Guide to Selecting the Right Micron Rating

With numerous micron rating options available, making the wrong choice can be expensive. If this occurs, the filtration system may either fail to remove contaminants effectively or remove too much, leading to rapid filter blockage, frequent replacements, and increased costs.

Understanding Filter Micron Ratings

A filter's micron rating indicates the size of particles it can successfully trap, measured in micrometers (μm). This rating is a crucial factor in determining a filter's capability to eliminate particular contaminants from liquids or gases. Nonetheless, the actual performance of a filter is also influenced by elements like the filter material, the nature of the particles, and the specific needs of the application.

Key Considerations for Choosing a Filter Micron Rating

1. Particle Characteristics

Particle size and shape significantly influence the choice of micron ratings. Real-world contaminants vary in shape, and some, such as agglomerates or gels, are soft and deformable. These characteristics complicate filtration, as such particles can extrude through filter media.

2. Application-Specific Requirements

Understand whether the application demands complete removal of all particles or just those above a specific size. For instance, in digital ink applications, removing too much pigment can impair performance.

3. Filter Type

Filters come in several types—depth, pleated depth, and membrane—each offering unique particle retention capabilities. Depth and pleated depth filters are primarily aimed at removing particulate but will have some bio reduction impact on larger organisms such as yeasts.

4. Filter Material

Filter material impacts performance against certain contaminants. For example, thicker non-woven media excel at capturing deformable particles and offer higher contaminant-holding capacity. Whereas thinner pleated depth medias are excellent at removing contaminates at a particular micron rating but have a more limited contaminant-holding capacity.

6. Regulatory Compliance

Industries such as food production and water treatment often have stringent regulatory requirements for filtration levels that must be achieved to ensure the quality of the final filtered product.

5. Cost Considerations

Ultimately the choice of micron rating will affect the overall financial cost of filtration. Finer micron ratings lead to higher costs and require prefiltration to prevent frequent replacements due to low service life.

The Importance of Getting It Right

Selecting an incorrect micron rating can lead to one of two undesired outcomes:

•  Insufficient filtration, allowing contaminants to pass through, which results in the final product being contaminated and failing quality inspections.
• Excessive filtration, causing filters to clog quickly and require frequent replacements, thereby increasing costs and possibly eliminating essential components of the final product.

Contaminant Categories

To begin with, it's crucial to identify what needs to be removed, as there are numerous contaminants. Generally, contaminants can be divided into two main categories: particulate and microbiological.

Making this simple distinction you have already make a key selection, as particulate contamination is removed by depth cartridge filters (pleated or spun) in nearly all cases. If it is microbial contamination, then you require a membrane to ensure that the microbial contamination is completely removed and grow through of the filter is prevented.

If for example you had a mixture of both particulate and microbial contamination, then you would use the depth filter first (Prefilter) and follow with a membrane filter (Final or Sterile filter)

A rule of thumb is that depth filters are typically used above 1 micron and membrane filters are used below 1 micron. If you have particulate contamination above 1 micron then ninety-nine times out of one hundred you will need a depth filter or pleated depth filter. However, that is not always true below 1 micron and very often you will find it is the combination of prefilter (depth) followed by final filter (membrane) that leads to the best solution.

In general, depth filters are typically used for particulate contaminants, while membrane filters are essential for microbial contamination. A combination of depth filters (prefiltration) and membrane filters (final filtration) is often the optimal solution.

Challenges with Deformable Contaminants

For deformable contaminants like gels or colloids, standard filters may allow particles to pass by altering shape. Hybrid depth filters with extended filtration thickness and filter area are designed to address this issue effectively blending the key characteristics of depth and pleated depth filters in a single product.

Typical Micron Ratings by Application

Below is a reference table summarizing common micron ratings used in various industries and applications:

Methods for Selecting the Right Micron Rating

1. Small-Scale Trials: Conduct pilot tests to determine the most effective filter media.
2. Particle Analysis: Test samples for particle size distribution and concentration.
3. Historical Data: Use past experience and supplier expertise for guidance.

For most users, the third method—relying on previous experience and supplier knowledge—is the most practical and commonly used.

By following these guidelines and using the reference table, you can make an informed decision to select the right micron rating and refine your filtration process.