidents. The aluminum alloy is susceptible to liquid corrosion. After cleaning, it is blown dry with a hair dryer, or inverted for a period of time to confirm that it can be used. Some blood stations imported centrifuges, and there should be 6 plastic trays in 6 aluminum cups. The plastic tray should be placed in a blood bag to avoid direct placement in the aluminum cup. Note the test tube for cracks. If the test tube (especially the test tube used repeatedly) has cracks, it must not be used. Otherwise, the test tube rupture will cause the rotor to lose its balance during rotation, which may cause a vicious accident such as broken shaft.

Broken shaft accident

The rotor is not placed well, or the sample imbalance is too large, and the centrifuge starts. Today's centrifuges have unbalanced protection, that is, when the unbalance amount exceeds a certain limit, the power should be automatically turned off to stop the centrifuge. However, under the above circumstances, it is already late, and a serious accident will occur. One of the malignant accidents is the broken shaft. Due to the sudden broken shaft in the high-speed rotation, the centrifugal rotor has no support, and the centrifugal machine is turned into a chaotic collision, which can make the centrifuge rotate the machine to a 270° angle. At this time, if there are people or equipment next to it, it will cause casualties and damage to the equipment.

Elimination of common faults in laboratory centrifuges

(l) After power-on, the motor does not turn: first check the power cord, plug, and socket. If it is damaged, it should be replaced. If there is no problem, check whether the band switch or varistor is damaged or the cable is disconnected. If it is damaged or opened, replace the damaged component and re-weld the wire. If there is no problem, check whether the motor field coil is broken or open (internal). If the coil is broken, it can be re-welded. If the coil is internally broken, it can only rewind the coil.

(2) The motor speed does not reach the rated speed: first check the bearing, if the bearing is damaged, replace the bearing. If the bearing is short of oil or too much dirt, the bearing should be cleaned and greased. Check whether the surface of the commutator is abnormal or whether the matching of the brush and the surface of the commutator is consistent. For example, if there is any abnormality on the surface of the commutator, if there is a layer of oxide, it should be sanded with fine sandpaper. If the matching between the commutator and the brush does not match, it should be adjusted to a good contact. If there is no such problem, check the rotor coil for short circuit. If it is, rewind the coil.

(3) Vibrate and loud noise: Check if there is any imbalance. The screw of the fixed machine is loose. If it is, tighten it. Check the bearing for damage or bending. Replace the bearing if any. The machine cover is deformed or the position is incorrect. If there is, adjust it.

(4) The low speed gear cannot be started when it is cold: the lubricating oil solidifies or the lubricating oil deteriorates and sticks. At the beginning, you can use your hand to help re-rotate after re-turning or cleaning.