Nominal vs. Absolute Ratings: What's the Difference? cover image

Nominal vs. Absolute Ratings: What's the Difference?

Kaitlyn ColliganKaitlyn Colligan avatar

Kaitlyn Colligan

3 minute read

Effective selection of industrial filters requires a solid understanding of the rating systems used in filtration. Nominal and absolute ratings are two different methods used to measure and classify the filtration efficiency of filters. These ratings determine the size of particles that the filter can capture, and the level of filtration it can provide. Understanding the difference between nominal and absolute ratings for filters will allow you to make informed decisions when selecting filters that align with your industrial filtration requirements.

Nominal Rating

Nominal ratings represent the average particle size that a filter is expected to capture efficiently. It indicates the filter's ability to retain a significant portion of particles at a specified size but does not guarantee the capture of all particles above that size. For example, a filter with a nominal rating of 10 microns means that it can efficiently capture a substantial portion of particles that are 10 microns or larger, but it may allow smaller particles to pass through.

Benefits of using Nominal Filters

  1. Lower Cost: Nominal filters are often more affordable than absolute filters due to their less strict standards.
  2. Less Restrictive: Nominal filters are less restrictive in terms of flow rate as they allow for a certain percentage of larger particles to pass through the media.
  3. Ideal for Large Particles: Nominal filters are ideal for applications that have large particles that need to be removed.

Absolute Rating

Absolute ratings, on the other hand, provide a more precise measure of a filter's filtration efficiency. Absolute rating refers to the thinnest particle size guaranteed to be removed by the filter. Unlike nominal rating, absolute ratings do not allow for any particles above a certain size to pass through the filter. They represent the filter's ability to retain a specified percentage of particles at a specific size. For instance, a filter with an absolute rating of 10 microns and an efficiency of 99% means that it can capture at least 99% of particles that are 10 microns in size, ensuring a higher level of filtration accuracy.

Benefits of using Absolute Filters:

  1. Accurate Filtration: Absolute filters are highly effective in removing particles from fluid and gas, ensuring that a clean product is produced.
  2. Consistent Results: Absolute filters provide consistent filtration performance because they do not allow any particles larger than the stated rating to pass through.
  3. Ideal for Small Particles: Absolute filters are ideal for applications that have small particles that need to be removed.

Choosing Between Nominal and Absolute Filters

When it comes to selecting the right filter for your application, it is important to determine the filtration level needed. For applications that require a higher degree of filtration, absolute filters are the best choice because of their guaranteed filtration level. Conversely, nominal filters are recommended for applications that require less strict standards and are more cost-effective. It is important to consider the flow rate of the application and the type of fluid or gas to be filtered when choosing between nominal and absolute filters. The micron rating and the efficiency of the filter are also crucial to components to consider when deciding between an absolute or nominal filter.

The key distinction between nominal and absolute ratings lies in the level of certainty they provide. Nominal ratings give a general indication of a filter's performance, while absolute ratings provide a more specific and reliable measure of its efficiency. While nominal filters are less expensive and less restrictive, they may not be effective in removing small particles in some applications. Absolute filters are highly accurate in removing particles but can be more expensive. Choosing the right filter can help ensure that the final product is of high quality and meets industrial standards. Not sure if you should go with a nominal or an absolute filter? Don’t worry, our filter experts are here to help! Contact us today!

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