But what exactly is a micron? How big is one micron? What does a micron rating signify? And why might two filters with the same micron rating yield different actual filtration results? Understanding these concepts helps you select industrial filter elements more accurately, avoiding issues such as reduced flow rates, increased pressure drops, or the need for frequent replacements caused by choosing the wrong filtration precision.
What is Micron?
Micron, also known as Micrometer, is a unit of length. Its symbol is μm. Micron is a very small unit of length. Due to the large number of tiny particles present in industrial processes, Micron is widely used to describe particle size, filtration precision, filter membrane pore size, and the structure of filter media.
How big is a micrometer? The diameter of a human hair typically ranges from 50 to 100 micrometers (μm); a 10-micrometer particle is far smaller than the diameter of an average human hair, while a 1-micrometer particle is even smaller. For this reason, the micrometer is a crucial unit of measurement in the field of industrial filtration. Many industrial media contain contaminants, dust, metal particles, and other solid particulates, the sizes of which are typically described in micrometers.
What is Micron Rating?
Micron Rating is a specification parameter used to describe a filter’s particle retention capacity. For example, a 5 μm filter means that the filter has a filtration capacity of 5 μm particles.
You can’t judge a filter’s performance simply by seeing “5 μm”.
You also need to know:
- Is it Nominal or Absolute?
- What is the filtration efficiency?
- What filter media is used?
- What is the pore size distribution?
- What is the flow rate?
- What is the initial pressure drop?
- What testing standards are used?
These factors all affect the final filtration performance under your operating conditions. Therefore, when purchasing industrial filters, Micron Rating should be one of the important selection parameters, but not the only one.
What Does “Micron” Mean in the Filtration Industry?
In the filtration industry, “micron” is commonly used to describe particle size and a filter’s ability to retain particles of a specific size. For example, you might see filter specifications like: 1 μm, 5 μm, 10 μm, 25 μm, 50 μm, 100 μm. Generally, the smaller the number, the smaller the particle size that needs to be filtered, and the finer the filtration required.
For example, a 1 μm filter provides finer filtration than a 10 μm filter.
However, there’s a very important point: Micron ratings alone do not represent the entire performance of a filter. Different filters may have different filtration efficiencies, structures, pore sizes, and testing methods. Therefore, two filters both labeled “10 μm” do not necessarily have the same actual filtration performance.
Why Do Filters With the Same Micron Rating Perform Differently?
This is a very common question in industrial filtration procurement. For example, two suppliers might both tell you: a 10 μm Stainless Steel Filter. The two products look exactly the same. However, in actual use, you may experience significantly different filtration efficiencies, pressure drops, and lifespans.
The reasons usually stem from the following:
Different Filter Media
Different filter materials have different structures.
For example:
- Woven mesh
- Sintered mesh
- Sintered powder
- Metal fiber
- PP material
Their pore structures are not entirely the same. Even with the same micron rating, actual filtration performance may differ.
Different Pore Size Distribution
The pore size of filter media is not necessarily completely uniform. Some filter media have a more concentrated pore size distribution, while others may have a wider pore size distribution. Pore size distribution directly affects your filter’s particle retention capacity and fluid resistance.
Different Filter Structures
Different filter structures will also produce different performance characteristics.
For example:
Even if they are labeled with the same Micron Rating, their filtration area, flow rate, and dirt holding capacity may differ.
Different Testing Methods
Different manufacturers may use different testing methods and conditions.
The bubble point test is currently the most common method for testing filtration precision; however, factors such as aging bubble point testing equipment or testing conditions that fail to meet standards can lead to deviations.
How to Choose the Right Micron Rating for You?
The first step in choosing a Micron Rating isn’t to directly ask the filter supplier, “What filtration precision do you offer?” Instead, determine your actual filtration needs.
Step 1: Determine the Particle Size You Need to Filter
First, determine what particles you need to remove. If possible, obtain the actual particle size distribution data. Your contaminants may not be of a single size. For example, your system might contain particles of 5 μm, 20 μm, 50 μm, and 100 μm. Understanding the particle distribution will allow you to determine a more reasonable filtration precision.
Step 2: Determine Your Filtration Requirements
Next, determine exactly what filtration effect you need to achieve. Do you need to: remove larger solid particles? Control fine particles? Protect downstream equipment? Improve product purity? Ensure the retention of particles of a specific size? The required filtration precision may vary significantly depending on the objective.
Step 3: Determine Your Filtration Flow Rate
The filter cartridge not only needs to filter but must also meet the system’s flow rate requirements. Therefore, when choosing a micron rating, you need to consider: Flow Rate + Micron Rating + Filter Area.
If your filtration precision is high but the filter area is insufficient, it may cause the pressure drop to rise rapidly.
Step 4: Consider Your Contamination Load.
If your medium contains a large amount of solid contaminants, then the filter cartridge’s contaminant holding capacity is very important. In this case, an overly fine filter cartridge may clog quickly. Consider increasing the filter area or adding a coarse filter upstream.
Step 5: Consider Your Pressure Drop.
Pressure drop is a very important parameter in industrial filtration. As contaminants accumulate, the filter cartridge’s resistance usually increases gradually. When the pressure drop reaches the system’s allowable range, the filter cartridge needs to be cleaned or replaced. Therefore, you should pay attention to both the initial pressure drop and the operating pressure drop when selecting a filter cartridge. You can refer to this article for information on pressure drop: Filter Pressure Drop: A Complete Guide to Calculation, Causes, Measurement and Solutions
FAQ
What Are The Micron-Level Filtration Accuracies of Stainless Steel Filter Cartridges?
Stainless steel filter cartridges offer a wide range of micron-level filtration accuracies, with common micron-level accuracies including 0.5, 1, 3, 5, 10, 25, 50, 100, and 200 microns.
Is Micron-Level Filtration Accuracy The Same As Pore Size?
No. Micron-level filtration accuracy is related to pore size, but they are not entirely the same. Pore size refers to the physical size of the pores in the filter medium.
Can A Filter Cartridge Maintain The Same Micron-Level Filtration Accuracy After Cleaning?
Occasional cleaning is fine, but repeated cleaning will eventually affect its lifespan and performance.
Whether a filter cartridge can maintain its original micron-level filtration accuracy depends on several factors, including:
- Cleaning method
- Cleaning pressure
- Cleaning temperature
- Chemical cleaning agent
- Cleaning frequency
- Filter media and structure
- Mechanical damage during the cleaning process
If the cleaning force is too great, the filter media may deform or be damaged, thereby altering its effective pore structure and filtration performance.
