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by Rogers Corporation
Elastomeric Material Solutions, Enclosure Institute
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Welcome to the Enclosure Institute™, your go-to resource for mastering enclosure design and sealing solutions.
In this blog, we explore a foundational concept in gasket engineering: understanding the difference between static and dynamic seals.
This distinction has significant implications for how a seal is expected to perform over time, and it plays a crucial role in selecting the right materials for durability, maintenance requirements, and long-term enclosure protection.
One of the most important questions to ask in enclosure design is: Will the seal stay closed for most of its life, or will it open and close repeatedly?
The answer determines whether you're designing a static or dynamic seal.
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A static seal is compressed once and stays in place. It is not designed for regular opening and closing, with servicing only performed by technicians when necessary. Common examples of static seals include:
Design Implications:
But what if the enclosure is meant to be opened and closed frequently? That’s where dynamic seals come in.
A dynamic seal, on the other hand, is one that is expected to open and close multiple times while maintaining its ability to reseal effectively. These seals must withstand repeated compression cycles and return to their original shape to ensure long-term performance.
Examples of dynamic seals include:
Image property of Marian Inc
Image property of Marian Inc
Design Implications:
To ensure long-term performance, a dynamic seal must exhibit the following properties:
These properties work together to ensure that each time a dynamic seal is compressed and released, it performs like new. In contrast, materials with poor compression set resistance and high stress relaxation may lose their sealing capability after repeated use—leading to gaps, leaks, and reduced protection.
Dynamic sealing introduces several mechanical challenges:
A common design example is an access panel with two hinges and a latch—similar to a door. In these cases, the sealing force is only applied at three points instead of continuously around the perimeter. If the enclosure lacks sufficient rigidity, the panel may warp or lift at the corners, creating leak paths.
A successful sealing design depends on balancing enclosure requirements with material performance. Materials like PORON® polyurethanes and BISCO® silicones offer excellent compression set resistance and low stress relaxation, making them ideal for both static and dynamic applications.
By selecting the appropriate material, engineers can ensure long-lasting, reliable sealing performance, whether the application demands a one-time factory seal or a reusable enclosure that opens and closes regularly.
Sealing challenges can make or break an enclosure’s performance. Whether you're designing for environmental protection, long-term reliability, or compliance with industry standards, selecting the right materials and understanding effective sealing strategies are critical. That’s why Marian Inc. and Rogers Corporation have partnered to bring you the Enclosure Institute™ — a free learning platform designed to help engineers navigate the complexities of enclosure sealing.
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The Enclosure Institute™ is designed for engineers at all levels, whether you're new to enclosure sealing or looking to refine your expertise.
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With nearly 200 years of material expertise, 70 years of fabrication development, decades of partnership, and thousands of applications designed together, Marian and Rogers bring unmatched knowledge to enclosure sealing. By combining Rogers’ high-performance materials with Marian’s precision converting capabilities, we deliver custom-engineered solutions that enhance durability, reliability, and performance.
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Whether you need expert guidance, high-quality materials, or precision-fabricated components, our partnership ensures your enclosures meet the highest industry standards while optimizing efficiency and cost-effectiveness.
If you have a specific enclosure challenge and need expert guidance, Marian’s team is ready to help. Contact Marian directly for tailored recommendations and support.
Published on Aug 06,
In industrial equipment sealing, rubber seals as a key component; their performance directly affects the reliability and safety of equipment operation. According to the different application scenarios, rubber seals can be divided into dynamic seals (dynamic seals) and static seals static seals) two categories. Although both take rubber material as the core, there are significant differences in structural design, mechanical properties, material selection, and failure mode. This article will start from the technical principles, in-depth analysis of the core differences between the two seals, to provide a professional selection guide.
The core task of dynamic seals is to solve the fluid leakage problem between moving parts, such as piston rod seals for hydraulic cylinders and oil seals for rotating shafts. Its structural design needs to meet three core requirements:
Dynamic compensation mechanism: O-ring, for example, dynamic sealing state to withstand the dual role of media pressure and friction, so the installation of the compression rate is usually controlled at 15%-30 %, and needs to cooperate with the retaining ring to prevent high-pressure extrusion failure. In contrast, the compression rate of static O-rings can be 8-25%.
Lubrication and wear balance: The Stribeck Curve reveals the lubrication threshold for dynamic seals: boundary lubrication leads to high wear, while full-fluid lubrication leads to leakage due to a thick film. Ideally, dynamic seals need to maintain a hybrid lubrication state, such as mechanical seals through the end face of the micro-convex body contact and fluid film shear synergistic effect, to achieve low leakage and long life.
Heat – force coupling failure control: high-speed rotary seals (such as centrifugal pump shaft seal), frictional heat, and material creep are the main failure modes. A chemical pump case shows that when the shaft speed exceeds 5m/s, the temperature of the lip of the ordinary NBR seal can reach 120℃, and it is necessary to change to fluorine rubber (FKM) and optimize the lip angle to reduce the friction coefficient.
Static seals realize sealing through preload, commonly used in flange connections, equipment housing, and other scenarios. The design logic focuses on:
Material deformation filling: Medium and low pressure static seals (≤35MPa) commonly use graphite gaskets, whose compression rate can be up to 40%-50%, through the fiber braided structure to fill the flange surface micro-cracks. High-pressure static seals (e.g., nuclear power equipment) use metal-wound gaskets, which can maintain sealing under 100MPa pressure through alternating lamination of metallic and non-metallic belts.
Long-term creep control: rubber sealant in the static seal needs to overcome the material creep caused by sealing force degradation. The experience of a petrochemical company shows that the use of silicone rubber sealant, 24 hours after the curing sealing force decreased by about 15%, indicating the need to maintain the long-term effectiveness of the secondary pressurization process.
Multi-material synergistic design: composite gaskets (such as metal + PTFE) combine the strength of the metal with the self-lubricating polymer, suitable for high temperature (≤ 260 ℃), strong corrosive media. A pharmaceutical reactor case shows that this structure reduces the seal leakage rate to below 0.1ml/h.
Abrasion resistance: rotary shaft seal commonly uses polyurethane (PU), its Shore hardness is up to 90A, abrasion resistance is 3 times that of nitrile rubber, suitable for linear velocity ≤ 5m / s conditions.
Low coefficient of friction: the dry gas seal adopts a silicon carbide/graphite combination, the coefficient of friction is as low as 0.01, which is suitable for high-speed centrifugal compressors (shaft speed> 10,000 rpm).
Dynamic adaptability: Hydraulic cylinder piston seal needs to balance hardness and resilience, a brand of products using 70A hardness of hydrogenated nitrile butadiene rubber (HNBR), in ± 10MPa pressure fluctuations can still maintain the leakage rate <0.5ml/min.
High-pressure bearing: metal C-ring realizes self-tightening through elastic deformation, suitable for pipe connection with a diameter ≤mm and pressure ≤35MPa.
Temperature limit: Perfluoroether rubber (FFKM) can be used in the range of -20℃ to 327℃, which is the preferred sealing material for the vacuum chamber of semiconductor equipment.
Balance of Economy: Nitrile rubber (NBR) is widely used for low and medium-pressure static seals, which is only 1/3 of the cost of fluoroelastomers and is resistant to mineral oil and water-based media.
Extrusion failure: a hydraulic system did not use the retaining ring, resulting in the O-ring in the 25MPa pressure being extruded groove. After the improvement program adopted a PTFE retaining ring, the working pressure was raised to 35MPa.
Thermal aging failure: ship tail shaft seal in the continuous seawater immersion, ordinary neoprene rubber (CR) life of only 6 months, changed to fluorosilicone rubber (FVMQ), life extended to 3 years.
Eccentric flange leakage: In a chemical plant, the flange bolts were tightened in the wrong order, resulting in insufficient local compression of the gasket. By introducing a torque control wrench, the leakage rate was reduced from 5ml/min to 0.2ml/min.
Adhesive Creep Failure: A food facility used an acrylate sealant that developed microbial infiltration after 6 months due to a lack of secondary pressurization. After changing to two-component epoxy adhesive, it passed FDA certification through 30 30-minute curing + 24 hours secondary pressurization process.
Hydrogen energy equipment: the seals are required to meet the -40℃ low temperature brittleness and 150℃ high temperature stability at the same time; hydrogenated nitrile rubber (HNBR) or perfluoroether rubber (FFKM) is recommended.
Lithium battery electrolyte: need to use strong acid and alkali resistant fluorine rubber (FKM) or ethylene-propylene rubber (EPDM), an enterprise measured data shows that FKM in the 1M LiPF6 solution immersed for 1,000 hours after the volume change rate <5%.
Clean room sealing: requires seals without precipitates, recommended the use of platinum vulcanized silicone rubber, with a volatile organic compounds (VOC) content <10μg/g.
Autoclave sterilization: 134 ℃ steam sterilization-resistant sealing materials, with fluorine rubber (FKM) as the main, a brand of products through the 500 sterilization cycle test, hardness change <5IRHD.
Dynamic seals and static seals belong to the same category of rubber seals, but their design logic and material selection are fundamentally different. For global buyers, the first step in the selection process is to define the working conditions of the equipment (pressure, temperature, medium, motion). It is recommended to give preference to products certified by ISO (dynamic seals) or API 6FA (static seals), and to request suppliers to provide material properties (such as hardness, compression permanent deformation rate, thermal aging coefficient) and failure analysis reports. By accurately matching seals with working conditions, you can significantly reduce equipment maintenance costs and improve productivity.
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