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Element Media Selection Considerations 18
SCHROEDER INDUSTRIES
Element Media Selection Considerations
The Right Media for the Right Application = Job Matched Filtration
Filtration
Application
Guidelines
Effect of
Ingression
Selecting the proper Schroeder media for your application is easy if you follow these simple guidelines.
Step 1. Remember that the key to cost effective contamination control is to maintain the systems
cleanliness at the tolerance level of the systems most sensitive component. So, the first step is to
identify the most sensitive component.
Step 2. Determine the desired cleanliness level (ISO Code) for that component by referring to Table 3
on page 13 or by contacting the component manufacturer directly.
Step 3. Identify the Schroeder filter medium referencing Table 6 that will meet or exceed the desired
cleanliness level.
Step 4. Remember to regularly check the effectiveness of the selected media through the use of
contamination monitoring equipment.
Table 6. Schroeder Element Media
Recommendations
Desired Cleanliness Levels
Schroeder
(ISO Code)
Media
20/18/15 -19/17/14
Z25
19/17/14 -18/16/13
Z10
18/16/13 -15/13/10
Z5
15/13/10 -14/12/9
Z3
14/12/9 -13/11/8
Z1
Filter element life varies with the dirt holding capacity of the element and the amount of dirt introduced
into the circuit. The rate of this ingression in combination with the desired cleanliness level should
be considered when selecting the media to be used for a particular application. Table 7 provides
recommendations accordingly.
The amount of dirt introduced can vary from day to day and hour to hour, generally making it difficult to
predict when an element will become fully loaded. This is why we recommend specifying a Dirt Alarm
�
.
Schroeder-designed Dirt Alarms provide a vital measure of protection for your system by indicating when
the filter element needs to be changed or cleaned. Schroeder filters are available with visual, electrical
and electrical-visual combination Dirt Alarms. These indicators may also be purchased as separate items.
For more information on Dirt Alarms, see Appendix A.
Desired
Schroeder
Cleanliness Levels
Ingression
Element
(ISO Code)
Rate
Medium
20/18/15
High
Z25
19/17/14
Low
Z25
19/17/14
High
Z10
18/16/13
Low
Z10
18/16/13
High
Z5
15/13/10
Low
Z5
18/16/13
High
Z3
15/13/10
Low
Z3
15/13/10
High
Z1
14/12/9
0
Low
Z1
Table 7. Recommended Schroeder Media to
Achieve Desired Cleanliness Levels
Based on Ingression Level SCHROEDER INDUSTRIES 19
Amount of Fluid
Filtered
Sizing a
Filter Element
To obtain the desired cleanliness level (ISO Code) using the suggested Schroeder filter medium, it
is recommended that a minimum of one-third of the total fluid volume in the system pass through the
filter per minute. If fluid is filtered at a higher flow rate, better results may be achieved. If only a lesser
flow rate can be filtered, a more efficient media will be required.
Systems operating in a clean environment, with efficient air-breather filters and effective cylinder rod
wiper seals, may achieve the desired results at a lower turnover rate. Systems operating in a severe
environment or under minimal maintenance conditions should have a higher turnover. Turnover must be
considered when selecting the location of the systems filter(s).
Since the pressure drop versus flow data contained in our filter catalog is for fluids with a viscosity
of 150 SUS (32.0 cSt), and a specific gravity of .86, we are often asked how to size a filter with a
viscosity other than 150 SUS (32.0 cSt) or a specific gravity other than .86. In those instances where the
viscosity or specific gravity is significantly higher, it may be necessary to use a larger element. To make
this determination, we need to calculate the life of the element, using the following equation:
EL = RC (H + E)
Where:
EL = Element Life (expressed in psi)
H = Housing pressure drop
RC = Relief valve cracking pressure
E = Element pressure drop
1. The housing pressure drop can be read directly from the graph. This value is not affected by viscosity
or the number of elements in the housing, since housing flow is turbulent.
2. The element pressure drop is directly proportional to viscosity, since element flow is laminar.
Schroeders rule of thumb for element life, as calculated from the above equation, is to work towards
a differential pressure drop that is no more than half (50%) of the bypass setting.
The interval between element changeouts can be extended by increasing the total filter element area.
Many Schroeder filters can be furnished with one, two, or three elements or with larger elements. By
selecting a filter with additional element area, the time between servicing can be extended for little
additional cost.
Fluid
Compatibility:
Fire Resistant
Fluids
Schroeder filters have been used successfully to filter a variety of fire resistant fluids for over five decades.
Filtering these fluids requires careful attention to filter selection and application. Your fluid supplier should
be the final source of information when using these fluids. The supplier should be consulted for
recommendations regarding limits of operating conditions, material and seal compatibility, and other
requirements peculiar to the fluid being used within the conditions specified by the fluid supplier.
High Water Content Fluids
High water content fluids consist primarily of two types: water and soluble mineral base oil, and water with
soluble synthetic oil. The oil proportion is usually 5%, but may vary from as low as 2% to as high as 10%.
Standard Schroeder Z1, Z3, Z5, Z10, and Z25 elements are compatible with both types of high water
content fluids. Filter sizing should be the same as with 150 SUS (32 cSt) mineral based hydraulic oil. Z1
and Z3 elements may be used; however, element changeouts will be more frequent. Some special factors
that need to be considered in the selection process include the following:
All aluminum in the filter housing should be anodized. This can be accomplished by using the W
adder as shown in the filter model number selection chart.
When using 95/5 fluids, check with fluid supplier for compatibility with aluminum.
Buna N or Viton seals are recommended.
The high specific gravity and low vapor pressure of these fluids create a potential for severe cavitation
problems. Suction filters or strainers should not be used. The Schroeder Magnetic Separator (SKB), page
266, with its low pressure drop, is recommended for pump protection from ferrous or large particles.
Invert Emulsions
Invert emulsions consist of a mixture of petroleum based oil and water. Typical proportions are 60% oil to
40% water. Standard Schroeder filters with Z10 and Z25 media elements are satisfactory for use with
these fluids. Filters should be sized conservatively for invert emulsions. These fluids are non-Newtonian
their viscosity is a function of shear. We recommend up to twice the normal element area be used as
space and other conditions permit. 20
SCHROEDER INDUSTRIES
Fluid
Compatibility:
Fire Resistant
Fluids
(cont.)
Some special factors that need to be considered in the selection process include the following:
Potential exists for cavitation problems with invert emulsions similar to high water based fluids. SKB
suction separators are recommended for pump protection from ferrous or large particles.
Buna N or Viton seals are recommended.
Water Glycols
Water glycols consist of a mixture of water, glycol, and various additives. Schroeder Z3, Z5, Z10 and Z25
elements are satisfactory for use with these fluids. Some special factors that need to be considered in
the selection process include the following:
All aluminum in the filter should be anodized. This can be accomplished by using the W option as
shown in the filter model number selection chart.
Potential exists for cavitation problems with water glycols similar to high water based fluids. SKB
suction separators are recommended for pump protection from ferrous or large particles.
Buna N or Viton
�
seals are recommended.
Phosphate Esters
Phosphate esters are classified as synthetic fluids. All Schroeder filters and elements can be used with
most of these fluids. Sizing should be the same as with mineral based oils of similar viscosity. Some
special factors that need to be considered in the selection process include the following:
For phosphate esters, specify EPR seals (designated by H seal option) for all elements. As a general
rule, all Z (synthetic) media is compatible and 10 and 25 � only E (cellulose) media with phosphate
esters.
For Skydrol
�
, only 3, 5, 10, and 25 � Z (synthetic) media should be used, and H.5 should be
designated as the seal option. The H.5 seal designation calls for EPR seals and stainless steel wire
mesh in element construction.
Pressure Drop Correction for Specific Gravity
Pressure drop curves shown in this catalog are predicated on the use of petroleum based fluid with a
specific gravity of 0.86. The various fire resistant fluids discussed in this section have a specific gravity
higher than 0.86, which affects pressure drop. Use the following formula to compute the correct
pressure drop for the higher specific gravity:
Corrected pressure drop = Fluid specific gravity x Catalog pressure drop
0.86
Viton is a registered trademark of DuPont Dow Elastomers.
Skydrol is a registered t