Category Archives: sealing technology

Sealing Solutions for Large Diameter Rotating Shafts: ZAVA V-Rings

First, What is a V-Ring?

The function of a V-Ring seal, or V-Ring, is to act as a centrifugal seal acting against the bearing face, pushing dirt and contaminants away from the bearing area.  V-Rings are not designed to seal against fluids or pressure differentials. However, as stated above, they are excellent at excluding all sorts of contaminants. They provide effective protection against loss and maintenance, reduce wear, increase the life of the retainer and bearings, and also work well in dry running applications.

V-Ring Applications

picture of zava seal v-ring
The most innovative V-Ring on the market: The Zava Seal with a quick-lock mechanism.

V-Rings are suitable for a whole range of sealing applications as well as rotary shaft applications such as electric motors, pumps, and agricultural machinery. This type of seal has proved to be reliable and effective against penetrating impurities such as dirt, sand, dust, greases, and splashes of water & oil in a variety of industries:

  • Pulp and paper
  • Steel mills
  • Cement mills
  • Mining
  • Rolling mills
  • Power generation
  • Fluid power
  • Chemicals
  • Food & Drink

How Do V-Rings Work?

V-Rings are flexible rubber seals that work by stretching and fitting onto a shaft and then rotating with the shaft against a counter face. They are designed to give the lips an automatic sealing action. They help to increase the sealing area by providing secondary sealing as pressure acting on the platform ring.

The Split V-Ring with ZAVA Quick-Lock

The V-Ring from ZAVA® Seal has a unique patented quick-lock that can be assembled quickly and easily, and in some cases can be installed without shutting down the filter. Because it’s mounted without vulcanizing, machinery downtime is significantly reduced. When “snapped in place,” the locking technology makes it impossible to detach. The quick-lock mechanism is made of acid-proof steel (SS 2343).  The split V-Ring from Zava can be made in many different lengths and cross sections and also in several different types of materials, specifications, and profiles.

Advantages of the Split V-Ring With ZAVA Quick-Lock

  1. Split and lockable
  2. Fast and easy to assemble
  3. Unique and patented quick-lock
  4. Elastic and workable
  5. Reduction in fiber loss
  6. Maximum leakage reduction
  7. No wear of the shaft
  8. A variety of different sizes

How Does the Quick-Lock Work?


For more information about the Zava Seal and to see if it might be the right fit for your application, contact Gallagher’s Engineering Department today.

Gallagher Fluid Seals is an authorized distributor of Zava Seal.

Freudenberg’s New Plastic Rotating Bearing

In an innovative first, Freudenberg Sealing Technologies has introduced a machine component that combines a plastic rotating bearing with a seal in a single, precisely matched unit.

The design offers significant weight, cost and friction advantages over separate bearings and seals and also improves the properties of the mated bearings and seals. Freudenberg has validated the advantages of this new component through extensive testing performed in a sensor housing unit including the seal-bearing component.

While mostly hidden from view, seals and bearings are nonetheless important components in automotive and industrial applications. They are key elements in operational safety and performance and their durability must be optimized to prevent system failure. At the same time, these bearings and seals must be small, lightweight and cost efficient in keeping with manufacturers’ efforts to remove cost and weight from vehicles without sacrificing performance.

Freudenberg has resolved this challenge with the introduction of its seal with integrated bearing (SWIB). The company spent two years developing this engineered solution and has successfully tested it in a sensor housing of a an electric power steering (EPS) system installed in an electric powered vehicle.

The sensor records data, like steering angle, which is critical to advanced driver assistance programs like electronic stability control (ESC). The seal inside the housing is responsible for protecting the sensor from the penetration of dust, splash water and other media over the entire service life of the vehicle. Bearings used in the assembly are also important; they must withstand significant mechanical loads – sometimes as much as 3,000 Newton (675 lbs) of radial force when a car drives over a curb with its wheels at an extreme angle.

Integrated system can reduce loads and vibration

picture of FST seal with integrated bearing

Freudenberg Sealing Technologies’ integrated solution offers significant improvements compared with separate bearings and seals. The rigidity of the integrated plastic bearing is higher so that its deflection is reduced by nearly 50 percent when lateral forces are exerted. This reduces the induced vibrations to increase the steering comfort for the driver. The seal, on the other hand, has 35 percent less friction, which reduces resistance during steering – especially important for highly automated driving. The weight of the overall solution is reduced by as much as 80 percent through integration. Freudenberg’s patented plastic bearing plays a major role in achieving these component breakthroughs.

Automotive safety applications are subject to many requirements which individual manufacturers define according to their own specifications. Freudenberg Sealing Technologies used common specifications – a temperature resistance of -40°C to 125 °C (-40°F to 257°F) under mechanical stress, for example – to test its integrated component during the past year. Extreme cases, such as direct exposure to high water pressure, which can occur in practice during engine washing, were also tested. The seal that includes an integrated bearing proved itself in all tests. “We can now commence with customer-specific series development at any time,” says Freudenberg expert Frank Schönberg.

The design offers significant weight, cost and friction advantages

Product experts at Freudenberg Sealing Technologies are already researching additional industrial applications for the new component. In addition to automotive applications, seals with integrated plastic bearings can likely bring benefits to many industrial operations. Freudenberg is also looking to the manufacturing process for further innovation: If the seal/bearing unit is currently still being assembled, it could be produced using new materials in an integrated two-component injection molding process in the future.


The original article can be found on Freudenberg’s website.

 Gallagher Fluid Seals is an authorized distributor of Freudenberg Sealing Technologies. To see if this seal is a right fit for your application, contact our engineering team today.

Metal Detectable & X-Ray Detectable Rubber Materials

Food, Beverage, and Pharmaceutical Regulations

picture of metal detectable o-ringStringent government regulations mandate that food, beverage, and pharmaceutical manufacturers keep foreign material out of ingredients to ensure food and drug safety for consumers. Preventing foreign material from entering the processing stream is of the utmost concern but there must also be measures in place to detect contaminated product and quarantine it before distribution.

Component parts that are used in food and drug processing equipment can become damaged by improper installation and/or excessive shear experienced during operation that causes fragments of rubber, plastic, and metal to contaminate ingredients. Chemicals used for cleaning and sterilization of equipment can cause rubber seals to degrade, increasing the probability of particles breaking off and entering the consumable products. Part failures causing product contamination can lead to machine down time, scrap product, product recalls and result in legal problems and negative media attention. All of which have a significant financial impact and can compromise brand loyalty within the market.

Hazard Analysis Critical Control Point (HACCP)

picture of precision metal detectable o-ringsMany processing operations now employ HACCP (Hazard Analysis Critical Control Point) programs which stipulate that all parts have to be metal detectable and X-ray detectable. This made it necessary to develop special rubber materials that would allow food processors to conduct routine inspections for this type of contamination utilizing in-line metal detectors and X-ray machines. Rubber must be compounded with special additives to make detection possible. However, certain foods have phase angles similar to metal detectable rubber so a complete understanding of the rubber product’s application is necessary for proper compound selection.

Metal Detectable O-Rings | X-Ray Detectable O-Rings

Precision Associates has developed four Metal and X-Ray detectable materials made with ingredients sanctioned under FDA Title 21 CFR 177.2600.

All four materials are 3A Sanitary 18-03 approved and are available in Silicone, Nitrile, EPDM, and FKM. Each is 70 durometer and blue in color. (The industry standard color is blue but materials can be colored for specific customer requirements and any polymer can be made metal detectable).

All compounds were tested by an independent laboratory and found to have magnetic properties that exceed industry standards.

picture of compound table precision o-rings


The original article was written by Precision Associates, Inc. and can be found here.

For more information about what Gallagher can offer through Precision Associates, or to talk to a technical sales expert about these materials, contact us today.

Accurate Long-Term Predictions for Seals

The static seals used in large energy and industrial facilities can be challenging to install and difficult to replace. They must, therefore, function flawlessly for periods longer than 20 years. Up until now, the existing tools used to calculate the long-term performance of sealing materials for these kinds of applications have often led to the components being larger than actually necessary.

Freudenberg Sealing Technologies has now developed a method that takes into account the material changes at the molecular level when predicting the long-term durability of seals. The new methodology is more reliable than previous models and ensure fewer materials to be used.

picture of wind turbinesThe seals used in plant engineering must have a very long service life. Once they are installed – to protect offshore wind turbine towers from salt corrosion, for example – customers typically require that they perfectly fit for more than 20 years. The service life of a seal is limited based on two things: First, by setting or stretching (physical relaxation). And second, chemical changes cause the material loses its elasticity over time.

Under the influence of atmospheric oxygen or ozone, two basic effects that influence the aging of seals can be observed: First, the polymer chains and networks can fracture under mechanical stress, and second, additional oxygen bridges can develop in the network as a result of oxidation processes. Both effects influence important properties of relevance for seals such as stiffness, contact pressures or the ability to regain their original shape after deformation, also referred to as resistance to deformation.

Extrapolation with the Arrhenius Equation

To determine whether a material actually meets the requirements for a specific application, engineers usually conduct so-called “storage tests” in which the test specimen is exposed to temperatures well over 100° C for a longer period of time – usually 1,000 hours – to predict temperature-dependent aging. Engineers typically extrapolate the measured values using the Arrhenius Equation, a method named after the Swedish chemist and Nobel Prize winner Svante August Arrhenius. Continue reading Accurate Long-Term Predictions for Seals

Sealing Solutions for Drinking Water and Service Water Systems

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Dr. Stefan Reichle, Market Unit Manager, Engineered Materials Group Europe.


picture of drinking waterWherever drinking water is obtained from any of its sources, pumped and processed, materials with low extraction levels and without any harmful ingredients are required. Sealing compounds for use in drinking water and heating applications are subject to diverse approval regulations. These regulations serve to assure the safety of water from the time of intake, via treatment, processing and transportation through to the consumer. Practically every country in the world has its own drinking water regulations specifying particular tests and including lists of approved ingredients. These regulations are complemented by physical and microbiological examinations.

The Parker Engineered Materials Group has developed a number of compounds, each of which meets a wide range of the required approvals, thus permitting the global utilization of sealing systems.

New universal compound combines excellent compression set and improved resistance against autoxidation

The peroxide-crosslinked plasticizer-free EPDM compound EJ820 was specifically developed for use in drinking water applications. The material conforms to all standard national and international drinking water approvals such as KTW, W270, W534, EN681-1 including the supplementary requirement, W534, NSF61, KIWA, WRAS, ACS. The material’s low compression set guarantees long life and thus permanent and reliable sealing of all fittings, valves and pipe systems. In addition, EJ820 exhibits enhanced resistance against autoxidation.

Parker materials cover a broad range of drinking and service water applications

  • Seals for solar thermal energy systems
  • Bathroom taps and shower heads
  • Press fittings
  • Heater valves and valve blocks
  • Drinking water applications
  • Heater pumps

Below are Parker material compounds and associated specifications:

picture of parker compounds

picture of regulations for drinking water


For more information about Parker products that are applicable for drinking water and service water systems, contact Gallagher’s engineering department.

The Danger of Complacency in Equipment Selection & Installation

Ensuring the correct materials are suitable for the application

When working with valves, flanges, and pumps, operators should never be complacent. The wrong gasket or packing in a deadly application could result in loss of life. Ensuring the correct materials are suitable for the application requires special attention because safety is critical. As Gordon DeLeys, compliance assistance specialist at the United States Occupational Safety and Health Administration (OSHA), said, “Safety should not be a company priority since priorities in an organization can and usually change. Safety and health need to be a core value of an organization. Safety is really a case of values versus priorities.”

picture of uss iwo jima
The USS Iwo Jima was an amphibious assault ship that experienced a catastrophic event in October 1990.

In October 1990, the USS Iwo Jima was heading into port for routine maintenance in Manama, Bahrain. The ship was the first to be designed and built from the keel up as an amphibious assault ship in Puget Sound Naval Shipyard, Bremerton, Washington, on Sept. 17, 1960.

Small packing leak can turn catastrophic

Valve 2MS-7 was a globe valve in the boiler room, and it needed to be repacked for a small packing leak and reconditioned while in port. The valve was worked on by an outside contractor who had limited understanding of military specifications and procedures.

The mechanic—who had 10 years of experience—decided to replace the fasteners on the bonnet because they were worn. Apparently, the mechanic asked one of the boiler room personnel for new nuts and bolts and was given permission to look through the boiler room’s spare parts bins. He selected four bolts, eight studs and 20 3/4-inch nuts. The mechanic had not noticed that some of the nuts were brass. Because those fasteners were covered with a manufacturer-applied black coating, they were mistaken for the correct grade 4 steel nuts. Closer examination and use of a scratch or magnetic test would have revealed their metal content, but instead the black brass nuts were installed.

The next day the valve was reinsulated with lagging. The foreman had not inspected the work done on 2MS-7.

The valve should have been reassembled using only B-16 steel studs—anything else was a violation of good engineering practice based on the service condition.

When the brass nuts were used on the studs holding down the bonnet of the valve, no one realized this was a critical mistake since the valve was going to be in service above 800 F and the temperature limit for brass is 400 F.

On Oct. 30, 1990, in preparation to get underway and proceed to her operating area, fires were lighted in the boilers of the vessel.

Shortly after, one side of 2MS-7 was initially pressurized with steam generated from Boiler No. 1. Three hours later, valve 2MS-7 was opened to supply steam to the generator that supplied electrical power to the vessel.

As steam at 600 pounds per square inch (psi) and 850 F began flowing through the valve, the brass nuts were expanding at a greater rate than the steel studs. The bolts started losing the strength to secure the bonnet to the valve body. After less than 30 minutes of operation, the valve failed catastrophically. Continue reading The Danger of Complacency in Equipment Selection & Installation

Friction Reduction in the Seal

Wettablility of the Sealing Lip

The optimum function of rotary shaft seals depends on many factors. One of them is the “wettability” of the sealing lip. This parameter plays a particularly important role with synthetic lubricants such as polyglycol. If wetting is too low, not only does wear on the sealing lip increase, but the contact with the rotating shaft can also damage the shaft itself. The engineers at Freudenberg Sealing Technologies (FST) and Freudenberg Technology Innovation (FTI) have developed a new coating that forms a flexible bond with the elastomer of the seal and significantly improves wetting with synthetic lubricants.

Thanks to different materials and shapes, radial shaft seals for sealing rotating shafts can be used in a wide variety of industrial applications. What they all have in common is the demand for the lowest possible friction, low wear, and reliable sealing effect. Optimum lubrication of the entire tribological system depends on permanent wetting of the sealing lip.

This poses a particular challenge for poorly wetting lubricants based on polyglycol, which are used in drive technology, for example in worm gears. Too little wetting increases wear on the sealing lip and can also lead to increased shaft runout due to contact with the shaft, which ultimately necessitates replacement of the machine parts.

A flexible bond over a long service life

picture of friction reductionFST has developed the new 75 FKM 585 plus coating to achieve optimum lubrication in gears and pumps with synthetic lubricants. “We have succeeded in coating the sealing lip in such a way that polar oils distribute much better,” explains Dr. Matthias Adler from FST’s global materials development department in the Simmerring Industry division. “The mechanics of the layer have been modified so that it forms a flexible bond with the elastic material of the elastomer over a long service life – even under dynamic load. In addition, the coating is applied where no wear occurs.” The current development was specially designed for customers who already use the standard Simmerring 75 FKM 585 in drives for which the use of polyglycol oils is recommended by the manufacturers.

The elastomer is coated using plasma-assisted chemical vapor deposition (PE-CVD). In this process, the elements in the process gas form a chemical bond with the surface of the base body. The decisive criterion for the optimization of the wetting behavior is the targeted modification of the interaction between the coating and the synthetic lubricant. The measurements show that by using special components in the new surface coating such as carbon, oxygen and silicon in a certain molar ratio, optimal wetting can be achieved compared to the standard material 75 FKM 585.

New technology can be transferred to other materials

The layer thickness of 75 FKM 585 plus is a few hundred nanometers and its properties meet the standards of the manufacturers of industrial gear units with regard to oil/elastomer requirements. Although it is designed for particularly low wear at high revolutions, it has been shown that the coefficient of friction is significantly lower than that of the standard material, even at low speeds such as in the breakaway forces and mixed friction ranges. The newly developed technology is not limited to applications with FKM, adds Dr. Adler, “but can also be transferred to other materials. Initial tests on NBR and EPDM have also shown positive results in optimizing the interaction between coating and poorly wetting oils.”


The original article was published by Ulrike Reich, head of media relations & internal communications at FST.

Gallagher Fluid Seals is an authorized distributor of Freudenberg Sealing Technologies. For more information about how we can help with your specific application, please contact our engineering department.

Spring Types and Materials in Sealing Systems

Springs are an integral part of all sealing systems. A simple air cylinder has O-rings to seal in the air, and the O-ring exhibits spring-like qualities to ensure a good seal over a broad temperature range.

But what are the different types of springs and materials in sealing systems? And how do you choose the best for your application?

image of metal spring types

Metal Springs

Metal springs, such as the Cantilever and Canted Coil spring, are used to energize polymers such as Teflon and ultra high molecular weight polyethylene (UHMW) to allow sealing in a wide range of temperatures. Selecting the correct spring material is critical to the life of the seal.

Metal energized seals are often subjected to a wide variety of fluids and temperature ranges, which then requires the correct material choice for the life of the seal in the application.

One of the earliest metal springs was the flat band or marcel expander, often made from common materials like 300 series Stainless Steel or heat treated 17-7 Stainless Steel.

These materials are often chosen for their tensile strength. But due to the cost to manufacture and the high volumes of spring required, these two expanders were often relegated to industrial or aerospace hydraulic systems.

If system fluids were not compatible with Stainless Steel, customers generally went to a different sealing system to avoid the high cost of short runs in these styles of energizers.

O-Rings cover a wide range of temperatures, and fluids, but generally not both. If there are multiple fluids involved, O-Rings often fail to provide compatibility over a range of fluids.

The use of Cantilever, Canted Coil or Helical coiled spring allowed for long runs and lower costs. The most common spring material is Stainless Steel, but these styles of spring lend themselves to materials that have a wide range of chemical and temperature range while maintaining tensile strength.

Alternative Spring Materials

Some of the more common alternative materials are Hastelloy and Elgiloy. While 17-7 is available, it’s seldom used because Elgiloy (while more expensive per pound) is often run at a higher volume, bringing the overall cost down making 17-7 less attractive due to cost.

Another style metal spring for polymers is the Garter spring. Garter springs are normally run on a per job basis, but because it’s made from wire, it can easily be wound from any material like Elgiloy or Stainless.

Garter springs are often used in rubber style lip seals, but we often find them coupled with polymer-style seals.

Mechanical Seals

Mechanical face seals typically marry a material with the fluids the seal will be running in. Mechanical seals have the overall body and internal springs made from specific materials capable of handling variations in temperature and fluids.

PEEK in Seals

Polymers are thought of as seal materials, but PEEK has been used as a spring in polymer-style seals. PEEK can be wound into helical style springs, and also formed into cantilever springs. As a Helical style, it can be wound into a diameter to energize Teflon or rubber lip seals.

If you consider radiation service, a PEEK spring makes an excellent choice keeping metals out of the seal.

How to Choose the Right Spring Material

While there are a variety of metals, often economics determine the practicality of specialty metals.

A consideration is reviewing the hardware used in the application as to what spring material is acceptable in an application. We often review what the customer is using in the rest of the service for determining a spring material.

Temperature is often a key factor in determining materials for spring. Elgiloy tends to do an excellent job in maintaining tensile strength at elevated temperatures.


The original article can be found on Eclipse Engineering’s website and was written by Cliff Goldstein.

Gallagher Fluid Seals is an authorized distributor of Eclipse engineering. For more information about choosing the right spring material for your application, contact our engineering department today.

A Short Guide for Rubber Seals & Design

Rubber seals are used in numerous industries to prevent the unwanted leakage of liquids and gases in various components such as pumps, valves, pipe fittings, and vacuum seals, to name only a few. However, all seals are not created equally. Rubber seal design consists of several elements to ensure that the seal delivers optimal performance in the given environment.

One of the most common types of industrial rubber seals, the O-ring, relies on mechanical compressive deformation to act as a barrier between mating surfaces, thus restricting the flow of fluid in predetermined areas. Several factors must, therefore, be taken into account in O-ring seal design to sustain the compressive force and maintain an effective seal.

Key Design Considerations

Rubber seals are available in a large number of material compositions, each with its own set of advantages and limitations. The selection of the appropriate material involves the consideration of specific factors including:

Dimensional Requirements

To provide a proper seal, the O-ring needs to be compressed between the mating surfaces. The deformation caused by this compression is what prevents fluid leakage. To achieve the proper compressive force and deformation, the cross section of the O-ring needs to be sufficiently larger than the gland depth.

As the two mating surfaces press together, the O-ring seal compresses axially and exerts an equal and opposite force at the top and bottom ends of the seal. If the O-ring is too small, the seal may not compress when the surface come together. On the other hand, an O-ring that is too large will over pack the gland and disrupt the connection between the mating surfaces.

Friction

Friction considerations are essential in dynamic applications – in situations that involve relative movement between the mating surfaces.

In reciprocating applications, these movements can generate frictional forces which may cause failure due to abrasion or extrusion and successive nibbling of the seal. In rotary applications, friction may generate excessive heat and seal expansion due to the Joule effect. In both of these applications, proper groove design, along with appropriate lubrication and speed of operation can help to avoid these issues. Silicone and related materials such as Fluorosilicone, liquid silicone rubber, and medical grade silicone are often avoided in dynamic applications due to their low abrasion/tear resistance.

temperature considerationTemperature

Long-term exposure to excessive heat can cause inappropriate rubber seals materials to deteriorate physically or chemically over time. Excessively high temperatures can cause specific materials to swell and harden, resulting in permanent deformation. Conversely, overly cold temperatures may cause material shrinkage and result in leakage due to loss of seal contact, or insufficient compressive force due to stiffening of the rubber compound.

Therefore, the appropriate seal material should be selected to withstand the expected temperature ranges of the environment. The length of exposure should also be considered. For example, would the temperatures be sustained in short intervals or at sustained levels?

Pressure

Differential pressures tend to push rubber seals (o-rings) to the low-pressure side of the gland causing it to distort against the gland wall. This action blocks the diametrical gap between the mating surfaces and results in the formation of a positive seal. Excessively high pressures can cause softer O-ring materials to extrude into the diametrical gap resulting in permanent seal failure and subsequent leakage. To avoid this situation, seal materials that operate optimally within the expected temperature range should be selected.

chemical compatibilityChemical Compatibility

One of the most critical considerations for rubber seals design and material selection is determining the material’s resistance to exposure to specific chemicals. Some fluids can react negatively with certain materials while having little to no effect on another. For example, Nitrile is highly resistant to petroleum-based oils and fuels, while the use of Butyl is avoided in applications with exposure to petroleum and other hydrocarbon-based solvents due to its poor resistance.

Remember to keep dimensional requirements, friction, temperature, pressure, and chemical compatibility in mind when it comes to customizing a rubber seal solution for your application.


For more information about custom seal designs or to see which seal might be the best fit for your application, contact Gallagher Fluid Seals.

The original article can be found on Precision Associates website, and was written in January 2019.

Parker’s EM163-80 Meets Both NAS1613 Revision 2 and 6, Is There a Difference?

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Dorothy Kern, applications engineering manager for the Parker O-Ring & Engineered Seals Division.


Perhaps you know Parker’s newest EPDM material is EM163-80. Featuring breakthrough low temperature functionality, resistance to all commercially available phosphate ester fluids, and the ability to be made into custom shapes, extrusions, and spliced geometries, EM163-80 represents the best-in-class material for applications needing to seal phosphate-ester-based fluids. The latest news is that EM163-80 meets the full qualification requirements of both NAS1613 Revision 6 (code A) and the legacy Revision 2 (no code). Parker has been inundated with questions about the specification differences between Revision 6 and 2, enough that it makes sense to devote a blog topic explaining the fluids, conditions, and dynamic cycling requirements which are required to qualify EM163-80 to each specification.

The easiest part of this comparison is evaluating the areas of Revision 6 which are very much a copy and paste from Revision 2. Compression set conditions, aged and un-aged, plus temperature retraction requirements, aged and un-aged, are identical. Lastly, both specifications require a test to verify the elastomers will not corrode or adhere to five different metal substrate materials. That is pretty much where the similarities end.  Now for the contrasts.

Specimen size

The first subtle difference is the specimen size. Both specs require testing to measure the change in physical properties and volume following a heated immersion in phosphate ester fluids. For the most part, No Code qualification requires testing to be completed on test slabs or O-rings, while the newer revision, Code A, requires testing on test slabs AND O-rings. Not a big difference, but still, a difference.

The fluid conditions are very similar in both specs, but not identical. There are only two temperatures for the short term 70 hour exposure: 160°F and 250°F. Another similarity is that the longer soaks are at 225°F for 334 and 670 hours. The more difficult A Code also requires 1000 and 1440 hours at 225°F. We begin to see the requirements for the later revision are more reflective of the industry conditions, right?

Fluids

Next, we look at the fluids, which truly are a key difference between the two documents. Revision 2 fluid is exclusively for AS1241 Type IV, CL 2 while revision 6 states the elastomers must meet “all commercially available AS1241 Type IV, Class 1 and 2, and Type V”. Table 1 outlines the AS1241 fluids in context of both NAS 1613 revisions.

Revision 2 Revision 6
Low Density Hyject IV A Plus AS 1241 Type IV class 1 X
Low Density Skydrol LD4 AS 1241 Type IV class 1 X
High Density Skydrol 500B-4 AS 1241 Type IV class 2 X X
Low Density Skydrol V AS 1241 Type V X
Low Density Hyjet V AS 1241 Type V X
Low Density Skydrol PE-5 AS 1241 Type V X

Basically, to pass Revision 6, the material must demonstrate compatibility for all six commercially available fluids, while Revision 2 only has one fluid which is must be verified for compatibility. Again, we see Revision 6 is much more comprehensive than Revision 2.

Endurance Testing

picture of o-ringsLast, we look at the functional testing of the materials, referred to as dynamic or endurance testing. Both specifications require endurance testing on a pair of seals, which have been aged for a week at 225°F. The appropriate fluids are outlined in the table above.

Revision 2 has a gland design per Mil-G-5514. There is a 4” stroke length and the rod must travel 30 full cycles each minute. The rod is chromium plated with a surface finish between 16-32 microinches. PTFE anti-extrusion back up rings are necessary for the 3000 psi high pressure cycling. A temperature of 160°F is maintained for 70,000 strokes and then increased to 225°F for an additional 90,000 strokes.

Revision 6 has a much more demanding endurance test with fives phases and slightly different hardware. The rod must be a smooth 8 to 16 microinches Ra with a cross-hatched finish by lapping, and the cycle is 30 complete strokes per minute but only 3” rather than 4”, which means the speed can be more conservative. A pair of conditioned seals are placed in AS4716 grooves, adjacent to a PTFE back up ring. Similarities to Rev 2 are that there is a pressure of 3000 psi for the dynamic cycling at both 160°F and 225°F, however before and after each high temperature cycle there is a low temperature, -65°F soak. The first soak is static for 24 hours, followed by the 160°F high pressure cycling. The second low temperature soak requires 10 dynamic cycles at ambient pressure followed by 10 cycles at 3000 psi. The final low temperature soak requires one hour static sealing at 3000 psi followed by an 18 hour warm down period.

If you read carefully through the tests, you begin to see the Revision 6 seals must go through a more rigorous test with harsh low temperature, low pressure conditions. However, Revision 2 is not without its own challenges. The required hardware configuration; ie, low squeeze and more rough surface finish, is far from optimum and not what we recommend in actual service conditions. Added to the difficulty is the longer stroke length and faster speed. The fact that EM163-80 has passed both specifications proves it is the next generation EPDM seal material ready for flight.


Gallagher Fluid Seals is an authorized distributor of Parker. To learn more about how Gallagher Fluid Seals can help you, contact our engineering department at 1-800-822-4063