Filter Connectivity - Why It Is Critical for Medical Device Applications

Author: Jacob Andrews - Filtration Technical Director  

In our blog post “Important things to consider when choosing a filter for your medical device application,” we touched on the impact a filter’s size, shape, and connectivity can have for medical devices.  In this post we provide more examples of the ways that a filter’s connectivity can be customized as well as the benefits this can bring to medical device designs, safety, and performance. 

The connection between a system and a filter is of critical importance.  Primarily, the connection must be leak-free – this requirement is universal and though it can be achieved by many common fitting connections, the application and risk assessment will dictate whether a specific fitting can provide the necessary assurance of a leak-free connection.  

Our applications engineers are often presented with system designs that incorporate adapters (e.g. reducer fittings and barb-to-thread adapters) to allow connection between the system and filter.  These adapters can often be eliminated by designing a filter with fittings that connect directly to the components upstream and downstream of the filter or (at a minimum) directly to the correct size of tubing.  In one example, Saint-Gobain was presented with a design incorporating an ‘off the shelf’ disc filter to purify gas used in a surgical device.  The off the shelf disc filter was manufactured with threaded male NPT fittings and in order to enable easy change-out by the end user, the inlet and outlet of filter were each connected to a threaded fitting and then to a quick connect fitting.  In addition to four unnecessary potential leak points, the use of these adapters increased both the material and labor costs of the finished device.  Through a rapid co-development between Saint-Gobain and the OEM, both the risk of leaks and additional cost were eliminated integrating the quick connect fittings directly into the molded shell of our disc filter.  Another representative example is shown in Figure 1, where Saint-Gobain was able to eliminate four unnecessary barbed connection points by providing a molded quick connect fitting design. 

Figure 1: 



Example of a filter connected to quick connect fittings by way of four barb-to-tube connections and a filter with quick connect fittings molded directly to the shell. 


Another way the connection of a filter can be optimized to provide further functionality is through the implementation of shut-off valves into the fitting.  Often coupled with quick connects for easy change-out, shut-off valves prevent liquid from spilling out of a used filter during change-out and can be implemented both within the filter as well as the connecting fitting on the device side.  Preventing spillage during filter change out can help to reduce the exposure of the user to the potentially harmful or contaminated liquids and can also prevent contamination and corrosion or other damage to the medical device. 

Finally, the connection of a filter can be selected to ensure proper installation into the medical device.  The correct directional installation of a filter is often critical to the proper function of the filter and associated medical device.  In some applications, filters are exposed to relative high pressures which they are only designed, validated, and capable to withstand when applied in the forward direction.  In these cases, incorrect installation of the filter in the reverse flow direction could result in damage to the filter and a reduction filtration efficiency.  This can present significant risk to patient safety if, for example, the filter is being used to remove microbial contamination from a fluid presented directly to a patient or a fluid used to sanitize medical devices between use.  Often a filter is designed with built-in prefiltration, asymmetric membranes or graded density filtration materials to achieve the required service life before plugging.  In these cases, the backward installation of a filter may result in premature blockage of the filter. 

Figure 2: 



Example of a filter with quick connect fittings that are gendered to ensure correct orientation and incorporate shut-off valves to prevent leaks during filter change out. 

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