Disc stack centrifuge lubrication is an essential part of the regular maintenance required to ensure the operating reliability of the centrifuge. Lubricating oil is the primary lubricant used in the disc centrifuge transmission housing.
The most important consideration when changing the oil is the type of lubricant and the frequency of oil change.
To understand the importance of lubrication in the disc stack centrifuge, we should first understand the working principle of the lubrication system.
The disc centrifuge lubrication system uses an oil splash type method to lubricate the bearings. The large bull gear is partly submerged in the lube oil sump. The constant rotation of this gear splashes the oil into the bearings on the horizontal and vertical shafts. This splashing oil lubricates and cools the bearings.
The following are the primary reasons to change the oil in the disc centrifuge lubrication system.
The constant meshing of the transmission gears of the disc centrifuge causes wear and tear on the gear teeth. This wear leads to metal particles getting into the lube oil and the bearings through the lubrication.
Lube oil with metal particles is the primary cause of bearing failure, which can have catastrophic effects on the centrifuge. The replacement of the old oil with new, clean oil thus prolongs bearing life and prevents unanticipated centrifuge breakdowns related to bearing failure.
Water contamination of centrifuge lube oil is a common occurrence. The most common source of moisture contamination is condensation. In humid climates, condensation accumulates in the gear housing and contaminates the oil.
Operating or process water can also seep into the transmission housing due to defective seals or O-rings. This type of water contamination is often quite severe due to the quality of water that can get into the oil due to a seal leak.
Lubricating oil containing water causes bearing failure because water does not have the lubricating properties needed to operate the bearing at high speeds as in a disc centrifuge.
Lube oil loses its lubrication properties over time due to chemical decomposition and temperature variations. Reliable bearing service requires good lubrication. Therefore, periodic replacement of lube oil in the centrifuge is essential for the reliable operation of the bearings.
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For the reasons mentioned above, lubrication oil replacement is a critical aspect of disc centrifuge maintenance. Since the cleaning of centrifuge lubricating oil is not feasible, periodic replacement is the only option.
The lubricating oil in a disc stack centrifuge should be changed every 2,000 operating hours or every 12 months, whichever is earlier. Changing the lube oil at the recommended time interval ensures the durability and longevity of the centrifuge. The centrifuge operation over a prolonged period without replacing the lubricating oil causes centrifuge breakdowns and cause catastrophic failure.
Larger centrifuges or belt-driven centrifuges have different oil change intervals. The user should consult the manufacturer or the operating manual for the correct frequency of lube oil change.
In a new installation or after the change of gear transmission, change the oil after 200 operating hours and clean the gear housing.
When the centrifuge is operated for short periods, lubricating oil must be changed every 12 months even if the total number of operating hours is less than stated in the recommendations above.
The manufacturer recommends the type of lube oil for disc centrifuges. Therefore, the user must refer to the centrifuge manual for the recommended lubricating oil.
Alfa Laval recommends the following grade of lubricant for its centrifuges.
|Viscosity grade VG (ISO 3448/3104)||220|
|Viscosity index VI (ISO 2909)||> 92|
The following table lists the recommended oil from the different lubricant manufacturers.
|Castrol||Alpha ZN 220|
|Esso Standard Oil/Exxon||Teresso 220|
|Mobil||DTE Oil BB|
|Shell||Tellus C 220 or Tellus C 220|
|Texaco/Caltex||Regal R&O 220|
It is imperative for the user to refer to the manufacturers’ recommendations for the type of oil. Different centrifuge manufacturers recommend different oils based on their centrifuge design and operating conditions.
The volume of lubricating oil required for each centrifuge depends on the size of the centrifuge. Larger centrifuges have a larger gearbox holding capacity, and therefore they need more lubricating oil.
Most disc centrifuges feature a sight glass on the bottom frame housing to show the level of lubricating oil in the gearbox. The oil level should be halfway in this sight glass after the lube oil replacement as shown above.
The following table lists the volume of oil required for some popular Alfa Laval disc stack centrifuges.
|Centrifuge Model||Lube Oil Volume (Ltr)||Lube Oil Volume (Gal)|
|Alfa Laval MAB 103||0.8||0.20|
|Alfa Laval MAB 104||0.8||0.20|
|Alfa Laval MOPX 207||7.5||1.95|
|Alfa Laval WHPX 510||12.0||3.10|
|Alfa Laval BRPX 213||12.0||3.10|
There are specific field lessons that can help the centrifuge operator monitor and maintain the oil in the centrifuge transmission. The following is a popular tip based on these lessons learned.
Using this tip, the operator can quickly check the quality of the lubricating oil and drain any accumulated water simultaneously.
During the centrifuge shut-down period, slowly unscrew the oil drain plug. Do not remove the plug altogether. Unscrew the plug until a small amount of oil starts to drain out. Collect this oil in a small container.
If the drained oil sample shows lots of water and or metal particles, it is vital to change it. This method allows the operator to drain small amounts of water, if necessary.
It is essential to replenish the removed oil with fresh oil to the original level in the oil sight glass.
This article is based on our 40 years of disc centrifuge experience. To know more about us, visit the About Us page.