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RPM vs Flow Rate: How They Affect Oil Cleanliness

The Role of RPM and G-Force

RPM is a measurement of how many times the centrifuge bowl spins in one minute. The centrifugal force (g-force) generated by the spinning bowl is directly related to the size of the bowl and RPM. In the case of the Ultimate Force Centrifuge with a bowl diameter of 9.5 inches and operating at 3,450 RPM , which is 57.5 revolutions per second, the resulting g-force is 1,650 times the force of gravity. This force drives contaminants out of the oil and towards the walls of the centrifuge bowl, where they can be trapped and separated.

However, a common misconception is that higher RPMs always lead to cleaner oil. This is not necessarily true. While increasing RPM does enhance the centrifugal force, which can improve the separation of smaller particles, the design of the bowl and the flow rate of the oil are equally, if not more, important.

The Impact of Flow Rate on Oil Cleanliness

Flow rate significantly influences the time oil spends in the centrifuge bowl—known as the residence time. The longer the oil remains in the bowl, the more time the centrifugal force has to act on the particles, improving the separation efficiency, and leading to cleaner oil.

The Ultimate Force Centrifuge is capable of handling up to 30 gph. However, the cleanliness of the oil is inversely proportional to the flow rate. Running the centrifuge at the maximum flow rate will not provide the cleanest oil. For the best results, reducing the flow rate to 15 gph, 10 gph, or even 5 gph allows the oil to spend more time in the centrifuge, enhancing the removal of contaminants.

How the Oil Flows Through the Centrifuge

To understand the relationship between RPM, flow rate, and oil cleanliness, let’s look at the process of oil purification in the centrifuge bowl.

1. Oil Entry and Acceleration: Oil enters the bowl at the center and is directed to the bottom by an accelerator cone which is built into the bowl lid. This accelerator or booster cone distributes the oil by forcing it to the very bottom of the bowl subjecting it to the maximum centrifugal force.

2. Centrifugal Separation: As new oil enters, it pushes the existing oil upwards along the bowl’s walls. The centrifugal force causes heavier particles, contaminants, and water to travel toward the bowl walls, where they get trapped.

3. Oil Exit: The cleaned oil moves across the top of the bowl, reaching the 3 lid breeches. It escapes through the grooves in the lid, spraying upward and out towards the edge of the centrifuge housing. The cleaned oil then escapes through the clean oil drain and into a container.

4. Contaminant Collection: When the unit is turned off, the residual oil (approximately half a gallon) drains through holes at the bottom of the bowl, exiting through the dirty oil port. The debris and matter inside the bowl can then be cleaned out and it’s ready for another run. Depending on the type of oil and level of contamination, the centrifuge bowl only needs to be cleaned every 300 to 500 gallons of oil.

The Importance of Bowl Design

Bowl design is a key component that overshadows the benefits of high RPM. Like the Ultimate Force Centrifuge, a centrifuge with an enclosed bowl design promises contaminants are efficiently trapped and forces the oil to travel along the bowl lid before escaping. In addition, an accelerator or booster cone should be mandatory when selecting a centrifuge. This cone directs the oil to the very bottom of the bowl ensuring it completely travels under the infliction of G-force. When an accelerator cone is not present the oil enters the bowl and splashes entering the oil curve midstream, resulting in sub-par cleanliness results. The bowl design should also allow for effective draining and cleaning of the bowl, for convenience and ease of use.

Practical Recommendations for Optimal Oil Cleanliness

To maximize the efficiency of oil purification using a centrifuge, the following practices are recommended:

1. Optimize Flow Rate: While the centrifuge may handle up to 30 gph, running it at lower flow rates between 5 and 10 gph—significantly impacts oil cleanliness. The extended residence time allows the centrifugal force to more effectively separate contaminants.

2. Regular Maintenance: Periodically inspecting and cleaning the bowl is crucial. After turning off the unit, allow a few minutes for the oil to drain before opening the bowl. This prevents the reintroduction of contaminants into the oil supply and maintains the efficiency of the centrifuge.

3. Monitor Performance: Regularly check the quality of the output oil. Adjust the flow rate as needed to ensure optimal cleanliness. If the oil is not meeting cleanliness standards, consider reducing the flow rate further.

4. Consider Bowl Design: Choose centrifuges with well-designed, enclosed bowls. The design will efficiently trap contaminants and is easy to maintain.

In Summary

In summary, while RPM and g-force are impactful factors for the operation of a centrifuge, they do not solely determine the cleanliness of the oil. The flow rate of the oil and the design of the centrifuge bowl are equally important. It is advised to operate your centrifuge with a flow rate between 5 and 10 gph. The Ultimate Force Centrifuge with its enclosed bowl design and following our flow rate recommendations, will give you high-quality clean oil which can then be used for fuel in diesel engines.