by Jackie Johnson Jackie Johnson No Comments

Most Common Questions about Canted Coil Springs

Here are answers to seven of the most common questions asked about canted coil springs.

Where Are Canted Coil Springs Used?

Canted coil springs can be used in many different ways, but many are not aware of exactly how versatile they are. In the medical industry, they are used to shield equipment from crosstalk that could compromise the integrity of data. The automotive industry depends on canted coil springs to achieve solid mechanical and electrical connections while reducing weight and minimizing the complexity of assemblies. 

In the oil and gas industry, they are used to achieve both electrical and mechanical connections in the rugged environment of downhole tools. Canted coil springs protect sensitive equipment from lightning strikes in the aerospace industry. And those are just a few examples of how they can be used.

What is a Canted Coil Spring?

Traditional springs have all the coils perpendicular to their longitudinal axis. Canted coil springs, on the other hand, have the individual coils parallel to each other and at an angle to the longitudinal axis. Because of how the coils are oriented, these springs can effectively serve a wide range of uses that traditional springs cannot.

Are There Any Other Names for a Canted Coil Spring?

Yes, as a matter of face there are. Canted coil springs are also called slant coil springs and cant coil springs, both in reference to the angle (or cant) at which the coils are parallel to each other.

What Makes a Canted Coil Spring Special?

Because of the cant of the coils, these springs have a flat load curve when compressed–which is rather unusual for a spring. This means that the load generated as these springs are compressed is predictable through their wide deflection range. 

What Can Canted Coil Springs be Used For?

Canted coil springs have four specific areas of application in which they excel: energizers for spring-energized seals, mechanical connectors, multi-point electrical connectors, and EMI/RF shielding.

Spring-Energized Seals

Canted coil springs are one of the options when specifying a spring-energized seal. Spring-energized seals provide outstanding performance in spite of issues such as uneven mating surface,  hardware gaps, runout, eccentricity, out of roundness, and seal lip wear. 

In that context of spring-energized seals, canted coil springs generate a flat load curve that in turn keeps friction at a predictable, constant level. This is extremely important in sealing applications for which friction and torque are critical to the functionality of a seal. In addition, canted coils do not experience compression set. Canted coil spring energizers work best when there are moderate to high speeds involved and are ideal for situations where friction needs to be highly controlled.

Mechanical Connectors

First, canted coil springs work well for latching, or fastening two parts together so they can still be disconnected when needed. They also work extremely well at locking, where two parts are permanently “locked” together. Holding is another task for which canted coil springs excel: two parts can be aligned and retained, but with sliding possible. Sliding is highly controlled by spring force generated when the canted coil spring is deformed.

In this type of application, canted coil springs can be fine tuned to achieve highly specific insertion and removal forces. This is made possible by the nearly constant spring force that these springs generate over their deformation range.

EMI/RF Shielding

One of the more interesting applications of canted coil springs is their ability to provide EMI/RF shielding.  Their electrical properties can be adjusted to meet specific impedance requirements to achieve optimal shielding for certain ranges of interference, including both conductive and radiated. And they work extremely well at shielding from crosstalk.

These springs can easily adapt to even the most uneven and irregular shapes, allowing them to provide a consistent level of shielding, and can be used with connect/disconnect assemblies, waveguide flanges, rectangular electronics enclosures, and both radial and coax connectors.

Multi-point Electrical Conductors

Canted coil springs can also serve as multi-point electrical conductors. Because surface area provided by the canted coils, they provide a cooler operating temperature which can be critical in certain designs, including those where space is highly limited. Canted coil springs can serve as both conductors and grounds, in both static and dynamic applications. Their multi-point contact system means they can keep electrical contact even in extremely harsh conditions, including those where vibration and shock are common. 

What Kind of Materials Are Canted Coil Springs Available In?

The three most common materials for canted coil springs are:

  • Hastelloy
  • Inconel
  • Elgiloy
  • 300 Series Stainless Steel (e.g., 316, 316L, 302)
  • Copper alloys

In addition, they can be nickel, silver, or gold plated if needed. 

If there is going to be extremely high temperatures and/or exposure to corrosive media, Elgiloy is typically recommended. For shielding or use as a multi-point conductor, stainless steel and copper alloys work extremely well.

What Kind of Options Are Available for Canted Coil Springs?

The basic options for canted coil springs outside of those related to materials are …

  • Wire diameter
  • Coil size (width and height) 
  • Coil cant angle 
  • Number of independent coils
  • Inner and outer diameter of the spring

By adjusting these parameters and material selection, specific performance goals can be achieved.

Conclusion

Canted coil springs are useful in so many different applications, and their performance is fully proven in the field. Whether you need highly reliable spring-energized seals for use in vacuum conditions, locking components for orthopedic implants, a way to protect rectangular electronics enclosure from a specific range of interference, or a multipoint conductor that also serves as a latching connector, canted coil springs are an excellent option.

And remember that Advanced EMC offers FlexForceTM canted coil springs. Our engineers can work with you to find the right combination of characteristics and properties to meet the needs of your application. Contact us today!

 

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Spring-Energized Seals for the Medical Industry

Spring-energized seals, when designed correctly, provide a highly-reliable sealing solution for medical applications where failure can be fatal. Selecting the right seal jacket material and energizer is critical, but also complex. In this week’s blog post, we will discuss spring-energized seals in the medical industry, the best materials, how they are used, and more!

Spring-Energized Seals in the Medical Industry

Spring-energized seals are regularly used in equipment that involves rotary motion, including a variety of surgical instruments such as high- and low-speed handpieces, surgical saws, bone shavers, oscillating saws, and bone drills.  They are also seen in rotary catheter systems, centrifuges, and both small motors and small pumps. 

Reciprocating equipment also may require spring-energized energized seals, with typical applications including respirators, oxygen compressors, dialysis machines, syringe pumps, and blood analysis equipment. In addition, spring-energized seals work exceptionally well in cryogenic applications.

How Spring-Energized Seals Work

A spring-energized seal makes use of an energizer, most often in the form of a spring, to enable the seal lip to stay in contact with the mating surface. For high pressure applications, the pressure of the media is usually able to keep the seal lip in contact with the mating surface and the springer-energizer then takes over for high pressures. On the other hand, when used in applications involving low pressures, the spring-energizer is responsible for keeping the seal lip in contact with the sealing surface at all times. 

Seal Jacket Materials

There is a wide variety of seal jacket materials that can be used, but the choices are significantly limited for medical applications. The materials used must be FDA, USP Class VI, and ISO 10993-5 compliant. This significantly limits what materials can be used for the polymer jacket. The three most common choices are these: UHMW PE, PTFE, and PEEK.

UHMW PE

UHMW PE (Ultra High Molecular Weight Polyethylene) is a high-performance engineering polymer that possess the following characteristics:

  • Low coefficient of friction
  • Good chemical compatibility
  • Low moisture absorption
  • Good dimensional stability
  • Good operating temperature range up to 180°F
  • Can withstand extended exposure to hot water and steam
  • Self-lubricating

In addition, it exhibits excellent wear and abrasion resistance. UHMW PE is also known for its high purity and is also commonly used in orthopedic implants, in part because of its strength and toughness.

PTFE

PTFE (Polytetrafluoroethylene), often referred to as Teflon, has the following properties:

  • Extremely low coefficient of friction
  • Excellent chemical compatibility
  • Good dimensional stability
  • No moisture absorption
  • Excellent operating temperature range up to 450°F
  • Self-lubricating
  • Can withstand extended exposure to hot water and steam
  • Low cost

The primary weakness of virgin PTFE is its wear resistance, making it best adapted to light-service duty applications. However, wear resistance can be significantly improved through mineral additives.

PEEK

PEEK (polyether ether ketone) offers these properties:

  • Extremely low coefficient of friction
  • Excellent chemical compatibility
  • Moderate moisture absorption
  • Good dimensional stability
  • Wide operating temperature range up to 480°F
  • Self-lubricating
  • Can withstand extended exposure to hot water and steam

It is also extremely tough, abrasion resistant, and known for its outstanding heat resistance. In addition, PEEK is also used quite often in medical implants because of its biocompatibility, stiffness, strength, and toughness. 

Spring Energizers

Spring energizer materials are either metal or elastomeric, with metal being the most common. For medical applications, the three most commonly used metals for the spring energizers are stainless steel, Elgiloy, and Hastelloy.

Metal energizers are ideal for several reasons, with the first being their natural stiffness. They also work well in applications that involve autoclaving because of their thermal characteristics and contribution to maintaining the shape of the seal jacket. In addition, a metal spring helps to dissipate heat, reducing the potential effects of thermal deformation in the seal jacket. 

In the medical industry, the energizing spring will fall into one of these categories: canted coil, helical, or cantilever. Because spring loads can be customized, canted coil springs (also known as slanted coil springs) can serve in a variety of operating conditions. Heavy force canted coil springs perform extremely well in high pressure applications but may experience more wear than other configurations. Springs designed to provide more of a light force are ideal for high-speed applications but should not be used in cryogenic environments or with vacuum pressures.

In general, helical springs for medical applications involving cryogenic temperatures, vacuum pressures, and high pressures with only moderate wear, but are not recommended for high speed applications. Helical springs work extremely well on seals interacting with lightweight gases or fluids.

Cantilever springs offer excellent performance in vacuum pressure conditions but, as with helical springs, should not be used in high speed applications. However, a high degree of wear is to be expected. And, because the energizing force will be concentrated at the very front of the seal, they work extremely well for scraping and exclusion applications. 

Choosing the Right Spring-Energized Seal 

Dynamic sealing solutions for medical applications can prove extremely tricky for several reasons. For example, seals can be exposed to a variety of fluids and media, which can include bodily fluids and materials such as adipose, hemoglobin, proteins, carbohydrates, and general bioburden. For such applications, PTFE with its natural hydrophobic properties is an excellent option.

For seals which may be exposed to abrasive materials such as bone shavings, wear and abrasion resistant polymers such as UHMW PE and PEEK work very well, although there are FDA-approved fillers for PTFE that can enhance its wear properties. 

Cleaning, sterilization, and disinfection are critical factors in deciding on an appropriate sealing solution. Sterilization in particular is the most aggressive of the tree, and may involve the use of autoclaves (also known as steam sterilizers) that require elevated temperatures and pressures. There are other methods, such as dry heat, plasma gas, VHP (Vaporized Hydrogen Peroxide), and chemical sterilization. 

Chemical sterilization may use bleach, ozone, hydrogen peroxide, or EtO (ethylene oxide). While all three materials have good chemical neutrality and handle heat quite well, warpage may occur due to residual stresses and should be considered when developing the seal jacket molding process. 

There may also be issues with the use of lubricants, therefore many medical sealing applications require the use of a self-lubricating material of which PTFE, UHMW PE, and PEEK all qualify. However, for the lowest coefficient of friction and least slip-stick behavior or startup torque, PTFE is optimal.

Conclusion

Many different factors go into choosing the right spring-energized seal for a mission-critical medical application, and engineers must consider factors such as pressure, sterilization methods, lubricants, chemical compatibility, wear, and other. There are, however, proven sealing solutions for medical industry applications.

If you need a reliable seal for  the complex environment of a medical application, contact the sealing group at Advanced EMC. We can put our years of experience in polymers, spring energizers, and mission critical sealing solutions to work for you. Contact us today!

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Best Materials for Spring Energized Seals

The polymers most commonly used in spring-energized seals are PTFE, PEEK, UHMW PE, Vitron, and Hytrel. All of these are high-performance engineering polymers, but some are better adapted for certain applications than others. In this week’s blog post, we will discuss the best materials for spring energized seals, and how they can be applied for each industry. 

Spring-Energized Seals with Polymer Jackets

Polymer sealing jackets are often chosen over their rubber counterparts for various reasons, including better performance at extreme temperatures, a wider range of chemical compatibility, and lower friction. And, depending on the material under consideration, polymers often provide better specific strength and stiffness. Because of these and other properties, they are often used as the sealing jacket for spring-energized seals.

However, knowing which polymer is best adapted for a specific application can be challenging, especially since there are a wide range of engineered polymers that offer excellent mechanical and chemical properties. What follows is a discussion of the most popular spring-energized seal materials for five industries.

Food and Dairy 

Food and dairy applications can make the design of spring-energized seals more challenging, especially when it comes to the choice of the seal jacket material. Materials must be compliant with FDA CFR 177, contained in Title 21 of the Code of Federal Regulations. And other standards may also apply, such as NSF/ANSI standard 61 for drinking water systems,  3A Dairy sanitary standards 18-03 and 20-27, and (EU) 1935/2004.

Because of such regulations, the two most commonly used jacket materials for spring-energized seals in the food and dairy industry are PTFE (both virgin and certain grades of mineral-filled) and UHMW PE (Ultra High Molecular Weight Polyethylene). Besides their FDA approval, these materials also provide low friction, compatibility with most cleaning and sanitation routines, and a good range of operating temperatures. In addition, both materials are self-lubricating, which eliminates the problem of finding a lubricant that is safe to use.

Aerospace and Defense

Aerospace and defense applications that require a spring-energized seal often turn to materials such as PEEK (Polyether ether ketone)  and PTFE. Spring-energized seals are used with hydraulic systems, fuel systems, actuators, and gimbal pods in everything from massive airliners and space rockets to lightweight, nimble drones. Operating environments may involve extreme temperatures, exposure to aggressive chemicals, and mission-critical performance. Some operating conditions may also involve cryogenic temperatures, for which PTFE and Hytrel work extremely well. Note that Hytrel is a TPC-ET thermoplastic polyester elastomer.

In space applications, temperatures can range from cryogenic vacuum conditions to extremely high temperatures and pressures. For spring-energized seals used in rockets, PTFE is the most common due to its wide operating temperature range, outstanding chemical compatibility, and extremely low friction. In addition, PTFE lends itself to the weight constraints and pressure fluctuations involved with space travel, and has been proven over and over that it can provide mission critical levels of reliability.

Automotive

Automotive seals must withstand rugged, extreme environments that may involve everything from corrosive chemicals to extremely high temperatures. When selecting a seal material for automotive applications, properties such as low friction, wear resistance, resistance to abrasion, and durability are major concerns. 

For automotive applications, the most common choice of seal jacket material for spring energized seals include PTFE and Viton (fluoropolymer elastomer). To provide the best performance in the demanding environment of automotive seals, additives such as MoS2 (Molybdenum Disulfide) or carbon may be added to increase strength, wear resistance, and stiffness or achieve low friction.

Renewable Energy

One of the most common areas in renewable energy that requires the use of spring-energized seals is wind energy. Seals for wind turbines can be extremely challenging to design because of the wide range operating temperatures involved, problems with lubricants that can freeze in cold temperatures, extremely low friction so that energy is not wasted, and reliable performance over a long life. Seals must also exhibit low moisture absorption. 

Wind turbine seals typically use PTFE and UHMW PE, known for their low friction and self-lubricating properties. They also offer extremely low moisture absorption, a good range of operating temperatures, and good wear resistance. In addition, they have good resistance to degradation under constant UV exposure.

Oil and Gas

In the context of the oil and gas industry, LNG plants figure heavily in applications that require the use of cryogenic spring-energized seals. For such cryogenic applications, PTFE and UHMW PE have been found extremely effective. For non-cryogenic environments, Hytrel (thermoplastic polyester elastomer) is another commonly used material along with PTFE. These materials offer good performance in sub-freezing temperatures and are reliable enough to support the spring-energized seal design as it prevents leaks that could be devastating not just to humans but to the environment as well.

For other applications, issues of extremely high temperatures and pressures are involved, such as sealing solutions for wellheads. For those jobs, PEEK is often the preferred material. It possesses low friction, excellent chemical compatibility, a wide operating temperature range, and high strength. In addition, it is also one of the few polymers that can maintain its performance in sour gas environments.

Conclusion

Spring-energized seals can provide gas-tight, highly reliable sealing solutions for some of the most difficult operating environments imaginable when combined with the right material. For many sealing solutions out there, high performance polymers are a perfect complement to the ruggedness of a spring-energized seal in many different industries. If you need a spring-energized seal, regardless of industry, we can help you select the right material to provide a durable, effective seal. Contact Advanced EMC today!

by Jackie Johnson Jackie Johnson No Comments

Polymer Seal Market to Add 1.7X Value by 2031

Polymer seals are becoming increasingly popular across a variety of industries from medical to oil and gas. Materials such as PTFE are leading the polymer seal market, with demand being especially high. As per Fact.MR analysis, the global sales of polymer seals are set to experience a healthy CAGR of close to 6% throughout the forecast period of 2021 to 2031.

In this week’s blog post we will discuss the key takeaways from Fact.MR’s market study.

Oil and Gas Get the Lion’s Share

According to the report, oil & gas end-use is expected to capture highest share and is set to create a US$ 5.5 billion opportunity over the forecast period. This makes sense, as the oil and gas industry has witnessed substantial growth over the past few decades. And due to increasing investments in oil and gas across the globe, it is expected to only grow.

This also effects the seal market, as demands for greater boundary pushing technologies increases with the industry’s growing need to discover new ways to obtain oil. Despite COVID-19 causing a massive downturn in both the oil and gas and the seal market, the FMI expects FMI expects global oil & gas seals market to grow at 3.3% CAGR through 2031.

Europe Leading the Way

Europe, as it turns out, manufactures over 25% of all cars in the world. This makes sense, as some of the world’s top car brands are based in Europe: Mercedes, Audi, Porsche, BMW and Volkswagen to name a few. All of these manufacturers will need polymer seals at some point during the manufacturing process. This high demand results in Europe being one of the largest consumers of polymer seals.

What about the Aviation Sector?

With increase in tourism in Asian countries as well as low air fare, the aircraft industry has experienced incredible growth around the globe. This growth has created the need for more aircrafts, which in turn create the need for more polymer seals.

In Canada and the United States, with leading aircraft manufacturers and OEMs, the market is particularly strong. Because aircraft manufacturing requires high quality seals, and because there are no safe substitutes, the market is set to grow over a rapid pace over the next few years.

COVID-19 and the Seal Market

Like most of the world, the seal market has been disrupted by the COVID-19 pandemic. Because of disruptions in the supply chain, the polymer seal industry has faced setbacks.

One industry that has seen an increase in the use of polymer seals is the healthcare industry. There has been a boom in seals manufactured for medical devices such as ventilators, to the point where many manufacturers were struggling to keep up with the demand.

In Conclusion

COVID-19 has been tough for everyone, and the polymer seal market is no exception. However, dispite facing an uphill battle, the industry has grown and will continue to grow at record rates. Whether it’s seals for oil and gas or aviation, polymer seals are becoming a hot commodity and is set to be one of the fastest growing industries in the next decade.

Need polymer seals? Contact us today!

by Jackie Johnson Jackie Johnson No Comments

Advanced EMC Technologies Now AS9100D Certified Seal Manufacturer

Advanced EMC Technologies is proud to announce that we are officially AS9100 certified! For the past several months we have worked tirelessly to earn our ISO 9001:2015 certification, and this week we have taken the next step in quality excellence by becoming AS9100D certified with SAE International, the leading professional association for engineering professionals. We are now an AS9100D certified seal manufacturer for companies in the aerospace industry. In this week’s blog post, we will discuss what the AS9001D certification is, why we decided to get certified and what this means for Advanced EMC and our customers!

What is AS9100?

AS9100 is an aerospace standard (the AS) that was released by the International Aerospace Quality Group (IAQP, the parent organization of SAE) in 1999 to create a standard quality management system across the aerospace industry, from suppliers to manufacturers.

Before its development, most large aerospace companies used the US Military’s two quality systems- MIL-Q-9858A, Quality Program Requirements, and MIL-I-45208A, Military Specification: Inspection System Requirements. When the US Government adopted ISO 9001, it width drew their quality standards and many commercial companies followed suit. They quickly found that ISO 9001 did not address the specific requirements of their industry, so several companies banded together to create AS9100, based on ISO 9001, to provide a quality management system specific to the aerospace industry.

It has gone through several revisions since its introduction in the late 90s. As ISO updated its standards, so did AS9100. Currently, it is on revision D, to reflect changes in ISO 9001:2015. These include a new awareness clause, counterfeit parts prevention, clearer configuration management and more.

Why We Got Certified and What That Means for You

At Advanced EMC Technologies, we strive to provide our customers with the highest quality products possible, ensuring that our products do the job they are intended to do, do it well, and do it for as long as possible.

We understand the critical nature of these parts in the aerospace industry. For the safety of all involved, it is key that all parts are working as they should. We want to make sure that everything we provide our customers meet the best manufacturing practices for aerospace. Following the AS9100 regulations allow us to meet those demands.

With our AS9100 certification, you can be sure that your product has met stringent requirements from every level from material selection to manufacturing. Our customer service is also held to a high standard, so we can provide the best experience for our customers.

In Conclusion

With our AS9100 certified status, we here at Advanced EMC Technologies can provide your aerospace company the best experience, and best product, possible. With standards set up by industry leaders, our seals, bushings, bearings and other parts will be built with safety and longevity in mind.

For more information, visit our Quality Management page HERE. For sealing solutions, contact us today.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

PTFE Spring Energized Seals for Cryogenic Applications

When cryogenic temperatures are involved, a failed seal can have extremely serious repercussions that can include personal safety, explosions, damage to local ecosystems, and highly expensive downtime. One of the most dependable solutions to date for sealing in cryogenic environments is PTFE spring-energized seals. In this week’s blog post, we will discuss PTFE spring energized seals for cryogenic applications!

https://www.dailymotion.com/video/x12638r_teflon-spring-energized-ptfe-seals-by-advanced-emc_tech

Cryogenic Applications of Spring-Energized Seals

There are a host of cryogenic applications that depend on spring-energized seals. In the medical field, they are indispensable for MRI (Magnetic Resonance Imaging) equipment. In space applications, spring-energized seals can be found in equipment for radio astronomy and infrared telescopes as well as rocket propulsion systems. LNG fueling systems and compressors depend on them, as well as speciality gas manufacturing. Spring-energized seals are also needed in both pharmaceutical and medical research and can be found in scientific instrumentation for a wide range of disciplines. They are also critical for many food, dairy, and pharmaceutical applications.

But why do so many cryogenic environments require the use of a spring-energized seal?

Sealing Issues at Cryogenic Temperatures

The temperature range for cryogenic applications ranges from below freezing at -32°F down to absolute zero at -460°F. At these cryogenic temperatures, many seal materials begin to behave unpredictably, often exhibiting stiff or even brittle behavior. And changes in temperatures will cause dimensional changes in the seal, often compromising the integrity of the seal. To complicate things further, media at cryogenic temperatures may be chemically aggressive toward certain seal jacket materials. Finally, lubricants are usually prohibited at cryogenic temperatures because of issues with freezing, which means that a suitable material should be low friction and dry running.

Using the right sealing solution, however, can provide a reliable, gas-tight sealing system. And that, in turn, supports compliance with applicable safety and environmental regulations. 

Spring-Energized Seals

Unlike traditional seals, spring-energized seals include an energizer that applies a near-constant load throughout the circumference of the seal. This allows the lip of the seal to remain in contact with the mating surface in a variety of situations, including …

  • Eccentricity
  • Out of round 
  • Misalignment
  • Wear
  • Pressure fluctuations
  • Temperature fluctuations

In the context of cryogenic applications, spring-energized seals are used to maintain contact with the surface during the dimensional variations that result from temperature changes. In addition, spring-energized seals can be used in both static and dynamic applications, including rotating and/or oscillating movement.

Spring-Energizers Suitable for Cryogenic Temperatures

Spring energizers come in many different geometries, but for cryogenic applications, metal V ribbon springs are typically used. V springs, also known as cantilever springs, are used in extremely harsh operating environments and work extremely well in both cryogenic and vacuum pressure applications. 

A key feature of metal V springs as an energizer is their ability to provide a moderate yet very consistent load over a wide range of deflection. This aids in securing the lip of the seal against the mating surface even during dimensional changes due to wide temperature variations. For cryogenic environments, the spring-energizer is typically manufactured from either stainless steel or Inconel, Elgiloy, or Hastelloy.

However, in some instances, elastomeric o-rings can be used as the energizer as opposed to using a metal spring. O-ring energizers are durable and work well under a wide range of temperatures, but are best used when metal must be avoided in an application. 

Media Involved in Cryogenic Applications

As discussed earlier, there are a wide range of applications that require highly reliable sealing solutions. Spring-energized seals are excellent at maintaining seal integrity under such conditions, but thought must also be given to the seal jacket material, which will be in direct contact with media at cryogenic temperatures.

The most typical media of concern include …

  • LOx (Liquid Oxygen)
  • LHE (Liquid Helium)
  • LH2 (Liquid Hydrogen)
  • LAR (Liquid Argon)
  • LN2 (Liquid Nitrogen)
  • Liquid Xenon
  • LCO2 (Liquid Carbon Dioxide)
  • LNG (Liquid Natural Gas)
  • LPG (Liquid Petroleum Gas)
  • LMG (Liquid Methane Gas)
  • Various refrigerants and coolants

When a spring-energized seal is being specified, it is extremely important to select a material that not only has excellent properties at cryogenic temperatures but is compatible with the chemicals involved.

PTFE Spring-Energized Seals

One of the most widely used seal jackets for cryogenic applications is PTFE, better known by the trade name Teflon. PTFE provides excellent performance at a range of operating temperatures, including cryogenic, as well as pressure fluctuations. Its wide operating temperature range is complemented by a wide operating pressure range that includes vacuum pressures.

Virgin PTFE has the lowest coefficient of friction of any solid material, and even with the addition of filler materials it still remains extremely low. Lubricants will not be needed when a PTFE sealing jacket is used because it is self-lubricating, dry running, and exhibits no start and stop behavior. PTFE is also the most chemically compatible polymer available, solving the problem of chemical resistance issues. And for food, dairy, and pharmaceutical applications, PTFE is available in FDA-approved grades.

Conclusion

Where reliable sealing is critical in the presence of cryogenic temperatures, PTFE spring-energized seals are a proven solution in applications ranging from the rocket propulsion systems to MRIs. If you are looking for the right seal that offers superior performance in a cryogenic operating environment, contact Advanced EMC today. Our team of sealing experts can guide you in the process of specifying the right kind of cryogenic PTFE spring-energized seal.

by Jackie Johnson Jackie Johnson No Comments

Energizers used in Spring Energized Seals

PTFE spring-energized seals are one of the most popular choices for engineers in a variety of industries including oil and gas, medical, food and more. The reasons for their popularity are many, including their long service life, even wear, and their ability to perform in some of the harshest environments.  They work well in extreme temperatures; can even perform well in situations where operating conditions can vary significantly.  They usually offer a low compression set, have a long shelf life, and work very well in non-lubricated applications. One of the main reasons for these is the use of energizers, of which there are several different kinds.

As one of the key components of spring energized PTFE seals (it’s even in the name!), each of these energizers offers a different set of characteristics that allow engineers to find just the type of seal to suit their application’s needs.

In this week’s blog post, we are going to look at five different types of energizers, and where they are best used: coil springs, V springs, helical flat springs, cantilevered finger springs, and elastomeric O-rings.

Coil Spring

When people picture the spring energizing seal, the first image that comes to mind may well be the wire coil spring, also known as a spiral pitch spring.  One of its outstanding characteristics is low friction.  The angled coil spring works well where low friction and high pressure are involved, and works best in medium speed applications

V Springs

The V Spring is a cantilever, general-purpose energizing spring, which offers good performance at a relatively low cost.  The V ribbon spring (V ribbon spring energized seal) is the one to look at for the harshest, most severe applications your industry has to face.  It has been accepted as an excellent candidate for cryogenic and vacuum applications.

The v shape of this spring provides a moderate load over a wide deflection range and is used in dynamic and static applications.

Helical Spring

The helical flat spring, also known as a compression spring, is another commonly used alternative. It is typically a cylindrical shaped spring, and uses it’s coiled, mechanical form to store and release energy, which then absorbs impacts or shocks to resist compression or pulling objects.

This energizer is well adapted to a wide range of pressures, from high all the way down to vacuum conditions. It has been found especially suitable for sealing in lightweight gases or liquids. It performs the best under medium speed conditions.

Finger Spring

One outstanding performer is the cantilevered finger spring, also known as a finger spring (probably because it the shape of it reminds you of the end of your finger).

Finger spring energized seals are suited for sealing viscous media as the load is applied to the edge of the sealing lips. Seals energized by this spring also have extremely low friction, and offer low to high pressure sealing. They are best adapted to applications with speeds ranging from low to medium.

Elastomeric O-Ring

While elastomer is often synonymous with rubber, it is actually a highly modifiable polymer. Because of its affordability, ease of installation, and small space requirements, the Elastomeric O-ring is known as one of the most widely adapted sealing solutions. Known for their durability and versatility, elastomeric O-rings are suitable for dynamic or static applications with a wide range of temperature requirements.

An elastomeric O-ring energizer is especially useful when the use of metal must be avoided. It’s adapted well to extreme pressures, much like the helical flat spring.  It also works well when dead volume needs to be minimized.

In Conclusion

PTFE spring energized seals offer extreme temperature, high pressure, chemically inert static and dynamic sealing for the most demanding applications. They achieve this by using a variety of energizers, each with their own benefits depending on the application.

Whether your application is dynamic or static, low pressure or high, there is a spring energized seal for you. And Advanced EMC Technologies can help you find it!

Want to learn more about spring energized seals? Visit our product page HERE! Need sealing solutions? Contact us today.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

PCTFE Ball Valve Seats for Low Permeation Applications

Ball valve seats that show signs of swelling, blistering, or “popcorning” have been permeated at a molecular level. Needless to say, this can cause some serious issues such as leaks and catastrophic failure. The solution is to find a ball valve seat material that is highly resistant to permeation and an excellent choice would be PCTFE. In this week’s blog post, we will talk about PCTFE Ball Valve Seats and how they are used in Low Permeation Applications.

Introduction

Certain types of media may permeate the ball valve seat, leading to swelling, blistering, and leakage. Applications such as chemical processing and petrochemical transport may require a seat material that is resistant to permeation but still exhibits key properties such as low friction, compressive strength, and resistance to deformation is still needed.

How Permeation Works

Permeation refers to the molecular level penetration of gases, vapors, and liquids through a solid material via diffusion. In diffusion, molecules pass from an area of high concentration to an area of low concentration. This can be extremely problematic when a ball valve is being used because of the potential distortion and leaking of the ball valve seat.

Keep in mind that permeation can take place through a surprising variety of materials, including metals and polymers. In addition, some materials are only semipermeable, which means that only ions or molecules with certain properties can pass through the material. 

The rate of permeation is directly related to crystal structure and porosity, which is why factors such as density and molecular structure are important when selecting materials for applications where low permeation is important. 

Why Permeation is a Problem for Ball Valve Seats

Gas permeation can not only compromise gas stream purity but also result in dimensional changes of the ball valve seat. One form of these dimensional changes is swelling, which can occur if the permeating media becomes a part of the molecular structure of the material. In reinforced polymers, such as glass-reinforced PTFE, swelling can cause separation between the glass fibers and the PTFE matrix. 

Another common manifestation of permeation is referred to as “popcorning” or “popcorn polymerization” which occurs due to a polymeric chemical reaction. And among the most notorious source of problems with popcorning and swelling are monomers with extremely small molecular sizes such as Butadiene and Styrene.

Both popcorning and swelling will lead to leakage, and over time popcorning will completely destroy the ball valve seat. This makes the choice of ball valve seat materials extremely important for applications where this is a problem.

PCTFE for Low Permeability Ball Valve Seat Applications

One of the best materials for a ball valve seat application where permeability is a problem would be PCTFE (Polychlorotrifluoroethylene), a thermoplastic chlorofluoropolymer. PCTFE is sometimes referred to as Modified PTFE or PCTFE, as well as by trade names Kel-F, Voltalef, and Neoflon. PCTFE is often thought of as a second-generation PTFE material that maintains the chemical and thermal resistance of PTFE along with its low friction. It is also similar to other fluoropolymers such as PFA or FEP.

One of the defining characteristics of PCTFE is that it has a much more dense molecular structure and a low void and micro-porosity content when compared to similar ball valve seat materials. This gives it a very low permeability coefficient, which means that the likelihood of it swelling or popcorning is far lower than other materials. For example, its permeability for O2, N2, CO2, and H2 are 1.5 x 10-10, 0.18 x 10-10, 2.9 x 10-10, and 56.4 x 10-10 darcy, respectively.

PCTFE also provides improved toughness and strength along with good deformation recovery and excellent creep and cold-flow resistance. In addition, it has a wide operating temperature range of -100°F to 500°F. In fact, it performs extremely well at cryogenic temperatures. Because of its low friction, it also results in a very low ball valve operating torque. PCTFE also exhibits zero moisture absorption and is non-wetting. 

PCTFE works well in operating environments where other polymers may fail. For example, it is well adapted to nuclear service that may involve high radiation exposure, is non-flammable (D 635), and is resistant to attack by the vast majority of chemicals and oxidizing agents. The only chemicals that might lead to slight swelling are ethers, esters, aromatic solvents, and halocarbon compounds.

In addition to its use in applications requiring low permeability, PCTFE is also considered an excellent choice for applications that need a low-outgassing material and is commonly used in semiconductor applications. Also note that there are PCTFE grades that are FDA approved, such as Fluorolon PCTFE 2800. 

Conclusion

Fuel processing and transport, chemical processing, petrochemical systems, and emissions control are just a few of the applications where low permeation materials may be necessary. For such applications, PCTFE is an excellent option for ball valve seat materials because it combines the basic properties necessary for a seat with an extremely low rate of permeation.

If you need a solution to blistering, swelling, or popcorning of a ball valve seat, contact the experts at Advanced EMC. Our sealing team will work with you to find the right ball valve seat material for your application.

by Jackie Johnson Jackie Johnson No Comments

Thermoplastics for Medical Devices

Thermoplastics for medical devices are becoming increasingly common. New materials are often the necessary building blocks for product development and technology breakthroughs in the medical device industry. With novel procedures and treatments emerging rapidly, the equipment and devices required to enhance such advances are frequently limited only by their materials of construction.

A wide variety of thermoplastic resins are used in the medical industry. Most applications have multiple requirements that must be met, which narrows the list of candidate materials considerably. Some of the most common selection criteria include chemical resistance, temperature resistance, impact resistance, elongation or flexibility, strength, stiffness, clarity, dimensional stability, and biocompatibility, among others.

In this week’s blog post, we will discuss some of the most common thermoplastics used in the medical industry.

PTFE

PTFE (Polytetrafluoroethylene), also known by its brand name Teflon, is a fluoropolymer most famous for its non-stick qualities. PTFE is inert to most chemicals and has the lowest coefficient of friction of any thermoplastic. It also has very good UV resistance, hot water resistance and electrical insulation even at high temperatures.

These features make it suitable for a variety of medical applications. It is most commonly used in tubing, keeping devices such as ventilators running smoothly. PTFE coating is also popular for use in vascular medical devices, such as catheters.

PEEK

Like, PTFE, PEEK (Polyetheretherketone) is well suited for a wide variety of medical devices. In particular, PEEK Optima and Zeniva PEEK are suitable for long term implants and have a uniquely similar structure to that of human bone. PEEK is also radiolucent which makes it well suited for dental implants and use in various medical instruments. Not only that, but PEEK is also able to be used continuously to 480°F (250°C) and in hot water or steam without permanent loss in physical properties.

For more hostile environments, PEEK is a high strength alternative to fluoropolymers. Because of this, PEEK is an increasingly popular FDA approved replacement for metal in the medical industry due to its lightweight nature, mechanical strength, radiolucent properties, creep and fatigue resistance, as well as its ease in processing.

UHMW-PE

UHMW-PE (Ultra-High Molecular Weight Polyethylene) is a low-pressure polyethylene resin that has a much higher abrasion resistance and impact strength compared to most plastics. Due to its self-lubricating, non-stick surface, it has a low coefficient of friction that makes it desirable in the medical industry. UHMW-PE’s biocompatibility has made it a popular biomaterial for joint replacements such as hips, knees and shoulders, for decades, as early as the 1960s.

Recently, the resin has been refined in such a way to serve the needs of surgeons doing minimally invasive surgical implants such as cardiovascular surgery. Because of its ability to be shaped into a range of textile constructions, UHMW-PE is suitable for enhancing the design of various implantable cardiovascular devices, including complicated stent grafts and covered stents.

TORLON-PAI

TORLON PAI (Polyamideimide) is one of the highest performing thermoplastics built from the TORLON resin. Its compressive strength is double that of PEEK when unfilled, and about 30% higher than ULTEM PEI. As a medical grade thermoplastic, Torlon offers high modulus, radiolucency, sterilization-compatibility and high wear resistance, making it ideal for components inside high performance and peristaltic pumps. Torlon’s extremely low coefficient of linear thermal expansion and high creep resistance deliver excellent dimensional stability over its entire service range.

In Conclusion

While we only went over a mere handful of thermoplastics, there are many more that are used in the medical device industry. Whether you need tubing for a pump, replacement for a bone, or more, there is a high-quality thermoplastic perfect for the task.

To learn more about polymers and their use in medical devices, check out this blog post HERE.

Need FDA approved seals for your medical device? Contact us today!

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Why PTFE and PEEK Are Used for Ball Valve Seats

There are two main categories of polymers used for ball valve seats: PTFE (both virgin and filled and PEEK. These are popular materials for several reasons, but each one has applications to which they are better adapted. 

Ball Valves

Ball valves are used to control the flow of water, oil, steam, air, slurries, and corrosive fluids. They can be found in HVAC systems, petrochemical processing, food processing, water distribution systems, automatic combustion systems, and instrumentation control. 

While there are various parts within a ball valve (e.g., stem, stem nut, ball, body), one of the most crucial parts is the ball valve seat. Ball valve seats have two main jobs: distribute seating stress uniformly and achieve a solid seal — and to accomplish this they must be made from the right material.

Key Properties of Ball Valve Seat Materials

There are six critical properties that any material for ball valve seats must possess: 

  • Low friction to reduce stem torque
  • Excellent wear resistance
  • Good stress recovery
  • Sufficient elasticity to maintain a solid seal
  • Dimensional stability
  • Chemical compatibility with the media involved

If the ball valves are used in connection with food, dairy, or pharmaceutical applications, they may also require materials that are FDA approved. And while there are a variety of polymer materials that can be used, PTFE, filled-PTFE, and PEEK are the most commonly used.

Material Properties for Harsh Environments

There are other considerations involved as well, with many depending on the operating environment. These can include dimensional stability and reliable performance at extreme temperatures (which may include cryogenic) as well as the ability to withstand sterilization routines that involve hot water, steam, and/or caustic cleaning materials. And if there is extended exposure to water or humidity, a ball valve seat must have a low coefficient of hygroscopic expansion. In addition, there may be a need for materials to be flame retardant, fire-resistant, or suitable for use in environments with radiation.

PTFE Ball Valve Seats

PTFE (trade name Teflon) has long been a popular choice for ball valve seat materials and is available in FDA-approved grades. Virgin PTFE has the lowest coefficient of friction of any thermoplastic in existence (even geckos cannot maintain their grip on Teflon) and filled-PTFE grades are available with very low friction as well. This polymer is also capable of dry running (and thus requires no lubricants) and exhibits no stick-slip behavior. 

PTFE provides excellent wear resistance and good stress recovery, which can be enhanced by the right choice of additives. It possesses enough ductility to provide a good seal, even in the presence of extreme temperatures and highly corrosive materials. It has both a low coefficient of thermal expansion and a good coefficient of hygroscopic expansions, making it stable dimensionally. It is also fire resistant, hydrophobic, and non-wetting

The chemical compatibility and high-temperature performance of PTFE mean it works well with applications that involve sanitation and sterilization. In addition, its chemical compatibility works well with a wide range of media with the exception of fluorine and liquid alkalis. Its operating temperature range includes cryogenic temperatures between -20°F and 400°F. Note, however, that the temperature performance of virgin PTFE is highly dependent on the operating pressure.

Among the drawbacks of PTFE is its susceptibility to cold creep, is best for temperatures no greater than 5 ksi, and has limited performance in the presence of radiation due to a maximum lifetime radiation dose of 1×104 rads. It is also subject to issues with decompression after it has been highly pressurized and should not be exposed to temperature fluctuations greater than 167°F.

Filled-PTFE Ball Valve Seats

In terms of filled-PTFE, the most well-adapted combinations are carbon graphite and glass filled.  Carbon graphite reinforced PTFE is chosen over virgin PTFE when high temperatures and pressures are part of the normal operating environment. It offers better wear characteristics and is less likely to cold creep than virgin PTFE while maintaining a fairly low coefficient of friction.

Glass-filled PTFE also retains many of the positive aspects of virgin PTFE while offering better extrusion resistance and better wear characteristics. It is often the ball valve seat material of choice for the food, dairy, and pharmaceutical industry and still maintains a fairly low coefficient of friction. Because of the glass fibers, however, it is more likely to be abrasive and is also incompatible with chemicals known to attack glass, such as hydrofluoric acid and strong caustics. Note that glass-filled PTFE is fire-resistant.

Another option is stainless steel-reinforced PTFE composed of 50% PTFE and 50% powdered 316 SS. This particular grade of filled PTFE offers a slightly larger operating temperature range than virgin PTFE (-20°F  to 550°F) and can handle much higher pressures. Its primary drawback is that the coefficient of friction is significantly higher, which can lead to faster wear and a high stem torque. It is, however, fire-resistant.

PEEK Ball Valve Seats

PEEK has much in common with PTFE, including an extensive temperature range from  -70°F to 600°F, and good chemical compatibility. Its coefficient of friction is not as low as PTFE but it does perform extremely well in applications that involve high temperature and pressure. It is also more abrasion-resistant and tougher than PTFE.

Unlike PTFE, it does offer excellent performance when exposed to radiation, making it well-adapted to nuclear applications, and works better in extremely high temperatures that PTFE cannot handle, making it an excellent choice for the oil and gas industry. It is also flame retardant.

PEEK does not have quite the range of chemical compatibility as PTFE, and should never be exposed to sulfuric acid or used in corrosive environments. However, it does perform well in situations that involve continuous exposure to hot water and steam as well as ultra-high vacuum pressures. In addition to being significantly harder than PTFE, PEEK does exhibit brittle behavior at lower temperatures.

Conclusion

PTFE, filled PTFE, and PEEK are excellent high-performance polymers for ball valve seats in a wide range of applications. From check valves for pharmaceutical processing to needle valves for automatic combustion systems, Advanced EMC can help you find the right polymer and fillers to achieve the results you need.