Editorial revision: 1 July 2026. Final operating limits must come from the approved centrifuge and rotor documentation.
RPM describes speed; RCF describes the force applied to the sample
Revolutions per minute state how quickly the rotor turns. Relative centrifugal force expresses the acceleration acting on the sample compared with gravity. Two centrifuges running at the same RPM can produce different RCF values because the distance from the axis of rotation to the sample differs between rotors.
For method transfer, procurement and protocol comparison, the force at the relevant sample position is normally more informative than speed alone. A quotation that lists only maximum RPM does not establish that a required separation force can be achieved with the intended tube, adapter and rotor.
Rotor radius changes the result
The commonly used relationship is RCF = 1.118 × 10−5 × r × RPM², where r is the radius in centimetres. The appropriate radius may be the maximum, minimum or average distance to the sample, depending on the method and the way the supplier reports performance. Buyers should ask which radius was used rather than treating every published RCF value as directly comparable.
Because speed is squared in the calculation, a modest speed change can produce a much larger change in force. The selected rotor must remain within its rated speed and loading limits; a calculated target is not permission to exceed the approved rotor manual.
Compare the complete rotor-and-vessel arrangement
- Rotor type: fixed-angle, swinging-bucket, vertical or specialised arrangements produce different pellet paths and separation behaviour.
- Tube and bottle compatibility: confirm vessel material, nominal volume, filled volume, cap or seal, adapter and position count.
- Rated limits: obtain the maximum permitted speed and force for the exact rotor, bucket, adapter and vessel combination.
- Sample containment: aerosols, hazardous materials or clinical specimens may require sealed rotors, safety cups or another validated containment approach.
- Temperature: refrigerated operation should be reviewed at the intended speed, load and ambient condition rather than assumed from a chamber set-point.
How to translate a method into a quotation request
State the target RCF and duration from the method, then identify the sample vessel, working volume, number of samples per run and required temperature. If the method gives RPM only, also provide the rotor model or effective radius used in the original procedure. This allows the proposed arrangement to be checked without guessing at equivalence.
| Buyer information | Why it matters |
|---|---|
| Target RCF and run time | Defines the separation demand independently of motor speed. |
| Vessel, cap and filled volume | Determines rotor, bucket and adapter compatibility. |
| Samples per batch and daily throughput | Influences rotor capacity and workflow planning. |
| Temperature and sample sensitivity | Determines whether refrigeration and monitoring are needed. |
| Containment or cleaning requirement | Affects rotor accessories, surfaces and operating procedure. |
Checks before technical approval
Ask for the exact centrifuge model, rotor code, bucket and adapter codes, rated speed and RCF, approved vessel list, imbalance and lid-lock information, utility requirement and operating manual. Any force claim should be traceable to that configuration. The laboratory remains responsible for its method, risk assessment, balance procedure, inspection schedule and operator training.
Primary documents to verify
- The approved centrifuge datasheet for the quoted model.
- The current rotor, bucket and adapter manual.
- The vessel manufacturer’s centrifugation limits.
- The laboratory method, SOP and sample-risk assessment.