Uncategorized

In cryogenic temperatures, most O-rings become brittle and fail. Many times cryogenic applications can also involve media that is not chemically compatible with traditional elastomeric materials. However, for axial sealing applications, there is an effective, dependable solution: encapsulated O-rings. 

What is an Encapsulated O-Ring?

In short, encapsulated o-rings combine the chemical resistance and extreme-temperature performance of FEP or PFA with the elasticity and resilience of silicone, FKM, or stainless steel energizers. Stainless steel springs or rugged elastomers are encapsulated within a durable, chemically resistant jacket made from FEP (fluorinated ethylene propylene) orPFA (perfluoro alkoxy copolymer). These o-rings are used with valve stems, flanges, joints, swivels, pumps, turbo expanders, and waterless fracking.

Materials Used With Encapsulated O-Rings

For the outside of the O-ring, the most popular materials currently in use are FEP, PFA, and PTFE. FEP is highly resistant to chemical attack, offers a low compression set, and has a low coefficient of friction. Its operating temperature range is -420°F through 400°F and is less expensive than PFA. In addition, FEP is available in FDA-approved grades. 

PFA is resistant to a wide range of corrosive chemicals, including naphtha, acid, aromatic solvents, petroleum, and alcohol. It has a wider operating temperature range than FEP, from -420°F through 500°F. It also possesses a low compression set and resistance to cracking and stress in addition to a higher overall mechanical strength when compared to FEP. It is also available in grades that have the following approvals: USP IV, FDA-compliant, EU Reg. 1935/2004, ADI-free, and 3-A Sanitary Standards.

The materials used for the interior energizer of encapsulated o-rings include 302 stainless steel for spring energized as well as silicone, FKM (trade name Viton), or EPDM. Whether its a spring-energized approach or a core of silicone, FKM, or EPDM, the interior of the encapsulated o-ring provides the additional resiliency that makes these o-rings so effective for cryogenic applications. Note that silicone and FKM ensure an even pretensioning at the sealing point.

Silicone provides a softer core than FKM and offers very good cold flexibility. Using FKM as the core material means that the o-ring will be able assume its original shape very quickly after installation/deformation due to its outstanding compression set characteristics. It is not, however, as temperature resistant as silicone. While EPDM can be used as a core material, it is not recommended because of how it reacts to the heat involved in manufacturing the encapsulated o-rings.

Solid-Core vs Hollow-Core Encapsulated O-Rings

The two basic types of encapsulated O-rings are solid core and hollow core. Solid core o-rings have an energizer made from either silicone or FKM (fluoroelastomer, trade name Viton). Both types of cores provide good elasticity and low compression set, but when used in cryogenic applications silicone is usually the better choice because it remains more flexible at lower temperatures. Hollow-core encapsulated o-rings, on the other hand, are used when there is a need for extreme elasticity or for fragile applications. 

Advantages of Encapsulated O-Rings

There are several advantages to using encapsulated O-ring, besides the fact that they  can outperform traditional seals in harsh environments that can include extreme temperatures and corrosive media. These o-rings are …

• Chemically resistant
• Available in non-contaminating and FDA-approved materials
• Low coefficient of friction that prevents issues with stick-slip behavior
• Low permeation
• Excellent corrosion resistance
• Low compression set
• Excellent service life
• Reliable sealing
• Cost effective

Encapsulated O-Rings for Cryogenic Operating Environments

For cryogenic environments, the best approach to encapsulated O-rings is the use of FEP or PFA exterior with a steel flat wound ribbon spring at the core. This configuration can handle cryogenic temperatures all the way down to -420°F and pressures up to 3000 psi as long as vented holes are placed in the FEP jacket to prevent dangerous blowouts. These encapsulated o-rings work best in static and slow dynamic applications and are ideal for applications that involve cryogenic media such as liquid oxygen, liquid nitrogen, hydrogen. These encapsulated o-rings are readily available in both metric and US cross-sections and a wide range of diameters.

Conclusion

For cryogenic applications where traditional o-rings have failed, encapsulated o-rings with an FEP/PFA exterior and a 302 stainless flat wound ribbon at the core is an excellent option. It has already been successfully used by NASA in not one but several successful rocket launches and has been incorporated into designs by Lockheed and Boeing.

Injection molding is one of the most popular methods of mass producing identical plastic products. It is fast, highly efficient, with the ability to produce an incredible amounts of parts per hour.

It has many benefits compared to other manufacturing processes. For example, once the initial costs have been met, the price per unit is actually extremely low compared to processes like CNC machining. This is in part because it is easier to mass produce products with injection molding, as well as reduced waste. Injection molding is also incredibly fast, almost entirely automated, and highly reliable.

In this week’s blog post, we will go over the many benefits of injection molding, and why it might be the manufacturing process your business needs!

How it Works

Injection molding works by using a screw-type plunger to heat and inject molten plastic material under pressure into a closed metal mold.

With thermoplastics, pelletized raw material is fed through a hopper into a heated barrel with a reciprocating screw. This melts the pellets into molten plastic, which is then poured into the mold.

When the material is cooled, it is removed from the mold, where it can be cleaned and inspected.

Benefits of Injection Molding

Fast Production

Injection molding is one of the fastest means of production out there, especially when compared to other methods. This makes the process highly efficient and cost-effective. While speed depends on the complexity and size of the mold, there are typically 15-120 second pass between each cycle time.

Furthermore, automation, see Low Labor Costs below, allows for making incredibly precise and accurate injection molds. Computer aided design (CAD) and computer aided manufacturing (CAM) allow close tolerances during the making of the molds, which in turn also enable fast production of products.

Complex Part Design

Another benefit of injection molding is that it can handle extremely complex parts. In addition, it can create large quantities of uniform parts, virtually indistinguishable from each other.

In order to achieve that level of uniformity, however, the mold must

High Precision

A huge benefit of injection molding is its ability to create complex part designs requiring tight tolerances. In fact, with injection molding, the designs can be as accurate to within +/- .005” or even closer depending on part design.

This is particularly important for industries such as the medical device industry, where parts need to be as accurate as possible to function properly.

Stronger Products

Thanks to the process used, injection molding can create incredibly strong products. With the molding, it is possible to use fillers in the material, which reduces the density of the plastic while it is being molded and adds greater strength to the completed part that other processes do not offer.

Flexibility

Since the molds are subjected to extremely high presser, the plastic is pressed harder and allows for a larger amount of detail than other methods of manufacturing. Injection molding can be used for complex or intricate shapes.

And with choosing fluoropolymers, there are a lot of materials to choose from. It is easy to find the material to suit your needs.

Low Labor Costs

Because injection molding is an automated process, with the majority of the process being performed by machines and robotics that can be controlled and managed by a single operator, the overhead cost is greatly reduced. With a lower overhead, the manufacturing is significantly lowered.

Product Consistency

As stated above, the process of injection molding enables manufacturers to mass produce identical products. With an accuracy rate of a 100^th of a millimeter, injection molding is a great choice if you need to mass produce products.

Ability to Use Multiple Plastics at Once

The ability to use different types of plastic simultaneously is another benefit of injection molding. This can be done with the help of co-injection molding, a process in which a second component (core) is injected into the first component (skin).

This can save costs by filling a material with a cheaper material such as regranulate, and it can also enhance the quality of a component by giving it a more reinforced core.

Reduced Waste

Since part repeatability is so high with injection molding, there is very little plastic waste involved. Compared to traditional manufacturing processes like CNC machining, which cuts away substantial percentages of material, injection molding produces very low scrap rates, and what excess material is left over can be re-used.

This makes the process a good choice for companies wanting to reduce their environmental impact.

Some Considerations for Injection Molding

• Design Considerations
  1. Design the part with injection molding in mind. While injection molding can make complex parts, simplifying 3D geometry early on will save time and money in the long run. Other things to keep in mind:
     • Keep walls thin, typically between 132” and 110”
     • To strengthen parts, use additional structures such as ribs instead of thicker walls
     • Round corners and edges whenever possible
     • If possible, add a slight taper to the sides to allow for easy release of the part from the mold.
• Production Considerations
  1. Try to minimize cycle time as much as possible. Using machines with hot runner technology will help.
  2. To keep production fast and easy, try designing your part specifically to minimize assembly. This can save on overhead!
• Financial Considerations
  1. While injection molding will save you money in the long run, preparing a product requires a significant initial investment.
  2. Be sure to determine the number of parts you need to produce to be the most cost effective beforehand.

In Conclusion

Injection molding is one of the best manufacturing processes for producing high quality products on a massive scale. With its high accuracy and repeatability, as well as it’s reduced waste, it can save manufacturers money. It is also great for producing stronger products with more complex designs, perfect for complex parts for complex machines.

If you are looking for injection molded polymer parts, contact Advanced EMC Technologies today and we will be happy to help you!

High-performance automobiles require seals that must face even more rigorous constraints and provide reliable performance in operating environments where standard seal designs would fail. In this blog post, we’ll review the various categories of seals used in automotive applications, discuss how high-performance automotive seals differ, and what sealing solutions are currently being used.

Automotive Seal Categories

Seals can be used for multiple purposes with the primary ones being the exclusion of contaminants, reduction of friction, leak prevention, and the containment of pressure. That said, there are several different categories of general automotive seals that also apply to high-performance automobiles.

Driveline seals are key to a smooth, reliable transmission and not only aid in reducing power losses but help to better optimize fuel consumption. In addition, driveline seals are critical to the overall performance of the transmission system. As a category of seals, they include axial seals, transmission seals, and bonded pistons.

While comfort is not typically a major concern for high-performance automobile drivers, braking capacity and the ability for the vehicle to hold the road certainly are–making high quality, reliable suspension seals essential to both safety and control in racing environments.

Keeping the oil or grease lubricant contained and uncontaminated in wheel bearings reduces friction and power losses. That happens to be the job of wheel-end seals, which must be able to withstand a wide range of temperatures and exposure to some extreme conditions, whether on a paved race track or in off-road competition. 

Engines seals include those for camshafts, crankshafts, valve stems, and auxiliary shafts. There are also seals required for spark plugs, valve stems, and injector tubes are well. Engine seals need to be extremely low friction to minimize power loss and provide the ability to integrate with sensors to track engine performance. Needless to say, the materials need to be rugged enough to withstand the heat and be compatible with all media involved, including fuel additives that can damage materials.

The purpose of bearing seals is to keep the lubrication in and contaminants out of the critical bearings in a vehicle. Because the bearing seals contribute to reducing friction, they also reduce power losses. If a bearing seal gives out during a race, it will result in serious power loss and one failure after another as related systems are impacted.

Sealing Challenges in Performance Motorsports

While there are challenges in the specification of seals for any automobile, the challenges are more complex and constraints far more stringent in the design of high-performance automobiles. When the ability to shave off a fraction of a second could make or break a successfully competitive design, weight becomes a major factor: every ounce counts when trying to maximize speed and minimize losses for Indy Car, Formula 1, NASCAR, Rally, and CART vehicles.

Reliability is extremely critical for racing: when a car is moving at extreme speeds, small problems can lead to massive disasters and potential death. And reliability is just as vital for endurance and off-road races where the ability to survive in rough conditions is part of the competition.

When vehicles are moving at the extremely high speeds involved in racing, everything becomes more intense and that includes vibrations and shock loadings. And for off-road competitions, the impact loadings are even more intense. Racing seals must be able to also retain their ability to exclude contaminants and retain media (whether its fuel or lubricant) even in the presence of these extreme loads.

Dynamic seals must also be able to handle continuously higher speeds than an average automotive seal, which can make the choice of materials even more challenging. The coefficient of friction and ability to dry lubricate (as is seen with materials such as PEEK and PTFE) becomes even more important. There are also extremes in both pressures in temperature that require seals with dimensional stability, often requiring spring-energized or labyrinth seals.

Chemical inertness is also vital, especially as some newer fuel additives for racing cars have proven incompatible with rubber hoses. Materials like PTFE and PEEK are chemically inert, but it is very important to check material compatibility before moving forward with a seal design.

Another challenge faced when designing seals for high-performance automobiles lies in available space: to keep weight down and ensure that the vehicle is aerodynamic, compact sealing solutions that take up a minimal amount of space are required. 

Solutions for High-Performance Automotive Seals

When designing seals for high-performance automotive applications, advanced polymer seals should be seriously considered. Polymer seals weigh a fraction of their metal counterparts and less than elastomeric seals. They involve far less friction and can be just as rugged and durable as well. Because materials such as PEEK and PTFE are dry-running and self-lubricating, they can sometimes eliminate the need for a bearing. Performance polymers also include additives that enhance the properties of a polymer, increasing its stiffness, impact resistance, and dimensional stability as well as reducing friction. 

Polymers are far less susceptible to corrosion than their metal counterparts and, when the right polymer is chosen, are less susceptible to chemical attack than elastomers. Polymers also lend themselves more readily to manufacturing with complex geometries than metals and offer more freedom as far as manufacturing methods than elastomeric materials. 

Engineering polymers also provide the resistance to wear, strength, and stiffness needed in the rugged environments and demanding operating conditions of racing. And the use of polymer seals as opposed to metal seals reduces problems with metal-to-metal contact such as galling and abrasion. Note, however, that in many instances, the seals required for high-performance automobiles must be custom-made to achieve the necessary level of performance while staying within design constraints. 

Conclusion

The design of high-performance automotive seals can be extremely challenging and many engineers are turning to polymer seals to effectively meet those challenges. Engineering polymers such as PEEK and PTFE, including the variety of grades and fill options available, are an excellent solution to many seal designs.

Last year the COVID-19 pandemic swept across the globe. It affected many industries, one such industry being the motorsports industry, with events and competitions having been canceled or postponed. But unlike other industries, this has not seemed to stop the motorsports industry, with it continuing to push the boundaries of automotive innovation, and finding new ways to improve upon high-performance vehicles as well as road-ready cars for the average consumer.

It has also provided innovation in the medical field, by developing new life-saving technologies.

And finally, while live races may have been canceled, the industry as looked to simulated races to increase viewership and ad revenue and found a new way to reach out to their fans.

In this week’s blog post, we will discuss the effects of the coronavirus pandemic on the motorsports industry, and how despite the hardship the pandemic brought, it refused to slow down and brought innovations, both automotive and medical, surprising uses for technology, and more.

Innovation in Electric Race Cars.

The COVID-19 pandemic has an obviously devastating impact on the automotive industry as a whole, with global light vehicle production declining by 18% during the height of the pandemic, there has been a ray of hope in the form of electric vehicles (or EVs).

And no one has been pushing the envelope further than the motorsports industry.

The sport seems an unlikely source of innovation in cleaner vehicles. But the racetracks and paddocks have often been a hotbed of design and engineering feats.

Formula 1 teams such as DuPont and Renault DP World F1 Team have spent 2020 looking at developments made on the racetrack, such as the modern Energy Recovery System found in Formula 1 cars, and using it to vastly improve upon road-ready, hybrid models that greatly reduce CO2 emissions and offer a fuel economy range of up to 217.3mpg.

Sim Racing

eNascar Racing During COVID-19

Many races were canceled last year due to the COVID-19 pandemic, leaving many fans disappointed. And the business of motorsports is, at the end of the day, a business of live events. It was a very challenging time for everyone in the industry.

In an experiment, NBC and Fox replaced the canceled races with sim races.

They were unsure if the computer-generated races would bring in as much money as the real races would. Their fears seemed to be unfounded, however, as ten months into the experiment sim races seemed to be paying off, as television and web audiences helped to salvage the 2020 season, pleasing networks and sponsors alike.

One such race was the eNASCAR race which drew in 910,000 viewers, which is admittedly fewer than the typical three million viewers on a typical NASCAR race, it was more than 400,000 of a typical virtual race.

Another race that blew past expectations was the first F1 replacement race, the Virtual Bahrain Grand Prix. It drew in a whopping four million total viewers on both digital platforms and tv, Once again, while that is less than the 34-million strong average for an actual race, it is far ahead of the typical 1.8 million viewers of previous pro digital races.

Project Pitlane

As demands for testing kits and ventilators increased during the COVID-19 pandemic, governments across the globe have reached out to various industries to help with supplies. One such industry was the motorsports industry. And they stepped up to the plate to help ease the burden this deadly pandemic has caused.

Because, if there is one thing that the motorsports industry is famous for, it is designing, building, and testing components and cars in incredibly short timeframes. And that is what they did with Project Pitlane.

At the height of the pandemic, UK-based manufacturers for Formula 1 put aside old rivalries to combine their resources to support health services and victims of COVID-19. This project became known as Project Pitlane.

UCL-Ventura

UCL-Ventura

In connection with the University College London, Mercedes HPP helped develop the UCL-Ventura, a respirator that works by pushing an air-oxygen mix into the mouth and nose at a continuous rate. This keeps both airways open and increases the amount of oxygen entering the patient’s lungs, a huge boon for COVID patients.

They didn’t stop there, however. Mercedes disassembled and reverse-engineered an off-patent device to improve its manufacturability to make it more suitable for higher production runs. In a little over a month, Mercedes had produced 10,000 units.

The UCL-Ventura has now received MHRA regulatory approval and is available to download for free at a research licensing website developed by UCL Business.

Blue Sky

Renault F1 in conjunction with Red Bull Advanced Technologies developed another ventilator, the Blue Sky portable ventilator.

They took the device from a prototype, which included miniature servos from a model aircraft, to a fully developed, certification-ready product.

Unfortunately, the UK government canceled the order for Blue Sky ventilators before the device was able to go through certification.

In Conclusion

Like many industries, the motorsports industry during Covid-19 has had to change dramatically. Unlike other industries, the motorsports industry, is, by it’s very nature, incredibly adaptable. This has served it well, leading to innovations in electric vehicles.

This drive has also led to innovations in the medical industry with the development of new life-saving ventilators, as well as the increased production of ventilators and other life-saving medical necessities.

And finally, let’s not forget the increase in popularity of virtual racing.

The motorsports industry is the pinnacle of automotive innovation, as it demonstrated in 2020. And as we dive further into 2021, it is clear that, like the race cars it produces, it has no signs of slowing down.

To learn more about how Advanced EMC Technologies can provide your motorsports company premium polymer seals, bearings and bushings, contact us today!

Image from AGC Chemicals

While the vast majority of people have never heard of fluoropolymers, they are everywhere in our lives. It is undeniable that because of their durability and versatility, this particular group of polymers is one of the most popular polymer materials to date. In this week’s blog post, we will explore this wonderful material, from its history to its uses.

What is a Fluoropolymer?

To start, let’s go over what a polymer is. A polymer is a material made of long, repeating chains of molecules. The materials have unique properties depending on the type of molecules being bonded.

A fluoropolymer is a fluorocarbon-based polymer with multiple carbon-fluorine bonds. It is characterized by high resistance to solvents, acids, and bases. The first, and best-known, fluoropolymer is polytetrafluoroethylene, also known as Teflon.

While Teflon is arguably the most famous fluoropolymer used today, it is certainly not the only one. Other popular fluoropolymers include:

• PTFE (Polytetrafluoroethylene)
• PFA (perfluoroalkoxy alkane)
• FEP (fluorinated ethylene propylene)
• ETFE (ethylene tetrafluoroethylene)
• PVDF (polyvinylidene fluoride)
• ECTFE (ethylene chlorotrifluoroethylene)

These may also be known by their brand names, including Excalibur, Algoflon, Xylan, Solef, and Fluon.

They also come in several different forms, making them well suited for several different applications. These forms include granulate, melt-processable, films, pastes, and dispersions.

Fluoropolymers are also used as a coating for products made of other materials. More on that later!

History of Fluoropolymers

While mineral fluorides were known as early as the 16^th century, modern fluoropolymers were not discovered until the early 20^th century. Fluoropolymers, as we know them, were first discovered in the form of polytetrafluoroethylene, better known by its brand name Teflon, or by its abbreviation PTFE.

It was discovered entirely by accident when in 1938, Roy J. Plunkett of Dupont accidentally froze a compressed sample of tetrafluoroethylene. This gaseous material became a white, waxy, and solid form that would, in 1945,  become marketed as Teflon.

Since than, of course, other fluoropolymers have been introduced, such as:

• FEP in 1960
• EFTE in 1970
• PFA in 1972

In 1985, Dr. Plunket was introduced into the National Inventors’ Hall of Fame, where he joined the ranks of distinguished scientists and innovators such as Louis Pasteur and the Wright Brothers.

Benefits of Fluoropolymers

Fluoropolymers are a unique group of materials with many benefits that make them well suited for a variety of applications.

Chemical Resistant

Fluoropolymers have a very high resistance to chemicals and solvents. This allows them to be used to seal or contain hazardous materials.

Electrical Resistant

With the ability to insulate up to 5,000 volts, Fluoropolymers make excellent insulators for things such as electrical wiring.

High-Temperature Resistance

The typical range of temperatures that fluoropolymers can cover ranges from -328 degrees Fahrenheit all the way to 500 degrees Fahrenheit. With such a vast range, fluoropolymers are a perfect material for extreme environments.

 Low Friction (AKA Non-Stick)

Because they shed a molecule every time something passes over them, fluoropolymers are incredibly smooth and thus incredibly non-stick. This property has made them popular with cookware manufacturers.

Non-Toxic

The smooth surfaces of fluoropolymers are non-microbial, which makes them suitable for use in the food, beverage, medical, and pharmaceutical industries.

Other benefits include:

• Durable
• Self-cleaning
• Corrosive Resistant
• Non-Flammable
• UV Resistant

Cons of Fluoropolymers

Price

Unfortunately, such a versatile material comes at a higher price point. Fluoropolymers are often more expensive to produce than other materials, and even other polymers, or plastics.

Production Sizes

Fluoropolymers are relatively more difficult to process and manufacture, and can not be as easily mass-produced as other materials.

Can Shape Under Pressure

Elevated pressures and temperatures can affect their surfaces and cause them to bend and bulk.

Extremely High Temperatures

While it can withstand high temperatures and is resistant to chemicals, it can melt at 680 degrees Fahrenheit, making fluoropolymers unsuitable for molten environments.

Other cons include:

• Cannot be Cemented
• Unweldable
• Decomposition Product Toxic

Uses of Fluoropolymers

Fluoropolymers are used in a wide variety of industries and applications, from the industrial to every day.

Industrial Applications

Because of their many benefits and versatility, fluoropolymers are frequently used in the industrial space.

The non-stick and chemical resistance makes them well suited for use in the processing of hazardous materials such as chemicals. This is particularly common within the oil and gas industry.

They are also popular materials with which to make machined parts. Because they are very durable on top of their aforementioned versatility, many manufacturers use fluoropolymers to make parts for machines, such as seals, backup rings, bushings, bearings, and canted coil springs.

Fluoropolymers are popular in the automotive industry, where fluoropolymer coatings help to prevent friction and corrosion in car parts. Another popular application is with the aerospace industry, where fluoropolymer coatings are applied to the wiring insulation.

Non-Industrial Applications

Fluoropolymers are also fantastic for the average consumer. Many everyday products are on the market today that use some form of fluoropolymer.

Teflon, or PTFE, is particularly popular. If you have a nonstick pan in your home, chances are it is made from Teflon. It is also used in waterproof clothing such as rain jackets and hiking shoes, self-cleaning ovens, microwave popcorn bags, pizza boxes, and more.

The demand for fluoropolymers is high. In fact, in 2011, it hit $7.25 billion. Thanks to innovative engineers, new uses and applications are constantly being developed.

In Conclusion

Fluoropolymers are one of the most versatile materials on the market. With high durability, high-temperature range, low-friction, and nontoxicity, fluoropolymers are often some of the best materials to choose for your project.

And if you need fluoropolymer products, Advanced EMC Technologies is the premiere one-stop solution. We provide many types of custom-made fluoropolymer products, including PTFE. We pride ourselves on being able to provide accurate, on-time solutions when you need them most.

Contact us today for more information!

Premature seal failure is a major problem that leads to expensive downtime as well as the potential for equipment damage, environmental impact, and even physical harm. When a seal does fail prematurely, it is important to track down the root cause of failure to prevent it from happening again with a new seal.

Normal Wear

All seals are going to experience normal wear and eventually reach the point where they need to be replaced. The signs of normal wear include an even, glossy circumferential pattern on the seal lip and on the hardware and a relatively small protrusion on the heel of the seal at the extrusion gap. 

When high pressures are involved, normal wear also entails circumferential wear patterns (which will be over a larger area) and a protrusion at the extrusion gap (which matt also be larger). In addition, grooving may be present on the sealing surface. While normal wear cannot be prevented, it can be minimized through proper installation and maintenance.

Shaft Surface Hardness

If the hardness of the contact surface of the shaft is not sufficient, excessive wear is likely to occur. In most cases, the shaft surface hardness should be at Rockwell 30C at minimum. In situations where there can be issues of the shaft being nicked or scratched prior to installation, operating speeds in excess of 15 fps, or the potential for abrasive contamination exist, then the minimum hardness should be 45C. In addition, the surface hardness should penetrate to a depth of 0.3 mm. If the shaft cannot be hardened enough, then a wear sleeve should be considered.

Signs of surface hardness issues include radial grooving with embedded metal filings and either axial or circumferential scratches on the dynamic surface. This type of damage can be prevented by ensuring that the shaft surface meets the appropriate hardness requirements for the application and seal jacket material.

Shaft Surface Finish

Another potential cause of premature shaft failure lies in the surface finish of the shaft because the sealing lip makes direct contact with the shaft. For most applications, the surface finish of the shaft should be between 10 and 25 𝝁in Ra but that is highly dependent on the seal material chosen and the shaft material. For example, PTFE is a dry-running material that needs a certain level of roughness on the shaft in order to create a low friction barrier between the materials and serves as an additional seal barrier.

In addition, there should be no machine lead (helical scoring or spiral lines). The presence of a lead can not only abrade the seal lip but can essentially act as a pump and lead to leaking. A lead essentially serves as a leak path, which is never a good thing.

The signs of having too rough a mating surface include radial grooving with metal filings embedded, axial nicks on the seal lip, and/or axial scratches on the dynamic surface. The appropriate surface finish and removal of the machine lead can both be accomplished through careful plunge grinding,

Chemical Compatibility

It is extremely important that the seal material chosen is compatible with the media it will be exposed to during operation. And when the media is changed, that can often necessitate a change in seals. Furthermore, media includes not just what is being sealed but the type of lubricant used with the seal. Signs of chemical incompatibility include cracks or holes in the seal jacket, pilling, corrosion, and/or circumferential grooving of the dynamic surface.

When issues with chemical compatibility arise, the best solution is to choose a seal jacket material that is chemically compatible with the media and the lubricant. While the base fluid may be compatible, lubricant additives may cause problems.  If lubricants are the problem, keep in mind that materials such as PTFE and PEEK are both highly chemically compatible and self-lubricating so that no lubricant is needed.

Compression Set

Compression set occurs when a seal has become less elastic, resulting in leaks even at low pressures. If this is a regular occurrence, it might be wise to choose a different polymer for the seal jacket. The primary sign of the compression set is a flat-sided seal cross-section where the flat side corresponds to contact with the mating surface.

High Pressures Extrusion

At high pressures, seals can be forced into the extrusion gap where the seal will experience excessive wear and may eventually be torn apart. The best approach to preventing damage resulting from high pressure is to use a thermoplastic seal in place of an elastomeric seal or to use a BUR (Back-Up Ring) to prevent extrusion.

Improper Installation

One of the most common causes of premature seal failure is improper installation. Using the right tools will help prevent common issues such as installing the seal backwards or damaging the seal during installation. 

Another common source of seal failure that is typically related to installation is misalignment and runout. This is caused when either the shaft or seal is out of alignment. In some cases, the alignment issues may not be apparent until the shaft is rotating. The signs of damage related to misalignment include an even pattern of wear on the seal lip with one part that is more heavily worn, heavy wear on one side of the seal, an offset wear pattern, or a combination of high and low wear spots.

The key to preventing failure associated with installation is quite straightforward:

• Follow any instruction provided by the manufacturer
• Use appropriate tools
• Verify that the seal is being installed in the right direction
• Check for any sharp areas that could damage the seal
• Ensure that the shaft and the seal are properly aligned

Conclusion

Premature seal failure does not have to be a repetitive cycle if the root cause is detected and addressed. However, just replacing a seal without tracking down the cause will simply mean high M&O costs and unnecessary downtime. By inspecting a failed seal, it is possible to narrow down what caused the failure and take steps to prevent it from happening again.

Spring-energized seals are able to provide reliable, consistent sealing where other seals fail. The key to their performance lies in the additional sealing force made possible through a spring, but not all springs provide the same type of performance. In this blog post, we are going to talk about the four most common types of spring energizes: canted coil springs, cantilever springs, V springs, and helical springs.

Canted Coil Spring

Canted coil springs are wound at an angle to the axis along the length of the spring. They are able to maintain a very consistent force of over a wide deflection range, which contributes their popularity as a seal energizer. The load is primarily applied at the tip, which is excellent for sealing unless abrasive media is involved.In addition, these springs can be tailored to achieve specific forces. They are ideal for applications where friction needs to be minimized, including flap actuators and encoder and are often found in applications that involve dynamic rotary or reciprocating motion. Canted coil spring energizers work best for moderate to high speed rotary applications.

Cantilever Springs

Cantilever springs, also known as finger springs, have a v-shaped cross-section.These springs have a linear load curve (deflection and force as linearly related). Because of their shape, the load is concentrated at the very front of the seal which makes them a good choice for exclusion  and scraping applications. Spring-energized seals with cantilever springs work well for low to medium speed applications and can be found on hydraulic cylinders, pumps, shocks, and compressors.

V Springs

The V spring, also called a V ribbon spring, is a general purpose energizing spring that provides good performance at a relatively low cost.  which offers good performance at a relatively low cost.  V spring energized seals are well adapted to severe applications, including vacuum pressures and cryogenic temperatures. These seals work well for applications that involve either rotary or reciprocating motion, but also perform well in static applications. In short, V spring energizers are ideal for general purpose applications.

Helical Spring

The helical springs, sometimes referred to as a helical wound spring, consists of a wound ribbon of metal that results in a relatively high load versus displacement curve, which also means their deflection range is quite small. Because of this, it can provide very tight, reliable sealing even in the presence of extreme pressures (including vacuum). Helical spring energized seals also work well for sealing in lightweight gases or liquids. However, they should be limited to either low speed, intermittently dynamic, or static applications where achieving a reliable seal is significantly more important than the effect of friction or the possibility of wear. Helical spring energizers are often used on pipe flanges and crush jackets where the seal jacket needs to be embedded into any surface irregularities.

Full Contact Spring

A Full Contact Spring provides a high-load, continuous spring contact along the entire circumference of the sealing lip. A full contact spring is recommended for extreme sealing conditions, such as those involving cryogenics, vacuum and/or light gases at low pressure. Because of its extreme chemical resistance and temperature applications, it is recommended for high-altitude aerospace and even space exploration missions. 

Conclusion

If you are looking for a sealing solution involving an application where other seals have failed, spring-energized seals are an excellent option. Not only do you have flexibility in the choice of sealing jacket, you can also find spring energizers adapted to the particular challenges you are facing.