The optimal ratio for O-ring gland volume is 15-25% empty space and 75-85% spaced filled by the O-ring material. This is necessary to ensure room for the O-ring’s thermal expansion (elastomers expand around 10 times more than metals), swelling due to soaking up fluids, and increasing width due to O-ring squeeze. The best rule of thumb to follow for groove dimensions stems from specifying the correct amount of volumetric space for the O-ring material to fill the groove. In general, an O-ring gland for a liquid fluid should be larger than one used for gas - the liquid interfacing O-ring should be about 10-20% larger. O-Ring Gland Width for Liquids versus Gases Another important rule to follow is to keep the percentage reduction in the cross-sectional diameter to around 50% of the percentage diameter stretch. Minimizing installation stretch can prevent an excessive buildup of stress in the material, reduce the cross-sectional area and reduce the % squeeze of the O-ring. This design allows for simple installation and uniform compression on all three sides of the O-ring that interface with the gland. One of the most common O-ring groove shapes is a rectangular divet with rounded edges. Specifically, every sharp corner needs an O-ring groove radius and all interfacing corners should be chamfered or rounded to limit damage to the O-ring while installing it. Generally, it’s good to focus on a groove shape design that’s easy to machine without sharp edges that can cause O-rings to deteriorate. The shape of the O-ring groove depends on the application for the O-ring and can range from triangular to rectangular to dovetail. Otherwise, the shape of the groove itself is not important. The most important consideration for gland design is that it allows for proper and complete compression between the groove and the surface mating to it. O-rings are more standard and are used for simpler mating conditions. That’s why gaskets are used in applications where sealing is needed for complex mating surfaces. O-rings are also specifically circular in shape, whereas gaskets take the form of many cross-sectional shapes. Gaskets can be made of many materials, including metal, while O-rings are only made of elastic materials. An O-ring is a type of gasket, but not all gaskets are O-rings. While O-rings and gaskets may seem similar, they are actually different methods of mechanical sealing. The groove that the O-ring fits into is also known as the gland. Some O-rings can withstand high pressures in the range of a few thousand PSI. What is an O-Ring (Refresher)Īn O-ring is a circular piece of elastomer material that’s used to form a mechanical seal resistant to pressure that seals off mating components. This guide will walk you through our best tips for designing O-ring grooves. But you need a good groove design for the O-ring to do its job properly. O-rings are reliable and affordable, which is why they’re a popular solution. To solve those problems, your first step is choosing the right type of mechanical seal. Perhaps your assembly has a fluid reservoir, requires cooling fluid to pass through, or you’re joining two components together and need them to sit flush. Or you have a maintenance project that requires additional sealing to a new joint. Let’s say you designed a mechanical assembly that requires some sort of mechanical sealing.
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