Dissolvable and degradable materials are used in oil and gas operations to create high pressures in hydraulically fractured wells, while also minimizing well intervention keeping wells flowing and preventing blockages. These materials are designed to withstand the high pressures and temperatures that are experienced during an application, and then gradually break down into tiny particles that do not need to be recovered. Because these materials naturally dissolve or degrade, operators are not required to run a wire line down the hole to drill them out — saving considerable time and reducing costs.
These innovative materials are gaining popularity in the oil and gas industry. As competition increases in the global energy market, producers seek technologies that will reduce costs and improve well efficiencies. It has been estimated that over the next two to three years, greater than 30 percent of well servicing and stimulation consumables will be dissolvable products (currently less than 10 percent).
Advantages of dissolvables and degradables
Dissolvable metals and degradable elastomers replace the traditional composite products used in completion operations and can be customized to the application, including diameter, composition, strength, and rate of dissolution for common wellbore fluids. More operators are using aluminum-based materials because they are stronger than magnesium alloys, allowing much smaller overlaps (1.8 percent) in ball and seat applications. Thermoplastic elastomers have consistent high tensile strength and elongations for ambient and elevated temperatures, which provides customers with consistent performance over a wide range of temperatures. Parker’s degradable elastomers can be custom designed providing specific engineered shapes meeting the customer’s needs.
Advantages of dissolvables and degradables include:
Dissolvable metals and degradable thermoplastics and elastomers must perform in harsh, corrosive down-hole environments in oil and gas wells. Parker’s dissolvable and degradable products are made with metal, thermoplastics, and thermosets (elastomers), providing operators with a wider range of material options. For example, Parker offers frac balls in delayed-reaction coatings such as Teflon, nickel, and epoxy. Our 94-Series provides a smooth C2-inhibitive coating with no cracks, rough spots, or nodules, which reduces corrosion and extends life cycle.
Because of our comprehensive range of material offerings, Parker can be an operator’s single provider of dissolvable products, allowing customers to reduce their vendor base. Parker also provides customers with inventory management options, further streamlining operations. Proprietary rate of dissolution (ROD) calculators are derived from broad-spectrum dissolution testing on our dissolvable metal products and are a handy tool for optimizing frac design and product selection for specific well conditions.
Parker engineers work with oil and gas design teams around the world to customize dissolvable and degradable materials for specific applications. Our proprietary materials are compounded in-house; this also allows us to provide quick-turn delivery production orders and sample requests in a matter of days, including optical inspection to ensure tight tolerances, custom labeling, laser marking, and packaging services.
Parker’s dedicated oil and gas sealing experts, dedicated development labs, and processing equipment are at the forefront of emerging applications for dissolvable/degradable technologies in the energy field. For more information, or to discuss your project needs with a Parker engineer, visit us at OTC, booth #3639. Not attending? Visit our webpage to learn more about our high-performance sealing materials for oil and gas applications.
Now, watch this video to find out more.
This article was contributed by Dana Severson, regional sales manager - oil & gas, Engineered Materials Group, Parker Hannifin.
My grandpa used to have a rusty, old air compressor in his shop. As a child, when my siblings and I would visit him, he’d use it to power air wrenches, grinders, and inflate flat soccer balls for us. I noticed it had a port labeled “ADD OIL DAILY” that was covered in the same thick layer of greasy dust as all the other unused junk in his shop. Knowing my grandpa, if asked about adding oil he probably would have said, “Oil is expensive. That’s how the companies get ya!” The compressor’s seals leaked so badly, you could hear the hissing even over the loud motor. I was certain one day it would explode.
Pneumatic tools are common in factories, tool shops, and DIY garages around the world. Using compressed air for power is convenient, simple, and — when maintained properly — safe and efficient. However, air treatment costs can add up fast. Traditional rubber seals used in air tools require clean, low moisture, compressed air with the proper amount of lubrication added. Good Filter/Regulator/Lubricator systems (FRLs) cost as much as the tools themselves! So, what would happen if we didn’t have to provide pristine air?
Today we have the technology to create seals for tools which don’t require daily or even yearly upkeep. You’ll find these tools labeled “maintenance-free,” which sounds great to the guy responsible for maintenance. It sounds even better to the guy paying for maintenance … and to engineers designing tools who want to keep warranty costs down.
Seal materials for dry running
Early pressure seals were made out of leather. My grandpa’s compressor probably wasn’t that old, but even since his time, we’ve come a long way.
When I’m asked for seal recommendations in totally dry-running applications, my mind clicks to a material called PTFE (chemical name polytretrafluoroethylene). Most people know PTFE by the brand name Teflon®1 and are familiar with its use when applied to cookware as a high temperature, slippery, non-stick coating.
PTFE is a semi-hard plastic which feels slick to the touch thanks to its low friction properties. It’s considered self-lubricating because it leaves micro deposits on the sealing surface and reduces friction after just a few strokes. Because of this, it’s good for high-speed sealing and can operate completely dry.
By adding fillers to PTFE, seal manufacturers can tailor materials for greater suitability in meeting performance requirements for a wide range of conditions. String-like additives including fiberglass and carbon fiber increase pressure rating, wear resistance and seal life. Dry lubricant-type additives such as graphite or molybdenum disulfide (MoS2) further increase a seal’s ability to run without lubrication, and at higher speeds and pressures. In pneumatic medical, pharmaceutical, and food processing systems, clean grade mineral-based strengtheners may be used as additives.
PTFE seals for dry running equipment are available in several profile configurations:
For more difficult dry-running applications, tougher engineered plastics such as Nylon, polyester, UHMW-PE, and PEEK are used.
Where cost is the over-riding factor, internally-lubricated rubber elastomer materials are recommended in common, standard profiles:
These common profiles are available in internally-lubricated XNBR (a tougher variant of NBR), which is my go-to rubber for low- and no-lube applications.
An air compressor was one of the first power tools I bought. I knew little about seals back then and just needed something to top off the air pressure in my car tires and power a nail gun. I purchased one advertised as maintenance-free because I am, after all, my grandfather’s offspring. Oil costs money.
Even though dry systems don’t benefit from the protective aide afforded by lubrication, the same set of “good seal design principles” apply whether the system is fully hydraulic, lightly lubricated, or completely dry. Let’s take a look at a few seal design concepts and elaborate on how a lack of lubrication affects them.Speed and pressure
The sliding movement of seals generates heat through friction. Rub your hands together and they get warm. Rub them faster or press together harder, and they get hot quicker. Excessive heat is the enemy of seals; they begin to soften and wear out faster. We counteract this by using tougher materials which can handle the temperature. Alternatively, we can design methods to cool the system.
Pneumatic systems are unique in that they either pull air from outside (compressors) or vent to atmosphere (tools and cylinders). Expanding gas has a small cooling effect on the latter.
Compressing gas generates heat, so compressors are a good example of a worst-case scenario. In addition, they operate at high speed and pressure. The housing of my compressor is covered with fins to help dissipate heat during long run cycles. Seal materials like PTFE, PEEK, and FKM (energizers) are often used because they can handle hot temperatures.Surface finish
Our catalog recommends a maximum surface roughness of 12 µin Ra for linear and rotary applications. PTFE will benefit from a smoother surface, creating a tighter seal and reducing wear. Applications where leakage is critical, like in cryogenics or when sealing explosive gases, a highly polished finish of 4-6 µin Ra is best.Surface hardness
A minimum hardness of 25 Rc is recommended for linear and rotary applications. Softer materials can be used in light duty applications, but the surface may wear or become grooved over time, especially in rotary applications.
Some PTFE fillers are abrasive. While tough fillers like fiberglass and carbon fiber provide superior wear resistance, we recommend a minimum surface hardness of 60 Rc to prevent abrasion of the hardware. Mild fillers such as graphite, bronze, and aramid fiber are okay with the minimum requirement of 25 Rc.Contamination
Dirty air is a problem in all pneumatic systems. If the system is exposed to contaminated air, or to a dirty environment, abrasive particles can accelerate wear of both the hardware and the seals. Using wear resistant materials (like fiberglass-filled PTFE) along with a hardened sealing surface will prolong the life of the equipment.
Seal geometry also plays a role here. Sharp-lipped profiles like our FBD-V FlexiSeal and PolyPak (SPP & DPP) prevent junk from building up under the seal lip and wearing it away. Filling the spring cavities of FlexiSeals with silicone is an option to make the seals easier to clean when used in extremely dirty environments that require equipment washdown.Fluid compatibility and moisture
Air and non-reactive gases like nitrogen are compatible with all seal materials (so long as they’re used within the material’s temperature capability range). Caustic gases like pure oxygen, chlorine, and hydrogen sulfide (H2S) will degrade many seal materials. PTFE is highly resistant to most forms of chemical attack and is a good choice when compatibility is a concern.
PTFE has one weakness and that’s water. The material is extremely hydrophobic. The protective layer that naturally deposits itself on the hardware gets washed away in wet environments. As a result, seals wear quickly. Carbon fiber-filled PTFE and UHMW-PE plastic are recommended in potentially wet applications.
Having helped design dozens of compressors, the geeky engineer side of me is waiting for the compressor I have at home to break so I can look at the seals. It is entirely possible, however, it will keep working for me for tens of years without failing and just maybe, will someday inspire a blog post from my grandkids.
As technology improves, customers are looking for tools which last longer and cost less to operate. At Parker, we are constantly working and testing to provide tougher seal materials and new designs to aid you in making better products. Take a look at our catalogs and reach out to us if you have questions. Thanks for reading!
Recommendations on application design and material selection are based on available technical data. They are offered as suggestions only. Each user should make his own tests to determine the suitability for his own particular use. Parker offers no express or implied warranties concerning the form, fit, or function of a product in any application.
1Teflon is a registered trademark of DuPont.
This article was contributed by Nathan Wells, application engineer, Engineered Polymer Systems Division.
Galvanic corrosion (also known as bimetallic corrosion or dissimilar metal corrosion) is the breakdown of metallic surfaces as a result of the difference in electrical potential of adjacent metals and the presence of an electrolyte.
Stated differently, when two dissimilar metals are in contact in a corrosive environment, one of the metals will begin to corrode. This process is the same one that occurs inside of a battery. The metal that will be corroded and the speed of this breakdown are dependent on the difference in metals and the environment.
Conditions for corrosion:
For galvanic corrosion to occur, three conditions must be met:
All metals have an electrical potential assigned to them, based on their nobility. Metals such as platinum, silver, and monel have lower corrosion potentials whereas metals such as copper, aluminum, and tin have much higher potentials. Any two dissimilar metals will have a galvanic mismatch and therefore a change of corrosion.
In situations of EMI shielding, the electrical path is inherently created by the conductivity of the gasket, coating, or sealant.
Examples of such fluids can include atmospheric humidity or salt fog environments. As this mist or moisture condenses and collects at the flange or gasket interface, it will create the electrolyte needed to start breaking down the metals.
Preventing galvanic corrosion while EMI shielding:
For aluminum substrates that are going to be exposed to harsh environments such as military and industrial applications, chromate conversion coatings (also known as chem filming) are recommended. On top of this coating would be a conductive or non-conductive top coat. For steels and coppers, nickel or tin plating is often used.
Corrosion-resistant conductive coatings, such as CHO-SHIELD 2000 series conductive paints, are developed with stabilizers to create a very conductive and galvanically inactive surface for high-level EMI shielding in harsh environments.Matching EMI gasket fillers to substrates
Because EMI shielding gaskets are in direct contact with structural metal substrates, the corrosion potential must be considered. Historically, conductive fillers have needed to adapt to increasing requirements of galvanic corrosion resistance. Only within the last couple of decades have filler systems such as silver-plated aluminum replaced traditional silver-plated copper or nickel-plated graphite, to dramatically improve corrosion resistance in enclosures that experience moisture and salt fog.Nickel-plated aluminum
Despite the excellent performance of silver-plated aluminum fillers, the development of a nickel-plated aluminum filler has set the gold standard for both EMI shielding levels as well as corrosion resistance. This filler system, utilizing inherently stable compounds, exhibits the best results on chem filmed aluminum flanges relative to any other filler system, with a 20-50% reduction even compared to silver-plated aluminum.
Design guide for corrosion control:
A properly designed interface requires a moisture-sealing gasket whose thickness, shape and compression-deflection characteristics allow it to fill all gaps caused by uneven flanges, surface irregularities, bowing between fasteners and tolerance buildups. If the gasket is designed and applied correctly, it will exclude moisture and inhibit corrosion on the flange faces and inside the package.
Follow the below steps to maximize corrosion resistance in enclosures:
Where other requirements are met, select nickel-aluminum filled elastomers for best overall sealing and corrosion protection.
Use silver-aluminum gaskets as the next best alternative to nickel-aluminum filled materials.
In aircraft applications, a “seal-to-seal” design can be used with the same gasket material applied to both flange surfaces.
Use a Co-extruded or Co-molded gasket – extruded or molded in parallel, these gaskets consist of a conductive and non-conductive elastomer in one piece. The non-conductive material is placed outboard to interface with the moisture, effectively minimizing a key condition causing galvanic corrosion.
Coat surfaces with a corrosion resistant plating.
Avoid designs that create areas for moisture to pool. Use drainage holes to allow liquids to flow away from the interface.
Avoid sharp edges or protrusions such as dovetail grooves that can damage gaskets.
Select the proper protective coating and use additional environmental sealants.
In order to conduct direct comparative shielding effectiveness testing of gasket panel sets before and after environmental exposure cycling in a standardized test set-up, Parker Chomerics established CHO-TP09. This test method is based on IEEE-STD-299 and takes into account environmental aging conditions such as salt fog, humidity, and extreme temperature cycling.
Proper enclosure design and the implementation of conductive filler systems engineered to minimize galvanic corrosion are key drivers in extending the life span of electronic enclosures and lowering long term maintenance/replacement costs.
EMI shielding gaskets such as conductive elastomer gaskets come in many different materials and almost a limitless number of shapes and sizes.
They are most commonly made of a base material of silicone or fluorosilicone with added conductive fillers such as silver, silver-plated aluminum, nickel-plated graphite, and others. Conductive elastomers represent one of the most versatile products in the category of EMI shielding gaskets.
From a manufacturing perspective, there are two key processes used to create these gaskets: splicing and molding. Check out the detailed list below for information about choosing the process that makes the most sense for you.Conductive elastomer gasket splicing
Conductive elastomer gaskets are often extruded in long strips, available in bulk or cut to specific lengths. To create custom sized O-rings, the extrusions are cut to the proper length and the ends are adhered (fused) together. Known as splicing, this process utilizes a proprietary adhesive to create an immensely strong bond.
Molding involves compressing uncured conductive elastomer material into a specially designed mold. The material takes the shape of the mold and retains this shape when cured.
Between molding and splicing, there is virtually an endless number of profiles and shapes that can be developed. For more information on choosing and designing an EMI shielding gasket, check out the Conductive Elastomer Handbook below.
This blog post was contributed by Ben Nudelman, market development engineer, and Scott Casper, applications engineer, Chomerics Division.
Have you had problems with your polyurethane seals degrading, especially when exposed to higher heat creating the need to replace your seals more often than you would like? As you probably know, seal replacement creates costly downtime that can be avoided if you have an appropriate seal for the job. Parker's Resilon® 4350 polyurethane is up for this task. Resilon 4350 is designed for sealing at higher temperatures up to 250°F continuous and can withstand short-term excursions of up to 300°F without leakage.Understanding the approximate temperature range of Resilon 4350
Resilon 4350 polyurethane was formulated to extend the high-temperature capability of Parker’s proprietary urethanes. Where current, more ordinary polyurethane seals have failed, Parker’s new Resilon 4350 has the highest temperature rating of any specialty polyurethane on the market. It was developed for applications where high temperatures or extended heat history cause failures with current polyurethane seal materials.
In a head-to-head comparison test at 250°F continuous, the Resilon 4350 material presented minimal leakage (< 5 grams) up to 250,000 cycles during a life test. This equates to a 33% longer lifespan compared to the standard 4300 material at this elevated temperature range (Figure 1).
Additional testing was completed showing the % seal force retention as the external temperature increased from about 160°F to 250°F. The three materials tested exhibited a linear relationship between the seal force retention and temperature. The Resilon 4350 had a 7-10% higher seal force retention beyond 4300 and the leading competitor of high-temperature polyurethane during this temperature range. The Resilon 4350 still exhibited a 20% seal force retention at 250°F (see Figure 2). Based on the results of this testing, this material is promoted as having a continuous operating temperature range of -65°F to 250°F.
Parker’s Resilon polyurethanes are provided in various profiles for use in a wide variety of applications. With the introduction of Resilon® 4350 the recommended operating temperature range for best performance can now be extended 20° to 25°F higher, giving design engineers the ability to push the envelope.
This article was contributed by Eric Woodworth, application engineer, Engineered Polymer Systems Division.
Technology advancements and new to world discoveries are constantly creating a new series of challenges for seal materials in the Oil and Gas industry. In today’s environments, seals are being pushed to perform in temperature, pressure and chemical extremes never before thought to be obtainable with rubber products. Application pressures exceeding 20,000 psi, service temperatures ranging from -40°F to upwards of 500°F and exposure to some of the most aggressive medias on the planet are placing immense amounts of stress on sealing elements. Parker’s FF400-80 compound has been formulated to provide a solution to all of these sealing challenges.Product features:
An Achilles heel of perfluoroelastomer (FFKM) compounds has long been lack of low-temperature flexibility and resilience. In a sealing application, the ability for a material to push back on the mating hardware is called resilience and is very important to prevent a leak. A method of measuring a rubber compound's low-temperature resilience is by performing a temperature of retraction test per ASTM D1329. See Parker’s O-Ring eHandbook for more information on low-temperature effects. Parker’s FF400 compound has a best in class TR-10 temperature of -23°F (-31°C). This property gives FF400 the low-temperature performance never seen before from an FFKM compound. The FF400 offers low temperature sealing capability approximately 45°F below a standard FFKM compound and has an overall recommended service temperature range of -40°F to 527°F. This low-temperature capability can be extremely valuable for surface equipment such as valves but can also give an advantage in high pressure applications where the glass transition temperature can shift causing a loss of resilience and flexibility.
FF400 also offers excellent resistance to Rapid Gas Decompression (RGD) damage. This compound has passed multiple industry standard RGD tests with perfect ratings of 0000 in multiple cross-sectional thicknesses. This characteristic is very important in applications such as compressors, valves, pumps, and various subsea equipment where a rapid reduction in gas pressures can cause significant damage to the seals. Having tested at multiple cross-sectional thicknesses, FF400 ensures that no matter the seal size the compound will resist damage caused by rapid gas decompression. It is very common for industry standard requirements such as NORSOK M-710, ISO23936-2, and TOTAL GS EP PVV 142 to be required by customers before a compound is considered for use in an application. Test reports and certifications can be supplied for FF400, as well as several other compounds, by Parker O-Ring and Engineered Seals Division’s Applications Engineering team.
Lastly, Parker’s FF400 compound provides an extremely broad compatibility spectrum for the harshest of oil and gas medias. Fluids such as crude oil, water, acids, aromatic hydrocarbons, bromides, brines, amines, and various gases are commonly seen in the oilfield and all can cause issues with rubber sealing compounds. However, one of the most common that is inquired about is compatibility with hydrogen sulfide (H2S) due to its toxicity, corrosive nature, and its presence of various concentrations in naturally occurring oil and natural gas reservoirs. Known also as Sour Gas, the higher the H2S concentration the sourer, more corrosive, and more aggressive the fluid stream becomes for sealing materials. Parker’s FF400 is a great option for these sour gas applications as it has the ability to resist chemical attack, and performs where H2S concentrations can be found at 20% and higher. All of these characteristics make the FF400 an optimal solution for use in compressors, pumps, valves, down hole tools, subsea chokes and other critical devices across the oil and gas industry.
For further information or to see how FF400 can benefit you, visit our website to chat with an engineer or give us a call at 859-335-5101.
For more than 100 years, the car has simply been used as a device for transporting a driver and passengers from point A to point B at speed with minimum effort.
With the introduction of Advanced Driver Assistance Systems (ADAS) and other semi-autonomous driving technologies, a different concept of the vehicle is emerging. In the future, the car will be a media playback center, telephone, office and extension of the home’s living room which also happens to be able to convey passengers from A to B.
This is having a profound effect on the characteristics and on the sheer number of electronics systems in new vehicles and this in turn will dramatically extend the demands on the EMI shielding devices used to attenuate the radiated emissions that could affect circuits in the car. EMI shielding materials will need to perform over a wide range of frequencies, in more applications as electronic systems take over more and more aspects of the car’s driving operations, while adding as little as possible to the weight of the vehicle.
The time for OEMs to consider the options for achieving EMC in new car designs is at the start of a new design project, before the electrical and mechanical features of the vehicle’s systems have been decided. This gives design engineers the opportunity to bring considerations of EMI and shielding devices into the design process and enable optimization of the size, cost and performance of EMI shielding in the final system.Top challenges of next generation 5G networks
The first challenge for automotive design engineers is the range of frequencies that need to be attenuated will be far greater in new cars than it was in the past. Until recently, the main frequencies of interest were the AM and FM bands used by radio and frequencies below 3GHz used by Bluetooth radio and mobile phone networks.
With the future introduction of 5G mobile phone network coverage, frequency coverage of EMI shielding materials will need to be extended. A higher frequency range is not the only issue. Cars are also going to support a much greater number of wireless communications systems within the vehicle.
The second challenge is that the effectiveness of EMI shielding is likely to be more tightly specified in the future as automotive manufacturers move towards a strict view of the functional safety of the electronics systems in cars, codified in the ISO 26262 functional safety standard.
So, what does this mean for the specification of EMI shielding materials?
Parker Chomerics maintains an intensive research and development program aimed at producing new filler materials for electrically conductive elastomer products. An important goal for this research program is to produce EMI gaskets that can cover the broader frequency range of interest in autonomous vehicles, while maintaining the desirable mechanical characteristics. Parker Chomerics CHO-SEAL conductive elastomers are widely used in automotive systems and offer useful properties, including resistance to high temperatures and contaminants, and the ability to provide environmental sealing to protect circuits from the ingress of liquids.
These elastomer gaskets resist compression set, accommodate low closure force, and help control air flow. They are available in standard sheet form, extruded or custom shapes.
In addition, Parker Chomerics CHOFORM Form-In-Place automated EMI gasket material can be dispensed directly onto castings, machined metal and conductive plastic and is widely used in tightly packed electronic housings. This advanced technology allows dispensing of precise positioned gaskets in very small cross sections and can free up valuable packing space of up to 60%. CHOFORM offers excellent shielding effectiveness which exceeds 100dB between 200 MHz and 12GHz.New opportunities for weight saving
The development of autonomous and semi-autonomous vehicles is leading to a huge increase in the number of electronics modules per vehicle. This increases the scope for car makers to reduce weight by replacing conventional metal housings with lighter conductive plastic housings. While the weight saving on each module might appear small, when multiplied across the 100 or more electronics modules, the total weight saving becomes invaluable.
Parker Chomerics PREMIER™ PBT-225 is a single-pellet conductive plastic for use in automotive housings. PREMIER PBT-225 offers excellent resistance to hydrolysis when exposed to extreme temperatures and provides for easy processing and uniform filler dispersion. As a result, EMI housings made from PBT-225 offer tightly controlled electrical and mechanical performance throughout complex geometries. A weight saving of 30% is also possible when replacing an equivalent metal or aluminium housing with PBT-225.
By collaborating early in development projects with Parker Chomerics, automotive system designers can ensure that their electronic and mechanical design is optimized for shielding purposes.
Learn more about Parker Chomerics EMI shielding and thermal solutions for the automotive Industry.
This blog post was contributed by Mel French, marketing communications manager, Chomerics Division Europe.
Honeycomb air ventilation panels are used in applications where superior electromagnetic interference (EMI) shielding must be incorporated with heat dissipation in the form of airflow. Every vent panel has a variety of design features, each providing benefits to end customers based on specific application needs. These design features can include framing, plating/painting, gasketing, and vent size control.
An often overlooked but highly important phenomenon to consider when designing EMI vent panels is that of polarity.
What this means is that honeycomb vents can have differences in shielding effectiveness, sometimes as great at 50 dB, depending on the direction of the electromagnetic waves.
For example, a basic aluminum honeycomb vent may provide shielding of 70 dB in the horizontal direction while only providing shielding of 25 dB in the vertical direction. This characteristic is due to the manufacturing process of standard aluminum honeycomb vent panels.
Basic aluminum honeycomb is created using thin ribbons of aluminum that are bonded using a non-conductive adhesive. Polarity is associated with seam leakage caused by the non-conductive bonds from cell to cell created during the manufacturing process of adhering aluminum ribbons together to make the honeycomb. While thin, this non-conductive gap is the cause of difference in shielding effectiveness (SE). It is important to note that polarity is only an issue for aluminum vents, not for steel, stainless steel, and brass honeycomb due to a different manufacturing process (steel and brass honeycomb use a welding process, eliminating the non-conductive gap). The below graph demonstrates the significant difference in shielding effectiveness in the horizontal and vertical directions.
Fortunately, there are several solutions to combat this polarity issue:Layered vents
With the addition of a second layer of honeycomb, offset at a 90-degree angle, the polarization effect can be dramatically reduced. The Chomerics term for these layered vents is Omni Cell. By rotating the second layer of honeycomb 90 degrees, RF wave interaction in both the X and Y axes are combated by the seam orientation of each layer of honeycomb. This means that while the electromagnetic waves may pass through one layer of the honeycomb, the offsetting layer will not allow them to pass through the entire vent assembly. Of note, airflow through the vent is not significantly impacted, allowing for enough heat dissipation.
While the maximum shielding effectiveness of the Omni Cell vents is nearly identical compared to that of a single layer vent, the directional consistency is instantly noticeable. There is no longer a difference in the horizontal and vertical shielding effectiveness, with the offsetting layers eliminating the polarity effect.Plating
Electroless nickel plating is an ideal plating option to combat polarity on aluminum vents. The nickel plating covers the non-conductive bonds and eliminates seam leakage between aluminum ribbons. The nickel plating electrically connects the aluminum ribbons which overcome the non-conductive adhesive. Not only does nickel plating effectively eliminate the polarity effect, it increases the durability of the vents and improves their lifespan in harsh environments.
As with Omni Cell vents, the polarization effect is eliminated with the vent exhibiting nearly no difference in shielding between horizontal and vertical testing. A properly plated vent will also increase the SE of the entire honeycomb array, creating conductive contact between every individual aluminum ribbon in the assembly. The nickel plating also improves the electrical connection of the honeycomb to the frame if the plating process is done after assembly.
Based on the above graphs, a conclusion can be made about the techniques used in eliminating the polarity effect. Since the plating process can eliminate the polarization effect AND increase the SE, this approach is most common. Omni Cell construction is effective if it meets the desired shielding effectiveness level. It is rare to see a nickel plated Omni Cell vent.
Individual project specifications such as airflow requirements, shielding performance, environmental exposure, budget and a myriad of others will drive the design process of EMI shielding honeycomb ventilation panels, but it is important to know about principles such as polarity in making final considerations.
As the defense industry continues to push the boundaries on advanced electronic systems and state-of-the-art communication devices, the requirements governing these programs must follow suit. Among the many technical requirements is Electromagnetic Compatibility, defined as the ability of a device to withstand both anticipated and unanticipated electronic interference (EMI) as well as minimize the interference being radiated.
It’s important to note that electromagnetic compatibility is a requirement across a variety of platforms in military technology including, but not limited to: missile and missile defense, ground vehicles, man-portable communication, electronic warfare/radar, stationary shelters, and avionics. Additionally, commercial technology such as aircraft and satellites often adopt military standards for electromagnetic shielding.Missiles and missile defense
Innovation and improvements in war-fighting over the past several decades have led to the improvement of key weapons systems, most notably the missile defense arsenal. As weapons improve range, minimize collateral damage, and attempt to outpace anti-missile efforts, a greater focus has been placed on electronic controls and built in fail-safe measures. These measures are developed to the highest EMI standards for the safety of military personnel, with elastomer gaskets and conductive paints serving to ensure weather sealing and minimization of interference.Ground vehicles
Humvees and tanks are built for durability in all environments, with safety of the crew a top priority. To ensure proper function of the engine components, weapons systems, and data transmission, these vehicles must meet EMI standards. Expanded aluminum gaskets for turret and antenna mounts are just one example of shielding efforts on both the interior and exterior of the vehicle
Defense research and development continues to optimize the gear used by servicemen and women, both in combat and support roles. The first line of communication is the direct unit carried by those who serve, whether built into helmets/headsets or carried in the form of hand-held devices. Each device is tested and retested, verifying that interference will not present hazards at the most inopportune times. EMI shielded displays on these devices ensure minimal interference with maximum information transmission.Electronic warfare/radar
Radar and electronic warfare modules come in all sizes, from under-wing units on fighter jets to stationary units the size of a small island. Each unit, whether stationary or mobile, must pass stringent electronic emissions and susceptibility standards to ensure that billions of dollars of development and manufacturing yield the most advanced technology.Stationary shelters
Ground control shelters have become mobile mission control hubs, storing a great deal of technology inside. EMI shielding caulks and compounds at the seams ensure that only the proper information is relayed as expected.
On-board electronics equipment such as flight recorders, navigation units, flight-control systems, and radios are perfect examples of components that must comply with EMI shielding specifications. These devices are mission-critical, with the slightest interference potentially causing communication delays or misinformation presented to the crew or ground control staffs. Commercial aircraft observe similar safety requirements, while including additional electronics such as in-flight entertainment units that utilize custom shielded display units.
EMI shielding is a crucial consideration in the safe and effective operation of defense electronic systems. Nearly every device developed for military and aerospace applications must utilize gaskets, coatings, adhesives, or a variety of other sub components in meeting rigorous military electronics standards. Additional technical information and specific metrics on defense requirements for electromagnetic compatibility can be found in MIL-STD 461G.
Article contributed by Ben Nudelman, Parker Chomerics Division
From the Parker O-Ring Handbook and Material Offering Guide to finite element analysis and blogs, our engineering experts run the gamut of all sealing solutions. So it's no surprise that the top blogs over the last six years fall into categories that highlight their recommendations on O-ring design tips, installation basics, and O-ring sealing alternatives.
Bookmarking these blog favorites are sure to come in handy for your future sealing challenges. Simplify your research by checking out these top ten sealing solutions and design blogs by Parker O-Ring & Engineered Sealing Division.
One of the decisions equipment designers need to make when installing O-ring seals in their applications is how much the O-ring will be squeezed by its mating hardware to create an effective seal.
Can O-rings be used in rectangular or non-circular groove patterns? This question comes up weekly, and the answer is a resounding “Yes!” however there are definite guidelines we want to follow.
The physics of creating a face seal is relatively simple. In most sealing systems, the objective is to prevent fluid from leaking from a high-pressure location to a lower pressure location through a sealing gap. Sealing fundamentals should be followed for trouble free application.
O-rings are the simplest, most readily available type of seal used across every industry and market. They are arguably the best seal for many applications, but perhaps daunting to an engineer with no experience in seal design.
Conventional wisdom says that the more an O-ring seal is squeezed (i.e. deformed relative to it’s “unsqueezed” state), the tighter the seal. More squeeze equals greater force between the O-ring and its mating hardware — which means that liquids, gases and dry powders are otherwise prevented from flowing between the rubber seal and mating hardware.
The proper method of applying a lubricant to an O-ring always seems to be an area of concern for many of our customers and there are many methods used in the marketplace.
Efficiency gains in the automotive industry are not limited to engine designs. Transmissions are also undergoing significant changes to increase fuel mileage. To reduce friction and cope with more gears (or even an infinite number of gears with a Continuously Variable Transmission (CVT)), new Ultra Low Viscosity (ULV) transmission fluids and CVT fluids have been developed. Fortunately, Parker has already performed a significant amount of testing in these new fluids.
If O-ring damage happens with high frequency, you could be wasting time and money on seal replacement. Luckily, there are some easy steps that can be followed to help prevent this from occurring. Parker’s recommended guidelines for installation include always using lubrication, good gland design, and ensuring correct sizing.
It isn’t all that uncommon for a groove to be cut in a flange and a novice designer learns the hard way that standard O-rings cannot fit in just any groove geometry. For hardware that has already been machined, frustration ensues as the caller learns the O-ring solution requires tooling. Parker offers a TetraSeal® solution, which often does not require tooling and can be made of many of the same materials used for O-rings.
Samantha J. Sexton, marketing communications manager, Parker O-Ring & Engineered Seals Division
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