Hettich Service FAQ
Q. Ok, I got my centrifuge out of the box and on the table. What do I need to do next to get this thing running?
A. First and foremost, remove those transport bolts. Many of the service calls have to do with customers not removing transport bolts. The documents that ship with the centrifuge indicate where you can find these bolts.
Next, put a little of the supplied Hettich grease on the motor shaft. This will help you to be able to remove the rotor in the future if necessary. It prevents the metal to metal binding that can be formed over long-term use that can make the removal of the rotor extremely difficult down the line, possibly causing damage and unnecessary expense.
Finally, install that rotor. Use the 5 mm hex wrench to tighten the nut in the center of the rotor that secures the rotor to the motor shaft.
Q. Does my centrifuge need to be serviced regularly?
A. Like any equipment, your centrifuge is an investment. You should care for it by cleaning and lubricating on a regular basis. Cleaning goes right along with Good Laboratory Practices. Lubrication on the pivot points of the rotor (called the trunnions) and buckets will result in better and consistent results. Lubrication also reduces vibration and wear and tear. Operators of centrifuges should check to make sure that the rotor is firmly attached and that the attaching nut is secured on a weekly basis.
Depending on usage, you want to make sure that servicing and maintenance is adequate and consistent with its use. Light use (2-3 times per day) may require lubrication of the rotor pivot points every 2-3 weeks, whereas 24/7 use may require weekly attention.
Validation of the functionality of the centrifuge should be done once every 6-12 months.
Q. What is the expected life of a rotor and buckets?
A. Rotor and bucket life times are now counted in terms of cycles; one centrifugation is equal to one cycle. The buckets and rotors of newer Hettich products come with a cycle count stamped into them. Also, the newer centrifuges are now being produced with cycle counters built into the firmware. The centrifuges display the cycle count accurately in the LCD display.
Q. Why do I need to buy four buckets in when I am only ever going to use two?
A. Safety is the key here. Using four buckets applies the g-force load on the rotor in all directions. Using only two across from each other applies force that will actually stretch the rotor in a shape and manner of a football (albeit in an exaggerated manner of speaking) This will then cause the gaps between the rotor trunnions to change widths, rendering the rotor out of spec over time. Centrifuge rotors must always be loaded in the most even manner possible, not just symmetrically.
Q. What is the difference between G-force (g’s) and RCF?
A. Nothing. RCF (Relative Centrifugal Force) and g’s are the same unit of measure. They are interchangeable.
Q. If my old centrifuge was set for 5000 RPM and my new and larger centrifuge is set for the same speed, then why are my results different?
A. It has to do with the radius of the spin. If you spin a sample at 5000 RPM at 100 millimeters from the center of spin, you will imply a force of 2795 RCF (g’s) onto the sample. Now, spin that same sample in a larger centrifuge at the same speed (let’s say 130 mm from center) and suddenly you’re at 3634 RCF (g’s). You raised the force by about 33% simply by using a larger centrifuge! So when you talk about protocols and spinning at a set speed, you need to know the radius of the spin as well to be sure you are still following your laboratory’s protocol.
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