Author: Joy Brim, Global Marketing Manager for Vernay
Published: April 29, 2015
Vernay global flow control company who produces components in a wide variety of custom elastomeric formulations. We have many industry known chemists and engineers on our staff globally. We often get asked ‘how do flow control valves work?’ Well, glad you asked… with over 65 years of experience in providing high precision components, check valves, and subassemblies in fluid control applications we have learned so much that we love to share our knowledge.
Check valves are pressure actuated by the operating force that comes from the fluid. Some non-zero force is always needed to make a seal. This can come from preloading the valve shut and/or also from fluid pressure in the reverse direction. Valves that are preloaded are called “normally closed” and will always require some degree of non-zero or positive pressure in the forward direction to make them open. Non-preloaded valves are called “normally open” and will begin to flow with the first application of pressure, but may also leak in the reverse direction until sufficient reverse pressure is applied to make a seal. All check valves have their flow curves specified with at least three pairs of data points. First, an opening pressure is defined as that pressure needed for a specified small amount of flow. Second, a “full flow” is at some higher pressure that is determined as appropriate to the end use application. Third, a maximum reverse leakage is determined at a set pressure or over a pressure range to determine how much reverse leakage is possible and therefore tolerable by the end use application.
Other factors to consider when choosing a check valve include: chemical and/or biological compatibility, fixed or changing orientation, needed speed of operation, maximum reverse pressure, available space and mounting needs. The next series of posts will be on how do different types of check valves and flow control valves work. For example, duckbills, umbrellas, bi-directional valves and more. If you want to learn more about any of our products or have additional questions please contact me.
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