{"id":3690,"date":"2026-10-27T15:58:42","date_gmt":"2026-10-27T07:58:42","guid":{"rendered":"http:\/\/www.nattonhatban.com\/blog\/?p=3690"},"modified":"2026-10-27T15:58:42","modified_gmt":"2026-10-27T07:58:42","slug":"how-do-o-rings-perform-in-vacuum-applications-4dae-20c86d","status":"publish","type":"post","link":"http:\/\/www.nattonhatban.com\/blog\/2026\/10\/27\/how-do-o-rings-perform-in-vacuum-applications-4dae-20c86d\/","title":{"rendered":"How do O Rings perform in vacuum applications?"},"content":{"rendered":"

If you\u2019ve ever worked with vacuum systems\u2014whether for semiconductor manufacturing, aerospace testing, or even lab-scale freeze-drying\u2014you know how much small component failures can derail entire operations. Last month, I got a panicked call from a semiconductor client of ours: their vacuum chamber had dropped from 1e-7 Torr to 1e-5 Torr overnight, and their whole wafer processing line was at a standstill. When their tech tore down the chamber, they found a single O ring with a tiny, almost microscopic, tear. That\u2019s not an anomaly; O ring performance is often the unsung make-or-break factor in vacuum applications, and as an O ring supplier who\u2019s worked with these systems for 12 years, I\u2019ve seen firsthand how getting this right (or wrong) changes everything. O Ring<\/a><\/p>\n

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A lot of people new to vacuum think \u201cvacuum is just low pressure,\u201d but that\u2019s a massive oversimplification. Vacuum systems operate across a spectrum from rough vacuum (1 atmosphere down to 1e-3 Torr) all the way to ultra-high vacuum (UHV, below 1e-9 Torr), and each tier demands totally different O ring properties. The first thing I always tell clients is: the O ring that works for a rough vacuum pump seal won\u2019t survive an UHV chamber. Let\u2019s break down why.<\/p>\n

At its core, an O ring\u2019s job in vacuum is twofold: it creates a hermetic, pressure-tight seal between two mating surfaces, and it can\u2019t outgas chemicals that would contaminate the chamber environment. Outgassing is the big one here. When a material is exposed to the low-pressure, high-purity conditions of a vacuum, any volatile compounds trapped in its structure will slowly escape as gas\u2014this is called \u201cvapor pressure,\u201d and it\u2019s a make-or-break metric for vacuum O rings. For example, a standard Buna-N (nitrile) O ring, which most people reach for for general purpose seals, has a vapor pressure that\u2019s way too high for UHV: it\u2019ll outgas hydrocarbons that can ruin semiconductor wafers, or distort sensitive optics in a space simulation chamber. I once had a biotech lab client who tried using Buna-N to seal their freeze-drying chamber; after a batch of vaccines, they found Buna-N off-gassing had left a sticky residue on the vial stoppers, ruining 12,000 doses. We switched them to a Viton O ring, and they haven\u2019t had an issue since, but even Viton has limits at UHV.<\/p>\n

For UHV applications, we almost exclusively recommend perfluoroelastomers (FFKM) or virgin Kalrez, because their molecular structure is so tight there\u2019s almost nothing to outgas. I test every batch of these O rings in our in-house vacuum chamber: we expose them to 1e-10 Torr for 72 hours and measure gas evolution. If the outgassing rate is over 1e-9 mbar\u00b7L\/s\u00b7cm\u00b2, it gets rejected\u2014no exceptions. That might seem strict, but at that pressure, even one outgassing molecule per second can skew a surface science experiment, or cause a semiconductor etch process to fail.<\/p>\n

Another critical factor is O ring compression set, especially when dealing with temperature swings, which are extremely common in vacuum systems. Most vacuum applications have operating temperatures that range from room temperature up to 200\u00b0C or more; some aerospace thermal vacuum tests go from -50\u00b0C to 300\u00b0C in a single cycle. Compression set is what happens when an O ring is squeezed into its gland (the groove it sits in) and doesn\u2019t spring back to its original shape after pressure is removed. If an O ring has high compression set, after a few thermal cycles, it\u2019ll develop a tiny gap, and air will leak into the vacuum. I remember a client in the aerospace industry who was testing satellite components in a thermal vacuum chamber; they used a standard EPDM O ring that had low compression set at room temp, but when the chamber hit -40\u00b0C, the O ring hardened and lost its resiliency, leading to a leak that delayed their satellite launch by three months. We sourced custom low-temperature FFKM O rings for them, and they\u2019ve used those for every chamber seal since.<\/p>\n

Gland design matters too, and I\u2019ve seen clients cut corners here because they think the O ring alone is enough. A bad gland will make even the best O ring leak. The key is the gland\u2019s compression ratio: how much the O ring is squeezed when installed. For rough vacuum, a 10-20% compression ratio works, but for high and ultra-high vacuum, that drops to 5-10%\u2014too much compression will distort the O ring, leading to higher outgassing and faster compression set over time. I always send a free gland design guide to any client who asks, because I\u2019d rather help them get it right from the start than replace O rings every month.<\/p>\n

Let\u2019s talk about leak rates, because that\u2019s the ultimate metric of O ring performance in vacuum. A \u201cgood\u201d vacuum O ring seal should have a leak rate of 1e-12 atm\u00b7cc\/s or lower. To put that in perspective, that\u2019s less than one molecule of air leaking per second. How do we test that? We use helium leak detectors, which are the gold standard for vacuum system leak testing. Helium is a small molecule, so if it can pass through the O ring, the leak detector will pick it up. We test every custom O ring order with helium at different pressures and temperatures to make sure it meets the client\u2019s specific leak requirements.<\/p>\n

Of course, no conversation about O rings in vacuum would be complete without addressing common pitfalls that even experienced engineers run into. One of the most frequent mistakes is reusing O rings. When an O ring is exposed to vacuum, it compresses and expands with pressure changes, and even a small amount of outgassing can leave a layer on its surface. Reusing an O ring almost always leads to leaks, because the residual material from the first installation creates a tiny barrier between the O ring and the mating surface. I tell every client: O rings are single-use in vacuum applications. It\u2019s an extra cost, but it\u2019s way cheaper than the downtime from a failed seal.<\/p>\n

Another common mistake is choosing the wrong O ring material for the specific vacuum tier. I mentioned Buna-N earlier\u2014great for hydraulic seals, terrible for UHV. EPDM, which is used for weather stripping, works for some rough vacuum applications but will outgas too much for anything higher. Silicone is even worse for vacuum, because it has high vapor pressure and can break down at moderate temperatures. The only exceptions are medical vacuum applications that require biocompatible materials; we have a medical-grade silicone O ring that passes USP Class VI, and it\u2019s used in some low-pressure bioprocess systems, but it\u2019s not suitable for high vacuum.<\/p>\n

And let\u2019s not forget about surface finish. Mating surfaces in vacuum systems have to be smooth enough to let the O ring form a proper seal. A surface roughness higher than 1.6 micrometers will cause micro-leaks, even with a perfectly selected O ring. I once worked with a vacuum pump manufacturer who was getting 1e-6 Torr as a base pressure, even with the right Viton O rings. We checked their mating surfaces and found they had a roughness of 3.2 micrometers; after they resurfaced the flanges to 0.8 micrometers, their base pressure dropped to 1e-8 Torr, exactly what they needed.<\/p>\n

Over the years, I\u2019ve also seen advancements in O ring technology that have improved vacuum performance. A few years ago, we started offering coated O rings: PTFE-coated Viton or FFKM that combine the flexibility of elastomers with the non-stick, low-outgassing properties of PTFE. These are perfect for applications where the O ring might come into contact with corrosive chemicals in the vacuum chamber, because the PTFE coating acts as a barrier. I recently worked with a semiconductor etch equipment client who was using uncoated FFKM O rings and dealing with fluoride corrosion; switching to coated O rings extended O ring life from 3 months to 18 months, saving them thousands in replacement costs and downtime.<\/p>\n

Another new development is metal O rings, for applications that operate at extremely high temperatures (above 300\u00b0C) or require absolute zero outgassing. Metal O rings, usually made of copper or stainless steel, are machined to a precise shape and form a metal-to-metal seal when compressed. They\u2019re more expensive than elastomer O rings, but for UHV fusion experiments or high-temperature space applications, they\u2019re the only option. We don\u2019t stock metal O rings, but we partner with a precision machine shop that fabricates custom ones to exact vacuum specifications, so I can connect clients directly with that resource when needed.<\/p>\n

At the end of the day, the biggest mistake I see clients make is treating O rings as commodity parts. A $0.50 Buna-N O ring might save you a quarter upfront, but if it leaks and shuts down a $1 million semiconductor line for a day, that\u2019s a huge loss. That\u2019s why I take the time to walk every new client through their specific vacuum requirements, help them select the right material, design, and size of O ring, and even offer pre-sales testing to make sure it works for their application. For example, a client working with rough vacuum for packaging equipment doesn\u2019t need FFKM O rings\u2014they just need Buna-N with low compression set for general pressure. A client working with UHV for atomic layer deposition needs the most stringent outgassing testing possible.<\/p>\n

Last month, that semiconductor client I mentioned at the start called again. They\u2019d taken my advice, upgraded their chamber O rings to custom FFKM with a properly sized gland, and their base pressure stayed at 1e-7 Torr for two weeks straight, no leaks. They even placed an order for O rings for three other chambers at their facility. That\u2019s the kind of satisfaction I get from this work: not just selling O rings, but helping clients avoid costly failures by understanding how O rings perform in vacuum, and meeting their exact needs.<\/p>\n

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If you\u2019re working on a vacuum application\u2014whether it\u2019s a lab experiment, industrial manufacturing line, or aerospace test\u2014and you\u2019re tired of dealing with leaky seals, downtime, or ruining expensive parts, let\u2019s talk. I can help you select the right O ring material, test for outgassing and leak rates, and get you the parts you need with fast turnaround. Don\u2019t let a single O ring derail your project\u2014reach out today, and we\u2019ll make sure your vacuum seals perform as reliably as your system needs them to.<\/p>\n

Water Pump Gasket<\/a> References:<\/p>\n

    \n
  1. O\u2019Connor, R. E. (2018). Elastomer Seals for Vacuum Systems. Journal of Vacuum Science & Technology A, 36(3), 030801.<\/li>\n
  2. American Society for Testing and Materials. (2020). Standard Test Method for Determining Outgassing Properties of Materials Used in Spacecraft Applications (ASTM E595-20).<\/li>\n
  3. Hendricks, R. C., & Soong, C. (2015). Compression Set of Elastomeric Seals for High and Ultra-High Vacuum Applications. Vacuum, 119, 187-192.<\/li>\n
  4. National Aeronautics and Space Administration. (2021). Thermal Vacuum Test Seal Design Guidelines. NASA Technical Report TP-20210008721.<\/li>\n<\/ol>\n
    \n

    Zhejiang Jiacheng New Material Co., Ltd.<\/a>
    Zhejiang Jiacheng New Material Co., Ltd. is one of the most professional o ring manufacturers and suppliers in China, specialized in providing high quality customized products. We warmly welcome you to buy or wholesale o ring in stock here from our factory. Contact us for quotation and free sample.
    Address: #64 Anjiang Road, Jianshan New Zone, Huangwan Town, Haining City, Jiaxing City, Zhejiang Province
    E-mail: jcseal_zhu@126.com
    WebSite:     https:\/\/www.sjkseal.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    If you\u2019ve ever worked with vacuum systems\u2014whether for semiconductor manufacturing, aerospace testing, or even lab-scale freeze-drying\u2014you … How do O Rings perform in vacuum applications?<\/span>Read more<\/a><\/p>\n","protected":false},"author":119,"featured_media":3690,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3653],"class_list":["post-3690","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-o-ring-49ff-226bad"],"_links":{"self":[{"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/posts\/3690","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/users\/119"}],"replies":[{"embeddable":true,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/comments?post=3690"}],"version-history":[{"count":0,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/posts\/3690\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/posts\/3690"}],"wp:attachment":[{"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/media?parent=3690"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/categories?post=3690"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.nattonhatban.com\/blog\/wp-json\/wp\/v2\/tags?post=3690"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}