Small Diameter Spring Energized Seals
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

How Spring Selection Defines Spring-Energized Seal Performance

Most failures blamed on PTFE actually originate in the spring. This blog post discusses the load-management system and key features of spring-energized seals for canted coil springs, V springs, cantilever springs, helical springs, and coil springs.

Canted Coil Springs (Slant Coil Springs)

Canted Coil Springs and Slant Coil Springs from Advanced EMC Technologies

These springs are wound so that individual coils are set at an angle to the longitudinal axis. They are highly versatile and often used for dynamic sealing applications. Their key feature of canted coil springs is the flat load curve they provide. These spring energizers generate a nearly constant force across a wide deflection range. The constant force allows precise control over friction and torque, making these spring energizers ideal for applications where these factors are critical. Canted coil springs are also unlikely to experience compression set.

Canted coil spring energizers work best in moderate to high-speed rotary applications. Beyond sealing, their unique design allows them to serve as mechanical connectors (latching/locking), EMI/RF shields, and multi-point electrical conductors.

V Springs (V Ribbon Springs)

The V spring is a general-purpose, cantilever-type energizer. They offer an excellent balance of performance and cost-effectiveness. In addition, V springs provide a moderate load over a wide deflection range. They function well in both static and dynamic applications, including those involving rotary or reciprocating motion.

V springs are frequently recommended for severe service conditions, including vacuum pressures and cryogenic temperatures. V spring energizers are often a preferred choice for harsh operating environments.

Cantilever Springs (Finger Springs)

Often referred to as finger springs, these spring energizers feature a V-shaped cross-section and are distinguished by a linear load curve, meaning the force increases linearly with deflection.

The load is concentrated at the very front edge of the seal lip, which provides positive wiping action and makes them particularly effective for exclusion and scraping applications. They also generate extremely low friction.

Cantilever spring energizers are well-suited for sealing viscous media. They are typically found in low to medium-speed applications, such as hydraulic cylinders, pumps, compressors, and shocks.

Helical Springs (Helical Flat / Compression Springs)

Helical springs consist of a wound ribbon of metal and are characterized by a high load-versus-displacement curve. Because they produce a very high unit load with a small deflection range, helical springs provide tight, reliable sealing. They are well-adapted for sealing light gases and liquids.

Helical springs are generally limited to static, slow-dynamic, or intermittently dynamic applications because friction and wear are less of a concern than seal reliability. These spring energizers are often used in pipe flanges and crush jackets where the seal must embed into surface irregularities. Experts highly recommend helical configurations for cryogenic applications.

Coil Springs (Spiral Pitch Springs)

When many people visualize a spring-energized seal, they picture this wire coil type. These spring-energizers actually perform best in high-pressure, medium-speed applications and are known for their low friction. 

Spring Materials

The performance of spring-energizers is also dependent on the material selection. The material selection is primarily determined by the chemical and thermal environments involved. At Advanced EMC, we recommend one of the following spring materials: 

  • Stainless Steel (300 Series, 17-7 PH, 301/304): Common for general-purpose and cryogenic applications
  • Hastelloy: Recommended for highly corrosive media
  • Elgiloy: Used for high heat, corrosive environments, and salt water
  • Inconel: Used in severe environments and cryogenic applications

Conclusion

When spring-energized seals fail, the problem is often not the jacket, but the spring. Knowing about load consistency, deflection behavior, and how that force is delivered over time is key to deflection, friction, wear, and whether a seal actually survives its operating environment.

At Advanced EMC, spring-energized seals are engineered as complete systems, not just components. Our team will assist you from spring selection to geometry and material pairing, aligning the seal design with real-world conditions. If you are troubleshooting a failure or designing for demanding service, contact Advanced EMC today.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Harsh Chemical Environments: Why Polymer Seals Outperform Metal

In industries where equipment is constantly exposed to harsh chemical environments, corrosion is a leading cause of premature seal failure, unplanned downtime, and costly maintenance. Even with protective coatings and careful material selection, metal is still vulnerable to pitting, stress corrosion cracking, and galvanic attack.

Certain engineering polymers are inherently resistant to the many forms that chemical degradation can take. They provide a proven and reliable solution to sealing even in some of the most corrosive environments. 

This article reviews the basics of corrosion, explains why corrosion is not a problem for polymers, and discusses the most common engineering polymers used in sealing solutions.

Metals Sealing Solutions and Corrosion

Metal seals used to be chosen for their strength and rigidity, but their metallic composition makes them susceptible to various forms of corrosion. For example, uniform corrosion can occur when the entire surface is exposed to a reactive chemical, causing the material to gradually thin. Another example is pitting corrosion, which is very common in chloride-rich or acidic environments. This type of corrosion generates localized damage that can quickly compromise sealing integrity.

Galvanic corrosion is another issue, especially when dissimilar metals come into contact in the presence of an electrolyte. In addition, stress corrosion cracking can occur when tensile stress and a corrosive atmosphere act together, leading to sudden and unexpected failure. Once corrosion begins, sealing forces diminish, leakage risk increases, and imminent failure awaits if the seal is not replaced proactively.

Why Polymers Excel in Harsh Chemical Environments

Polymers do not experience galvanic corrosion because they are non-conductive. In addition, some high-performance polymers (e.g., PTFE) are chemically inert, meaning they will not react with acids, bases, or solvents. This level of chemical stability allows them to maintain their dimensions and mechanical properties even after years of exposure to aggressive media. When used with compatible chemicals, several engineering polymers do not experience pitting or stress corrosion cracking. 

In addition to corrosion resistance, polymers offer low friction and reduced wear rates, which can extend the service life of both the seal and the mating surface. Some, like PTFE and UHMW-PE, provide self-lubricating properties that enable dry running. Their lighter weight can also benefit marine and transportation applications where every pound matters.

Polymer Beads

Commonly Used Materials for Seals in Harsh Chemical Environments

PTFE (Polytetrafluoroethylene)

PTFE (commonly known as Teflon) is one of the most widely used polymers for seals due to its exceptional chemical resistance, extremely low friction, and broad operating temperature range from -200°C to +260°C. It remains stable in the presence of almost all industrial chemicals, making it ideal for O-rings, gaskets, and dynamic seals used in even the most aggressive environments.

PEEK (Polyetheretherketone)

PEEK is a go-to choice for sealing applications that demand both chemical resistance and mechanical strength under high temperature and pressure. It maintains integrity in aerospace, oil and gas, and chemical processing environments where seals are subjected to extreme loads and aggressive media.

Hytrel (Thermoplastic Polyester Elastomer)

Hytrel has an unusual combination of flexibility with chemical resistance, making Hytrel sealing solutions exhibit reliable performance across a wide temperature range. It is commonly used in automotive, hydraulic, and pneumatic seals where both elasticity and resistance to fuels, oils, and industrial fluids are critical.

Kynar (Polyvinylidene Fluoride, PVDF)

Kynar, sometimes referred to as PVDF, provides excellent resistance to acids, bases, and organic solvents. Its stability under long-term chemical exposure makes it a reliable material for seals and gaskets in chemical processing equipment, including pumps, valves, and pipelines.

PPS (Polyphenylene Sulfide)

PPS offers high-temperature capability and chemical resistance, making it a strong candidate for sealing in automotive and industrial applications where both thermal cycling and aggressive fluids are present. It retains dimensional stability and mechanical performance under prolonged exposure to harsh conditions.

Performance Benefits in Harsh Chemical Environments

Polymer sealing solutions can avoid the problematic degradation mechanisms plaguing traditional metal seals. Corrosion immunity combined with other key seal properties allows them to maintain sealing pressure and integrity over more extended periods, reducing the frequency of replacements. Also, lower maintenance requirements translate into both cost savings and less downtime.

Materials with dry-running capability, such as PTFE or filled PEEK, allow operation without lubrication. This can be critical in environments where lubricants could be washed away or contaminated. In aerospace systems, the weight savings from polymer components alone can improve energy efficiency and handling.

Conclusion

When corrosion is a constant threat, polymer seals offer a long-lasting, low-maintenance alternative to traditional metal designs. The chemical resistance, dimensional stability, and low-friction properties of engineering polymers make them ideal as sealing solutions for harsh chemical environments. By specifying polymer seals early in the design phase, engineers can improve system reliability, reduce downtime, and lower lifetime costs.

Contact Advanced EMC or request a quote to discuss polymer sealing solutions engineered for your specific operating conditions and chemical challenges.