Hydraulic oil contamination in the extrusion industry is a common problem that needs constant attention. A centrifuge-based hydraulic oil cleaning system is a perfect fit for this industry to avoid excessive losses related to equipment breakdown from contaminated oil.
This article will discuss understanding your hydraulic oil analysis report, the effects of oil contamination, prevention, and monitoring of extrusion press hydraulic oil. And finally, using a hydraulic oil centrifuge to maintain extrusion press hydraulic fluid.
The following is a chart of elements found in a spectral analysis report of aluminum extrusion hydraulic oil.
The chart above shows the different elements a “Spectral” or Spectrographic Analysis would find in oil. The Rexroth Bulletin also illustrates this difference. This chart helps one discern the difference between additives, wear metals, and other contaminants.
***Carbon is not listed because Spectrographic Analysis does not test for this contamination in Hydraulic Oils***
In an oil report, the particle analysis often registers high contamination in the lower-level micron size ranges. Similarly, the spectrographic or spectral analysis registers may show low levels on the wear-metal items.
The most likely reason for the high particle count is higher carbon, degradation, or even coke, which will not register on the spectrographic analysis.
A particle analysis machine counts Coke and Carbon as particles. If this carbon/degradation, especially coke contamination, is not dealt with by removing it from the oil, devastating domino effects will occur to extrusion presses. Additionally, wear metals and dirt (silica) causes your pumps, valves, and cylinders to wear extensively.
Carbon in itself is not a wear particle. Carbon contamination results from the splitting of oil molecules due to high heat and extreme pressure or pump slippage. An extrusion press is a perfect environment for all these things.
The bi-product from spitting the oil molecule is also known as degradation. When Carbon is present in the oil, a hydraulic system will either develop high acid or produce coke or worse; both could occur.
A) Acid causes deterioration of parts. Acid also diminishes the additive packages in oil. As long as Carbon is continually being removed from the equation, acid can’t form. Too high acid levels can even cause the cooler to dissolve copper into the oil.
Filters cannot remove degradation or submicron particles. The centrifuge system removes degradation and Carbon (submicron particles down to and below 1/10th of a micron).
B) Grease contamination is usually caused by excessive heat and pressure when introduced to the oil molecule. The shearing effect on the oil molecule itself can also create grease. Shearing to the oil molecule often occurs when a pump is slipping.
Pumps generally begin slipping since, over time, the wear rate has worn the pump so much that the pump efficiency drops off significantly. This wear causes the inner components to begin slipping.
It is critical to keep high oil cleanliness standards for the lubrication system and implement a pump manufacturer schedule to check for pump slippage periodically throughout the year.
When grease-contaminated oil passes through small orifices (such as in valves) at extreme pressures of 3,000 to 5,000 psi or higher, it produces extreme heat at the point of the orifice, thereby coking the oil.
Coke is a highly abrasive wear contaminant that will range in any particle size as a final bi-product. Coke, by itself, will jam or cause sticking valves.
As previously mentioned above, the jamming of valves can begin the devastating domino effect on hydraulic systems. Coke will also cause pumps and valves to wear, causing the contamination levels of wear metals to multiply to a critical state as well.
Other disc-centrifuge articles of interest......
Disc Centrifuge Backpressure - Comprehensive Guide
9 Steps to Selecting & Buying the Right Industrial Centrifuge
Centrifuge RCF and RPM | Difference & RCF Calculation
Disadvantages of a Disc-Stack Centrifuge | Illustrated Guide
Difference Between Decanter & Disc Centrifuge | Technical Comparison
The detrimental effects of coke on key extrusion press components are listed below.
1) Cartridge Valves, can cause cracking of pressure lines, blowing of seals, and breakage of main housings.
2) Flow Divider / Proportional Valves; it can cause the main housing to crack. Also, the aluminum waste product will increase if this valve is jamming. If the valve is restricted, it can cause irregularities in the aluminum product itself, even to the point of wasting an entire run of extruded aluminum which is deemed unsuitable for product distribution.
3) Servo Valves can slow or stop the operation of an extrusion press. This issue can cause the main housing to crack, seals to blow, and pressure lines to crack. If the pressure lines do not crack first, then the manifolds could end up cracking or breaking.
This failure can bring down an extrusion press for over a month to a month and a half. Profits lost during this oil-related downtime and the expense incurred to bring the press back online can financially devastate a company.
Note: ***Valves sticking or jamming can even cause the housing on pumps to crack, causing breakers to burn out; therefore, the motors can also fail and burn up. ***
Companies must have in place a good Preventative Maintenance Program. Extrusion companies that facilitate these programs and stress their importance are more successful than their competitors. The following are some of the reasons why:
If oil cleanliness levels are maintained at or cleaner than the hydraulic equipment manufacturer's specified requirements, oil can then extrusion companies experience extended life of pumps, valves, and seals, reducing oil-related maintenance costs and problems.
Additionally, an extrusion company could avoid long or short-term detrimental oil-related downtime that could otherwise occur due to contaminated oil (as listed previously under “Harmful Effects…”).
Currently, the aluminum extrusion industry's average downtime per press is about 125 hours. Dolphin Centrifuge customers benefit the most in the area of oil cleanliness because their industrial centrifuge systems enable an extrusion press to operate at its optimum performance and efficiency while reducing oil-related downtime by as much as 98%. Secondly, customers have reduced their oil waste disposal and new oil purchases by as much as 99%.
Thirdly, coolers can operate more efficiently because the heat-causing carbon contamination, which insulates heat within the oil, is removed. This efficiency allows the optimum heat transfer to occur as the clean oil passes through the cooler.
Thereby less energy is needed to cool the oil; (the centrifuge technology has reduced press operating temperatures by as much as 10 degrees or more in some cases).
Finally, aluminum product waste is reduced because the clean oil allows the entire hydraulic system to operate optimally. Some customers have mentioned they even have better product dimensional consistency.
Foremost, all of these benefits combined mean increased production and profit margins per press, per year, for the extrusion companies’ bottom lines.
Extrusion companies should keep track of their oil cleanliness levels monthly to know their presses’ operating conditions. The oil analyses will show if the oil is in a critical state or not or meet or exceed hydraulic manufacturing specs for oil cleanliness. Keeping a monthly track record of the oil cleanliness in extrusion equipment also helps in preventative maintenance.
For example, an oil report can forewarn companies of potential problems that could arise, not to be caught off guard shortly. For example, when a pump goes out, an oil report would have detected the Iron and Bronze contamination earlier, which comes from the pump as soon as it begins to wear.
This detection allows a company to prepare and budget for a pump they may need to purchase in the coming months. Always take oil samples off the bottom of the sump before sending them to the lab for analysis; taking the sample off the bottom of the reservoir shows a more accurate and correct depiction of the press’s working conditions.
Keeping track of their oil cleanliness helps us monitor the centrifuge system’s performance. It also helps our customers in preventative maintenance, wherein we can troubleshoot their extrusion equipment as needed.
In general, extrusion companies that do not employ centrifuge technology can have 40 ppm of Iron and 70 ppm or greater of copper. In such cases, the pump’s life expectancy decreases from six months to a year.
Our goal is to bring added value education and much-needed technology to these companies that have yet to experience these benefits.
Centrifuge customer’s oil analysis indicates wear metals reduce the point where it is minimal or no wear on the pumps. A significant reduction in wear metals extends the life of new pumps by 2 to 4 times. Used pumps also see similar extended operating life.
Extrusion companies should align their pullback rams as much as every week (preferably by laser alignment). This alignment will also extend the life of their hydraulic equipment and its produced parts as well.
Note: Older versus newly designed hydraulic systems for extrusion presses. Most new extrusion systems do not have coke-causing hydraulic design problems. On the other hand, many older presses have hydraulic system design flaws, causing coking to occur as part of their regular operation. In this case, we strongly recommend these companies fix their coke-causing hydraulic design problems as soon as possible.
A hydraulic oil industrial centrifuge system provides the only proven state-of-the-art solution to combat oil-related problems experienced by heavy industry, especially plaguing the extrusion industry.
Customers benefit by saving hundreds of thousands annually per extrusion press by drastically reducing their oil-related downtime to as much as 98 percent.
Here at Dolphin Centrifuge, we take pride in the technology we provide to all industries, especially the extrusion industry. Any company that employs Dolphin Centrifuge industrial centrifuge systems on their hydraulic power units will reap huge benefits and significantly increase their bottom-line profit margins.
Contact Dolphin Centrifuge for more information or to discuss your particular application with our centrifuge experts!
by Sanjay Prabhu MSME
Engineering Manager, Dolphin Centrifuge