CENTRIFUGES (USE, TYPES AND MAINTENANCE)
Centrifuges are medical equipment used in laboratories, clinics and others, for the separation of solutes from their solvents. For example, in the clinical laboratory branch, for blood analysis, it is usually necessary to separate the plasma from the other components in order to be analyzed.
There are several basic types: low-speed serum or plasma separation centrifuges (Macrocentrifuge, between 2,000 and 6,000 RPM approximately),
centrifuges for microhematocrits (Microcentrifuge between 10,000 and 18,000 RPM approx.) and ultracentrifuges (from 20,000 to 75,000 RPM) for protein separation. They can also be cataloged based on other characteristics, such as: large, medium and small; or floor, table, refrigerated, etc. According to their rotor (spider) and their sample tubes they can also be cataloged, as there are various shapes and sizes.
The main parts of this equipment are as follows:
2. Chamber or cabinet
4. Power switch
5. Time Marker
8. Speed control
• Cover. Prevents access to samples while they are in motion. In most models it works automatically, so it cannot be opened while the centrifuge is running.
• Chamber or cabinet. It is the physical space where the centrifugation process is carried out. Inside this the rotor (spider) rotates.
• Base. It is generally built of heavy materials, and with fixing systems to the surfaces, so that it provides stability to the equipment.
Controls are usually located here.
• Ignition switch. It allows control of the power supply to the equipment, such as turning it on, turning it off, and generally includes selection of the operating mode.
• Time control. Allows you to control the centrifugation time.
Generally, it also allows you to view the elapsed or pending time for the completion of a selected process.
• Tachometer. Shows the speed at which the rotor rotates, ie the centrifugation speed (in revolutions per minute, RPM).
• Brake. Some centrifuges, depending on the model, have this control, which allows either to make the centrifuge stop process faster, or to stop it in emergency situations. Its specific function is determined by the manufacturer, therefore it must be used with caution according to its instructions.
Other parts not shown in the figure, but important in the centrifuge are:
• The rotor. Also known as spider, it is the part in which the sample holders are placed. For its conservation it is important to follow the loading instructions of the centrifuge.
• Sample holder. They are a kind of containers where the samples are placed. Its size depends on the application for which the equipment is designed: blood bank, hematocrit, etc.
These components may vary depending on the complexity and quality of the equipment.
Loading the centrifuge in an adequate way is very important for its correct operation and its preservation. A procedure
incorrectly loaded, causes the centrifuge to vibrate during the centrifugation process, which causes the rotor to suffer damage that may lead to its replacement.
A correct loading procedure involves placing the loads on the rotor in a balanced manner. Centrifuges are designed to achieve balance when in motion. For this it is necessary to meet the following requirements:
a) Arrange the charges so that charges having the same mass or
weight are positioned oppositely on the rotor. If you have an odd number of samples to load, find another sample of equal weight so as to always form opposite pairs of equal weight; never place an odd number of samples into the centrifuge.
Use the balance to be sure of equal weights.
b) In addition to having the same mass (weight), they must have the same center of gravity, that is: do not place tubes and containers as pairs
opposite, that have different shapes, sizes, thickness, etc.
c) Operate the centrifuge by placing all the accessories on the rotor, since these equipments have been designed to work with them.
d) Use the original equipment rotor and accessories. Non-original parts can produce an imbalance and shorten the useful life of the equipment.
e) Supplement these recommendations with the manufacturer's instructions.
Other Recommendations for Use
In addition to following the recommendations in section IV.2, it is important to take into account others to keep the centrifuge in the right conditions:
1. Keep the centrifuge clean of sample debris, glass, or dust.
2. When spinning, keep the lid closed. If something breaks, immediately turn off the equipment and do not open it until it stops or the
lid open indicator indicates so.
3. Replace metal cups that are warped, as they cause non-uniform pressure on the sample tube.
4. Do not use scratched or cracked glass equipment, because centrifugal pressure can cause these points to rupture, pulverizing the
glass and contaminating the other samples.
5. Replace the buffer plugs on the sample holders.
When a glass tube deteriorates and/or breaks, clean the remains (macro centrifuge).
6. Check that the surface where you have the equipment is perfectly level, since otherwise it would cause vibrations.
7. Check the operation of the equipment by performing the following steps:
− Load the centrifuge correctly and close it.
− Make sure that the centrifuge is well closed.
− Turn on the power switch, previously setting the centrifugation speed and/or time (if the equipment has these controls).
− Observe the operation carefully; If there is no problem continue with your work.
− If there are vibration problems, balance the sample holders correctly. If the equipment does not work, check the electrical connection cable, carbons or fuses.
Operator Preventive Maintenance
1. Take a tissue moistened with water and wipe the camera internally and externally; then gently wipe with a dry tissue. If you have
stains put a little detergent on the damp handkerchief, if the stains persist report them to maintenance. Remember that the
Urine and blood are highly corrosive, so clean up immediately as detailed above when spilled.
2. Check that the door safety mechanism works properly.
3. Check the operation and accuracy of the time and speed control, if any.
4. Check the condition of the automatic or manual brake, if any.
5. Check the rubber gasket(s), in most cases the capillary tube (in the microcentrifuge) punctures the gasket, throwing out the blood sample, the plasticine and/or pulverizing the capillary tube. There is no need to change the packaging, just peel it off with a lot
carefully and rotate it a third of the space between mark and mark of one capillary tube and the other; paste it again with cobbler's glue.
This procedure can be done up to two times, then change it.
6. Check the electrical supply of the equipment to detect possible peeling, cuts or degradation of the insulating material.
7. To change the carbons, some centrifuges have direct access to it, and it is enough to remove the covers of the carbon holders and
check their status. If they are well worn (between 60% and 75% of their normal size), cracked or chipped, replace them
immediately. Both carbons are always changed, only one should never be changed. In most centrifuges, access to the
coals are held at the bottom of the equipment, simply remove the sample holders and invert the equipment, with a flat or phillips screwdriver
(depending on the case), remove the screws from the bottom cover; verify carbons using the above criteria. Before doing this
procedure it is important that the maintenance technician has explained how to do it, otherwise report the failure to maintenance.
8. Verify that when centrifuging the samples, there is no excessive vibration. If there is, check the loads; if these are OK and the vibration persists, report it to the facility's maintenance department.
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