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Lube Oil Filtration System (with high contamination load)

Lube Oil Filtration System (with high contamination load)


this is my first post here and I hope I deliver the required information to get some valuable advise.

I am currently looking for alternative lube oil filtering. This is due to a high volume of contaminants in the lube oil system which requires very frequent cartridge filter exchange. Currently running 40 micron filter cartridges we go through two per month, the By-Pass Filter cycle can hardly operate as its 20 micron filter clog up within 20 minutes. We have been at the point of making them last for approximately 5 days after cleaning the whole cycle, however the exchange frequency increases significantly within the next weeks.

Looking at your product range I cannot find a specific Dirt Holding Capacity, information about prices and if applicable duration of filter exchange. Can you please provide me with these information regarding the specs below? Council towards applicability is welcome.

The over-all goal is reducing the amount of labour (Filter Exchange), cost (Filter Unit Price per kg of contamination removal) and a minimum cleanness of 40 micron (depending on the other factors desirably 20 micron).

Remarks: The tank contains a 149 micron (100 mesh) filter element, followed by the pump, followed by a set of 2 filters of which one is always in standby as the system is critical and lubrication cannot be paused, additionally there is a kidney loop system operating on the by-pass

Points of interest regarding this are:

1.) Dirt Holding Capacity or Alpha Rating
2.) Unit Cost
3.) Involved Labour Cost

The systems specifications are roughly as follows:
In-Line System:
Pressure 720 kPa (Low Pressure System)
Flow Rate 150 l/min
Oil Operating Temperature 70 °C
Lubricant Fuchs Renolin CLP 320
Kidney System:
Pressure ??? kPa as far as I can tell at the moment it is roughly 200 kPa
Flow Rate 50 l/min
Oil Operating Temperature 70 °C
Lubricant Fuchs Renolin CLP 320

Currently I am evaluating the following methods can you please comment on them? Especially the negative points are those I am looking for as this is rarely what you find on OEM's homepages (Example Self Cleaning Wedge Wire Filters, they can not keep all they promise... why make them easy to disassemble if they run for ever and never weak off?):

1.) In-Line Centrifugal Filter between low-pressure Pumps and current Cartridge Filters
2.) Exchanging Kidney Loop Filter (Cartridge) with Centrifugal Filter, CLC Filter, Wedge Wire (Self Cleaning as I do not think backflow is possible) or Filter Bag based system.


RE: Lube Oil Filtration System (with high contamination load)

Fix the source of the contamination. If the rate of contamination being added to the lubricant decreases, the rate at which it needs to be taken out will also decrease.

For specifics about filters, contact their applications engineers. The web pages cannot be full design guidelines.

RE: Lube Oil Filtration System (with high contamination load)

Where is the contamination coming from? You have a bigger problem than filters.
If for some process reason you have to live with this then you need to look into adding more stages for the filtration.
Talk to engineers from the filter company, they will suggest a sequence of filters.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Lube Oil Filtration System (with high contamination load)

I don't work in this area...

Can heating the oil help in the extraction by reducing the viscosity?

Do they have filters, at least for initial filtering, that can be reused to reduce costs?

Is there any centrifugal processes that can be use?

Are there any 'multi stage' filters that as a combined unit start at say 100 mesh, 40 mest and then 20 mesh?

Just some ramblings...


RE: Lube Oil Filtration System (with high contamination load)

what exactly is the oil used for? given the product name i assume it is used in a large gear system operating at relatively slow speed.

another question: what kind of contamination do you experience? again, a guess based on the data supplied, suggests iron particles will be most prominent, eventually also thermal degradation products and or water. the latter two will increase the viscosity and will make filtration far more difficult.

do you have any clue as to what level of cleanliness the system is running on? a gear set need and cannot be kept on the same level of cleanliness as a high pressure hydraulic system...

we will need some more information about the system to come up with useful suggestions.

some additional remarks: the strainer for the pump can hardly be regarded to act as a filter - it is just there to prevent loose nuts and bolts that somehow entered the tank entering and subsequently destroying the pump. given the very short time the filters last, you may have a problem that cannot be solved with just a higher capacity filter. of course a larger filter can hold more dirt, but you can only do so much. a better way to start is to look at the type of contamination, where it comes from and why it is there at all. maybe some parts of the machinery are not adequately lubricated and a better supply of lubricant to selected parts might improve the situation. another remark: if the filter is clogged, will the level of contamination in the lubricant increase over time appreciably faster or justt just at about the same rate as when the filter is changed? if the latter is the case, changing filters will not improve the situation, but only increase running costs.

remember: adequate filtration is based on the idea that you can keep contamination levels at such a level that the machine will reach its design life - "better" filtration may help a little in terms of longer machine life but does not necessarily reduce the cost per unit of output produced. depending on the type of machinery different types of filtration may be optimal - not every machine is served best with very fine filtration, whereas some machinery depends on accurate filtering. for gears a simple magnetic plug in the tank should be able to get rid of most of the contamination produced by the gears - and is effective both for small and coarse particles. if thermal degradation products or water is the problem other types of filters are to be preferred, and as far as water is concerned, it is best to prevent water entering into the system at all.

RE: Lube Oil Filtration System (with high contamination load)

Are you trying to maintain production after an unfortunate contamination event?
Shutting down and a proper reservoir cleaning is certainly the best choice.

Something like this may help buy some time

RE: Lube Oil Filtration System (with high contamination load)

@#DDave: Thank you for your comment. However, I do not need a whole design guide I was asking for input as towards filtration methods which can help improve the situation as filtration is a strongly neglected area at university and I am pretty new to practical work life.
Furthermore, the source of contamination cannot be fixed for a while. I am aware that filtration in the way it is being planed is fighting a symptom not the cause.

@EdStainless and Dik: Thank you for your comments! Filtration stages are definitely a great approach, but more or less just shifting the work input as we currently do not filter very fine (40 micron). A centrifugal Kidney Loop System seems to be most desirable at this stage, though I haven't had any realistic report on their functionality. Talking to a sales engineer about the maintenance of the product and the wear parts usually ended up in "Its barely any work.... Sooo fast and easy...".

@Tmoose: thank you for your post, but I think this is not applicable here.

@romke: Thanks for the comment!!
1.) The oil is used for a trunnion Gear which is spinning relatively slow (mill).
2.) Main particle source in the oil is iron, furthermore there are nickel and chromium which I believe to be signs of wear due to the relatively bad oil condition filtered at 40 micron. Water ppm ranges around 10 to 50 and isn't too bad, viscosity of the oil is relatively high though as it operates at 70-80 degrees Celsius.
3.) I haven't had a look at this in detail. Could you please elaborate what you mean by increasing costs and not having an effect? The goal is reducing the time involved in dealing with this issue and creating a buffer in regards to DHC. furthermore the filters we use in kidney and in-line system are close to ten thousand dollars a month. Thus, I think using cheaper filter elements with higher DHC could save costs and reduce labour hours.

I am aware that the source is the actual issue. However, I do not see how we can improve the sealing at the trunnions, even if we shut down it would be a task which is hardly realisable.
The high amount of contamination is also a result of the fact that the area which is being sealed is enormous.

We have several magnetic plugs in the tank already (they helped quite a bit).

RE: Lube Oil Filtration System (with high contamination load)

I did not suggest a design guide - I suggested talking to an application's engineer.

For specifics about filters, contact their applications engineers.

RE: Lube Oil Filtration System (with high contamination load)

Have you done an analysis of the fluid to determine the constituents?


RE: Lube Oil Filtration System (with high contamination load)


What i was referring to is that a finer filtration system not always will help. In a gear type application you will always have a certain amount of iron wear particles, because complete hydrodynamic lubrication cannot always be maintained. Thus a large number of wear particles are generated. You can try to filter these out, but that not necessarily stops the generation of new wear particles, because of the fact that the wear itself is caused by lack of lubrication and not by the lubricant acting as a kind of "grinding paste" because it contains wear particles.

In your case I understand that the wear partly is caused because dirt is entering from outside because of the difficulty with sealing. If that cannot be improved, you somehow must see to live with it.

A solution that might improve the situation is the use of a centrifugal type of filter. A centrifugal filter filters particles out based on their density, regardless of their size. It can thus filter out both large particles and very small ones that otherwise would require very fine filters that would clog up quite easily. It is important though that the difference in density between oil and contaminants is sufficiently large to be effective. It still will not take away the cause, but it may keep the situation under control. A centrifugal filter does not need a replacement cartridge, when it is (nearly) full it can be taken apart and cleaned. That might reduce filtering costs quite a bit.

RE: Lube Oil Filtration System (with high contamination load)

Completely off of the cuff, but... if contamination is heavily iron-based, would a simple magnetic-based pre-filter system prevent a good chunk of contaminants from ever hitting the cartridge filters? Don't know what happens at such small particle sizes, but I would think wiping off a magnet catch once a month (at practically zero cost) is preferable to changing out expensive filters.

Dan - Owner

RE: Lube Oil Filtration System (with high contamination load)

" @Tmoose: thank you for your post, but I think this ( filter cart) is not applicable here."

Off-line Filtration -
Filter carts can be mounted permanently to a machine to supplement filtration.

I'd be looking to the cart to correct the contamination problem, and then continue to "polish" the lubricant after the machine'e shaft etc sealing deficiencies were addressed.

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