Filtration Flow

[luizventura]

I am working on a hydraulic system improvements. My plan is to analyze the filtration system and make some improvements.
I am filtering oil (ESSO Anti Wear 1376). The system use cardridge filters in the cooling circuit in order to retain particles from main circuit. There are filters on cooling circuit (after main circuit and before heat exchangers) and protection filters before directional valves (only pilot oil valve), and ther is not filters in the main circuit (due pressure and flow surges). All the filters are (today) nominal filters. We do not have any absolute filter in the system.
The main funcion of the hydraulic system is to drive four hydraulic intensifiers. Each intensifier has one sub-system and each sub-system there are two main pumps (PF and PV axial piston Vickers pump), one supercharge/pilot oil pump (double vane Vickers pumps), pressure valves, flow valve (for cooling circuit) and directional valves (main directional and pilot oil valve) The subsystems share the same reservoir and the cooling circuit. Each main circuit has 6" ND pipe and work with 2191,6 l/min (~580gpm).

Is there any relationship between the filtration flow (sum of flow of each filter in the system) and the total volume of the hydraulic system? If possible send the reference literature.
If the information above is not enough, some general rule or guideline for filtration (regarding flow and total system volume) would be usefull.
Thank you and regards

 

[lowpsi]

luisventura,

In response to your question, your first step should be to complete a particle count on your system to see how contaminated your system is. I would think with nominal rated filters that, unless your cooling circuit turns over your reservoir capacity numerous times per day, your fluid is fairly contaminated. Compare your oil cleanliness level to the contamination level recommended by your hydraulic component manufacturer. To determine the cleanliness level that is desireable for your system you should choose the recommended contamination level for that component which is most sensitive to contamination (i.e. servo valve). You mentioned that you had PF and PV pumps. The minimum contamination level for these pumps, if they are operating in the 2000-3000 psi range, is an 18/16/14 as recommended by the manufacturer. You would then pick this contamination level as your target to achieve. Since you appear to know the difference between nominal and absolute filters you are probably aware that you need to increase the efficiency of your filters by going to the absolute filters which are 98.7% efficient. You most likely want to use at least a 5 micron or less filter to achieve the best cleanliness level for your components. You must check what the clean element pressure drop is to make sure it does not exceed 1/3 of the indicator setting, which is recommended by most filter manufacturers to maximize element life after you have cleaned up your oil with the smaller micron rated and higher efficient filters. I am involved in the hydraulics industry and take this approach with numerous customers. Hydraulic filtration has made giant leaps in the last 20 years. We have finally fiqured out that finer filtration and higher efficiency filters leads to longer component life. When you change to a smaller micron and higher efficient filters you will consume a lot of elements. The life of each replaced element getting longer as you are cleaning your hydrauic fluid.

 

[EdDanzer]

With out a full circuit diagram, my suggestion is to put a separate filtration circuit on the tank that has 5 micron filter elements and turns the tank volume a few times per hour. Be sure the filtration suction is away from the main pump inlets and the filtration return is positioned to turn the oil in the tank.