Norgren Collateral

A white paper - Right Connections and Fittings for Manifolds 03 Flat bottom sealing fittings Selecting a material for fittings in most life science programs is primarily driven by the intended media the device will be running. However, consideration should be given when using small plastic fittings, as they are more susceptible to damage during assembly, shipping or handling. In addition to design and material requirements, an engineer should make note of the impact different fittings may make on both the assembly and testing of the fluidic device. With most life science equipment, leakage testing is performed to ensure no external leakage is occurring in normal operation at the final end-of-line verification test. It is desirable to complete this testing with fittings installed to ensure there is no leakage at the connection point between the manifold and fitting. Cartridge, push-to-connect style fittings tend to be favorable during the assembly process, as they can simply be seated using an arbor press. Creating a fixture to interface into the ports of these fittings for purposes of production testing can be simple if the fluidic porting is located on a single or opposing faces. With porting on multiple faces, test operators can still make connections with tubing, but care will need to be taken to ensure the O-ring does not become damaged from improperly cut tubing. Thread in barb fittings used in life science applications are often small due to the low flow rates and low sample volumes, and require delicate handling during assembly to ensure the fittings do not become damaged. Operator handling during production testing tends to be more labor intensive, as designing clamping fixtures to supply pressure to the manifold become difficult to develop. Further, when using NPT style thread in fittings, fitting alignment can be very difficult. This is especially true when using a stainless- steel fitting in a stainless-steel manifold, and in some cases, it can become impossible to align the fitting and achieve proper sealing. In these types of applications, it is generally recommended to use either a swivel style fitting or a non-tapered thread style fitting. There are a vast number of fittings available to today's fluidic system design engineers. Sturdy connections and leak-tight performance of an integrated system is paramount. Ease of manufacturing the assembly is critical for repeatable performance and reliability. It is critical for engineers to be familiar with all the options available to them to ensure a robust fluidic system design. The method of sealing between the manifold and fitting itself is important to consider. Increasingly, life science fitting manufacturers are using flat bottom sealing style fittings for lower pressure applications. These fittings can reduce concern for damage to the sealing surfaces during assembly, as they are recessed within the port rather than on a main external face of the manifold. More traditional thread-in style fittings are common on many life science manifolds as well. Sealing is typically achieved through an O-ring or gasket on the fitting that is compressed once the fitting is fully threaded into the port. Tapered threads, such as an NPTF thread, are also used for certain applications. These fittings rely on contact between the mating threads to provide a seal without the need for a separate O-ring or elastomer, and require the manifold material to be able to withstand the hoop stress imparted during assembly. Often these fittings can be supplied with a dry thread sealant or thread locker to ensure proper sealing and eliminate an assembly operation. Fitting to Manifold Interface Manufacturing Considerations Push-to-connect fittings in an acrylic manifold

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