Relationship Between Oil Leaks and Contamination

[Rolly]

Hi,

I would like to ask some expert opinion wether there is a direct relationship between oil leaks specifically hydraulic oil and contamination. Since oftentimes, an engineer will try to modify the strenght or material of the seal, however from what I know is that if there is leaks then there is ingression of contamination and water, hence, to me it sounds logical to say that with water, silicon and all sorts of contamination, and oil oxidation, this will accelerate the wear of seals and result is leaks, I would like to confirm this if there is direct relationship if the oil is dirty then system is more prone to leaks and if oil is maintained clean at certain ISO standards then leaks can be addressed to a minimum or not at all. I need this answer ASAP, hope you dont mind and thank you for allowing me to post this question

 

[Neil Womack]

Rolly

I'm far from an expert. Several guys on this site are hydraulics experts and maybe they will give us an expert opinion.

In the mean time all you get is my .02.

If a system is contaminated with dirt. The dirt will wear the seals at the point where metal and seal come together and should be seperated by an clean oil film.

If a system has water in it then the metal will rust creating a rough spot that will wear at the seal.

Either way you get a leak causing more dirt and water entry into the system and then more wear.

 

[Rolly]

Hello Niel !


Thanks, appreciate your answer a lot, happy to have people like you answering my querry. This was one of the questions posted to me when I was training oil analysis, I just want some confirmation.

 

[Robbie Alexander]

I would say yes there are based on all my samples.

Some will be greater leaks than others and some areas can last a lot longer than others but they all will create MORE wear one way or another. Sometimes the wear will be light and gradual and other times it comes up like a rocket.

If oil is getting out, then dirt is getting in.

Any contaminate that you can prevent lill provide a longer life for all components.

Now Hydraulics are something I'm suppose to get into and haven't, but I do know depending on the application, it can be very cost effective to prevent down time.

 

[MolaKule]

Rolly,

If the leak is on the high pressure side, then you simply waste fluid. If the leak is on the low pressure side, then you will engress moisture and dirt. 75% of all hydraulic system problems involves dirt and moisture contamination.

Now some moisture is going to be evaporated IF the fluid is allowed to attain operating temps. Most dirt should be taken out by the hydraulic filter. Draining and flushing the system on a regular basis will remove most contanminants not picked up by the filter, such as some solubles. A good sump strainer and frequent hydrualic oil filter cleaning/changes (respectively) will help the system as well. I prefer 10 um filters if the system flow allows it.

Since you didn't mention the where the seals are or what type of pump you have, it is difficult to determine seal damage and where it might occur. If the seals are pump seals, then abrasive dirt and small particles of metal will tear at the seals until they eventually degrade and leak. Again, proper filtering and flushing will reduce particle contamination.

Used Oil Analysis with a thorough particle count is one of the better non-invasive ways to determine oil quality and system health.

End plates in hydrualic pumps are usually made of brass which would would show copper and tin wear. If the pump is a gear pump, then gear and bore wear would show up as iron or Fe wear.

Oxidation and TAN numbers from analysis would also help to determine the condition of the oil.

A rule of thumb is to design the reservoir or sump or accumulator with 3X the flow rate of the system. This helps to cool the oil and deareate the oil. If not, then an oil cooler or heat exchanger is necessary.

 

[Robbie Alexander]

quote:

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Originally posted by MolaKule:
-*-* I prefer 10 um filters if the system flow allows it.
-*-*

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Do they make them with filters, bypass AND magnet?

What would be the STANDARD, 25 microns>???

And is there a ststem you would allow higher than a 10 micron?

What would be a system you would require less than the 10 micron, if any or if they make the filters?

 

[Rolly]

Hello Molekule,


Appreciate all your feedback, I was just curious also like Robbie, regarding the 10 micron filter, what beta rating would you actually recommend for a 10 micron filter 200 or 1000 ?


thanks,


Rolly Angeles

 

[Hankster]

10 micron is usually a basic figure for filtration. If there are servo valves in the system 5 or even 3 micron is common.
Hank

 

[MolaKule]

Neil, good explanation.

For the systems I design and build (woodsplitters), I use a Hastings HF922 with Cross 3/4" filter ports that have a 35 psi bypass valve. The HF922 is rated at 10 um with an approx. beta of 125.

Hankster is correct, if servo valves are used, then 5 um filters are the norm, since servo valve seats are more prone to particle errosion. Filter betas of 200 should be used here.

For the above systems, I use Prince manual control valves that aren't that sensitive to 10 um particles.

 

[GeorgeCLS]

In determining filtration needs, it is recommended to use one of the 'target' determination work sheets developed by Hydac and others. This worksheet breaks down the system needs and you can easily determine the optimum target ISO for your system, then secure the appropriate filter for desired results. i.e. if the sytem is high pressure (3,000 psi+) and has servo valves in the system, an ISO cleanliness of 15/13/10 would be optimum. Eventually getting to a 3 micron beta 200 filter would be the final filter, very likely going in steps of 10 micron, 6 micron, and then finally 3 micron when the system was cleaned up..
George Morrison

 

[MolaKule]

Very true George, albeit those considerations have to be balanced with flow requirements as well.