On the Surface, the Inline Check Valve is Deceptively Simple

Thursday October 16, 2014
by Anand Thadani: Product Manager

The role of the inline check valve is simple: to ensure that fluid travels only in the direction intended. To achieve this, the valve needs to open to allow forward fluid flow and close to prevent fluid backflow (also called retrograde flow). Simple, right? But In order to perform properly — which I’ll discuss further in this article — you need a uniform structure that provides just the right compression in the system. Vendors do not set the opening pressure; this is established by the ISO 8536-12 international standard. Improper valve seals can create a pathway for backflow. Or the seal can be so compressed that the delivery of fluids is compromised. Being able to deliver forward flow while preventing backflow is a critical balancing act that requires invention and attention at both the design and manufacturing stages.

NP Medical’s in-line check valves, the A200 and A500 series, are the valve of choice for OEMs, with over a billion valves sold. New manufacturers are jumping into the check valve market every day. Our valves are based on a proprietary design and manufactured with rigorous controls. But what does that actually mean? What can an OEM or clinician look for to actually distinguish one check valve from another? In this Tech Forum, I’ll look at two of the things that are required to ensure the dependable performance of an inline check valve: the seal and placement of the diaphragm.

The diaphragm seal. The check valve should have a uniform 360-degree seal or pressure between the diaphragm and the seal surface. A uniform seal means that the internal pressure is evenly distributed. If there is an imbalance, the pressure may be the same but because it acts on different areas, the resultant forces are higher in certain regions and lower in others; this imbalance can create a pathway for fluid to leak in the forward or backward direction.

Precise placement of the diaphragm. Centering the diaphragm ensures that it touches the inlet surface evenly and completely. During the manufacturing process, we assure that the diaphragm is placed within extremely close tolerances.  All of NP Medical’s inline check valves are manufactured, tested and packaged in the U.S. This ensures that we have the degree of control that we require during assembly. Future Tech Forum topics will cover some of the other manufacturing and quality assurance procedures we use in our factories to ensure that every valve we sell performs correctly each time, every time, from the first to the billionth.

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