Therefore, you have to convert g force (RCF) into revolutions per minute (rpms) and vice versa. Unfortunately, many protocols are written in hurry and instructions are given in RPMs. It depends on the revolutions per minute (RPM) and radius of the rotor, and is relative to the force of Earth’s gravity.Ī good, precise protocol for centrifugation instructs you to use the g force rather than RPMs because the rotor size might differ, and g force will be different while the revolutions per minute stay the same. G Force or Relative Centrifugal Force (RCF) is the amount of acceleration to be applied to the sample.
The RPM is the bowl speed indicator, but the RPM does not convey any useful information for the application or the process.Rotational radius of centrifuge for converting RPM to g force (RCF). These two terms are significantly different, as explained above.įor the end-user, the RCF (aka g-force) is a crucial term because it defines the effectiveness of the centrifuge. RCF and RPM are commonly confused and interchanged terms in the centrifuge world. They can also separate immiscible liquids with small specific gravity differentials due to their high g-force. Therefore, these centrifugal separators can separate much smaller particles than other centrifuges. This higher force allows the disc-stack centrifuge to have higher separation efficiency. The Relative Centrifugal Force (RCF) is the crucial factor differentiating a disc-stack centrifuge from other types of centrifuges.Īn Alfa Laval disc centrifuge generates a higher centrifugal force (g-force) than simple open-bowl or decanter centrifuges. RCF = 1.18×R×1000/RPM RFC in Disc Stack Centrifuge The diagram also illustrates the two terms, namely RPM and bowl radius (r), in the context of the centrifuge bowl. The following formula calculates a centrifuge's Relative Centrifugal Force (RCF) based on the RPM and Centrifuge Bowl Radius.
Therefore, if the user selected the centrifuge solely based on RPM, they would make the wrong choice based on centrifuge effectiveness. The centrifuge’s separation efficiency with the 7,000g RCF will be much higher than that of the centrifuge with the 1,400g RCF. However, for the same RPM, the RCF generated by the second (larger) bowl is 7,000 g-force! One bowl has a radius of 5 cm, while the other has a radius of 25 cm.īased on the formula, the RCF for the first bowl is 1,400 g-force. RCF in a Centrifugeįor example, consider two centrifuge bowls rotating at the same speed, say 5,000 RPM. In conjunction with the RPM, the rotation radius determines the centrifugal force shown by the RCF formula below. The centrifuge RPM merely indicates the bowl speed but does not define the centrifugal force. This is because the RCF indicates the centrifuge force exerted, which defines the centrifuge’s separation efficiency. This force (g-force) is directly related to the efficiency of the centrifuge. Why use RCF and not RPM?Īs explained above, the RCF measures the centrifugal force generated by the centrifuge. While the RPM is the speed of rotation of the bowl, the RCF functions as the RPM and the rotating object’s radius. The RCF of a centrifuge is the actual centrifugal force (or g-force) generated by the centrifuge bowl rotation. Though RCF and RPM are units of measurement related to centrifuges, they are fundamentally different. RPM is a unitless number independent of any object's properties. In a centrifuge, the RPM indicates the number of rotations the centrifuge bowl completes in one minute. It is a measure of the speed of rotation of any object. RPM is the abbreviation for Revolutions Per Minute. Therefore it is also referred to as g-force.
In other words, RCF is the centrifugal force ratio to gravitational force. RCF is this centrifugal force expressed in terms of gravity. The force experienced by any mass (solid, liquid, or gaseous) that rotates around a fixed axis is known as the centrifugal force. RCF stands for Relative Centrifugal Force. Though the two terms are related mathematically, they are vastly different from the application’s perspective. This article explains the difference between the two terms and why RCF is more relevant to centrifuges. RCF and RPM are standard terms in the context of centrifuges.
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