How do You Compare Centrifuges, by RPM or RCF?


Although a centrifuge is not particularly difficult to build, a good centrifuge requires good engineering. There are several centrifuge manufacturers out there offering their products by RPM and a few manufacturers specifying G force. So what really matters and how do you compare centrifuges?

What is RPM?  Revolutions Per Minute

What is RCF? RCF Relative Centrifugal Force or G force. How many times the force of gravity.

Since a centrifuge is a “high gravity” settling machine, knowing the G force is important.

G force is the actual power of the centrifuge, similar to horsepower of a motor.

US Filtermaxx 10,000 G Force Centrifuge

You specify a motor by horsepower not RPM, for example, “My Dodge Charger has a 372 horse power motor,” not “My Dodge Charger has a 4500 RPM motor.”

RPM has little to do with actual power output in an engine or a centrifuge.  The COX gas engine in my model airplane ran at 17,000 RPM and produced .08 horsepower.

A stationary Diesel operates between 60 and 200 RPM and may produce over 100,000 horsepower.

Similarly, actual centrifuge power is not rated by RPM, but by G force.  For example, 1200 Gs is 1200 times the force of gravity.   3000 G is 3000 times the force of gravity. Now you have a way to compare the power of a centrifuge.

If a manufacturer doesn’t quote the G force, then they either don’t want you to know what it is, or they don’t know how to calculate it. Either way, you have no idea what you are buying if you don’t know the G force of the centrifuge. A properly engineered centrifuge starts with specifying the required G fouuuuurce, and then the machine is designed to meet the stresses produced at that G force. Building a centrifuge with no idea of the stresses produced when running at speed is like designing brakes on a car with no idea of the force required to stop.

Summarily, one should be skeptical of manufacturers offering centrifuges without specifying their G force.  How much engineering could be involved in a piece of machinery where the maker only knows how fast it goes?  Look under the hood. You wouldn’t buy a Corvette with a 4 cylinder engine. When shopping for a centrifuge, ask for the G force so that you can properly compare units.

cylinder centrifuge
USFiltermaxx 17,000 G Force Tubular Centrifuge





What are People Saying About Cleaning Waste Motor Oil and Making Biodiesel with a USfiltermaxx Centrifuge?

Dear Steve at USFILTERMAXX.COM I run WVO through 2 of your centrifuges at 50 gallons per hour and sell that as base for a degreaser. The third centrifuge runs WVO at 25 gallons per hour and I sell it for biodiesel. The oil temperature leaving … Continue reading What are People Saying About Cleaning Waste Motor Oil and Making Biodiesel with a USfiltermaxx Centrifuge?


How to choose and implement VFDs to optimize efficiency, control, motor life and other parameters

Variable frequency drives can be used to operate pumps

Variable frequency drives (VFDs) have been used to control the speed of three-phase alternating current (AC) induction motors since the 1980s. They also provide adjustable acceleration and deceleration, overload protection and start-stop control of motors. These and other features make VFDs a good choice for fans, blowers, centrifugal pumps, mixers, agitators and conveyors – which require variable horsepower and torque – and for applications in which energy is saved by operating at reduced speed.

VFDs convert single- or three-phase AC input power to direct current (DC), and then invert it back to three-phase AC output power. Before it is converted to the output, the VFD varies the frequency and voltage of the inverted power, allowing it to control motor speed based on the setpoint, which is either set at the VFD or more commonly sent to it by the automation system.

A VFD is often not the best choice for a constant-speed application requiring controlled stops and starts because the electronic conversion of AC to DC to AC results in an efficiency loss of about 4 percent. However, if a variable motor speed is needed, the benefits of a VFD are typically more than sufficient to overcome the efficiency loss. To realize these benefits, consider the top 10 tips for specifying and using VFDs described in this article.

1. Understand & use the benefits & features

The benefits of using VFDs include energy savings, adjustable motor speed and torque, reduced motor inrush when starting, and controlled stopping and reversing. Probably the biggest benefit is reduced energy consumption when operating devices such as blowers, fans and centrifugal pumps at slower speeds.

For example, reducing the speed of a blower to 50 percent reduces the air flow by 50 percent as well, but cuts the power requirements by 87.5 percent. Required fan, blower and centrifugal pump power is proportional to the cube of motor speed, saving significant energy at lower speeds (see Image 1).

The VFD’s ability to vary motor speed allows the optimization of the work required by a machine or process because only the needed speed is provided. This contrasts with running the motor at full speed and throttling the output, which is inefficient, decreases motor life, and increases maintenance for the motor and the throttling equipment.

Torque can also be limited to protect machinery or product from possible damage. These adjustments can be made automatically using a programmable logic controller (PLC) or other controller, or manually using a keypad or potentiometer on the drive.

The VFD can reduce motor starting currents that can be more than eight times the full-load current of a motor. With larger motors, this full-load starting places significant demand on the power distribution system. These high demands can result in a voltage dip or voltage sag when the motor starts at full voltage. A controlled acceleration start, provided by a VFD, addresses this issue.

With VFDs, controlled acceleration reduces starting current and extends motor life. This is especially true in applications that require frequent starting and stopping. Additionally, the VFD eliminates the need for a reversing starter. The controlled acceleration and deceleration provided by a VFD reduce equipment wear and tear and related breakage and loss (see Image 2).

Variable frequency drives are used in conveyor applications

Image 2. A VFD reduces impacts and breakage in conveyor and other applications by starting and stopping a motor using controlled acceleration and deceleration.

2. Choose the VFD based on load size

Sizing VFDs often requires more than just matching the horsepower rating to the motor. The operating profile of the load it controls must be considered. Constant or variable loads, frequent starts and stops, or continuous operation must also be considered when selecting the equipment.

The torque and highest peak current at any time during operation should be determined. This starts by confirming the motor nameplate full-load amps (FLA). However, rewound motors may have higher FLAs than what is listed on the nameplate.

The VFD should be sized based on peak torque demand instead of just horsepower. Under certain conditions, the motor may demand more power and/or torque, and oversizing may be necessary when dynamic loads or impact loading creates temporary overload conditions. In these and other high-demand situations, the VFD must provide enough current to ensure acceptable motor performance.

For example, more power from a VFD is required to provide additional breakaway torque to start a fully loaded conveyor. While many VFDs can operate for 60 seconds at 150 percent overload, higher overloads may be seen for short durations. Whether the overload duration is short or long, an oversized VFD may be required to provide the headroom required by the application. Even high-altitude installations may require oversizing because less air cooling of the VFD is available.

3. Determine braking options

A VFD may also need a little help when decelerating a load. While it can stop moderate inertia loads, high-inertia loads may cause an overvoltage condition in the drive. For quick deceleration of heavy loads, an external dynamic braking resistor should be considered.

The braking resistor allows the VFD to produce additional braking torque by reducing the voltage generated by a decelerating motor. Without the braking resistor, typical VFDs provide approximately 20 percent braking torque. The external braking resistor can significantly increase the VFD’s braking torque for the fast deceleration of heavy loads, and reduce the heat in the drive caused by frequent starts and stops.

4. Interface to the VFD

VFDs are controlled by either hardwired, discrete and analog input/output (I/O); or by digital communications. The discrete inputs to the VFD, usually outputs from a PLC, are used to start and stop the drive, although manual pushbuttons and selector switches can be used as well.

Other configurable drive inputs include jog, fault reset, accelerate/decelerate select, preset speed (step) selection, proportional-integral-derivative (PID) control and others. Discrete outputs from the VFD include fault present, frequency attained, non-zero speed and local/remote indication. Some higher-end drives also include frequency outputs for speed reference. A drive’s analog input typically accepts a speed command from a PLC or remote potentiometer. These analog signals are typically 0 to 10 volts DC, 4 to 20 milliamps or something similar.

The drive’s analog output, where available, also has the same signal levels. The analog output can provide a speed reference signal proportional to the motor’s speed. This speed signal can be used to command downstream VFDs’ speeds in a master-follower setup. This configuration can synchronize several VFD motors’ speeds. Alternatively, the analog output can provide analog speed, current and torque signals to the PLC.

Variable frequency drives are used in web-converting processes

Image 3. While V/Hz drives are popular, printing presses and other web-converting applications benefit from the precise speed regulation of closed-loop control VFDs.

5. Understand digital communication options

Digital communication protocols allow commands and information to be communicated between a PLC and the VFD across a single cable, as opposed to the many wires and cables required for hardwired I/O. Protocols range from simple serial interfaces such as Modbus RS-232/RS-485 to more advanced Ethernet and fieldbus communication options such as EtherNet/IP.

These communication interfaces allow the VFD to be controlled by a master device, such as a PLC or other advanced controller. This interface can eliminate the need for hardwired discrete and analog I/O, and enables the monitoring of the drive’s speed, current, fault and other parameters. A serial, RS-232 connection to a drive works well for single drive applications located near the PLC. If multiple drives are needed, an RS-485 network can handle multiple drives in a daisy-chain, multidrop configuration and stretch the communication distance up to 4,000 feet.

An Ethernet interface provides higher performance in terms of speed, bandwidth and network configuration options. Multiple drives can be controlled by a single PLC using industrial Ethernet protocols such as Modbus TCP/IP or EtherNet/IP, simplifying VFD wiring and providing an easy way to remotely configure drives.

6. Apply the right control mode

The application often determines the type of VFD control mode: volts-per-hertz (V/Hz), sensorless-vector or closed-loop. V/Hz controls the ratio between voltage and frequency to vary the motor flux, which supplies the operating torque to the motor. V/Hz drives work well for most applications, such as fans and pumps.

Sensorless-vector VFDs are known for their accurate speed control across a wide speed range without the need for encoder feedback because they work well in open loop. A closed-loop VFD uses encoder feedback for accurate speed control by monitoring actual motor speed and slip information. Sensorless-vector and closed-loop VFDs provide excellent speed regulation, providing tight speed control for paper mills, web handling, printing presses and other converting applications (see Image 3).

7. Define motion profiles

How a VFD’s motion profile is configured depends greatly on the application. Motion profile parameters include motor speed, acceleration, deceleration, ramp linearity, torque control, braking and PID. Most VFDs in the market include these parameters, although PID may only be available on more advanced drives.

These parameters can be accessed and programmed using the operator keypad and display or via digital communications. Careful review of the manual will help users understand these parameters and ensure proper installation, setup and control.

8. Outline the installation requirements

Following the installation requirements is important because VFDs generate significant heat while operating. Frequent starting and stopping can cause the drive to heat up an enclosure, requiring ventilation to keep the temperature within drive specifications. The manual provides information to help calculate the expected heat output of the VFD during different operating conditions. A standard induction motor can overheat if run at low speed for an extended period. If low speed operation is required, an inverter-duty-rated motor should be specified.

9. Specify operation parameters

From a control standpoint, the VFD should not be routinely stopped by opening a contactor on the input voltage supply because this reduces its operating life. This should only be done for emergency stop purposes. The drive I/O or communications should control the start-stop in all other instances. These and many other installation and operation procedures are outlined in the manual and should be followed carefully, and the VFD supplier should be contacted with any questions.

10. Handle noise & harmonics

VFDs generate electrical noise and harmonics that may cause damage to motors, equipment, transformers and power wiring. Fortunately, filters and line or load reactors can minimize many problems. Most VFD installation instructions recommend the use of passive harmonic filters, such as AC line reactors and chokes. These devices reduce harmonics and protect VFDs from transient overvoltage on the line side of the drive.

On the line side, active harmonic filters invert the harmonic current waveform and feed it back to the line to counteract the noise generated by the VFD. On the load side, a load reactor protects the motor cable insulation from short circuits and reflective wave damage. Including these reactors in all applications with standard inductive motors and in any application where the VFD-to-motor distance exceeds 75 feet are good design practices.

Joe Kimbrell is product manager, Drives, Motors, and Motion Control, for AutomationDirect. He may be reached at


One Pass #Oil Cleaning and the Automatic #Centrifuge Controller

Our tests show that #wastemotoroil (WMO), typically contains between 3 to 5 percent solids. When cleaning #WMO, the solid particulates become concentrated next to the bowl wall and clean oil floats to the center of the bowl, spilling over the top edge and going out of the centrifuge through the clean oil output port.  As the solid particles move to the bowl wall, some of the solid matter sticks to the sides of the bowl;Solid Particulates in Used Motor oil. however, much of it is concentrated as a slurry of solid particulates in oil. If you feed the WMO, or oil, slow enough for long enough time so that all the particulates move to the wall, you could remove all the particulates as solid matter stuck to the sides of the bowl. However, such a slow feed rate and the amount of time spent scraping solid matter from the centrifuge bowl are too impractical and labor intensive for actual production.  Much of the solid matter can be removed before the bowl fills up. Draining the slurry from the centrifuge before the bowl fills up allows a higher feed rate without sludge spilling over into the cleaned oil. This greatly extends the run time between bowl cleanings and also reduces or eliminates the sludge that spills into the cleaned oil.

The amount of WMO sludge concentrated in the centrifuge bowl depends upon:

1. The #Gforce, with higher G force having a higher rate of concentration

2. The feed rate, which must be low enough for the centrifuge to do its job and settle the sludge to the outer wall (again, higher G force = faster and higher concentration of #sludge).

At some point, the bowl will fill with sludge and spill over into the cleaned oil. At this point, the centrifuge is removing very little if any #contaminants as they spill over into the cleaned oil as fast as they are removed. Two remedies for this situation are:

1. Slow the feed rate so low that all the particulates move to the outer wall and only cleaned oil is discharged, but we have already seen that this is impractical.

2. Stop the centrifuge and drain the sludge before it spills over, contaminating the cleaned oil.

The size of the bowl dictates the volume of oil processed between draining.

How often should the centrifuge be stopped and the bowl drained? An approximate starting point is determined by the bowl size. The #USFiltermaxx #WMO centrifuge has about 165 cubic inches sludge capacity.

5% =.05

3%= .03

1 gallon = 231 cubic inches

165 cubic inches / .05 = 3300 cubic inches of oil

3300 cubic inches / 231 in3/gal = 14.3 gallons

165 cubic inches / .03 = 5500 cubic inches

5500 cubic inches / 231 in3/gal = 24 gallons

So the optimal range of oil fed to the US Filtermaxx centrifuge between bowl draining is between 14 and 24 gallons. Running any centrifuge longer at the bowl capacity is like trying to put 10 gallons of sludge in a 5 gallon bucket.

Run time between draining will vary by G force, #viscosity of the oil and percent #contamination, however; volume between draining will remain about the same.

The volume between draining for other sized bowls is calculated in a similar manner.

A centrifuge bowl capacity of 1 pint = 28.875 cubic inches

28.875 / .05 = 577 cubic inches

577cubic inches / 231in3/gal = 2.5 gallons

For a bowl capacity of 1 quart = 5 gallons

Nobody wants to sit around and wait to drain their centrifuge bowl, so here at USFiltermaxx, we design a variety of programmable automatic centrifuge controllers to remove the burden of manually draining the sludge from the centrifuge, allowing #automatic one pass cleaning.


US Filtermaxx Dual Centrifuge Controller

#Catoilandgas #DieselProgress #Caterpillarinc #wasteoil #oil #oilrecycling #Biodiesel #Industrial #Heavuequipment #hempoil #hemp #CBD #RT #Oilpurifier #Algae #Green #Fuel #diesel #transferpump #12vpump #electricpump #wastemotoroil #wvocentrifuge #wmocentrifuge #slurry

7 Remarkable Benefits of Spirulina, the Nutritious Blue Green Algae


● Spirulina is one of the most sought after superfoods today
● It’s a blue green algae that’s partly responsible for oxygen in the air
● Spirulina is considered to be an “all in one” source of nutrients
Loaded with nutrients, Spirulina is one of the most sought after superfoods
today. It is now available in the form of tablets, capsules and even powder
that you can add to smoothies . Spirulina is the blue green algae that are in
fact partly responsible for the presence of oxygen in the atmosphere, which
eventually allowed other small organisms to develop on earth billions of
years ago. What is really fascinating is that it is an edible algae, and can
truly be an effective vitamin supplement.
Being the oldest life form on earth, it is interesting to note that spirulina was
used by the Aztec people in Mexico in the 16th century. Later it was
cultivated in Chad, which is surrounded by Libya, Sudan and Nigeria.
However, it did not become a major part of the diet of the people till the
1960s. By the 1970s it had attained worldwide production and was on its
way to becoming the most nutritious food source. Just like a lot of people
detest consuming aloe vera due to its bitter taste, it is the same case with
Spirulina. It tastes slightly bitter thus is usually mixed with fruit juice or
yoghurt to improve the taste.
Spirulina is a form of cyanobacteria, which grows in fresh, warm lakes. In
India, it is widely cultivated in Auroville, Tamil Nadu. The hot climate in the
southern parts of India helps aid spirulina growth using eco-friendly methods
with minimal usage of pesticides and other harmful farming chemicals.
Benefits of Spirulina
Spirulina is considered to be an “all in one” source of nutrients. In fact, it
even has the potential to overpower meat and eggs as protein sources in the
years to come. Dr. Anju Sood, a renowned nutritionist, suggests a list of
benefits of spirulina –
1. Excellent Source of Proteins
Due to its high source of protein content , spirulina is frequently referred to
as the “lean, green, protein machine”. In order to keep our health and
well-being intact, a certain amount of protein is required by the human
body . While non-vegetarians gain this protein through meat and eggs ,
spirulina is an excellent alternative for vegetarians. It consists of 60 percent
proteins, most of which are plant based. Proteins are essential to enhance
the functioning of the heart as well as improve our hair health.
2. Helps Build Immunity
The immune system is made of T cells, B cells and natural immune cells.
Spirulina consists of certain elements that improve the functioning of these
cells and hence builds the immune system.
3. Improves digestion
Spirulina contains amino acids that provide digestive enzymes, which
facilitates healthy digestion . It also helps fight intestinal infections as it has
immune cells, which fight off virus and thus promote digestion.
4. A Great Source of Antioxidants
Carotenoid is the world’s most powerful antioxidant, and spirulina is a rich
source of this. An increase in free radicals in the body tends to aid wrinkling,
bad skin and could also lead to cancer and heart diseases . Antioxidants work
wonders to fight against free radicals.
5. Good for Growing Children
Spirulina facilitates healthy growth of children due to its numerous nutrients.
It improves eye sight , helps build concentration, builds muscular growth as
well as enhances tissue development.
6. Improves Energy Levels
Dr. Anju Sood sasy, “1 gram of protein gives the individual 4 Kilo calories of
energy and since spirulina is loaded with proteins, it works as a great energy
booster “.
7. Anti-Inflammatory Properties
Spirulina contains phycocyanin, which helps fight free radicals. This
substance gives spirulina its great anti-inflammatory properties.
To sum it up, spirulina is a boon for the body, regardless of the age of the
individual. It is known to be one of the most powerful natural sources both
to the environment as well as human beings to maintain a healthy balance.
The best way to make the most of these nutrient-rich algae is to consume it
raw. However, today it is also available in powdered form as a vitamin
Please note: Spirulina as a vitamin supplement must only be
consumed after consultation with a doctor or a specialist.
The opinions expressed within this article are the personal opinions of the
author.  Not responsible for the accuracy, completeness, suitability,
or validity of any information on this article. All information is provided on an
as-is basis.

7 Answers to Your Transfer Pump Questions

Here at US Filtermaxx, we are staffed by Mechanical Engineers who are extremely knowledgeable in their field.  Our customers know to take advantage of this knowledge by asking us questions.

Here are the 7 questions we hear most often regarding our oil and fuel transfer pumps.

  1.  Are Your Pumps self priming?  YES.  Life is hard enough without having to sit there and suck on tubes or try to fill your hoses with fuel by dancing around with one end high and the other  end low.  Take it easy.  Let the pump do  the work.
  2. Is thick oil O.K.?  YES.  These pumps are powerful enough to move the thickest oil.
  3. Is Dirt O.K.?  YES.  Dirty oil and fuel is our business.
  4. Is sludge O.K.?  YES.  These pumps will chew through and move almost anything.
  5. Does it pump Diesel?  YES
  6. Does it need a filter on the input??  NO!   Dirt and sludge are O.K., just no nuts and bolts.To filter your dirty oil or fuel down to 1 micron use a US Filtermaxx Centrifuge
  7. Is it durable?  YES! We receive countless calls from customers who bought a pump from one of our competitors and it failed after about 4 months.  We have NEVER had a pump failure that was the fault of the pump.  With proper usage you just can’t break them…and if anything should happen, we have an Onsite Shop and we will make it right.
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