Low-Speed Centrifuge: 300–6,000 rpm Speed Range, Ultracentrifuge Speed Reference, and Advantages

Low-Speed Centrifuge: 300–6,000 rpm Speed Range, Ultracentrifuge Speed Reference, and Advantages

　　I. Classification of Centrifuges

　　Centrifuges use centrifugal force generated by high-speed rotation to automatically separate substances of different densities – heavier substances sink, and lighter substances float. From cells and viruses to proteins and nucleic acids, centrifuges play an indispensable role in scientific research, clinical applications, and testing.

　　Centrifuges come in a wide variety of types, from micro-centrifuges to floor-standing models, and from low-speed to ultra-speed centrifuges, each with its unique application. According to different classification criteria, centrifuges can be divided into several types:

　　1. Classified by Rotation Speed

　　Low-speed centrifuges: Rotation speed typically ranges from 4000-8000 rpm, centrifugal force range: 1000-10000g, suitable for separating coarse particle suspensions.

　　High-speed centrifuges: Rotation speed ranges from 10000-25000 rpm, centrifugal force range: 50000g, mainly used for separating emulsions and fine suspensions.

　　Ultra-speed centrifuges: Rotation speed ranges from 50000-150000 rpm, centrifugal force range: ≥505000g, suitable for separating ultra-fine particle suspensions and high-molecular colloid suspensions.

　　Ultra-speed centrifuges include a vacuum system. A cooling system is essential. They require significant space and are generally floor-standing models.

　　2. Classification by Capacity

　　Microcentrifuge (benchtop): Suitable for processing small volume samples (such as 2mL or less), commonly used for separating cell culture supernatants, micro-volume serum, and DNA/RNA extraction.

　　Medium-throughput centrifuge (benchtop): Suitable for processing medium-volume samples, widely used in the separation of cell and tissue samples.

　　Large-capacity centrifuge (benchtop and floor-standing): Suitable for processing large-volume samples, commonly used in large-scale experiments such as blood separation and cell culture.

　　3. Classification by Temperature Control Function

　　Room temperature centrifuge: Suitable for samples that are not sensitive to temperature.

　　Refrigerated centrifuge (optional parameter): Equipped with a cooling system, suitable for processing temperature-sensitive samples, preventing sample denaturation due to temperature increase during centrifugation.

　　4. Classification by Structural Form

　　Benchtop centrifuge: Compact in size, suitable for laboratories with limited space.

　　Floor-standing centrifuge: Larger in size, suitable for laboratories that need to process large-volume samples.

  Two concepts related to centrifugation and centrifuges: Separation Factor and Centrifugal Force

Centrifugal separation occurs through a centrifugal force field created by the high-speed rotation of materials within the centrifuge drum. The magnitude of the centrifugal force is directly proportional to the mass of the rotating material, the diameter of the drum, and the square of the rotational speed. Therefore, changing the rotational speed is the simplest and most effective way to change the centrifugal force.

In centrifuges, the separation factor (Fr) is typically used to measure the strength of the centrifugal force field. The separation factor is the ratio of the centrifugal force (Fc) experienced by the material in the centrifugal force field to its gravitational force (G) in the gravitational field. Clearly, the separation factor is also the ratio of centrifugal acceleration to gravitational acceleration.

The separation factor is a crucial indicator of centrifuge performance, reflecting its separation capacity. A higher Fr value indicates a greater separation driving force (Fc) and better separation effect. Therefore, for suspensions with small solid particles and high liquid viscosity, or emulsions with small density differences that are difficult to separate, centrifuges or separators with a higher separation factor should be used.

Increasing the rotational speed is more effective than increasing the drum diameter in improving the separation capacity of a centrifuge. However, the improvement in the separation factor (Fr) is limited. For a drum of a given diameter, the limiting value of Fr depends on the strength and density of the drum material. Currently, the commonly used Fr values for centrifuges are approximately between 300 and 1.000.000. Since gravity is negligible compared to centrifugal force, its influence can be completely ignored in centrifuge design. Therefore, the position of the centrifuge drum axis depends only on structural and operational convenience and can be placed anywhere in space.

Centrifuge Classification

Centrifuges are widely used in industrial production. To meet the needs of different production processes, there are many types and specifications of centrifuges, and many methods of classification exist. The main methods are as follows:

1. Classification by Continuity of Operation

① Intermittent Centrifuges. The processes of feeding, separation, and unloading are all performed intermittently. Some processes (feeding and unloading) often require slow speed or shutdown. Examples include three-legged and top-suspended centrifuges.

② Continuous operation centrifuges. All operations are performed automatically (continuously or intermittently) at full speed. Examples include horizontal scraper discharge centrifuges, piston pusher centrifuges, and screw discharge centrifuges.

2. By separation process:

① Filtration centrifuges. Examples include three-legged, top-suspended, and horizontal scraper discharge centrifuges.

② Sedimentation centrifuges. Examples include three-legged sedimentation centrifuges, scraper discharge sedimentation centrifuges, and screw discharge centrifuges.

③ Separators. Includes tubular separators, chamber separators, and disc separators.

3. By separation factor:

① Normal speed centrifuges. Separation factor Fr < 3500. with Fr = 400~1200 being the most common. These include both filtration and sedimentation types. These centrifuges are suitable for separating suspensions containing large or medium-sized solid particles and fibrous solids. They have a lower rotational speed but a larger drum diameter and a larger loading capacity.

② High-speed centrifuges. Separation factor Fr = 3500~50000. These centrifuges are typically sedimentation and separation types, suitable for separating thin suspensions and emulsions with a slurry-like or fine particle texture. Their drum diameter is generally small, and their rotational speed is high.

③ Ultra-high-speed centrifuges. Separation factor Fr > 50000. These are separation types. These centrifuges are suitable for separating difficult-to-separate, highly dispersed emulsions and colloidal solutions. Due to the very high rotational speed, the drum is often made into a long, thin tube.

4. Classification by Discharge Method

Centrifuges can be classified according to different discharge methods, including manual discharge, mechanical discharge (scraper discharge, piston pusher, screw discharge, etc.), and inertial discharge (centrifugal force discharge, vibration discharge, precession discharge, etc.).

In addition, they can also be classified according to the spatial position of the centrifuge drum axis, such as vertical and horizontal types.

There are many ways to classify centrifuges, but because centrifuges are a type of complex chemical machine, no single classification method can fully reflect the structural and operational characteristics of a specific type of centrifuge.

Centrifuge Selection

1. Selection Parameters

(1) Material Name and Characteristics (e.g., corrosiveness, abrasiveness, toxicity, etc.)

(2) Feed Rate

Feed rate refers to the amount of material the centrifuge is required to process per unit time during production. Process professionals should generally provide the minimum, normal, and maximum processing capacities. Common units are kg/h and m³/h.

(3) Suspension (Slurry) Temperature T

This refers to the temperature of the inlet medium at the centrifuge feed. The minimum, normal, and maximum temperatures of the inlet medium during operation should generally be provided. Common units are ℃.

(4) Material Density

Divided into solid density ρs, liquid density ρL, and suspension density ρ, etc., with units of kg/m³. These can be converted between each other.

(5) Particle Size

This refers to the average size of solid particles in a suspension. It can be expressed as the Stokes diameter (dst) or the median diameter (d50).

The Stokes diameter (dst) is determined by sedimentation in a gravitational or centrifugal field. dst is close to the actual size, and the sample can generally be obtained from a centrifuge manufacturer.

The median diameter (d50) refers to the particle size (mm) of 50% of the sample mass during sieving. It ensures that the mass fraction of particles larger and smaller than this diameter is equal. This method is the simplest, but has a large error and cannot measure very fine particles.

(6) Suspension Solid Concentration (φ)

The suspension solid concentration refers to the content of solid particles in the suspension. It is generally expressed as a mass fraction, that is, the proportion of the mass of solid particles in a unit mass of suspension. It can also be expressed as a volume fraction or the mass of solid particles contained in a unit volume of suspension, such as g/mL or g/L.

(7) Viscosity

Viscosity is divided into liquid viscosity (γf) and suspension viscosity (γ). Kinematic viscosity is commonly used and is measured in mm²/s (1 mm²/s = 1 cSt). Other types include dynamic viscosity and Engler viscosity.

2. Performance Indicators

(1) Production Capacity [Q]

This refers to the amount of material processed by a single centrifuge per unit time. For dehydration processes, the production capacity is generally measured by the amount of filter residue produced. For clarification processes, the production capacity is generally measured by the amount of filtrate produced. Units are m³/h and t/h.

(2) Separation Factor

The ratio of centrifugal acceleration to gravitational acceleration generated during centrifuge operation is called the separation factor.

The higher the separation factor Fr, the greater the centrifugal force on the material, and the better the separation effect. For small particles and difficult-to-separate suspensions with high liquid viscosity, centrifuges with a high separation factor are required. The separation factor range of industrial centrifuges is shown in the table of types and performance characteristics above.

The separation factor Fr is directly proportional to the drum radius of the centrifuge and the square of the drum speed. Therefore, the way to improve the separation factor of a centrifuge is to increase the drum radius and the drum speed, and increasing the drum speed is much more effective than increasing the drum radius. Therefore, centrifuges with high separation factors, such as disc centrifuges and tubular centrifuges, generally use small-diameter, high-speed models.

(3) Speed

The rated speed of a centrifuge refers to the allowable drum speed for centrifugal separation, measured in r/min.

(4) Shaft Power

Shaft power refers to the power transmitted from the drive motor to the main shaft of the centrifuge under given operating conditions, measured in kW.

Basic Selection Principles

The principles for centrifuge selection are related to its application, and are described below. (1) Selection Principles for Dehydration Processes

① When the solid concentration in the suspension is high, the particles are rigid or crystalline, and the particle size is large, a filter centrifuge can be used. If particle crushing is permissible, a horizontal scraper discharge centrifuge can be used; if particle crushing is not permissible, a horizontal piston pusher centrifuge or a centrifugal discharge centrifuge can be used.

② When the solid concentration in the suspension is low, the particle size is very fine, or the particles are amorphous mycelia, a filter centrifuge is not suitable because the particle size is too fine, resulting in significant material leakage from the filter screen. If a finer filter screen is used, the dehydration performance will decrease, and amorphous mycelia and oily solid particles will clog the filter screen. In this case, a sedimentation centrifuge, such as a screw discharge sedimentation centrifuge or a three-legged sedimentation centrifuge, should be used. If the particle size is very uneven, coarse particles can be filtered out first using a sieve, and then dehydration can be performed using a centrifuge. ③ When the density difference between the solid and liquid phases in the suspension is very small, and the particle size is above 0.01 mm, a filter centrifuge can be used. For large-scale processing, a continuous filter centrifuge can be used.

(2) Selection Principles for Clarification Processes

① When there is a large amount of liquid phase and a small amount of solid phase with very small solid particle size (below 10 μm), or amorphous mycelium, a screw discharge sedimentation centrifuge, disc separator, or tubular separator can be used. When the solid content is less than 1% and the particle size is less than 5 μm, a disc manual slag discharge separator or a tubular manual slag discharge separator can be used. When the solid content is less than 3% and the particle size is less than 5 μm, a disc piston slag discharge separator can be used.

② A tubular separator can separate fine particles of about 0.5 μm, and the resulting clarified liquid has a high clarity. However, the single-machine processing capacity is small, and the solid residue after separation adheres tightly to the inner wall of the drum, requiring disassembly for manual cleaning. It cannot be used for continuous production.

③ The disc piston slag separator can separate fine particles of about 0.5μm, producing a highly clear clarified liquid. After separation, the solid slag deposits on the inner wall of the drum. When a certain amount is accumulated, the machine can automatically open the piston to partially discharge the slag while continuously feeding. Because the piston opens instantaneously during operation, the solid slag cannot be completely discharged. Therefore, after a certain operating cycle, feeding should be stopped, and the piston should remain open for a longer period to completely discharge the solid slag.

(3) Selection Principles for Concentration Processes

The concentration process enriches the small amount of solid phase in the suspension.

① For materials with a large density difference between the solid and liquid phases, a hydrocyclone separator can be used.

② For materials with a small density difference between the solid and liquid phases, a disc nozzle slag separator can be used.

③ The screw discharge sedimentation centrifuge is also commonly used in the concentration process. Because it lacks a filter screen and nozzles, it does not cause material blockage. The moisture content of the discharge from the screw discharge sedimentation centrifuge is lower than that of the disc nozzle slag separator.

(4) Selection Principles for Grading Processes

① Generally, a screw discharge sedimentation centrifuge can be used. Based on the density difference between the solid and liquid phases and the particle size dk, a suitable separation factor and slip are selected. Particles larger than dk settle and are discharged from the solid phase, while particles smaller than dk remain in the liquid phase and are discharged with it, thus achieving particle grading. To prevent particles smaller than dk from being carried away by larger particles during sedimentation, appropriate speed, slip, and the position of the feed pipe inserted into the centrifuge's screw conveyor inner cylinder must be adjusted.

② If the throughput is very small, a three-legged sedimentation centrifuge can be used. Adjusting the appropriate separation factor allows for particle grading.

(5) Selection Principles for Liquid-Liquid and Liquid-Liquid-Solid Separation

Liquid-liquid and liquid-liquid-solid separation refers to the separation of two or three immiscible materials. The principle of separation is based on density differences. Examples include oil-water separation in edible oils, and the separation and purification of oil, water, and solids in fuel oils and lubricating oils.

① For small-scale liquid-liquid and liquid-liquid-solid separation, tubular separators can be used; for large-scale separation, disc-type manual slag discharge separators or piston slag discharge separators can be used.

② Due to the different contents of the liquid and liquid phases (e.g., more light phase A and less heavy phase B; or less light phase A and more heavy phase B), adjustment is required using regulating rings in both tubular and disc separators.

　III. Operating Procedures and Precautions for Ultracentrifuges

　　1. Centrifuge Operating Procedures

　　1). Connect the power supply and open the centrifuge lid; assemble the centrifuge tubes as required.

　　2). Install the centrifuge rotor as required; close the centrifuge lid.

　　3). Input centrifugation data and program the centrifugation process.

　　4). Evacuate the chamber and start the program.

　　5). After the program ends, release the vacuum; open the centrifuge lid and remove the rotor.

　　6). Remove the centrifuge tubes and perform analysis.

　　2. Precautions for Using Ultracentrifuges

　　1) The centrifuge rotor and sleeves must correspond to each other, and the matching centrifuge tubes must be used. This ensures the compatibility of the rotor and centrifuge tubes, avoiding operational problems or safety risks due to incompatibility.

　　2) Balancing is crucial; the mass difference should not exceed 0.2g. Imbalanced weight distribution can cause uneven force on the rotor shaft, which may damage the centrifuge or cause safety accidents. When the centrifugal speed reaches 10,000-50,000 rpm, if there is a 1-gram difference between symmetrical tubes and the rotor radius is 5 cm, the centrifugal force formula is F = m × RCF.  Looking up the table, at 10,000 rpm, RCF = 6000, so F = 1 × 6000 = 6 kg. At 50,000 rpm, RCF = 150,000, so F = 1 × 150,000 = 150 kg. This imbalance can cause a force of 6-150 kg, which is very damaging to the centrifuge and will at least shorten its lifespan.

　　3) After setting the centrifugation conditions, evacuate the chamber before starting centrifugation. This step helps improve centrifugation efficiency and ensure the accuracy of experimental results.

　　4) After use, return the rotor to the 4°C refrigerator before defrosting. This helps maintain the centrifuge's performance and extend its lifespan.

　　5) Avoid over-speed centrifugation, ensuring that the maximum speed and centrifugal force limits of the centrifuge are not exceeded to prevent equipment damage or sample loss.

　　6) During ultracentrifugation, the centrifuge tubes must be filled with liquid.  Because vacuum is required during ultracentrifugation, only filling the tubes completely will prevent deformation.

　　If the centrifuge tube lid has poor sealing, the liquid cannot be completely filled (for high-speed centrifugation using an angle rotor) to prevent spillage. Consequences of spillage: contamination of the rotor and centrifuge chamber, affecting the normal operation of the sensors.

　　7) When using an angle rotor, remember to cover the rotor lid. If not covered, a large vortex resistance and frictional heating will be generated in the centrifuge chamber, which adds an extra burden to the centrifuge's motor and refrigeration unit, affecting the centrifuge's lifespan.

　　III. Classification of Ultracentrifuge Tubes

　　1. Quick-Seal Tubes

　　Quick-Seal tubes can be used with fixed-angle rotors, swing-out rotors, vertical rotors, and near-vertical rotors. These single-use tubes require heat sealing after sample loading. Quick-Seal tubes are suitable for samples that are radioactive, pathogenic, or otherwise hazardous.

　　1. Quick-Seal tubes are made of polypropylene (PP) and ultra-clean (UC) materials.

　　2. Based on the top structure, Quick-Seal tubes are divided into dome-top and bell-top types.

　　3. Based on the bottom structure, they are divided into round-bottom and conical-bottom types.

　　2. Optiseal Tubes

　　Optiseal tubes are single-use centrifuge tubes specifically designed for certain rotors, used with fixed-angle rotors, swing-out rotors, vertical rotors, and near-vertical rotors, and are available in dome-top and bell-top types.

　　Optiseal tubes come with a plastic sealing plug, allowing for convenient and quick use without tools or heating. During centrifugation, a spacer is required to seal and support the top of the tube. The spacer ensures the Optiseal tube is properly sealed.

　　3. Open-Top Tubes

　　Open-top tubes are divided into thin-wall and thick-wall types and can be used with fixed-angle and swing-out rotors. When using open-top tubes with fixed-angle rotors, a tube cap and capping tool are required, as indicated in the rotor manual.

     1. Thin-walled open-top tubes are for single use only, and are made of polypropylene (PP) or ultra-clean (UC) materials.

When using a horizontal rotor, the sample should be filled to approximately 2-3 mm from the top of the tube to support the centrifuge tube.  A cap is usually required when using an angle rotor.

     2. Thick-walled open-top tubes are made of polypropylene (PP) and polycarbonate (PC) and are reusable.

　　4. Centrifuge Bottles

　　Centrifuge bottles are made of polycarbonate (PC) and polypropylene (PP). They can be used with fixed-angle rotors. Centrifuge bottles include a lid, inner plug, O-ring, and other lid components that seal the bottle. Lids are available in metal and plastic.

　　Note: When using ultracentrifuge tubes, it is essential to use the corresponding adapters, spacers, and other accessories. Please refer to the rotor manual for detailed information.

　　IV. Materials and Selection of Ultracentrifuge Tubes

　　For ultracentrifugation, the compatibility, sealing, and durability of the consumables are crucial for sample safety and centrifugation results. 1. Materials of Ultracentrifuge Tubes

　　Commonly used ultracentrifuge consumables are mainly made of plastic materials, such as polypropylene (PP), polycarbonate (PC), and polyethylene terephthalate (PET). They differ in their performance regarding centrifugal resistance, transparency, and resistance to high temperature and pressure.

　　2. Selection of Ultracentrifuge Tubes

　　Common types of ultracentrifuge consumables include: centrifuge bottles, thin-walled centrifuge tubes, thick-walled centrifuge tubes (wall thickness ≥1mm), heat-sealable tubes, and microcentrifuge tubes resistant to high RCF. The appropriate type should be selected based on the centrifugation method and rotor configuration.

　　1) For differential centrifugation experiments that require sample recovery by decanting, centrifuge bottles or thick-walled tubes are preferred for fixed-angle rotors, while thin-walled open tubes are recommended for swing-out rotors.

　　2) For density gradient centrifugation, due to varying subsequent sample recovery methods, and considering that most require piercing the tube wall, thin-walled open tubes or heat-sealable tubes are recommended.

　　3) For experiments requiring strict tube sealing, heat-sealable tubes are preferred.

　　4) Microcentrifuge tubes are only suitable for some small-volume rotors.

　　3. Number of Uses for Ultracentrifuge Tubes

　　Quick-seal tubes, OptiSeal tubes, ultra-clean tubes, and thin-walled open tubes are for single use only and are convenient for subsequent piercing and sampling in density gradient centrifugation. Thick-walled open tubes and centrifuge bottles can be reused, but it must be confirmed that the tubes or bottles have no cracks or deformation before use.

　   V. Sterilization and Cleaning Methods for Ultracentrifuge Tubes

　　Sterilization of Ultracentrifuge Tubes

　　1. Polypropylene (PP) Centrifuge Tubes

　　PP centrifuge tubes can be sterilized by high-temperature and high-pressure autoclaving.

　　Before autoclaving, place the centrifuge tubes vertically in a tube rack or beaker with the opening facing downwards. Avoid bundling or stacking to prevent pressure buildup.

　　Set the sterilization temperature and time to 121°C for 20-40 minutes. After sterilization, allow them to cool naturally to room temperature before use. To avoid deformation of the centrifuge tubes, drying is not recommended. If drying is necessary, the temperature should be kept below 40°C.

　　2. Polycarbonate (PC) and Ultra-Clean (UC) Centrifuge Tubes

　　High-temperature and high-pressure sterilization of PC centrifuge tubes will affect their lifespan, so cold sterilization is recommended.

　　For PC and UC centrifuge tubes, immerse them in 6-10% hydrogen peroxide or 5% sodium hypochlorite in a clean bench for 20-30 minutes.

　　After pouring out the hydrogen peroxide or sodium hypochlorite, rinse with sterile water several times. Finally, air-dry the treated centrifuge tubes before use.

　　3. Sterilization of Metal Tube Caps

　　All metal tube cap components can be sterilized by high-temperature and high-pressure autoclaving at 121°C for 30 minutes. The components need to be disassembled before sterilization.

　　4. Sterilization of OptiSeal Finger-Seal Tube Plugs

　　70% alcohol and 6-10% hydrogen peroxide can be used for the sterilization of plastic plugs in finger-seal tubes, as well as other plastic components in tube caps.

　　2. Cleaning of Ultracentrifuge Tubes

　　For reusable centrifuge tubes, please note the following during cleaning:

　　1. When cleaning centrifuge tubes, centrifuge bottles, adapters, and other accessories, use a mild detergent, such as Solution 55 diluted 10 times with water, and clean with a soft brush.

　　2. Polycarbonate (PC) centrifuge tubes and bottles are susceptible to corrosion from alkaline solutions and detergents. Therefore, use a detergent with a pH less than 9, such as Solution 55, for cleaning.

　　Also, avoid using brushes with exposed metal to prevent scratching the PC centrifuge tubes and affecting their use.

　　3. Many centrifuge tubes are not resistant to alcohol, acetone, etc. Before cleaning centrifuge tubes with these solvents, please check their chemical resistance.

　　4. After cleaning, do not dry in an oven; air drying is required.

Centrifuges are essential pre-processing equipment in laboratories. Low-speed centrifuges, in particular, are widely used in clinical medicine, biochemistry, immunology, industry, food analysis, and other fields, and are a conventional instrument for centrifugal sedimentation in laboratories. They are suitable for sample centrifugation before experimental testing in hospital departments, biochemical analyzers, and immunoassays.

The following is a brief analysis of several application scenarios:

01. Medical:

Blood sample centrifugation:

Typically requires a speed of 3000 rpm for about 10 minutes;

Urine sample centrifugation:

Typically requires a speed of 1800 rpm for about 5 minutes;

Stool sample centrifugation:

Typically requires a speed of over 1000 rpm for about 10 minutes;

02. Beauty salons and dental hospitals:

PRP application:

Typically around 3000-3500 rpm, centrifugation time of about 5 minutes, performed twice or multiple times;

PRF application:

Typically around 2000-3000 rpm, centrifugation time of about 7 minutes, completed in a single centrifugation;

CGF application:

Typically consists of 3 or 4 steps of variable speed centrifugation;

03. Food analysis:

Sample centrifugation in vegetable or food pesticide residue testing:

Typically requires around 4000 rpm, centrifugation time of 5 minutes.

04. Biological laboratories:

Cell culture medium centrifugation:

Typically requires several hundred g-force (relative centrifugal force), and it is recommended to choose a low-speed horizontal rotor.

Precautions for use are as follows:

01. Installation:

The centrifuge must be installed on a solid, flat, and level surface, ensuring that all four feet of the centrifuge are in contact with the surface. Do not install the centrifuge on a sliding surface, as this may cause significant vibration.

The ideal ambient temperature is 20℃±5℃, and the ambient temperature should not exceed 30℃. Avoid direct sunlight on the centrifuge.

Ensure a 10cm gap on both sides of the centrifuge and a 30cm gap at the back to ensure proper air cooling.

There should be no heat sources or water leaks near the centrifuge, otherwise, it may cause the sample temperature to rise or the centrifuge to malfunction. Ensure a good ground connection and avoid touching power cords with wet hands to prevent electric shock.

02. Rotor Inspection:

Before use, check the rotor for corrosion or scratches. If any problems are found, stop using it. Do not use other incompatible rotor models on the main unit. Before use, ensure that the rotor is securely tightened to the spindle and that the lid is securely fixed to the rotor if a matching lid is available.

03. Sample Balancing:

Ensure that each sample centrifuge tube is weighed on a balance and check that the samples are symmetrically installed. Even a slight imbalance can lead to dangerous accidents. Common balancing methods are as follows:

04. What is the maximum capacity of the centrifuge tube?

It is recommended not to exceed 80% of the centrifuge tube's maximum capacity.

05. How is centrifugal force calculated?

RCF = 11.17 x (rpm/1000)² x R, the larger the radius, the greater the centrifugal force; the higher the speed, the greater the centrifugal force.

06. How to disinfect the centrifuge rotor?

Plastic rotors: If there is sample leakage, a neutral absorbent liquid can be used for cleaning and wiping, but UV disinfection should not be used, as it will make the material brittle and affect its lifespan;

Aluminum alloy rotors: Can withstand 121 degrees Celsius, high-temperature and high-pressure sterilization, and there is no limit to the number of sterilization cycles.

Introduction

A low-speed centrifuge is one of the most commonly used laboratory instruments, widely applied in clinical, research, and industrial laboratories. Compared with high-speed centrifuges, low-speed centrifuges focus on gentle separation, ease of operation, and sample integrity.
Below is a comprehensive Q&A guide explaining what a low-speed centrifuge is, how it differs from a high-speed centrifuge, its speed range, applications, and key advantages.

Q1: What Is a Low-Speed Centrifuge?

A low-speed centrifuge is a laboratory centrifuge designed to separate samples at relatively low rotational speeds. It uses centrifugal force to separate components of a mixture based on density differences, typically for applications that do not require extreme centrifugal force.

Low-speed centrifuges are commonly used for:

• Blood sample separation

• Cell harvesting

• Urine and biological sample preparation

• Routine laboratory analysis

They are ideal for samples that are sensitive to high centrifugal stress.

Q2: What Is the Difference Between a High-Speed Centrifuge and a Low-Speed Centrifuge?

The main differences between high-speed and low-speed centrifuges lie in their speed range, centrifugal force, and application scenarios.

Feature	Low-Speed Centrifuge	High-Speed Centrifuge
Maximum Speed	Typically up to 6,000 rpm	Usually 10,000 rpm or higher
Centrifugal Force	Low to moderate	Very high
Sample Type	Blood, cells, suspensions	Proteins, organelles, viruses
Sample Damage Risk	Low	Higher if not controlled
Cost & Maintenance	Lower	Higher

Low-speed centrifuges are preferred for routine laboratory work, while high-speed centrifuges are used for advanced biochemical and molecular research.

Q3: What Is the Minimum Speed of a Centrifuge?

The minimum speed of a centrifuge depends on the model and design, but most low-speed centrifuges can operate at speeds as low as 300–500 rpm.

Such low speeds are useful for:

• Gentle sedimentation

• Preventing cell rupture

• Handling fragile biological samples

Some advanced models allow precise speed adjustment to meet specific experimental requirements.

Q4: What Is the Maximum Speed of Low-Speed Centrifugation?

The maximum speed of a low-speed centrifuge generally ranges between 4,000 and 6,000 rpm, depending on rotor type and manufacturer specifications.

This speed range provides sufficient centrifugal force for:

• Plasma and serum separation

• Cell pelleting

• Routine clinical and laboratory workflows

Compared with high-speed centrifuges, low-speed centrifuges prioritize stability and sample safety over extreme force.

Q5: What Are the Applications and Advantages of Low-Speed Centrifuges?

Applications

Low-speed centrifuges are widely used in:

• Clinical laboratories and hospitals

• Medical testing and diagnostics

• Biotechnology and pharmaceutical labs

• Educational and research institutions

• Food and environmental testing labs

Advantages

Key advantages of low-speed centrifuges include:

• Gentle separation, protecting delicate samples

• Simple operation, suitable for routine use

• Lower noise and vibration

• Cost-effective, with lower purchase and maintenance costs

• High reliability for daily laboratory tasks

These benefits make low-speed centrifuges an essential tool for laboratories requiring efficiency and consistency.

Conclusion

Low-speed centrifuges play a critical role in routine laboratory operations, offering reliable separation at controlled speeds. With lower rotational speed, reduced sample damage, and broad application coverage, they are an ideal choice for clinical diagnostics, research labs, and industrial testing environments.