{"id":2671,"date":"2026-07-30T15:02:35","date_gmt":"2026-07-30T15:02:35","guid":{"rendered":"https:\/\/www.fhysilicone.com\/?p=2671"},"modified":"2026-07-30T15:03:36","modified_gmt":"2026-07-30T15:03:36","slug":"silicone-duckbill-valve-design-guide-crack-pressure-flow-rate-and-backflow-prevention","status":"publish","type":"post","link":"https:\/\/www.fhysilicone.com\/fr\/silicone-duckbill-valve-design-guide-crack-pressure-flow-rate-and-backflow-prevention\/","title":{"rendered":"Silicone Duckbill Valve Design Guide: Crack Pressure, Flow Rate and Backflow Prevention"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Silicone duckbill valves are compact, one-piece elastomeric check valves that allow fluid or gas to flow in one direction while restricting reverse flow. They contain no metal spring, ball, hinge or separate moving mechanism, making them suitable for applications where small size, quiet operation, corrosion resistance and low opening pressure are important.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Parmi les applications courantes, on peut citer :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Medical fluid delivery systems<\/li>\n\n\n\n<li>Breast pumps<\/li>\n\n\n\n<li>\u00c9quipement respiratoire<\/li>\n\n\n\n<li>Soap and lotion dispensers<\/li>\n\n\n\n<li>Machines \u00e0 caf\u00e9<\/li>\n\n\n\n<li>Water appliances<\/li>\n\n\n\n<li>Packaging closures<\/li>\n\n\n\n<li>Automotive fluid systems<\/li>\n\n\n\n<li>Fuel-tank ventilation<\/li>\n\n\n\n<li>Drainage devices<\/li>\n\n\n\n<li>Instruments de laboratoire<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Despite their simple appearance, duckbill valves are highly sensitive to lip geometry, slit quality, silicone hardness, wall thickness and installation compression. A small dimensional change can significantly affect crack pressure, forward flow and reverse leakage.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-1024x576.png\" alt=\"\" class=\"wp-image-2674\" srcset=\"https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-1024x576.png 1024w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-300x169.png 300w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-768x432.png 768w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-1536x864.png 1536w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-18x10.png 18w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1-600x338.png 600w, https:\/\/www.fhysilicone.com\/wp-content\/uploads\/2026\/07\/Silicone-Duckbill-Valve-Design-Guide-1.png 1672w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A reliable design must therefore balance three main performance targets:<\/p>\n\n\n\n<ol start=\"1\" class=\"wp-block-list\">\n<li>Low enough crack pressure to permit the required forward flow<\/li>\n\n\n\n<li>Low enough pressure drop at the target flow rate<\/li>\n\n\n\n<li>Sufficient backflow sealing under the specified reverse pressure<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\">What Is a Silicone Duckbill Valve?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A duckbill valve normally consists of:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>An inlet barrel<\/li>\n\n\n\n<li>A mounting flange, sleeve or push-in feature<\/li>\n\n\n\n<li>A tapered flexible body<\/li>\n\n\n\n<li>Two flattened lips<\/li>\n\n\n\n<li>A precision slit between the lips<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">When pressure at the inlet exceeds pressure at the outlet, the lips deform and separate, creating a flow path. When pressure drops or reverses, the elasticity of the silicone and the reverse pressure force the lips together.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This provides passive one-way flow control without an external actuator.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Minivalve describes duckbill valves as one-piece elastomeric backflow-prevention devices whose lips open under forward flow and close when exposed to reverse pressure. <a href=\"https:\/\/minivalve.com\/valve-school\/duckbill-valves-how-they-work\/\" rel=\"nofollow noopener\" target=\"_blank\">Minivalve: How Duckbill Valves Work<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why Use LSR for Duckbill Valves?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Liquid silicone rubber is particularly suitable for small, flexible valve geometries because it offers:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>High molding precision<\/li>\n\n\n\n<li>Good flexibility across a broad temperature range<\/li>\n\n\n\n<li>Consistent elastic recovery<\/li>\n\n\n\n<li>Resistance to weathering and aging<\/li>\n\n\n\n<li>Availability in multiple hardness levels<\/li>\n\n\n\n<li>Low-viscosity filling of thin valve sections<\/li>\n\n\n\n<li>Clean molding for medical and food-contact applications<\/li>\n\n\n\n<li>Compatibility with automated, high-volume production<\/li>\n\n\n\n<li>Good colorability<\/li>\n\n\n\n<li>Potential for biocompatible and regulatory-compliant grades<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">LSR injection molding can produce thin, complex lip geometry with repeatable dimensions. However, the finished slit and valve performance still require careful process control.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Crack Pressure, Opening Pressure and Forward Flow<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Crack pressure is commonly defined as the differential pressure at which measurable forward flow begins.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The pressure differential is:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u0394P = Inlet pressure \u2212 Outlet pressure<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, the term \u201ccrack pressure\u201d can be misleading for duckbill valves.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Many duckbill valves are effectively normally open or begin deforming at a very low differential pressure. There may not be one sharp pressure point at which the valve changes instantly from fully closed to fully open.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Instead, the valve lips gradually separate as differential pressure increases. For this reason, crack pressure should always be connected to a defined flow threshold.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, a specification should not state only:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Crack pressure: 2 kPa<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">A more useful requirement would be:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Forward flow must reach at least 5 mL\/min at a differential pressure of 2 kPa using water at 23\u00b0C.<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Alternatively:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Opening pressure is the differential pressure measured when airflow first reaches 100 mL\/min under the specified test conditions.<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Vernay notes that the measured opening pressure depends on the flow threshold used to define valve opening. A higher measurement threshold can produce a higher reported opening-pressure value even when the valve itself has not changed. <a href=\"https:\/\/vernay.com\/resources\/duckbill-check-valve-design-guide-opening-pressure-reverse-flow-prevention-and-material-selection\/\" rel=\"nofollow noopener\" target=\"_blank\">Vernay Duckbill Check Valve Design Guide<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Important Valve Performance Terms<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Several performance terms should be defined separately.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>Performance term<\/th><th>Meaning<\/th><\/tr><tr><td>Crack or opening pressure<\/td><td>Differential pressure at which a defined forward-flow threshold is reached<\/td><\/tr><tr><td>Forward pressure drop<\/td><td>Pressure difference across the valve at a specified flow rate<\/td><\/tr><tr><td>Maximum forward flow<\/td><td>Highest required flow under defined system conditions<\/td><\/tr><tr><td>Pression de fermeture<\/td><td>Pressure condition at which the lips return to their sealing position<\/td><\/tr><tr><td>Reverse leakage<\/td><td>Quantity of fluid or gas passing backward at a specified reverse pressure<\/td><\/tr><tr><td>Maximum reverse pressure<\/td><td>Highest backpressure the valve must withstand without inversion, damage or excessive leakage<\/td><\/tr><tr><td>Burst pressure<\/td><td>Pressure that causes structural rupture or permanent failure<\/td><\/tr><tr><td>Dur\u00e9e de vie<\/td><td>Number of opening and closing cycles completed while meeting the performance limits<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These values must include test media, temperature, fixture condition and measurement method.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What Controls Duckbill Valve Crack Pressure?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Crack pressure is influenced by the combined stiffness and initial contact condition of the valve lips.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Duret\u00e9 du silicone<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A harder silicone compound generally requires more force to deform. Increasing hardness may raise crack pressure and reduce lip movement at a given pressure.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A softer compound may provide:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Lower opening pressure<\/li>\n\n\n\n<li>Greater lip movement<\/li>\n\n\n\n<li>Higher flow at low pressure<\/li>\n\n\n\n<li>Better conformity between sealing surfaces<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">However, excessively soft silicone can cause:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Instabilit\u00e9 dimensionnelle<\/li>\n\n\n\n<li>Difficult demolding<\/li>\n\n\n\n<li>Lip distortion during assembly<\/li>\n\n\n\n<li>Valve inversion under backpressure<\/li>\n\n\n\n<li>Increased sensitivity to compression<\/li>\n\n\n\n<li>Slower elastic recovery<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Hardness should not be selected alone. Modulus, elongation, tear strength and compression set also affect valve behavior.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">ASTM D2240 is commonly used to measure rubber durometer hardness, but hardness remains an empirical control value rather than a complete description of valve stiffness. <a href=\"https:\/\/store.astm.org\/d2240-15r21.html\" rel=\"nofollow noopener\" target=\"_blank\">ASTM D2240<\/a><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Lip Thickness<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Lip thickness is one of the strongest design variables.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Thinner lips generally:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Open more easily<\/li>\n\n\n\n<li>Reduce crack pressure<\/li>\n\n\n\n<li>Increase deformation at low forward pressure<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Thicker lips generally:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Require more pressure to open<\/li>\n\n\n\n<li>Provide greater resistance to inversion<\/li>\n\n\n\n<li>Improve dimensional stability<\/li>\n\n\n\n<li>Reduce maximum opening area at the same pressure<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Very thin lips may tear during slitting or repeated cycling, especially if the slit ends contain notches.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Slit Length<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A longer slit can create a larger flow opening and may reduce the differential pressure needed to achieve the required flow.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, an excessively long slit can increase:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Reverse leakage<\/li>\n\n\n\n<li>Lip instability<\/li>\n\n\n\n<li>Risk of tearing at the slit ends<\/li>\n\n\n\n<li>Sensitivity to particles<\/li>\n\n\n\n<li>Variation caused by blade positioning<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The slit length must be balanced against lip thickness, valve width and expected backpressure.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Lip Contact and Preload<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The two lips may be designed with light contact, controlled interference or a nearly neutral resting condition.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Greater lip contact can improve reverse sealing but may increase forward opening pressure.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Insufficient contact may reduce crack pressure but allow leakage before enough reverse pressure develops to force the lips together.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Duckbill Length<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A longer tapered section is generally more flexible, while a short valve body is usually stiffer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Increasing length can reduce the force required to deform the lips, but too much length can lead to:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Buckling<\/li>\n\n\n\n<li>Sideways collapse<\/li>\n\n\n\n<li>Unstable flow<\/li>\n\n\n\n<li>Excessive movement inside the housing<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Lip Angle and Taper<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The transition from the round inlet to the flattened outlet controls how pressure is distributed through the valve.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A smooth taper can improve deformation and reduce local stress. Abrupt transitions may create high stress around the slit or produce unstable opening behavior.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Installation Compression<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The housing can alter valve performance after assembly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Radial or axial compression may:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Increase crack pressure<\/li>\n\n\n\n<li>Force the lips together<\/li>\n\n\n\n<li>Distort the slit<\/li>\n\n\n\n<li>Restrict the inlet<\/li>\n\n\n\n<li>Improve or worsen reverse leakage<\/li>\n\n\n\n<li>Shift the valve away from its intended position<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Performance testing should therefore be conducted in the production-intent housing rather than only on an uninstalled valve.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Design Variables and Their Typical Effects<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Design change<\/td><td>Typical crack-pressure effect<\/td><td>Typical flow effect<\/td><td>Possible risk<\/td><\/tr><tr><td>Silicone plus souple<\/td><td>Inf\u00e9rieur<\/td><td>Higher at low pressure<\/td><td>Distortion or inversion<\/td><\/tr><tr><td>Silicone plus dur<\/td><td>Plus \u00e9lev\u00e9<\/td><td>Lower at the same pressure<\/td><td>Poor low-pressure operation<\/td><\/tr><tr><td>Thinner lips<\/td><td>Inf\u00e9rieur<\/td><td>Plus \u00e9lev\u00e9<\/td><td>Tearing or inconsistent slitting<\/td><\/tr><tr><td>Thicker lips<\/td><td>Plus \u00e9lev\u00e9<\/td><td>Inf\u00e9rieur<\/td><td>Excessive pressure drop<\/td><\/tr><tr><td>Longer slit<\/td><td>Often lower<\/td><td>Plus \u00e9lev\u00e9<\/td><td>Increased leakage or tearing<\/td><\/tr><tr><td>Shorter slit<\/td><td>Often higher<\/td><td>Inf\u00e9rieur<\/td><td>Restricted flow<\/td><\/tr><tr><td>Greater lip preload<\/td><td>Plus \u00e9lev\u00e9<\/td><td>Lower initially<\/td><td>Difficult opening<\/td><\/tr><tr><td>Stronger housing compression<\/td><td>May increase<\/td><td>May decrease<\/td><td>Valve distortion<\/td><\/tr><tr><td>Larger inlet passage<\/td><td>Limited direct effect<\/td><td>Higher potential flow<\/td><td>Larger package size<\/td><\/tr><tr><td>Longer flexible bill<\/td><td>Often lower<\/td><td>May improve low-pressure flow<\/td><td>Buckling or unstable opening<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These are directional tendencies, not universal design rules. The interactions between geometry, material and housing must be verified through testing.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Designing for the Required Flow Rate<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">After the lips begin to open, forward flow depends on the effective opening area and pressure differential.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The flow curve usually shows:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Differential pressure on one axis<\/li>\n\n\n\n<li>Flow rate on the other axis<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">At very low pressure, the slit may open only slightly. Flow then rises as the lips separate further. At higher pressure, the surrounding tube, housing or fluid channel may become the main flow restriction.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Factors That Affect the Flow Curve<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Forward flow is influenced by:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Slit length<\/li>\n\n\n\n<li>\u00c9paisseur des l\u00e8vres<\/li>\n\n\n\n<li>Duckbill width<\/li>\n\n\n\n<li>Inlet diameter<\/li>\n\n\n\n<li>Module de silicone<\/li>\n\n\n\n<li>Available lip movement<\/li>\n\n\n\n<li>Housing clearance<\/li>\n\n\n\n<li>Upstream and downstream tubing<\/li>\n\n\n\n<li>Test-fluid viscosity<\/li>\n\n\n\n<li>Fluid density<\/li>\n\n\n\n<li>Gas compressibility<\/li>\n\n\n\n<li>Temp\u00e9rature<\/li>\n\n\n\n<li>\u00c9tat de la surface<\/li>\n\n\n\n<li>Particulate content<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A valve tested with air cannot be assumed to produce the same flow behavior with water, oil, medication or a viscous cosmetic fluid.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Pressure Drop Must Include the Complete Assembly<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Testing only the loose silicone component may provide misleading results.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The production assembly can introduce restrictions through:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A small inlet port<\/li>\n\n\n\n<li>A retaining ring<\/li>\n\n\n\n<li>A narrow connector<\/li>\n\n\n\n<li>A sharp housing transition<\/li>\n\n\n\n<li>Incorrect valve compression<\/li>\n\n\n\n<li>Insufficient downstream clearance<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The valve and housing should be evaluated as one fluid-control system.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Avoid Designing Only for Maximum Flow<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A large slit and highly flexible lip may provide excellent forward flow but poor low-pressure sealing.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The target is not maximum possible flow. The target is adequate flow throughout the required operating-pressure window while still meeting reverse-leakage and durability requirements.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Pr\u00e9vention du refoulement<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">When pressure reverses, the outlet pressure presses the two lips together. As reverse differential pressure increases, contact force between the lips normally increases.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is the main sealing mechanism of a duckbill valve.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, backflow performance is not absolute. Every practical valve specification should state a maximum allowable leakage rate under defined conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Par exemple :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Less than 0.2 mL\/min of air at 5 kPa reverse pressure<\/li>\n\n\n\n<li>No visible water leakage for 60 seconds at 20 kPa<\/li>\n\n\n\n<li>Pressure loss below a specified limit during a 30-second decay test<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Minivalve notes that reverse leakage should be expressed as a measurable flow amount over time at a stated backpressure rather than simply described as \u201cno leakage.\u201d <a href=\"https:\/\/minivalve.com\/valve-school\/the-flow-curve\/\" rel=\"nofollow noopener\" target=\"_blank\">Minivalve: The Flow Curve<\/a><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Low Reverse Pressure<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Some duckbill valves require a small amount of reverse pressure before the lips are forced into full contact.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the application requires sealing at an extremely low backpressure or at zero pressure differential, a duckbill valve may need:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Greater lip preload<\/li>\n\n\n\n<li>A modified slit<\/li>\n\n\n\n<li>A different housing condition<\/li>\n\n\n\n<li>Surface treatment or lubrication<\/li>\n\n\n\n<li>A different elastomeric valve type<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">An umbrella valve, diaphragm valve or spring-assisted check valve may be more suitable for some zero-pressure sealing requirements.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Maximum Reverse Pressure<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">High backpressure can cause:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Lip inversion<\/li>\n\n\n\n<li>Duckbill collapse<\/li>\n\n\n\n<li>Slit extension<\/li>\n\n\n\n<li>D\u00e9formation permanente<\/li>\n\n\n\n<li>Valve displacement from the housing<\/li>\n\n\n\n<li>Flange pull-through<\/li>\n\n\n\n<li>Material rupture<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The valve, housing and retention method must all withstand the maximum reverse-pressure event, including pressure spikes.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Designing the Slit<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The slit is the most critical functional feature of a silicone duckbill valve.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Slit Manufacturing Methods<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Depending on valve design and production requirements, the slit may be produced by:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Precision blade slitting<\/li>\n\n\n\n<li>Automated die cutting<\/li>\n\n\n\n<li>Punch slitting<\/li>\n\n\n\n<li>Laser cutting for selected applications<\/li>\n\n\n\n<li>A molded opening, where technically appropriate<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Blade slitting is widely used because it can produce a fine, normally closed interface. However, performance depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Blade sharpness<\/li>\n\n\n\n<li>Blade thickness<\/li>\n\n\n\n<li>Cutting angle<\/li>\n\n\n\n<li>Slit depth<\/li>\n\n\n\n<li>Slit position<\/li>\n\n\n\n<li>Valve support during cutting<\/li>\n\n\n\n<li>Cutting speed<\/li>\n\n\n\n<li>Tool wear<\/li>\n\n\n\n<li>Duret\u00e9 du silicone<\/li>\n\n\n\n<li>Lubrication or surface condition<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Slit-End Stress<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The ends of the slit act as stress-concentration areas. Repeated opening can cause a small defect to grow into a tear.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">High tear-strength LSR, suitable lip thickness and a controlled cutting process are therefore important.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">ASTM D624 provides a method for evaluating rubber tear strength, although test-sheet results must still be supported by cycle testing on the actual valve. <a href=\"https:\/\/www.astm.org\/Standards\/D624.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM D624<\/a><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Slit Cleanliness<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A damaged or contaminated slit can cause reverse leakage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Parmi les contaminants potentiels, on peut citer :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Silicone flash<\/li>\n\n\n\n<li>Cutting debris<\/li>\n\n\n\n<li>Poussi\u00e8re<\/li>\n\n\n\n<li>Particules m\u00e9talliques<\/li>\n\n\n\n<li>Fibres<\/li>\n\n\n\n<li>Mold-release residue<\/li>\n\n\n\n<li>Packaging particles<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Medical and other clean-fluid applications may require controlled slitting, washing, inspection and clean packaging.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">LSR Material Selection<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The material should be selected according to the fluid, temperature, life cycle and regulatory requirements.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Duret\u00e9 et module de Young<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Lower hardness may support low-pressure opening, while higher hardness can improve stability. The final choice should be based on measured valve performance rather than hardness alone.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">R\u00e9sistance \u00e0 la d\u00e9chirure<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">High tear resistance is important because the lips repeatedly flex around a slit that already acts as an intentional discontinuity.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Compression Set<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">If the valve is compressed inside a housing for long periods, excessive compression set may change the lip position and cause performance drift.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Fluid Compatibility<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The material must be tested with the actual media, including:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Eau<\/li>\n\n\n\n<li>Saline<\/li>\n\n\n\n<li>Medication<\/li>\n\n\n\n<li>Detergent<\/li>\n\n\n\n<li>Soap<\/li>\n\n\n\n<li>Cosmetic liquids<\/li>\n\n\n\n<li>Food and beverage ingredients<\/li>\n\n\n\n<li>P\u00e9trole<\/li>\n\n\n\n<li>Fuel<\/li>\n\n\n\n<li>Produits chimiques de nettoyage<\/li>\n\n\n\n<li>D\u00e9sinfectants<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Standard VMQ silicone may perform well with water and many aqueous fluids but may not be suitable for prolonged fuel or hydrocarbon exposure. Fluorosilicone or another elastomer may be required for some applications.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">R\u00e9sistance \u00e0 la temp\u00e9rature<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Temperature can change silicone stiffness and fluid viscosity. Both effects alter valve performance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Testing may be needed at:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Minimum operating temperature<\/li>\n\n\n\n<li>Room temperature<\/li>\n\n\n\n<li>Maximum continuous temperature<\/li>\n\n\n\n<li>Temporary temperature extremes<\/li>\n\n\n\n<li>Sterilization temperature<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Regulatory Requirements<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Depending on the application, material requirements may include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>FDA food-contact compliance<\/li>\n\n\n\n<li>Classe VI de l'USP<\/li>\n\n\n\n<li>ISO 10993 biocompatibility evaluation<\/li>\n\n\n\n<li>RoHS<\/li>\n\n\n\n<li>REACH<\/li>\n\n\n\n<li>Phthalate restrictions<\/li>\n\n\n\n<li>Customer-specific extractables requirements<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A regulatory material declaration does not automatically qualify the completed valve. The finished part, manufacturing process, additives, pigments and intended contact duration must also be considered.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">LSR Injection Molding DFM<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Duckbill valves often contain thin sections that require precise mold construction.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Gate Location<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The gate should support balanced filling without creating excessive stress or weld lines near the slit area.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A gate placed too close to the lips may cause:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Dimensional distortion<\/li>\n\n\n\n<li>Uneven lip thickness<\/li>\n\n\n\n<li>Difficult gate removal<\/li>\n\n\n\n<li>Cosmetic defects<\/li>\n\n\n\n<li>Localized stress<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u00c9vacuation<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Air must escape from the thin lip region during filling. Poor venting can produce:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Prises courtes<\/li>\n\n\n\n<li>Burned or damaged areas<\/li>\n\n\n\n<li>Air emprisonn\u00e9<\/li>\n\n\n\n<li>Incomplete lips<\/li>\n\n\n\n<li>D\u00e9fauts de surface<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Because uncured LSR flows easily, vent dimensions must be small enough to limit flash.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Parting-Line Position<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The parting line should not interfere with the lip-sealing surfaces or slit.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Flash near the slit can prevent complete closure and cause reverse leakage.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Mold Surface Finish<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Surface finish can affect:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>D\u00e9moulage<\/li>\n\n\n\n<li>Lip friction<\/li>\n\n\n\n<li>Slitting<\/li>\n\n\n\n<li>Fluid interaction<\/li>\n\n\n\n<li>Particle adhesion<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The selected finish should be consistent across production cavities.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">D\u00e9moulage<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The valve must be removed without stretching or damaging the lips.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Demolding design may require:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Sufficient draft where appropriate<\/li>\n\n\n\n<li>Air-assisted release<\/li>\n\n\n\n<li>Carefully positioned ejector features<\/li>\n\n\n\n<li>Manutention robotis\u00e9e<\/li>\n\n\n\n<li>Controlled mold coating<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Installation and Housing Design<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Duckbill valves are commonly installed using one of three configurations.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Flanged Valve<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A flange is clamped between housing components.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Parmi les avantages, on peut citer :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Positive axial retention<\/li>\n\n\n\n<li>Simple assembly<\/li>\n\n\n\n<li>Integrated sealing potential<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The clamping force must not excessively deform the inlet or lips.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Push-In Valve<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A molded retention feature locks into a housing bore.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Important dimensions include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Bore diameter<\/li>\n\n\n\n<li>Interference<\/li>\n\n\n\n<li>Insertion force<\/li>\n\n\n\n<li>Pull-out force<\/li>\n\n\n\n<li>Retaining-bead geometry<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Sleeved Valve<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The valve fits over a rigid tube or nipple.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The interference must hold the valve securely without narrowing the flow path or distorting the duckbill.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Housing Clearance<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The lips need sufficient space to open freely. Contact with the housing can restrict flow or produce asymmetric opening.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The downstream cavity should also avoid sharp features that may damage the lips during assembly or operation.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Performance Test Plan<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A complete validation plan should evaluate both forward and reverse performance.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Crack-Pressure Test<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The test setup should include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Controlled pressure source<\/li>\n\n\n\n<li>Pressure regulator<\/li>\n\n\n\n<li>Calibrated pressure sensor<\/li>\n\n\n\n<li>Flow meter<\/li>\n\n\n\n<li>Production-intent housing<\/li>\n\n\n\n<li>Defined test media<\/li>\n\n\n\n<li>Temperature control when required<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Pressure should be increased at a controlled rate. The opening-pressure result should be recorded when the specified flow threshold is reached.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Forward Flow Test<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Measure flow at several differential pressures across the operating range.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A useful flow curve includes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Low-pressure region<\/li>\n\n\n\n<li>Nominal operating point<\/li>\n\n\n\n<li>Maximum operating pressure<\/li>\n\n\n\n<li>Any plateau or instability<\/li>\n\n\n\n<li>Pressure after repeated cycling<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Reverse Leakage Test<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Apply reverse pressure and measure:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Leakage volume<\/li>\n\n\n\n<li>Taux de fuite<\/li>\n\n\n\n<li>Pressure decay<\/li>\n\n\n\n<li>Bubble formation<\/li>\n\n\n\n<li>Time to stabilize<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The method must specify whether the media is air, water or the actual application fluid.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Maximum Reverse-Pressure Test<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Increase backpressure to the required proof level and inspect for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Valve inversion<\/li>\n\n\n\n<li>D\u00e9formation permanente<\/li>\n\n\n\n<li>Flange movement<\/li>\n\n\n\n<li>Slit damage<\/li>\n\n\n\n<li>Leakage change<\/li>\n\n\n\n<li>Rupture<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Cycle-Life Test<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Repeatedly open and close the valve under representative pressure and flow conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">After cycling, recheck:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Crack pressure<\/li>\n\n\n\n<li>Forward flow<\/li>\n\n\n\n<li>Reverse leakage<\/li>\n\n\n\n<li>Visual condition<\/li>\n\n\n\n<li>Slit length<\/li>\n\n\n\n<li>D\u00e9formation permanente<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Environmental Conditioning<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Performance may also be tested after:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Heat aging<\/li>\n\n\n\n<li>Low-temperature exposure<\/li>\n\n\n\n<li>Cycles thermiques<\/li>\n\n\n\n<li>Humidity aging<\/li>\n\n\n\n<li>Fluid immersion<\/li>\n\n\n\n<li>Exposition aux UV<\/li>\n\n\n\n<li>Nettoyage<\/li>\n\n\n\n<li>St\u00e9rilisation<\/li>\n\n\n\n<li>Transportation vibration<\/li>\n\n\n\n<li>Storage aging<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Common Duckbill Valve Problems<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Problem<\/td><td>Cause possible<\/td><td>Recommended action<\/td><\/tr><tr><td>Crack pressure is too high<\/td><td>Lips too thick, material too hard or excessive housing compression<\/td><td>Reduce stiffness or revise installation<\/td><\/tr><tr><td>Crack pressure is too low<\/td><td>Lips too flexible or slit too long<\/td><td>Increase lip control and evaluate reverse leakage<\/td><\/tr><tr><td>Forward flow is too low<\/td><td>Restricted slit, small inlet or insufficient housing clearance<\/td><td>Review complete flow path<\/td><\/tr><tr><td>Reverse leakage is excessive<\/td><td>Damaged slit, contamination or insufficient lip contact<\/td><td>Improve slit quality and sealing geometry<\/td><\/tr><tr><td>Valve leaks only after assembly<\/td><td>Housing distorts the valve<\/td><td>Revise bore, clamp or interference dimensions<\/td><\/tr><tr><td>Valve inverts under backpressure<\/td><td>Insufficient structural support or material stiffness<\/td><td>Strengthen body or reduce unsupported length<\/td><\/tr><tr><td>Slit tears during cycling<\/td><td>Poor cutting edge, low tear strength or high local strain<\/td><td>Improve slitting and lip design<\/td><\/tr><tr><td>Results vary between cavities<\/td><td>Tooling, wall thickness or slit-position variation<\/td><td>Audit cavity dimensions and cutting fixtures<\/td><\/tr><tr><td>Results drift with temperature<\/td><td>Material modulus or fluid viscosity changes<\/td><td>Test across the full temperature range<\/td><\/tr><tr><td>Valve sticks closed<\/td><td>Excessive lip contact or surface adhesion<\/td><td>Review surface treatment, geometry and storage<\/td><\/tr><tr><td>Particles become trapped in slit<\/td><td>Contaminated fluid or insufficient cleaning<\/td><td>Add filtration and controlled cleaning<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Prototype Development Strategy<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A reliable custom valve is normally developed through several prototype iterations.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. Define the System Requirements<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Pr\u00e9cisez :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Fluid or gas<\/li>\n\n\n\n<li>Fluid viscosity<\/li>\n\n\n\n<li>Temp\u00e9rature de fonctionnement<\/li>\n\n\n\n<li>Minimum forward pressure<\/li>\n\n\n\n<li>Nominal and maximum flow<\/li>\n\n\n\n<li>Maximum pressure drop<\/li>\n\n\n\n<li>Reverse leakage limit<\/li>\n\n\n\n<li>Maximum backpressure<\/li>\n\n\n\n<li>Cycle-life target<\/li>\n\n\n\n<li>Sterilization or cleaning method<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. Select an Initial Valve Configuration<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Choose:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Flanged, push-in or sleeved installation<\/li>\n\n\n\n<li>Valve diameter<\/li>\n\n\n\n<li>Duckbill length<\/li>\n\n\n\n<li>\u00c9paisseur des l\u00e8vres<\/li>\n\n\n\n<li>Slit length<\/li>\n\n\n\n<li>Duret\u00e9 du silicone<\/li>\n\n\n\n<li>Housing compression<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">3. Produce a Prototype Matrix<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Instead of testing only one geometry, compare controlled variations such as:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Two lip thicknesses<\/li>\n\n\n\n<li>Two slit lengths<\/li>\n\n\n\n<li>Two hardness levels<\/li>\n\n\n\n<li>Different housing interference levels<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">4. Test in the Actual Housing<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Loose-part tests are useful for screening, but final performance must be verified in the production-intent assembly.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">5. Complete Pilot Production<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Pilot production confirms:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Molding consistency<\/li>\n\n\n\n<li>Slitting repeatability<\/li>\n\n\n\n<li>Stabilit\u00e9 de l'assemblage<\/li>\n\n\n\n<li>Cavity-to-cavity performance<\/li>\n\n\n\n<li>Test-fixture capability<\/li>\n\n\n\n<li>Packaging and cleanliness<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Production Quality Control<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Important production controls may include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>LSR material lot<\/li>\n\n\n\n<li>Proportions de m\u00e9lange<\/li>\n\n\n\n<li>Temp\u00e9rature du moule<\/li>\n\n\n\n<li>Temps de durcissement<\/li>\n\n\n\n<li>Critical lip dimensions<\/li>\n\n\n\n<li>Slit length and position<\/li>\n\n\n\n<li>Blade-life monitoring<\/li>\n\n\n\n<li>Inspection rapide<\/li>\n\n\n\n<li>Visual contamination inspection<\/li>\n\n\n\n<li>Crack-pressure sampling<\/li>\n\n\n\n<li>Forward-flow sampling<\/li>\n\n\n\n<li>Reverse-leak testing<\/li>\n\n\n\n<li>Cycle testing by production lot<\/li>\n\n\n\n<li>Housing dimensional inspection<\/li>\n\n\n\n<li>Part and cavity traceability<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For critical applications, performance data should be analyzed by cavity rather than combining all molded parts into one general sample group.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">RFQ Checklist for Custom Silicone Duckbill Valves<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">To receive an accurate engineering review and quotation, provide:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>2D drawing or 3D model<\/li>\n\n\n\n<li>Available installation space<\/li>\n\n\n\n<li>Preferred valve type<\/li>\n\n\n\n<li>Fluid or gas type<\/li>\n\n\n\n<li>Fluid viscosity<\/li>\n\n\n\n<li>Temp\u00e9rature minimale et maximale<\/li>\n\n\n\n<li>Minimum forward pressure<\/li>\n\n\n\n<li>Required flow rate<\/li>\n\n\n\n<li>Maximum permitted pressure drop<\/li>\n\n\n\n<li>Defined crack-pressure threshold<\/li>\n\n\n\n<li>Maximum reverse leakage<\/li>\n\n\n\n<li>Reverse-leak test pressure<\/li>\n\n\n\n<li>Maximum backpressure<\/li>\n\n\n\n<li>Dur\u00e9e de vie requise<\/li>\n\n\n\n<li>Silicone hardness preference<\/li>\n\n\n\n<li>Exigences en mati\u00e8re de couleur<\/li>\n\n\n\n<li>Exigences r\u00e9glementaires<\/li>\n\n\n\n<li>M\u00e9thode de st\u00e9rilisation<\/li>\n\n\n\n<li>Housing material and dimensions<\/li>\n\n\n\n<li>Expected annual volume<\/li>\n\n\n\n<li>Quantit\u00e9 de prototypes<\/li>\n\n\n\n<li>Inspection-report requirements<\/li>\n\n\n\n<li>Packaging and cleanliness requirements<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Avoid specifying only \u201clow opening pressure\u201d or \u201cno leakage.\u201d Both requirements must be converted into measurable acceptance criteria.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Foire aux questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">What is the typical crack pressure of a silicone duckbill valve?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">There is no universal value. Some duckbill valves begin flowing at very low differential pressure, while others are designed for a higher threshold. Geometry, hardness, slit design, housing compression, test media and flow threshold all affect the result.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Are duckbill valves normally open or normally closed?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Many duckbill valves are described as normally open because they begin forward flow at a very low pressure. However, the lips may still touch at rest. The terminology should not replace an actual flow and leakage specification.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Does a longer slit always increase flow?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A longer slit usually provides more potential opening area, but it can also increase leakage and slit-end stress. Flow may still be limited by the inlet, housing or tubing.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Can a duckbill valve prevent all reverse leakage?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No practical seal should be specified as absolutely leak-free without defining a test resolution. Reverse leakage should be stated as a maximum flow or pressure loss at a specified backpressure and test time.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Why does the valve leak after installation but not before installation?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The housing may be compressing, twisting or misaligning the valve. Installation dimensions should be included in performance validation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Which silicone hardness is best?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The correct hardness depends on the required opening pressure, flow, backpressure and valve geometry. A softer material is not automatically better for every low-pressure application.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Can a silicone duckbill valve be used with oil or fuel?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Standard silicone may not provide adequate resistance to some hydrocarbon fluids. Fluorosilicone or another elastomer may be required. Compatibility testing with the actual media is essential.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">How is the slit produced?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The slit is commonly created as a controlled secondary operation using a precision blade or cutting fixture. Slit position, length, blade condition and particle control directly affect performance.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Can duckbill valves handle particles?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The direct flow path can accommodate some suspended particles better than certain rigid check-valve designs. However, a particle trapped between the lips can still cause reverse leakage.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Un post-durcissement est-il n\u00e9cessaire ?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">It depends on the LSR grade, regulatory requirements, volatile limits and application. Material-supplier recommendations and final-part validation should determine the post-curing process.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Conclusion<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A successful silicone duckbill valve is not designed around crack pressure alone. Opening pressure, forward flow and reverse leakage are interconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Reducing lip stiffness may improve low-pressure flow but weaken reverse sealing. Increasing lip contact may reduce leakage but raise opening pressure. Housing compression may improve retention while unintentionally restricting the valve.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The most reliable development process includes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Clear flow and leakage specifications<\/li>\n\n\n\n<li>Production-intent material selection<\/li>\n\n\n\n<li>Controlled lip and slit geometry<\/li>\n\n\n\n<li>Housing-level validation<\/li>\n\n\n\n<li>Forward and reverse pressure testing<\/li>\n\n\n\n<li>Conditionnement environnemental<\/li>\n\n\n\n<li>Cycle-life testing<\/li>\n\n\n\n<li>Pilot production before mass manufacturing<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For a custom silicone duckbill valve project, provide the operating media, required flow curve, acceptable reverse leakage, maximum backpressure, installation geometry and annual demand. These details allow the manufacturer to recommend a suitable LSR grade, valve structure, slit specification and test plan.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>","protected":false},"excerpt":{"rendered":"<p>Silicone duckbill valves are compact, one-piece elastomeric check valves that allow fluid or gas to flow in one direction while restricting reverse flow. They contain no metal spring, ball, hinge or separate moving mechanism, making them suitable for applications where small size, quiet operation, corrosion resistance and low opening pressure are important. Common applications include: [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2674,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[2392,2395,2397,2390,2400,2393,2396,2401,2402,2399,2394,2398,2391],"class_list":["post-2671","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry-news","tag-backflow-prevention","tag-crack-pressure","tag-custom-duckbill-valve","tag-duckbill-check-valve","tag-flow-rate","tag-liquid-silicone-rubber-valve","tag-lsr-valve","tag-medical-silicone-valve","tag-one-way-silicone-valve","tag-opening-pressure","tag-reverse-leakage","tag-silicone-duckbill-valve-design","tag-silicone-valve-molding"],"_links":{"self":[{"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/posts\/2671","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/comments?post=2671"}],"version-history":[{"count":1,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/posts\/2671\/revisions"}],"predecessor-version":[{"id":2675,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/posts\/2671\/revisions\/2675"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/media\/2674"}],"wp:attachment":[{"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/media?parent=2671"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/categories?post=2671"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fhysilicone.com\/fr\/wp-json\/wp\/v2\/tags?post=2671"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}