Innovations in Seals and Gaskets Boost Reliability

New designs and materials overcome high temperatures, pressures and aggressive media

In the chemical process industries (CPI), standard equipment is often capable of working universally across many applications. However, this same notion does not apply to the sealing elements used in chemical processes, where it is imperative that seals and gaskets not only suit the application, but can also safely handle any environmental variables, such as aggressive media, high temperatures and pressures and cleaning regimes. Fortunately, advanced seals and gaskets are being developed that overcome CPI challenges to ensure a proper seal that encourages the highest reliability in a variety of traditional and emerging applications.

“Each industry faces its own inherent challenges specific to its processes, but the overarching challenge across all industries and applications is to increase the plant’s overall reliability,” says Alan Evans, global director, product line management for the mechanical seal business with A.W. Chesterton (Groveland, Mass.; www.chesterton.com). “Reliability touches on sealing concerns, such as aggressive temperatures; high pressures and temperatures; emissions; and health and safety and impacts the financial performance of the plant. Sealing challenges are tied into plant reliability, but it isn’t until there is a good understanding of what causes failure that you can begin to mitigate these challenges.”

 

Enhanced reliability

The best way to understand and address these challenges is by realizing that seals and gaskets are part of the overall system in which they are contained, continues Evans. “Nothing operates in isolation,” he says. For this reason, sealing device designers and manufacturers are striving for a better understanding of the factors that contribute to failure and are trying to mitigate the impact on the sealing device itself to provide better operating life and reliability.

“Part of our engineering team’s philosophy is to design for reliability,” notes Evans. He explains that there are five key features that help mechanical seals operate more reliably and that Chesterton is building these features into new sealing products, as follows:

• Protected springs to maintain free motion within the seal between the rotary and stationary seal faces
• Balanced design to decrease the amount of pressure applied to the seal faces from the sealed fluid to reduce heat generation, minimize distortion and increase the operating envelope of the seal
• Non-fretting design so the machine or internal metal components of the seal are not damaged in a way that interrupts the seal’s operating capabilities and to improve the ability of users to replace wearable parts and return the seal to operation versus having to purchase a new seal
• Monolithic seal faces so the seal face is composed of one homogeneous material to reduce the effects of temperature distortion, which will limit the seal’s performance concerning leakage and lower emissions performance
• Stationary design so the seal only makes one adjustment to misalignments that are inherent to all rotating equipment

Recently, Chesterton released a line of high-performance seals that incorporate these features. Chesterton’s 1810 (Figure 1) is a scalable mechanical sealing solution that can be used in a variety of pumps to provide a reliable and economical sealing solution. The 1810 mechanical seal can be configured with several different face profiles and auxiliary components for demanding applications. For example, a hydropad face option can be applied for use in hot process media or a line-to-line face option may provide greater sealing security in chemical slurries. Meanwhile, the 2810 is a double seal with advanced features that provide superior emissions control, safety and reliability. Suitable for sealing hazardous or dangerous process fluids, the 2810 offers a patented diffuser sleeve that increases buffer/barrier fluid flowrates and disperses the cool fluid directly at the seal face interfaces, collecting and removing the hotter fluid and transporting it back to the seal tank system.

Another development aimed at providing a tighter and more reliable seal is the ability to accommodate more complex geometries, says Tom Rimel, president at Stockwell Elastomerics (Philadelphia, Pa.; www.stockwell.com). “Traditionally, O-rings and circular shapes were the common offerings, but there are often intricate patterns that require cutting materials or using multiple seals or gaskets around a complicated shape,” explains Rimel. “But recently we’ve been able to provide more complex geometries using waterjet cutting, CNC flash cutting and a variety of 3-D molding capabilities [Figure 2]. This allows us to provide seals and gaskets in more intricate shapes for applications in controls equipment, valve actuators and sensors, and provide a better seal around a complicated shape without using multiple gaskets. Because the ability to provide complex geometries enables a tight seal using a continuous piece of material versus multiple gaskets, which tend to leave a seam and reduce the reliability of the seal, it is a game changer in many applications.”

 

Innovations meet challenges

While seals can be designed to provide higher levels of reliability, it is sometimes still a challenge to find a seal that not only meets the needs of the application but also the demands of the environment in which it will operate, says Oliver Cann, product and engineering director with Vulcan Seals (Sheffield, UK; www.vulcanseals.com). “A lot of processors specify seals to suit the direct application with which they are working, but there are a lot of other variables to consider,” he says. “It is possible that the material that is ideal for the media doesn’t jive with the temperatures, pressures or cleaning process, which can make it difficult to effectively specify a commercially viable or commercially reasonable sealing technology that covers all the application parameters.”

As a solution, Vulcan Seals offers encapsulated seals in a variety of materials. “Our FEP- (fluorinated ethylene propylene) and PFA- (perfluoroalkoxy alkane) encapsulated seals [Figure 3] are resistant to a wide range of chemicals and serve as a universal O-ring that can work in a variety of applications,” notes Cann. Vulcan’s encapsulated seal products are O-rings that are bound by a seamless and uniform FEP/PFA encapsulation, which encloses an elastomeric core, completely protecting it from the media. They combine the energizing properties of an elastomeric O-ring with the resilience to extreme temperature and hostile chemicals provided by FEP/PFA.

“The rubber creates a unique energy whereby under compression it creates load, which is essential for creating a pressure-tight seal that is able to block a barrier while also allowing the use of a highly inert and chemically resistant material as the contact barrier,” explains Cann. “Traditionally a PTFE (polytetrafluoroethylene) would be the commercially viable seal material used in difficult applications, but it doesn’t provide the energy that is achieved via the rubber elastomer core. Here, we get the energy needed from the rubber elastomer, but protect it with a highly resistant barrier and use a process to make the encapsulation around them seamless to provide a leak-tight seal that resists damage from chemicals and other process variables that are common in the chemical industry.”

Another sealing challenge in the CPI is the requirement for cleaning-in-place (CIP) and sterilization-in-place (SIP) regimes. Often, seals that suit the other aspects of the application cannot withstand the demands of these processes, making it difficult to find a reliable seal, especially in food-and-beverage applications.

“The sealing environment for food-and-beverage processing is one of the most demanding,” says David Kaley, global segment manager with Trelleborg Sealing Solutions (Trelleborg, Sweden; www.trelleborg.com). “Seals are essential to food safety, ensuring that contaminants do not come in contact with the food. Seal failure can lead to potential contamination, resulting in line stoppages, recalls or, in the worst case, harm to consumers. Materials, whether elastomer or plastic, must cope with the processing of a broad variety of food types along with CIP and SIP regimes, which can quickly destroy incorrectly specified seals. On top of this, seals must comply with various global food contact regulations.”

To provide sealing solutions that meet the needs of food-and-beverage processors, Trelleborg offers a family of EPDM (ethylene propylene diene monomer) rubber materials, specifically designed to meet the unique requirements of the food-and-beverage industry. Called the FoodPro EPDMs [Figure 4], the seals comply with the most comprehensive global food contact material regulations, are suitable for use with virtually all food and beverage products and can withstand harsh CIP and SIP processes. They are compression and injection moldable, which means they can be used for O-rings, static seals and engineered molded parts, and they offer dynamic properties with improved tensile strength, reduced elongation and tear and wear resistance.

 

‘Green’ energy applications

Innovation and developments in sealing technologies come at a time when they are needed in new applications surrounding the burgeoning green energy market.

“Sealing technologies help simplify energy transition for process industries,” says Leo Konradsson, global segment manager, power and process industries, with Roxtec International AB (Karlskrona, Sweden; www.roxtec.com). “Oil-and-gas companies are making moves to upgrade their operations to reduce their carbon footprint and, for many energy providers, energy transition is moving higher on the agenda every year. When adding units for hydrogen, carbon capture and biofuels, they need safety and quality, as well as sealing expertise within these energy transition projects. And while sealing products may be small components in large capital projects, they play an important role in safety and serve as important solutions for any operation that handles explosive and flammable gases.”

Further, for decarbonization projects, seals are used in hydrocracking units, electrolyzers and biofuel plants handling renewable natural gas (RNG), steam methane reforming is) and dairy manure, as well as in e-fuel production facilities and carbon-capture units. They secure green-hydrogen-generation plants attached to ammonia and fertilizer plants. “In these applications, Roxtec seals are installed around cables and pipes in buildings, containers and cabinets and provide approved solutions for hazardous locations,” says Konradsson. “As with any hazardous industry, the main concern and top priority is safety and reliable operation. The risks of production disruptions, severe accidents and worst-case loss of life must be minimized and avoided. This is done by using seals that prevent potentially explosive gases from entering cabinets and equipment in ATEX-classified areas, as well as by protecting buildings from fire and ingress of water.”

In answer, Roxtec provides HD EX transit solutions (Figure 5). “HD stands for high density and refers to the high number of cables that can be safely routed through a minimum area of a cabinet,” explains Konradsson. “This migration from traditional cable glands has resulted in smaller and lighter cabinets, which saves money, time and space in projects. These seals also allow for late cable changes and modifications without having to do drilling or welding on site. Users simply open the seal, route the new cable through and use the compression unit to seal the opening again. Roxtec seals can be used with both standard and armored cables. The BG (bonding and grounding) modules come fitted with an integrated copper braid, which bonds the armor in accordance with Underwriters Laboratories Standard UL 514B.

Also realizing the need to create seals that are compatible with the green-energy movement, Chesterton has a dedicated research and engineering team that works on designs to meet the specific requirements of these types of applications. “For example, we have designed and implemented a gas-operated seal for a new green-energy technology that extracts energy from a plant’s waste-steam streams,” says Evans. “This energy is then put back into the plant’s electrical system for reuse, both saving the plant money and reducing their waste energy stream for greater sustainability and reduction of their carbon footprint.”

And, the fuel-cell market is also necessitating the use of novel sealing technologies, as well, says Stockwell’s Rimel. For example, fuel cells, which are a growing technology in decarbonization efforts as they are devices that generate electricity through an electrochemical reaction rather than combustion, require gaskets that offer temperature resistance, strength and inertness, says Rimel. Stockwell offers platinum-cured silicone rubber that can be molded into flat, window gasket configurations or made with added sealing beads for these applications. Fuel-cell gaskets of this material can be die cut, waterjet cut or molded to custom geometries as needed and offer improved compression set properties. “The improved compression set, along with the purity of the platinum-cure silicone have found favor with the fuel cell industry,” he says.

Similarly, he says, electric vehicle (EV) batteries require a lot of seals, because most of the structures have multiple layers of materials that must be built into a self-contained unit. “EV batteries can have issues with heat buildup and, if there is too much heat, it can degrade the battery and shorten its lifespan, or worse, generate fire that must be prevented from spreading,” he explains. “There are opportunities there for elastomers, membranes and other materials that deliver specified performance. The seals and gaskets in these applications must have different fire ratings and temperature ranges than traditional automobile seals and gaskets.”

He continues: “As we continue to see more green and sustainable technologies, there will be a call to provide different seal and gasket materials and technologies to match the needs of these niche applications.”

Joy LePree