Knowledge Page

Terms, topics and information that can be helpful when selecting the correct filter.

1. Filtration in Brief

Contamination Control in the hydraulic system is a very wide and complex matter; the following is just a short summary.
Our Customer Service is at your disposal for any further information.
The function of the fl uid in the hydraulic systems is transmitting forces and motion.
In view of a reliable and effi cient operation of the system, it is very important to select the fl uid considering the requirements of the system and the specifi c working conditions (working pressure, environment temperature, location of the system, etc.).
Depending on the required features (viscosity, lubricant capacity, anti-wear protection, density, resistance to ageing and to thermal variances, materials compatibility, etc.), the proper oil can be selected among a number of mineral oils (the most popular), synthetic fl uids, water based fl uids, environmental friendly fl uids, etc.
All the hydraulic fl uids are classifi ed according to international standards.
Solid contamination is recognized as the main reason for malfunction, failures and early decay in hydraulic systems; it is impossible to eliminate completely it, but it can be well kept under control with proper devices (fi lters).
No matter which fl uid is used, it must be kept at the contamination level required by the most sensitive component used on the system.

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2. Media Chemical Compatibility

The chemical composition and temperature of the process fluid must be considered in order to ensure the integrity of the filter media construction for the specified application. Certain chemicals and temperature combinations can cause degradation of the filtration media resulting in failure of the media and downstream contamination in the process.

The attached chart provides a general guide for temperature and chemical compatibilities of the filter media Flow Tech offers.

Contact your Flow Tech Account Manager for further information and guidance on filter media selection.

	Polypropylene	Nylon	Polyester	Aramid
Max Temp (F)	200	275	275	375
Max Temp (C)	95	135	135	190
Specific Gravity (gr/cm3)	0.91	1.14	1.38	1.38
Weak Acids	Excellent	Fair	Very Good	Fair
Strong Acids	Excellent	Poor	Good	Poor
Organic Acids	Excellent	Poor	Good	Poor
Weak Alkali	Excellent	Excellent	Good	Excellent
Strong Alkali	Excellent	Excellent	Poor	Excellent
Aliphatic Solvents	Fair	Good	Good	Good
Aromatic Solvents	Poor	Good	Good	Good
Alcohols	Good	Good	Good	Good
Ethers	Poor	Good	Good	N/A
*Note: This guide is for general information only – Process trails are required to confirm compatibility.*

3. Particle Size VS Particle Count

We are often asked, or even recommend, that a particle size analysis (PSA) be conducted on a fluid sample. In this work, we take the sample, run it through a laser particle counter and collect data for various channel /sizes of particles. From this type of work, you may get a data table

In this case, we see 1.7 million particles between 0.5 and 1 micron and almost 1.5 million particles between 1 and 2 microns. Looking at this data, our first reaction may be, “well I see your problem, you have a massive number of particles below 2 microns”. While this certainly is an accurate statement, it is not the whole story. The performance of a filter is based on mass or volume, not particle numbers. For instance, we do not report cartridge capacity in terms of 4 million counts, but rather 110 grams of capacity. Therefore, these counts need to be converted into a mass or volume value. We can only es3mate the mass/volume since we do not have particle specifics, so we generally make an assumption (wrong, but workable) that the particles are spherical and have all the same density, thus we can calculate a simple volume number based on volume of a sphere, V = 4/3 π r3 . When you do this, you get a very different picture.

Size	Counts
0.5	1,716,032
1	1,473,303
2	965,268
5	632,222
10	254,988
15	165,336
20	76,392
25	25,638
50	4,505
75	1,902
Total	5,315,586.00

So, as we can see, even though the small particles are present in huge numbers, they really contribute very little to the overall particle volume in the sample. You now find that the larger particles are the real issue even though they are a any fraction of the small particle counts. If we created a filtration solution using particle counts, we would focus on 1-micron filters which would lead to rapid plugging. Whereas looking at mass or volume, we can see that we need a filtration scheme that captures particles 10 micron and above in order to have a cost-effective process.

Size	Counts	Volume	% Total Volume
0.5	1,716,032	35751	0. 007%
1	1,473,303	245551	0. 045%
2	965,268	1287024	0. 236%
5	632,222	13171292	2. 410%
10	254,988	42498000	7. 777%
15	165,336	93001500	17.01%
20	76,392	101856000	18.64%
25	25,638	66765625	12.21%
50	4,505	93854167	17.17%
75	1,902	133734375	24.47%
Total	5,315,586.00	546,449,285

4. Protocols for Cleanrooms & Contaminant Mitigation

The production of computer chips from raw silicon requiressome of the cleanest environments in the world. Far cleanerthan a hospital operating room, the slightest impurity can leadto chip failures, product recalls and customer dissatisfaction.Therefore, semiconductor manufacturing work is conducted in acleanroom with strict personnel, chemical and environmentalstandards to limit sources of contamination.

Types of contaminants:

There are multiple types of contaminants, each of which has itsown impact on semiconductor manufacturing. Roughly, theseare grouped into particulate, biological and chemicalcontamination pathways.

Particulate:

With transistor spacing under 32 nm, or nearly 5,000 times smaller than the diameter of a human hair, any speck of dust isa major problem. Even inert substances that will not chemically react with the silicon are still a concern. Particles interfere with exposure during lithography steps, generate coating defects and change the topography of the wafer during other processing steps. Furthermore, charged particles can land on wafers and discharge, blasting away fine details, as a nanoscale version of arc flash discharge.

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Have a question for us? Call us at 269-375-1290 or toll free at 877-375-1290 or email us your requirements to sales@flowtechfilters.com