Tag Archives: EPDM

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

Tackling Flavor Transfer with Seals Made from Globally-Certified Materials

The popularity of multi-flavor drink dispensers, those touch screen wonders that offer dozens of beverage and flavor options to consumers, has grown during the past decade. Manufacturers are installing these complex machines in venues and locations throughout the world.

Elastomers and flavor transfer

But what’s great for an individual customer – a cherry-ginger-lime cream soda, for example – can play havoc with the elastomer seals inside the machine. Add in hygienic cleaning requirements and proper food contact certifications and equipment manufacturers can find themselves spending months chasing challenges like flavor transfer, leaks and material compliance approvals.

Freudenberg-NOK Sealing Technologies, a leading specialist in advanced sealing applications, has a portfolio of solutions to resolve these issues. The company, which runs the business operations for Freudenberg Sealing Technologies in the Americas, will showcase a variety of globally-certified material options at the 2018 BevTech®, the annual meeting of The International Society of Beverage Technologists (ISBT), taking place April 30-May 2 in Albuquerque, N.M.

“Flavors are almost never the same. They are a diverse mixture of ingredients with very different chemical properties.”

“Flavors are almost never the same. They are a diverse mixture of ingredients with very different chemical properties,” said Christian Geubert, Global Application Engineering Manager for Freudenberg Sealing Technologies’ Process Industries organization. “Some of these chemicals are very good solvents for rubber, which means they can destroy rubber seals and their performance. Only through extensive testing and analysis can industry challenges with flavor transfer and cleaning solutions be isolated, understood and successfully addressed with sealing materials and designs that address an entire range of conditions.”

Geubert will discuss the complex factors associated with flavor transfer and their impact on material properties and performance during a presentation at the 2018 BevTech® meeting. Following this presentation, Geubert and a team of Freudenberg experts will be on hand in booth #45 to answer questions and explain the advantages of a trio sealing materials including 70 EPDM 291, 70 FKM 727, and Fluoroprene® XP. Each of these materials is globally-certified for food contact in the United States (NSF-51) and the European Union (EC 1935/2004).

picture of flavor transfer seals

With its outstanding qualities in critical media, Freudenberg’s 70 EPDM 291 is the first choice for a wide variety of O-Rings, formed parts and diaphragm applications in the food and beverage industry. 70 EPDM 291 is compatible with bag-in-box (BIB) syrups, is suited for exposure to dispenser cleaning fluids, and is specifically formulated to resist flavor transfer.

Dynamic sealing at dispensing temperatures just above 32°F (0°C) is problematic for most Fluorocarbons (FKM) due to reduced flexibility. Freudenberg’s 70 FKM 727 is the only globally-certified, low-temperature FKM in the food and beverage industry. While maintaining compatibility with BIB syrups and cleaning agents, 70 FKM 727 adds best-in-class flexibility in this critical temperature range.

When standard EPDM and FKM materials fail to perform in particularly demanding food and beverage applications – including those found in high-ratio, multi-flavor dispensers – Freudenberg’s Fluoroprene® XP can be called into action. This unique, highly-fluorinated FKM is not only compatible with non-polar materials like oils, it also offers excellent compatibility with polar fluids like acids and bases and provides best-in-class flavor transfer resistance.


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

To learn more about Freudenberg products, speak to a Gallagher representative today by calling 1-800-822-4063

A Guide to Elastomer Technology in Mechanical Seals

Elastomer Technology in Mechanical Seals

Evaluate properties of rubber during installation and seal life.

Elastomers (or rubbers) are a ubiquitous family of materials whose use stretches across nearly the entire range of mechanical seal designs.  From plant-sourced natural rubber, so named by John Priestly in 1770 for its utility in rubbing away pencil graphite, to petroleum-sourced synthetic rubber first developed around the turn of the 20th century, the “elastomer” and their properties are familiar but should not be overlooked—especially when dealing with mechanical seals.

How Elastomers Work in Mechanical Seals

Rubber seals come in a variety of profiles—O-rings, cup gaskets, bellows diaphragms, sealing/wiper lips and many others. They are classified as either static or dynamic and create positive pressure
against surfaces to eliminate or control the leakage of liquids and/or gases while preventing the entrance of external contaminants such as dust and dirt. Static sealing occurs between adjacent surfaces with no relative motion, such as between the pump casing and cover. Due to frictional wear and heat generation, dynamic sealing is less straightforward, occurring between adjacent surfaces that are continuously or intermittently moving relative to another, such as between the pump casing and shaft.

In mechanical face seals, elastomers tend to take second chair because the primary seal—the dynamic seal between the housing and rotating shaft—is achieved by sliding contact between the pair of stiffer, lapped-flat sealing faces, one stationary in the housing and one rotating with the shaft. In many designs, rubber provides the secondary seal between each seal face and adjacent surface. One seal face is fixed and sealed statically using an O-ring or cup gasket. The other is spring-loaded and requires a semi-dynamic seal to accommodate some axial play, such as a dynamic O-ring in pusher-type mechanical face seals or elastomeric bellows in nonpusher ones. These semi-dynamic applications (involving flexing and sliding of the elastomer) can be critical for maintaining proper contact between the faces through face wear, shaft movement, etc.

Although the seal face pair tends to be the most critical design feature, mechanical face seals are  often used in the most demanding applications.

Rubber technology features prominently in radial lip seals, where typical applications have lower pressurevelocity (PV) values relative to those involving mechanical face seals. Still, the flexible elastomer lip must handle considerable relative motion in the form of shaft/bore rotation, reciprocation or a combination of both. In addition to standard designs and sizes, numerous customizations and proprietary approaches exist. The simplest designs rely on a single rubber lip’s inherent resiliency, although common enhancements include multiple sealing lips, a circumferential garter spring installed in a groove over the sealing lip to maintain contact with the shaft, and an auxiliary wiper lip or “excluder” to prevent abrasive dust or debris from compromising the primary sealing surface. For improving service life and performance in rotary applications, unidirectional or bidirectional hydrodynamic pumping aids can be added in the form of custom-shaped extrusions on the backside of the sealing lip to return leaked fluid to the sealing interface, increase lip lubrication and lower operating temperatures.

Diagram of secondary, dynamic elastomeric seals in mechanical face seals.

Benefits of Rubber

The definition of an elastomer provides initial insight into where rubber gets its resilient sealing quality: “a macromolecular material which, in the vulcanized state and at room temperature, can be stretched repeatedly to at least twice its original length and which, upon release of the stress, will immediately return to approximately its original length.”

When the rubber is squeezed by the adjacent surfaces of the clearance gap to be sealed, it has the characteristic
properties of malleably deforming and taking the shape of each  surface in response to the stress and applying a force back against the surfaces in its attempt to return to its original dimensions. Elastomers consist of large molecules called polymers (from the Greek “poly” meaning “many” and “meros” meaning “parts”), which are long chains of the same or different repeating units, called monomers, usually linked together by carbon-carbon bonds (the
most notable exception being silicone elastomers, which are linked by silicon-oxygen bonds). Soft and hard plastics are also composed of polymers. However, the regularity of the monomers in their polymer chains allows neighboring segments to align and form crystals, making the macromolecular plastic material rigid and inelastic.

One can prevent this crystallization by breaking up the regularity of the polymer chain, resulting usually in a viscous “gum” that is readily shaped into molds. At the molecular level, the polymer chains are similar to spaghetti-like strands flowing past each other.

During the process of vulcanization, Representatin of three polymer chains after formation of crosslinking via vulcanizationor curing, the viscous liquid is heated with sulfur or peroxides and other vulcanizing agents, and crosslinks form between polymer chains, tying them together with chemical bonds, converting the gum into an elastic, thermoset solid rubber that retains its shape after moderate deformation.

In addition to the selection and preparation of base polymer(s) and cure system ingredients, formulating the final rubber product, also known as compounding, involves five other broad categories of ingredients, which have percentage compositions expressed in parts per hundred rubber (phr). Fillers include various powders that thicken the polymer mixture, improve strength and resistance to abrasives, and reduce final cost. Plasticizers are oils and other liquid hydrocarbons that lower viscosity to ease processing, soften the final compound and in some cases improve low temperature performance. Process aids are specialized chemicals added in low concentrations to improve mixing, flow properties and final appearance.

Antidegradants protect the rubber from environmental attack. Finally, various miscellaneous ingredients may be added for special purposes, including foaming agents, dyes, fungicides, flame
retardants, abrasives, lubricants and electrically conductive particles. A simplified description of processing these ingredients includes mixing via tangential or intermeshing mixers, forming into desired shapes and vulcanizing into the final product.

Continue reading A Guide to Elastomer Technology in Mechanical Seals

The Continuous Improvement of Elastomers: Part 2

The spectrum of elastomers range from very simple forms, like the natural rubber already in use in the 19th century, to modern, high performance elastomers from the second half of the 20th century.  They are continually being improved.

This blog article is the second in a two-part series discussing the many different elastomer materials available today, as discussed in Freudenberg’s The World of Freudenberg Sealing Technologies.
The first post discussed Natural Rubber (NR), Nitrile Rubber (NBR), and Hydrogenated Nitrile Rubber (HNBR).

Polyacrylate Rubber (ACM)
Elastomers - ACMACM elastomers are made of polar acrylic acids. As polar materials, they display good resistance to high-additive lubricating oils. Due to its saturated¹ main chain, the material exhibits good resistance to ozone, weather and heated air. Petroleum-based oils and fluids (for engines, transmissions and automatic transmissions) cannot harm them. But the material offers only moderate strength and low elasticity while displaying limited cold behavior.

Continue reading The Continuous Improvement of Elastomers: Part 2

Your Guide to O-Ring Materials

o-ring materialsAs we’ve discussed in past entries on this blog, O-Rings can come in a variety of sizes and have a wide range of uses.

They can also be made from a number of different substances. Here’s a guide to the kinds of O-Ring materials we use, how they are used, and when to avoid using them.

Continue reading Your Guide to O-Ring Materials