Centrifuges

1. Centrifuges

2. Topics • Principle of Operation • Diagrams • Applications • Types of Centrifuges • History • Safety • Operation • Preventive Maintenance • Common Failures • Basic Troubleshooting

3. Principle of Operation • A centrifuge is a piece of equipment, generally driven by an electric motor, that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis to separate substances of different densities. • Tubes in the centrifuge are tilted so centrifugal force can pull denser substances towards the bottom of the tube. • Relative Centrifugal Force (RCF) measures acceleration applied to the sample • RCF=(r*ω2)/g • r=distance from center or motor to sample • ω= angular velocity (radians/ second) • g=9.8m/s2

4. Principle of Operation

5. Diagrams Rotor Power LED Timer

6. Diagrams Power Source Motor Power Distribution Board Safety Switch Power Indicator LED Timer

7. Applications • Separate solids from solution • Used during urinalysis to separate disease identifying components • Separate blood into plasma and cellular components

8. Types of Centrifuges • Centrifuges are generally divided into 3 categories based on their maximum attainable speed: 1. "Low-speed": max ~5 x 103 rpm. 2. "High-speed": max ~2 x 104 rpm. 3. "Ultracentrifuges": max ~105 rpm • Others • Variable Temperatures • Vacuum Capabilities

9. History • English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag. • In 1864, Antonin Prandl invented the first dairy centrifuge in order to separate cream from milk. • In 1879, Gustaf de Laval demonstrated the first continuous centrifugal separator, making its commercial application feasible.

10. Safety • Always use PPE. • Before using, read the owner's manual. • Do not operate a centrifuge untilhaving been shown proper use by anexperienced operator. • Check that the centrifuge chamber and drive spindle of the rotor are free of scratches or burrs. • Decontaminate centrifuge of biological hazards before servicing.

11. Safety • Never repair a cracked or bent rotor. • If rotor has been replaced, tighten knob/screw fastening rotor to the shaft to prevent hazardous loosening. • Prolonged contact w/ some disinfectants can cause damage to rotor and other components (e.g. 10% sodium hypochlorite). • Never attempt to touch or stop a spinning rotor by hand or with another tool or object.

12. Operation • Place tubes in centrifuge. • Always use correct size tubes to prevent tube damage. • Always using a counterbalance: • By mass NOT volume • Put the tubes opposite each other in the centrifuge. If you have more than two tubes, only the ones opposite each other have to be equal in mass. • If centrifuge has variable speeds, enter RPM. • Close lid. • Turn timer on or press start. • Remove the tubes carefully after the centrifuge has completely stopped spinning to prevent remixing.

13. Operation • Result of unbalanced centrifuge

14. Preventive Maintenance • Lubricate and clean motor. • Clean case. • Inspect power cords and plugs. • Inspect controls and switches. • Ensure appropriate menu settings for proper use. • Ensure tightness of rotor. • Check lights and indicators. • Verify that alarms are operating properly. • Ensure safety switch is functioning. • If refrigerated, ensure temperature reading is working. • Replace/repair gaskets, seals, and vacuum pump (if applicable).

15. Common Failures • Machine will not start. • Power supply is faulty. • Safety switch or timer not working properly. • Motor not working properly. • Motor making noise. • Rotor is broken. • Lid will not open or close.

16. Basic Troubleshooting • See flow chart.