What is Centrifugal Filtration?

Centrifugal Filtration

 

What is Centrifugal Filtration?

Centrifugal filtration or centrifugation is a process that is used to separate or concentrate contaminants suspended in a liquid medium. A centrifuge will spin the oil at high rotational speeds and separate the particulates from the liquid. The process of centrifugation takes advantage of the difference in the specific gravity of a fluid and the particulates within to rapidly accelerate the separation process using centrifugal force rather than the force of gravity.

A centrifugal filter replaces the gravitational force with the centrifugal force.

Centrifugal filtration is a form of the process known as sedimentation, the separation of particles that naturally occurs due to gravity. A centrifugal filter replaces the gravitational force with the centrifugal force, which can be thousands of times stronger than the latter. Simply put, centrifugal filtration increases the rate at which the natural process occurs. A centrifugal filter spins the lube oil at a high rotational speed and separates the particulate from the liquid. The centrifugal filter forces the heavier solids to the outside of the separator bowl producing a firm sludge cake.

Users of a single filter system to clean oil are familiar with the cycle of inconsistent oil cleaning quality, replacement of filter elements, the disposal of oil and filter elements, and purchasing and storing new filter elements. A common cartridge filter system works to capture particles that are larger than the filter mesh. There is an upper limit to ideal cleaning effectiveness: as the filter begins to reach its capacity, its cleaning efficiency will decrease. The contaminants that were previously collected will be released whenever the filter experiences pressure shocks due to start and stop conditions. As soon as a filter is full and no longer completing its duty, filter elements must be disposed of and replaced with new ones.

Because of the inline full-flow filters, the larger particles found in the fluid medium cannot pass through the perforated layers of filter media. However, fluids and particles smaller than the full-flow filter mesh can still pass through the filter mesh under pressure, vacuum, or gravitational force. A centrifugal filter is essentially a type of bypass oil filter that processes a small percentage of the oil flow so as not to starve the machinery of oil and sometimes cause irreparable damage.  Unlike other filtration processes, with centrifugal filtration, there are no filter media, the unit is not disposable, and in some cases, the unit can remove particles even as tiny as nanoparticles.

 

Why Use Centrifugal Filtration?

The use of rotating machinery is necessary for almost every industry. Although this equipment is common in various applications, there are still a vast number of opportunities that can increase performance, reduce maintenance downtime and increase the life of such equipment—ranging from steam turbines and diesel engines to the use of pumps and actuators. Within many of these systems is a lubrication oil which can be beneficial or detrimental to how long such equipment will stay in service.

Increase the Lifespan of Your Machinery!

In summary, that means materials are subject to various types of wear, including friction and abrasion. However, in our scope, we will focus on maintaining the oil that lubricates such machinery. Regularly scheduled machine maintenance and oil cleanliness are two (2) key factors in determining how long a piece of equipment will last. Finding ways to improve equipment’s lifespan and efficiency is a struggle not limited to just one industry. Finding solutions that assist in achieving those goals are often expensive, and there is no clear-cut answer as to which of these choices is the best.

A simple and effective way to improve these qualities for lubricated equipment is to improve the quality of the oil used to operate it. Having a regular schedule to change filters and fluids is a great start. However, it is possible that even oils bought off the shelf still contain contaminants. To ensure clean oil is used, engines use various oil filters to prevent major component damage and excessive wear. Some systems even utilize more than one filter at a time to increase the time between oil changes by removing as many contaminants as possible.

Removing all harmful particles from a lubrication system ensures that the operated equipment will be around for many years. Determining which solution best fits your needs is the first step in establishing an upkeep solution that will reduce operating costs for such equipment.

Common Types of Filters:

1. Cartridge Type

Cartridge-type oil filters are a type of full-flow filter that is utilized in a large variety of applications. These filters are among the most often used types, intercepting and decontaminating the oil before it’s pumped through the engine. Oil filters of the cartridge type use a porous filter media that keeps larger contaminants from traveling within the lubrication system and allows oil to flow uninterrupted by long dwell times.

These filters capture and hold damaging contaminants and ensure the equipment will make it to its next service interval.  These filters are non-serviceable. However, they are replaceable. The most considerable drawback of this type of filter is the limited size of the particulates they can remove. Due to limitations of the filter media mesh, smaller wear particles can pass through almost freely, sapping engine life and further deteriorating the lubrication oil.

As a primary filter, this type does its job adequately, but when paired with a centrifugal oil filter, the number of contaminants removed is greatly increased. The main reason these are the oil filters utilized most is cost, and they have a relatively small carbon footprint compared to some of the other types of oil filtration solutions. It is not uncommon for these types of filters to be disposed of in a bin where they will later be collected and recycled.

2. Centrifugal Type

A centrifugal type of oil filter is a type of bypass system that utilizes the pressure created by the engine oil circulating to spin a turbine and create centrifugal force. Centrifugal forces grant this type of filter the ability to remove particulates that would remain within the system after passing through a full-flow cartridge-type filter. Bypass filtration systems use around 10 percent (10%) of the flow that would have proceeded to feed the engine and cycle it through a high-efficiency full-flow filter and back to the sump.

By taking advantage of bypass filtration, the oil filtration rate is increased significantly, removing much smaller pore size contaminants while maintaining the normal operating oil pressure of the engine. The final result: much cleaner oil is returned to the sump.

Smaller contaminant particles that the full-flow filter cannot capture can now be removed from the system by the centrifugal oil filter. Utilizing a system that combines the use of both a full-flow filter and a centrifugal filter will generate tangible benefits, including lower wear particles in the oil, lower oil consumption, greater combustion efficiency, and extended lubricating oil life (proven by ISO code testing).

Centrifugal filters have rather simple construction, making maintenance easy and relatively inexpensive. When servicing a centrifugal oil filter, the only components that need to be changed from the whole assembly are the bowl liner and O-rings (if damaged or brittle). The disc stacks used should only be replaced when they become damaged; otherwise, they can be cleaned of debris and reused. Keeping schedule to service the centrifugal oil filter is just as important as changing the disposable full-flow filter and the engine oil. Using centrifugal oil filters in tandem with cartridge filters is also beneficial in decreasing the amount of waste produced by extending the filter life. The centrifugal filters themselves do not require replacement.

 

How does a Bypass Centrifugal Oil Filter Work?

As stated previously, a centrifugal oil filter utilizes centrifugal force to provide a greater separation efficiency. Oil is directed into the centrifuge via the oil inlet at the bottom of the unit. The oil then travels into the bowl of the centrifugal oil filter through the bottom impeller. It is at this point that centrifugal filtration begins.

As the oil comes in through the impeller, the impeller is forced to spin. The higher the oil pressure, the higher the resulting revolutions per minute (RPM). Higher RPMs result in greater centrifugal force as well as greater separation efficiency. Clean oil travels up the centrifugal oil filter through the disc stacks and out of the unit through the top impeller.

Contaminated lube oil circulates from your machine into the centrifugal oil filter. Inside the centrifugal oil filter, the centrifuge bowl will spin at speeds of up to 8,000 RPMs. The centrifuge’s speed solely depends on the pressure from the oil inlet. The resulting centrifugal force sends the contaminant particles outwards against the centrifuge bowl wall while the newly cleaned oil returns to the machinery it’s meant to protect.

The denser particles are forced to the outer wall of the centrifuge bowl and stick to the paper insert forming a thick sludge cake. A variety of contaminants, including soot, dirty, carbon, and wear metals, are removed during normal engine operation by the centrifugal oil filter. The centrifugal force of the centrifugal oil filter removes impurities from oil according to their relative density. For a contaminant to be removed with a centrifuge oil filter, it must have a density greater than the working fluid (engine oil, transmission oil, etc.).

During centrifugal oil filter maintenance, the paper liner and resulting sludge cake are removed from the unit. The technician then cleans the centrifugal filter, adding a new paper insert to it before returning it to operation. Necessary downtime for maintenance of a centrifugal oil filter is kept to a minimum to ensure it can go back to completing its goal of improving oil life.

 

Disc Stack Technology

In addition to using centrifugal force to remove contaminants, the performance of a centrifugal oil filter is greatly improved by using disc stack technology. The purpose of the disc stacks is to create more surface area for the oil to contact and extend the amount of time it will spend inside the centrifuge. The more time spent within the separator bowl, the cleaner the oil will be. By utilizing disc stacks, the separation efficiency of a centrifugal oil filter is drastically enhanced.

Bowl Discs increase the separation efficiency and provide more separation surface area!

As discussed earlier, the disc stacks also act as guides for the lubrication oil to follow up and out of the centrifuge through the top impeller. During the centrifugal oil filter maintenance, these disc stacks are removed and cleaned of the contaminants that would typically be found within the lubrication oil. In the case of the IOW Group centrifugal oil filter, these disc stacks are made of plastic, unlike those found in large industrial centrifugal separators, which utilize disc stacks made of metal. The IOW bowl disc allows for ease of service and removes a safety hazard that comes with maintaining this type of equipment.

Centrifugal filters that utilize bowl disc technology have:
– Increased separation efficiency 
– Faster separation
– Increased surface area
– Better results

Bowl Discs dramatically speed up the precipitation of the solids from the liquid.

Disc stack separators are ideal for a large variety of separation tasks that require removing smaller particle and droplet sizes. The most challenging separation tasks may often involve the particles to be separated being rather minuscule in size. In these cases, no other technology can compete with disc stack technology. The IOW Group centrifugal oil filter is the only centrifugal oil filter on the market that utilizes disc stack technology for all the added benefits.

 

Why Use a Centrifugal Oil Filter?

The utilization of a centrifugal oil filter comes with many benefits. Using an IOW centrifugal oil filter can extend engine life by up to 2-to-3 times in some applications. Intervals between oil changes can be increased as most contaminants are removed within the centrifuge and disposed of during service. Carbon deposits lead to decreased efficiency, and other particulates cause microscopic yet significant damage to an engine if not properly managed.

A centrifugal oil filter can help mitigate this problem and adds a much-needed safety net to the lubrication system. This extension of the engine and fluid life translates to lower operating costs and maintenance costs, making such a system’s retrofit economically viable. In addition, by extending the life of the oils run through these systems, sustainability efforts are also impacted as centrifugal filters help reduce the amount of wasted oil. With the use of a centrifugal oil filter, it has been proven that the primary filter’s life can also be extended.

The centrifugal oil filter is not replacing the existing full-flow filter but rather acting as an assistant that ensures no tiny detail will be missed and will help prevent a failure for an even more extended period.

According to the Society of Automotive Engineers (SAE), particles as small as 4 microns can be responsible for up to 77% of engine wear. Full-flow oil filters alone generally filter out particles down to 25 microns. A 25-micron filter is roughly 80% effective, meaning 20% of particles smaller than 25 microns pass through the filter and continue to wear out your engine’s components. The combination of full-flow and centrifugal oil filters can assist in removing particles smaller than the 25-micron range. The use of centrifugal force also provides a means to remove contaminants from 1 to 10 microns that encourage engine wear and decrease oil life.

Adding a centrifugal oil filter seems to be a clear choice in improving the machine’s lubricating oil quality, leading to economic and environmental improvements. Centrifugal oil filters are simple to service and have longer in-service periods than their cartridge filter counterparts. This improved cleanliness of the lubrication oil can lead to more excellent machine reliability. With the previously mentioned benefits created by using a centrifugal oil filter, a better question is, why wouldn’t you use one? The overwhelmingly positive results produced by such a system should be testament enough to, at a minimum, get the gears turning to consider procuring such a system for yourself.

In Summary

We have discussed many reasons centrifugal oil filters would be beneficial for use in a lubrication system. By removing soot and reducing the frequency of oil changes, centrifugal oil filters provide a positive environmental impact. For such a simple solution, centrifugal oil filters provide great value in maintenance savings and equipment life extension. Results of the benefits of centrifugal oil filtration have been proven by conducting oil analysis before and after the installation of such a system: the resulting ISO codes have shown engine life extension between 2 to 3 times.

For all your centrifugal oil filter needs, look no further than IOW Group. IOW Group is a leading manufacturer of separation, filtration, and fluid transfer products. To learn more about IOW Group’s wide range of centrifugal devices, visit our IOW Group Centrifugal Oil Filter webpage or visit the IOW Group Centrifugal Filtration website.