Selecting the Correct Filter Media: What Questions Should You Ask?

Author: Cavon Cormack – Application Engineer

  1. Why are you filtering / what is your filtration application? 

  • It’s imperative to have a firm grasp on the type of filtration you anticipate performing as that will dictate how you should move forward when selecting the appropriate type of filter. For example, the filters used in mechanical ventilation differ from those used in endoscope reprocessing. Mechanical ventilation generally demands a hydrophobic (water resistive) membrane to separate contaminants from the oxygen used in respiratory systems. Endoscope reprocessing generally demands a hydrophilic (water attractive) membrane to separate contaminants from the potable water that will be used to sterilize endoscopes. 


  1. What are your process conditions / requirements? 

  • Being armed with the knowledge of the desired or expected flow rate, pressure drop, and throughput of your process will assist in narrowing down your choices of filters that will meet those demands. These three particular parameters are always dependent on your system and will be affected by any changes within your system, and over time if their values begin to fall short of expectations this change serves as an important first step for troubleshooting your system to determine potential failures. Additionally, it’s worthwhile to consider how the fluid within your system will be driven (e.g. vacuum pressure, gas pressure, peristaltic pump) and the operating temperature of your system since both conditions influence filter performance and service life. 


  1. What are the characteristics of your contact fluid(s)? 

  • Having a clear understanding of the type of fluid being used in your filtration application will save you a ton of time and reduce frustrations so it’s always advisable to consider if your filtration fluid will be gaseous or aqueous, its properties, and its composition. For example, you may select a filter that is hydrophobic (water resistive) for an application but if you neglect to account for the fluid being a mix of water and IPA (isopropyl alcohol) then that filter’s performance can be reduced since hydrophobic filters will experience increased wetting when exposed to IPA. 


  1. What filter characteristics are most important for your process? 

  • There are many filter characteristics to consider prior to selecting the most appropriate filter for your process. Let’s look at two of these characteristics – filter capacity and recovery efficiency. A filter’s capacity will correlate to how much particulate a filter can capture before plugging occurs. While thinking about your filtration process you may need a filter with a higher capacity to serve as a pre-filter to capture larger sized particles first so that your main filtration media does not clog unexpectedly. Also, a filter may remove particles that are essential to your process and the likelihood of this occurring is gauged by the filter’s recovery efficiency. The recovery efficiency provides insight on the amount of material recovered relative to the amount of material originally in place. 


  1. Will the filter need to be sterilized or sanitized?  If so, how often? 

  • With respect to sterilization, there may be a need to pre-sterilize filters because they will be used in a clean room where the particulate level is required to be as close to zero as possible. Additionally, it’s important to consider the need for sterilization early in the decision stage because each filter has different options of sterilization (gamma, ETO, autoclave), and each filter must be compatible with the sterilization method chosen. Finally, there are only a certain number of cycles of sterilization a filter can undergo, therefore it’s important to know how often sterilization will be performed. 


  1. What, if any, dimensional restrictions are there for the size and shape of the filter? 

  • A clear time and money saver is knowing the sizing constraints that your filtration process may impose on your potential filter. Selecting an incorrectly sized or shaped filter will most assuredly compromise the efficiency and efficacy of your process. A competitive advantage we have at SGFT is developing and deploying custom solutions for our clients where we can help decrease the number of adapters or parts used in a system. This customization results in reducing the complexity of a system’s assembly which is advantageous when you consider the increased probability of failure or performance drop off that comes with introducing too many variables. 


  1. How will the filter connect to your system? 

  • Connectivity plays a meaningful role within the filter selection process, particularly when we think about leakage. Similar to having an incorrectly sized or shaped filter in your system, a poor connection will cause a performance reduction. SGFT carries one of the broadest lines of filter connections, so we are uniquely situated to provide a custom connection for your custom needs. Our customization capabilities with respect to fittings and connections also allows us to readily integrate our filters into tubing that are used in large filtration assemblies, therefore we offer a level of versatility and adaptability unmatched by many of our competitors. 


  1. What, if any, regulatory, quality, or validation requirements are there for the filter? 

  • You should always consider the regulatory or other quality control standards that may be imposed upon your filtration application so that your potential filter is compliant. For example, Saint-Gobain Filtration Technologies offers filters that are certified under ISO 13485 which sets the standards and requirements for designing and manufacturing medical devices. A few of the ISO 13485 criteria of note include cleanliness, biocompatibility, and shelf life. Knowing early on what regulatory requirements must be met can prevent you from selecting a filter that may be non-compliant thus saving time and money. 


  1. What is your project timeline? 

  • Understanding your project timeline plays an important role in acquiring the best filter for your application. An advantage that Saint-Gobain Filtration Technologies has in comparison with our competitors is while we carry standard “off-the-shelf” filters that are readily available, we also have the ability to customize a filter. However, this customization process will take time so identifying the need for a custom solution or product is extremely beneficial during the early stages of the selection process.

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