Category Archives: Elastomers

Elastomers, Parker Hannifin Seals

What does a good seal engineering drawing look like?

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

Original content can be found on Parker’s Website and was written by Fred Fisher, technical sales engineer of the Engineered Materials Group.

seal drawingYou just spent 6 months testing, stretching, aging and exposing your new seal design to 12 different chemicals. Finally, you are done. So what does a good technical drawing for a seal include? For most companies, the drawing is simple. For an O-ring, we draw a generic circle and show an ID and width with some sort of material call out.

But now fast forward 20 years. Someone consults the drawing – how do they know the criteria you used to select the seal specified?

Just last week I asked my customer, who was having seal failure, about the issues on their engine sensor: “Was the original seal specified to be compatible with biodiesel?” The engineer consulted their drawing, but besides the generic circle, it lacked any background on what material compatibility was considered when the seal material was selected. The ASTM description on the drawing did not include a reference to or indicate compatibility with biodiesel.

Be specific with materials

Over time, the operating parameters of a system or product can change, so it is important to know what parameters were used for the original seal selection. The goal of the drawing is to assure that the engineers and procurement team understand what performance is required from the seal and why the specific elastomer was chosen.

So how do you make your drawing more valuable to your company?

  1. Define and list on your drawing all the operating conditions you anticipate the seal will see, such as temperature, pressure, and any other application specific operating conditions.
  2. Prepare a list of fluids as well as the concentrations of each fluid that your seal will be exposed to. Add these on your drawing. In addition, make sure you consider fluids that could come into contact with the seal indirectly through failure of other systems that are part of the product or even by cleaning the product.
  3. List the selected compound and manufacturer on the drawing. Clearly define what testing the compound was put through or what testing is required for approval.
  4. If you select a compound that was resistant to compression set, high temperatures or low temperatures, as well as explosive decompression, this should be clearly stated on the drawing.
  5. List clearly the industry standards the seal is required to meet, such as UL, FDA or NSF.

List fluid compatibility requirements

fluid compatabilityTime and time again, I see seal quality and performance failures when a new supplier is selected and the real requirements for the seal were either forgotten or not clearly defined. Clearly defining these parameters and making them transparent will allow your purchasing and technical team to understand, select, and evaluate the correct compound that meets your products sealing requirements.

Once you select a compound for your specific application, it is important to test and validate that the compound chosen is compatible with the fluids you are using. Parker can typically supply small compound samples for soak testing in the fluids your seal is exposed to. If you choose to list an alternate compound on your drawing, that compound must also be tested and validated for compatibility.

Remember when developing drawings standards, assure yourself that if someone consults a drawing that is 2 years old, 5 years old or even 20 years old, they will know the intent of the original seal design.

For more information about custom sealing solutions or information about Parker seals, please contact Gallagher’s engineering department.

elastomeric seals, Elastomers, Uncategorized

Heisman Winner… and Rubber Salesman?

Jay Berwanger, Heisman Winner.

To football aficionados, Jay Berwanger is well-known as the winner of the first Heisman Trophy and the first player chosen during the National Football League’s first draft. Less well-known is that he achieved his athletic successes at the University of Chicago, a school now more closely associated with Nobel prizes than big-time football. Berwanger, a halfback, played for the University of Chicago Maroons at a time when Chicago was a member of the Big Ten Conference–before Robert Hutchins, the University’s president, famously abolished varsity football in 1939.

Even in an era before football teams were divided up into offensive and defensive squads, Berwanger was renowned for his versatility.

Berwanger PosingIn 23 varsity games in three seasons with the Maroons, he scored 22 touchdowns and kicked 20 extra points. He gained 1,839 yards on 439 rushes for a 4.2 average. As a sophomore, he played 60 minutes of every Big Ten conference game and was voted the team’s MVP. During his collegiate career he returned 54 kickoffs and punts for a 31.8-yard average, completed 50 of 146 passes for 921 yards and caught 12 passes himself for 189 yards. He averaged 38 yards on 233 punts and 46.3 yards on 34 kickoffs. He once recorded 14 tackles playing linebacker in one half.

In 1935, the Chicago Tribune awarded Berwanger the Silver Football for Most Valuable Player in the Big Ten. His coach, Clark Shaughnessy, called him “every football coach’s dream player. You can say anything superlative about him, and I’ll double it.” Of the 107 opposing team players he faced during his senior year, 104 said the six-foot, 195-pound Berwanger was the best halfback they had ever seen.

In November of 1935, Berwanger received a telegram from Manhattan’s Downtown Athletic Club, informing him that he had won a trophy for being the “most valuable football player east of the Mississippi,” as well as a trip for two to New York. “It wasn’t really a big deal when I got it,” Berwanger recalled in 1985. “No one at school said anything to me about winning it other than a few congratulations. I was more excited about the trip than the trophy because it was my first flight.” The prize was later renamed the John W. Heisman Memorial Trophy, after the club’s athletic director, the following year.

He was born John Jay Berwanger in 1914 in Dubuque, Iowa. In high school, he excelled at wrestling and track as well as football, winning renown as an all-state halfback. After graduation, Iowa, Michigan, Minnesota, and Purdue all tried to recruit him, but he opted for Chicago, which had offered only a basic tuition scholarship of $300 a year. To meet his expenses, Berwanger waited tables, cleaned the gymnasium, fixed leaky toilets, and operated elevators. “Times were tough then,” he said. “I wanted to attend a school that would give me a first-rate education in business, without special treatment, so that I would be prepared when opportunities were certain to return.”

During his freshman year, Berwanger was coached by the legendary Amos Alonzo Stagg, who helped define the game of football as we see it today. Berwanger’s first year at Chicago was Stagg’s last. As well as captain of the football team, Berwanger was captain of the track team, senior class president, and head of his fraternity, Psi Upsilon.

Berwanger was the only Heisman recipient who was ever tackled by a future president of the United States–Gerald Ford, during a 1934 game between Chicago and Michigan. “When I tackled Jay in the second quarter, I ended up with a bloody cut and I still have the scar to prove it,” President Ford recalled. “Jay was most deserving of his Heisman Trophy. He could do it all. He was an outstanding runner as well a passer, he could kick, punt, and make field goals–and in those days the ball was round so it was much harder to throw. He and I had met several times in the years since that game and I remember him fondly as one of the greatest athletes I’ve known.”

Berwanger was also the first player chosen for the National Football League during its first-ever draft in 1936. After the Philadelphia Eagles signed him, Coach George Halas of the Chicago Bears acquired the signing rights. But when Berwanger asked for $25,000 over two years, Halas decided that was too much money, so Berwanger took a job as a foam-rubber salesman.

Jay Berwanger, Rubber Salesman and Lieutenant Commander

Shortly after starting his job as a rubber salesman, Berwanger enrolled in the Navy’s flight training program and became a Naval officer during World War II. He eventually earned the rank of lieutenant commander.

After the war, Jay Berwanger founded Jay Berwanger, Inc., a manufacturers’ sales agency specializing in rubber, plastic, urethane and other elastomeric materials for car doors, trunks, and farm machinery. His company established a guiding philosophy to create superior value for all customers and principals through dedicated service and by providing integrated solutions to customers’ applications.  Jay sold his company in the early 1990’s when its annual revenue was $30 million.

Post-Heisman and Rubber

Berwanger Heisman and FootballBerwanger was never sure what to do with his Heisman Trophy, which was too wide for a mantelpiece and too large for a coffee table. For years, his Aunt Gussie used it as a doorstop. Berwanger eventually gave the trophy to the University of Chicago where it is on display.

In 1954, Berwanger was inducted into the College Football Hall of Fame. In 1989, he was included on Sports Illustrated’s 25-year anniversary All-America team, which honored players whose accomplishments extended beyond the football field.

Berwanger died in the summer of 2002 and is survived by three children, three step-children, 20 grandchildren, and 13 great-grandchildren.

Information for this article was gathered from Sports Illustrated’s vault, the University of Chicago, and New York Times.

Gallagher has no relationship or partnership with Jay Berwanger Inc. If you liked this article or have an idea about another topic, please let us know!

Elastomers, Prototypes

Modulus of Elasticity for Rubber Sealing Compounds – The Tensometer

Tensile Strength | Ultimate Elongation | Modulus of Elasticity

Rubber Compound Data sheets usually display a number of physical properties as recorded from standard test methods. Among the most common are three measured on the Tensometer:

  1. Tensile Strength (at break)
  2. Ultimate Elongation
  3. Modulus of Elasticity

The Test

Picture of TensometerThe Tensometer stretches a specimen, or dumbbell, cut from a sheet of rubber, until it breaks. During the test, the force required and length of the gauged section are measured continuously. These measurements are used to calculate the various results, which considers the actual dimensions of the test specimen.

While Tensile Strength and Ultimate Elongation are pretty well understood by most, Modulus is not as well understood. Unlike the other two, the Modulus values are not usually reported at break, but rather at various elongation percentages as recorded during the test. Modulus is reported in pounds per square inch (psi) or Megapascals (MPa) at a given elongation percentage as below:

Modulus @ 100% Elongation: 610 psi 4.2 MPa

The Results

You might ask, “What does knowing the Modulus do for me?” While Modulus and Durometer are somewhat related, there can be a pretty large variance in modulus values between two compounds of the same durometer. In an application that requires a rubber seal to be stretched into place, a low modulus compound might be considered to make assembly easier. On the other hand, a firmer compound would be preferable in an application where stretchiness is not desirable. In this case, a high modulus compound would be superior. Higher modulus is also a good indicator of a compound’s ability to resist extrusion in high pressure sealing applications.

This article is not intended to explain at length, the technical aspects of tensometer testing and resultant properties.  To see an actual test performed on an 80 Durometer EPDM, look below:

The original article can be found on Precision Associates website.

Gallagher Fluid Seals is a preferred distributor for Precision Associates. For more information, or if you have a custom engineering question, please contact our Engineering Department.

Elastomers, Freudenberg Sealing

The Future of Seals – Identifying and Communicating Levels of Wear

Seals do their jobs tirelessly, usually behind the scenes. Until now, machines mostly had to be dismantled to check the condition of these parts. That’s expected to change: At Freudenberg Sealing Technologies, a cross-disciplinary team is testing seals that identify and communicate their level of wear. They are based on a novel material that functions as a sensor.

It’s time for maintenance at a beverage bottling facility. Different components of the equipment are opened up, and the seals on tubes, pumps and valves are checked. If they are worn out, they have to be replaced. But if they are still intact, the check itself – a common yet expensive process – is superfluous. What would happen if the seals themselves could autonomously measure and transmit information about the level of their wear? And determine the exact point – no sooner and no later – when little of the seal lip is left and the seal has to be replaced? The future of seals may lie in self-identifying seals.

Seals Identifying Wear Automatically

A cross-disciplinary research team at Freudenberg Sealing Technologies addressed this question. Working with a customer from the process industry, experts developed a seal that measures its own wear. The key benefit: The maintenance of processing equipment – filling equipment in this case – could be performed based on actual need. Moreover, the service staff would have the opportunity to time the maintenance perfectly for the equipment’s operating schedule. Unplanned stoppages due to leaks would become a thing of the past.

Measurement Principle
The seal lip serves as an insulator. If it is worn, the capacity between the electrically conductive seal body and the housing changes.

Electrically Conductive Rubber

Seals are mostly made of elastomers that, in their pure form, are unable to process signals. To arm them with intelligence, it is possible to integrate a sensor or a microchip into a seal. But since the integrated element is a foreign body, it could impair the seal’s functioning. “So we focused our attention on approaches where the intelligence comes from the material itself,” Dr. Boris Traber, who is in charge of the development of new materials at Freudenberg Sealing Technologies. The researchers equipped a sealing material with special fillers to make the elastomer electrically conductive. At the same time, the material had to have qualities that are just as functional as those of a conventional seal. And, since the seals come into direct contact with the food during the filling process, they can only contain components that are on the positive list approved by the EU and the FDA.

Electric Signal Points to Leakage

The design and measurement principles that the seal uses to convey the level of its wear are just as important as its material mixture. In this particular application, an external transducer sends an electric signal over a lead to the seal. This creates voltage between the electrically conductive portion of the seal and the external housing, and the seal lip in-between insulates the two surfaces from one another. The greater the wear of the seal, the less it can effectively insulate the two electrodes from one another. As a result, the electrical capacity changes. If you measure the change, you can draw conclusions about the condition of the seal lip.

Development to Production Readiness

This smart seal is now due to be developed to production-readiness for specific applications. The effort involves material developers, product developers, process specialists and sensor experts who are working hand-in-hand with colleagues from operating areas, the Freudenberg Sealing Technologies sales organization and the customer’s application experts. Of course, it would take a good many experts to actually make seals that were talkative. But it would be possible – that much is clear, and the future of seals is looking bright.

For more information about sealing technologies, and to find out which seal might be a fit for you, contact Gallagher’s Engineering Department.

The original article was featured on Freudenberg’s website and can also be found in the May 2019 edition of their ESSENTIAL magazine.

elastomeric seals, Elastomers, O-rings, sealing technology

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.

elastomeric seals, Elastomers, Technetics

Inflatable Seals

Designing with inflatable seals for the medical industry

Seals are central parts of the design of medical equipment with moveable, interlocking parts that must be secured for sanitary, thermal, or radioactive reasons.

Designing with inflatable seals requires the inclusion of a source of compressed gas, which is used to inflate seals in the medical device industry and it is often already available on the plant floor, in a laboratory, or medical environment. It is also possible to inflate with liquids rather than gas in demanding applications, and water would be an acceptable inflation media in this sector, although not common. For some low-temperature applications, a seal may be inflated with a blend of glycerine and water.

Designing with inflatable seals

Seals used on doors and openings should be part of the early phases of product design. In some cases, contact seals may be effective, but they often require substantial force be applied to load the seal, which impacts product design and increases manufacturing cost. Inflatable seals enable more cost-effective machinery fabrication for two reasons:

  1. Inflatable seals are more forgiving because the seal can inflate to close a gap between structural members and achieve equal sealing pressure around the flange as long if the gap falls within a broad tolerance. An inflatable seal will work whether the gap spans 3mm or 10mm, for instance. A compression seal or other contact seal will not be effective unless the seal and flange contact each other with great precision, which can be difficult to achieve on new equipment. Even a robust and precision-manufactured machine with well-designed flanges will lose some of its geometric integrity as hinges and other components deform or bend over years of use. Throughout the course of the equipment lifecycle, a contact seal may become problematic and exhibit leakage.
  2. Inflatable seals enable lighter and more affordable methods of equipment fabrication. The force exerted on the chassis of a piece of equipment means doors and related components must be thicker, and perhaps machined instead of welded. These components are typically made of stainless steel, and inflatable seals might be attractive due to lowered material costs.

Which equipment needs inflatable seals?

  • Isolators — where a leak-tight enclosure can be critical for environmental health protection due to hazardous substances or processes. — can secure glove boxes, access gates, transfer systems and filtration systems that handle toxic or sterile components.
  • Sterilizers — which may rely on heat, chemicals, irradiation, or filtration — may be suitable for desktop autoclave sterilizers, sterilizing tabletop autoclaves and static air depyrogenation sterilizers.
  • Dryers and freeze dryers – used to sterilize everything from machine components to glassware.
  • Material handling functions – to raise, lower, or grasp objects.

Continue reading Inflatable Seals →

elastomeric seals, Elastomers, O-rings, Oil & Gas, oil and gas, Parker Hannifin Seals

Degradable Materials Simplify Well Completions in Oil & Gas Extraction

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

Original content can be found on Parker’s Website and was written by members of the O-Ring & Engineered Seals Division. Jacob Ballard – research and development engineer, Jason Fairbanks – market manager, and Nathaniel Sowder – business development engineer.

degradable materials for offshore drillingThe emergence of degradable and dissolvable materials is providing oilfield service companies an opportunity to increase efficiencies and cut costs in the oilfield by simplifying well completions. These materials replace their conventional metallic and polymeric counterparts in completion tools, but eventually break down and disperse when exposed to common completion fluids. This eliminates the need for well interventions to mill out or retrieve used tools. This can result in a reduction of drill time, a safer work environment, and monetary savings for the operator. Parker Hannifin produces dissolvable and degradable metal alloys, thermoplastics, and elastomeric materials that can enhance your well completions.

Degradable Elastomers

Parker O-Ring and Engineered Seals (OES) Division produces degradable elastomer formulations that can be used in frac plugs, liner wipers, and other sealing applications common in the completions segment. These elastomer formulas have tough physical properties and low compression set and are designed to replace materials such as Nitrile or HNBR in conventional tool designs. With proper design, tools using Parker degradable elastomer can withstand the high pressures (>8,000 psi) generated during hydraulic fracturing while still eventually deteriorating away, allowing well production without having to be drilled out. These degradable elastomers can be produced in a variety of desired forms such as O-rings, custom molded shapes, and packing elements. They can also be bonded to dissolvable metal alloys to produce completely degradable solutions. If needed, Parker offers a product engineering team to assist with the design of components and rapid prototyping services to help cut down on development timelines.

Degradable Thermoplastics

Parker Engineered Polymer Systems (EPS) Division manufactures engineered degradable Thermoplastic materials which can be used in many types of completion tools that traditionally use non-degradable elastomers. Parker EPS’s high-grade thermoplastic materials have increased physical properties over conventional elastomers making it ideal for both high pressure/high temperature and wear resistant applications. The increased physical properties of EPS thermoplastics provide enhanced resistance to extrusion, temperature and wear over most degradable non-metallics in the market. These unique thermoplastic materials may be manufactured in both homogenous as well as bonded components such as Packers, Parker back-up rings, Frac Plugs and liner wipers and are ideal for hot trouble well applications.

With a wide range of wellbore temperatures and completion fluids seen across the industry, selecting the right degradable compound can be complicated. Gallagher Fluid Seals, in coordination with Parker, can help assist in recommending the proper paramaters for using degradable elastomers.

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

Elastomers, O-rings, Parker Hannifin Seals, sealing technology

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

elastomeric seals, Elastomers, O-rings, Uncategorized

What to Know, Avoid, and Consider When Planning Seals for Medical Devices

Seals are one of the most important components in many medical devices. While small in cost, seals for medical devices have a profound affect on the function of said device and the outcome of a medical procedure.

Engineered sealing solutions have advanced to meet the new medical device designs due both to new materials and to new processes for producing these seals. An understanding of the fundamentals of seal design, the tools available to assist in the manufacturing process and pitfalls to avoid will help in achieving a successful seal and medical device outcome.

Classifying the three basic seal designs

When approaching a new seal design, It is important to classify the seal based on its intended function. All seals fall into one of three distinct groups. While certain applications may combine more than one group, there is always one that is dominant. The three basic seal designs are:

Static — seal applications where there is no movement.
Reciprocating — seal applications where there is linear motion.
Rotary — seal applications where there is rotation.
Static seal applications are the most common and include those that prevent fluids and drugs from escaping into or out of a medical device. The seal design can range from basic O-rings to complex shapes. Static seals can be found in the broadest range of medical devices from pumps and blood separators to oxygen concentrators.

trocar design
New advances in trocar designs incorporating specialized seals allow multiple instruments to be inserted in the single trocar.

A reciprocating seal application with linear motion would include endoscopes that require trocar seals. These trocar seals are complex in design and allow the surgeon to insert and manipulate instruments to accomplish the medical procedure. These procedures range from relatively simple hernia repairs to the most difficult cardiac procedures. All of these minimally invasive surgeries employ endoscopes with seals that rely on seal stretch, durability and ability to retain shape during lengthy and arduous procedures. This particular seal application combines both reciprocating and rotary motion with the main function being linear motion.

A rotary seal application most commonly includes O-rings used to seal rotating shafts with the turning shaft passing through the inside dimension of the O-ring. Systems utilizing motors such as various types of scanning systems require rotary seals but there are many other non-motorized applications that also require rotary seals. The most important consideration in designing a rotary seal is the frictional heat buildup, with stretch, squeeze and application temperature limits also important.

Function of a particular seal design

What is the function of the seal? It is important to identify specifically if the design must seal a fluid and be impermeable to a particular fluid. Or will the seal transmit a fluid or gas, transmit energy, absorb energy and/or provide structural support of other components in device assembly. All of these factors and combinations need to be thoroughly examined and understood to arrive at successful seal design.

A seal’s operating environment

In what environment will a seal operate? Water, chemicals and solvents can cause shrinkage and deformation of a seal. It is important therefore to identify the short and long term effects of all environmental factors including oxygen, ozone, sunlight and alternating effects of wet/dry situations. Equally important are the effects of constant pressure or changing pressure cycle and dynamic stress causing potential seal deformation.

There are temperature limits in which a seal will function properly. Depending on the seal material and design, a rotary shaft seal generally would be limited to an operating temperature range between -30° F and +225°F. To further generalize, the ideal operating temperature for most seals is at room temperature.

Expected seal life – How long must the seal perform correctly?

Continue reading What to Know, Avoid, and Consider When Planning Seals for Medical Devices →

Elastomers, Food Processing, Freudenberg Sealing

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