Keep it clean. Often easier said than done. Recently, efforts to improve disinfection and sterilization in healthcare facilities were spurred by Medicare reimbursement cuts to hospitals along with new guidelines from the U.S. Centers for Disease Control and Prevention (CDC). Despite the renewed focus, in 2011 there were still 721,800 cases of Healthcare-Acquired Infections (HAIs) with 75,000 deaths.

Lots of work remains to be done to reach disinfection and sterilization standards

As it stands, only 30 percent to 38 percent of U.S. hospitals are in full compliance with the CDC’s current infection control guidelines. 100 percent compliance is a reasonable goal, but there remains a sizeable gap to close. Getting there starts with the creation of reliable, affordable and easily obtainable antimicrobial products so healthcare providers can better-prevent device-associated infections.

Antimicrobial coatings vs. homogenous antimicrobial materials

While antimicrobial coatings may be an attractive option for some applications, they have their shortcomings. Coatings are often limited in efficacy to the surface of the device, not to mention the uniformity of their application must be closely monitored during a secondary, and often costly, manufacturing process. On the other hand, homogenous antimicrobial materials are effective immediately out of the mold or die and retain their efficacy even when damaged or abraded.

Parker has overcome many of the polymer processing limitations that have traditionally plagued antimicrobial compounds. Our elastomers with select antimicrobials additives have shown excellent antimicrobial efficacy (99.99 percent) and biocompatibility while maintaining virtually all mechanical properties and processing capabilities.

What to consider when designing medical devices

Device manufacturers are encouraged to be as specific as possible when providing their initial design parameters. Antimicrobial polymers are available in several HAI-resistant applications, including vascular access, fluid management, instrument housing, airway management, laparoscopy, wound dressings, Class I, II, and III medical devices and more. Beyond the functionality requirements of a given device, consideration should be put into how damp the end-use environment will be, how long a device will be used, and what color/transparency/translucency requirements a device may have. Discussing as much as possible up-front allows for a quicker development stage and better, more cost-effective results overall.

Parker provides several solutions for medical device and component manufacturers

• Customize antimicrobial polymers for your device’s preferred base polymers, aesthetics and functionality.
• Retain virtually all mechanical and physical properties of conventional (non-antimicrobial) polymers.
• Choose between silver (wide medical industry acceptance) and non-silver (similar efficacy to silver with less cost and less discoloration) based antimicrobial additives.
• Avoid predictable costly issues before they occur with thermoplastic molding simulation and virtual prototype evaluation.
• Reduce time-to-market:
  • Start your device design process with polymers that have proven ISO 22196 antimicrobial efficacy and ISO 10993 biocompatibility.
  • Receive finished antimicrobial components from Parker’s ISO 13485 certified production facilities, ready for integration into your medical devices.

Not only are HAIs costly to healthcare providers, many of them are preventable with the right antimicrobial devices. With so much room for improvement in HAI prevention, now is the perfect time to become an industry leader and join with Parker to create safer healthcare devices and environments.

This article was contributed by Saman Nanayakkara, Division Laboratory Manager and Sr. Chemist, Parker Hannifin Medical Systems Division.

If you would like to speak with our team directly, Parker will be at the MD&M West Conference and Exposition, Booth 2801,  February 9-11, 2016 at the Anaheim Convention Center, Anaheim, California.

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Gas springs that enhance comfort are found in a wide range of consumer goods and everyday devices. But in industry, as well, gas springs are increasingly being used to improve process reliability and efficiency. To deliver dependable performance in their respective applications, all gas springs require an absolutely reliable sealing system that corresponds exactly to their specific requirements profile. 

The gas spring is a pneumatic spring. It is energized by a highly compressed gas. The system, which is basically of a relatively simple design, consists of a cylinder, piston, piston rod and the closure package with the seal as its core elements. Initially introduced nitrogen generates the service pressure and a few cubic centimetres of – typically synthetic – lubricants assist in performing the desired function. The gas pressure acts on the cross-sections of the piston, which vary in size, and generates a force in the outbound direction of travel when the piston rod enters the the piston. The job of the rod seal is to protect the amount of gas that has been introduced into the cylinder from leakage and to thereby prevent loss of the spring’s functionality. 

The GS rod seal has been specifically developed for the challenging demands of gas spring applications. Apart from small housings, they include long service life and maximum gas tightness with low friction. These properties make the seal, in addition to its use in gas springs, suitable for applications in hydraulic and pneumatic equipment that involve the same demands.

The short contact space of the sealing area guarantees low friction values. Back-up rings or retainers are not required due to the special shape. The seal can be used in both hydraulic and pneumatic systems with oiled air. 

The GS rod seal is available in various Parker-Prädifa Ultrathan® (TPU)-compounds  and can thus be matched to the respective requirements. It is compatible with the time-tested C1 seal profile and fits into the same housings.

Compared to conventional seals made from NBR or FKM materials, the GS rod seal reaches an up to 10 times longer service life.

• Excellent wear resistance
• Very low permeation rates
• Very broad media resistance
• Broad temperature range
• Easy assembly
• Suitable compounds available for special requirements of the chemical process industry and the food industry
• Installation in closed and undercut grooves

For more information about the GS gas spring seal, please download our brochure
or contact the experts at Parker-Prädifa.

Article contributed by Stefan Reichle,
Market Unit Manager Industrial/Consumer/CPI,
Engineered Materials Group,
Packing Division Europe.

Parker Hannifin Corporation is launching a new, interactive digital reference guide to enhance and broaden the customer reach of the existing Parker O-Ring Handbook. For more than 50 years, the Parker O-Ring Handbook has been an engineering staple of the sealing industry.

“I’m constantly amazed and honored at how often I run across it in unexpected places,” says Dan Ewing, Sr. Chemical Engineer and Materials Manager at Parker O-Ring Division, “I've come to expect to see a well-used copy sitting on a customer's desk, but I'm pleasantly surprised when I find it cited in academic papers, referenced in reports written by government agencies and discussed in industry association meetings.”

Since its debut in 1957, the handbook has become a fixture on the reference shelves of engineers and seal specifiers worldwide. According to Steven Weinzierl, Ph. D., Parker's Global e-Business Customer Support Manager, "Parker's O-Ring Handbook is one of the world's most complete reference books for everything and anything related to the technology and application of O-rings. It is downloaded thousands of times a month from Parker's website, making it one of Parker's most downloaded knowledge assets." Weinzierl observes, "This new, interactive version should significantly increase the accessibility of this outstanding resource."

Parker is strengthening its dedication to premier customer service by enhancing its commitment to digital tools and communications. Ewing says, “The new eHandbook takes the next step in enhancing the customer experience by transforming the static PDF version of the handbook into an interactive and more user-friendly tool.”

Key Components:

• Short, engaging animations
• Snippets of real material test procedures
• Direct links to accelerate the sales process
• Online Chat with an Engineer capability within each page
• Design analysis via Mobile inPHorm™ (Parker’s O-Ring Calculator)

The O-Ring eHandbook is expected to bridge the generation gap, filling the need for all learning and reference styles. The original formats of the printed catalog and searchable pdf will still remain available via Parker’s Catalog Services and the O-Ring Division website. The O-Ring eHandbook will provide visual learning, interesting excerpts and summarized information that makes finding what you need effortless. New content will be added as needed and because the format is web-based, content updates will become quicker and more efficient. "I like the simplicity the eHandbook brings to O-ring design and material selection," says Dorothy Kern, Parker O-Ring Division Applications Engineering Manager. "The original handbook is rich with details for all elements of O-ring design, but 292 pages can be overwhelming to a new engineer. The eHandbook simplifies the main design concepts and utilizes updated graphics to illustrate just the highlights, making it a great resource."

For more information on the O-Ring eHandbook or other Parker O-Ring Division support tools, contact the experts at the O-Ring Division online or directly at 859-335-5101. 

    This article is contributed by Samantha J Sexton, Marketing Communications Manager,

    Parker Hannifin O-Ring Division.

Additional support videos of customer interest:

• Proper Installation of an O-Ring: Full and Half Dovetails
• Proper Installation of an O-Ring: Face Seal Gland
• Proper Installation of an O-Ring: Standard Female Gland
• Proper Installation of an O-Ring: Standard Male Gland
• Diagnosing a Damaged O-Ring

Other blogs from Parker O-Ring Division:

• Do Your Seals Meet the Demands of the Oil and Gas Industry? 
• New Fluorocarbon Seal Material Extends Safe Life of Jet Fuel O-Rings

From popular pedometers to life-changing glucose monitors, more and more people are adopting medical technologies they can wear. Over 20% of consumers claim to have purchased a wearable device, and some estimates foresee 3 billion wearable sensors in use by 2025. Even though wearable devices seem to be a shoe-in solution for monitoring our bodies and our activity levels, for a device to be successful, it should offer a genuine benefit and demonstrate the ability to improve quality of life.

Wearables in healthcare are currently geared toward allowing patients to perform some preventive healthcare solutions without visiting hospitals or seeing caregivers. Many wearable devices can also shorten hospital stays or make day-to-day life simpler by streamlining some at-home processes or making them less painful and less cumbersome. In a nutshell, wearables today best-offer peace-of-mind and mitigate some common physical challenges and discomforts.

The future of wearables is bright. Right now, a bigger challenge to the industry than determining the possibilities of wearables is determining which of those many ideas offer the best solutions for patients in the near future. Although the potential of interventional measures is attractive, for the most part devices that offer them remain a ways off.

Between where wearables are now and the future they could provide, there is a large need for two things: data and data analysis. Lots of talk is heard about the ability of wearable devices to collect information, but then what? Until enough data is collected and that information analyzed and proven to have significant insights, many of the potential applications of wearables will remain just that — potential. This means one of the key challenges to wearables in the years ahead is to offer real benefits to patients who use the devices while collecting data that could have substantial impact in the future.

Even today wearable devices can go well-beyond monitoring vital signs and activities.

• A more recent technology called electroactive polymers (EAPs) allows expandable sensors to measure volume, which could have significant effects in spirometry or even vascular applications.
• Small EKG/ECG pads provide monitoring and detection for cardiac conditions and can be woven directly into clothing fabrics.
• Several insulin and oxygen advances have led to wearables small and light enough to be worn on a belt in a device the size of a cell-phone.
• A new patch for diabetes patients ,which is about the size of a coin, can be worn on the arm and entirely eliminates pin pricking for the blood samples required for glucose monitoring.

Along with these innovations, there are now clothing pieces capable of detecting indications in the skin that could serve as early warning signs for diseases such as cancer. However, early detection of diseases like cancer raises an important question about the value of what people can know and the viability that they would want to. This same conflict was also raised by advances in molecular genetic testing, which can discern the predisposition of patients toward possible diseases and defects.

Wearables are more than cool tech. They are tools that can and will change the way the world views and handles healthcare. The future of these devices holds more than awe-inspiring advances; serious questions are arising about what health information can and should be known and by whom. What we do know is that good wearable device development in the near future should offer services to patients that make their everyday lives easier and their long-term care less overwhelming.

With our unparalleled engineering tradition, Parker is positioned at the forefront of several wearable technologies and is the perfect partner to help any OEM from initial design to prototyping to testing to distribution. We offer an extensive breadth of wearable technologies, including EAP sensors, EMI shielding, seals and O-Rings and homogenous antibacterial polymers among others. Our experts, facilities and experience will get your products to market faster, more cost-effectively and with more success.

To learn more about all that Parker has to offer the medical device industry, visit www.parker.com/medical.

This article contributed by Brad Kraus, Global Account Manager, Life Sciences, Parker Hannifin Corporation.

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O-rings are the simplest, most readily available type of seal used across every industry and market. They are arguably the best seal for many applications, but perhaps daunting to an engineer with no experience in seal design. The O-Ring Basics chapter of Parker's eHandbook provides an overview of what an O-ring is, how it works, and finally, the benefits over other seals.

The original content found in the O-Ring Handbook has been streamlined into the eHandbook, presenting O-ring designers with essential information to utilize when teaching sealing principles. Based on the foundation outlined in the industry's standard reference guide, users will still find the same rich information the O-Ring Handbook is known for but in a much more abbreviated and dynamic format.   

After reading the eHandbook O-Ring Basics section, an engineer or student will have a solid visual picture of how an O-ring works to contain fluids. Concise summaries and clear visuals illustrate the fundamental principle of an O-ring in an application, engergized by fluid pressure, creating a powerful and effective sealing element. The final section will detail advantages for using an O-ring as a sealing profile of choice.

Do you need your material to be highly saturated? fluorinated? Do you want a nitrile or tetrafluoroethylene-propylene? The language of rubber materials is somewhat confusing and can become overwhelming. Parker's O-Ring eHandbook covers industry terminology and much more in the O-Ring Elastomers chapter. Much like a cake has a recipe, including basic ingredients such as flour, eggs, and sugar; a rubber compound is made according to a recipe that includes key ingredients such as a polymer, accelerator, and curing agents. The O-Ring Elastomer chapter breaks down the benefits of these key ingredients, explaining why they are important and what role they play in your application. 

Further subsections of the Material Selection Guide feature a compound family overview including a description of compound advantages, typical temperature maximum/minimum, and compatible fluids. A list of incompatible fluids are also detailed, allowing the user to receive a concise summary of the most common, and even the more obscure elastomer types. 

Check out the Parker O-Ring eHandbook sections highlighted above or visit the Parker O-Ring Division for further information and useful tips on how to select an O-Ring. 

This article was contributed by:

Parker-Prädifa has developed nobrox®: a new, versatile material that opens up new avenues in sealing technology while being equally well suited for engineered components in diverse industrial and consumer goods.

The material exhibits excellent wear resistance, chemical resistance and resilience, reliability, ease of assembly and economy.

nobrox® is suitable for for sealing, guiding and anti-extrusion elements in hydraulics and many other sealing technology applications, as well as for engineered components without a sealing function in a wide range of industrial equipment and consumer goods: from automotive engineering through to food and pharmaceuticals production. 

Extensive design freedom thanks to unique combination of the material’s properties: outstanding wear resistance, media resistance, permeation properties, plus excellent resilience Easy, robust installation System integration of multiple functionalities (e.g. sealing, guiding, carrier/housing element) Economy nobrox® provides an attractive alternative to PA, POM, PE, etc., depending on the application profile

 

For engineered components, a comparison with polyamides would seem natural, albeit with two major differences. The water absorption of nobrox® is significantly lower and its ultimate elongation clearly higher. Consequently, nobrox® components have greater dimensional stability, as there are no variations in moisture absorption that might result in variances. Additionally, they are more resistant to heavy or sudden loads. Compared with PEEK plastics, which are very resistant as well, nobrox® is clearly more elastic. Less costly than PEEK, nobrox® might be referred to as “PEEK light.” As such, nobrox® offers similarly outstanding benefits as PEEK, a material that has been equally known for high performance and relatively high cost.

Compounds of the new nobrox® family of materials can be precisely adapted to the relevant customer requirements such as friction, pressure and temperature conditions, as well as media resistance. The seals and engineered components are subsequently produced in a very cost-efficient manufacturing process which is reflected in a favorable cost-benefit ratio for the customer as well. Additional cost benefits for the user result from the long service life, as well as robust and easy assembly of seals and engineered components made of nobrox®.

Article contributed by
Thomas Braun,
Marketing und Engineering Manager,
Engineered Materials Group,
Packing Division Europa

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Pharmaceutical manufacturing is a very precise science with little to no room for variation in the synthesis process. Companies spend millions of dollars on research and development to perfect drug formulas before they can go to market. With all of the time and money spent on developing these drugs, companies often overlook the importance of proper sealing for medical containers. Each year, pharmaceutical companies lose hundreds of thousands of dollars of finished goods due to contamination during canister sterilization and transport. Parker’s custom Gask-O-Seal technology combines 316 stainless steel with Parker’s E3609-70 ethylene propylene to provide superior sealing throughout pharmaceutical packaging and transportation.

Pharmaceutical containers are highly regulated by the Food and Drug Administration (FDA) and must be sterilized before and after the drugs have been placed in the containers. Parker Composite Sealing Systems Division has developed three Gask-O-Seals to alleviate the common issues facing previous sealing methods. Typically, PTFE rings are used to seal each canister. However, when these canisters go through the sterilization process, the high temperature (124°C) and steam cleaning causes these rings to relax. With the loss of torque each canister would fail the helium leak test causing downtime in production, as well as loss of finished goods during transit. Parker's seals were designed to solve these leak problems by using an elastomeric seal with a metal retainer providing a more robust and complete sealing solution. With the elastomer acting as the sealing element and the metal retainer acting as a compression limiter between the canister and the lid, they no longer experienced torque loss. In the elastomer selection process, we put multiple compounds through a moisture vapor transference test in order to make the best selection. This test data proved that our E3609-70 ethylene propylene was best suited for keeping moisture out of the canisters due to its temperature capabilities and superior vapor resistance.

In order to prevent cross contamination between our seal and the pharmaceuticals in each canister, our seals had to be designed without the use of chemical bond to keep the elastomer attached to the metal retainer. In order to do this, our engineers designed this seal utilizing mechanical bonding techniques to prevent our chemical bonding agents from contaminating the chemical formulations.

Pharmaceutical canisters are not the only viable market for a product like these Gask-O-Seals. I-Line gaskets are used in the processing pipeline systems for the food, dairy, beverage and bio tech industries, as well as the pharmaceutical industry, all of which require similar standards in their sealing options. Our product has already proven its exceptional performance during sterilization while eliminating the possibility for cross chemical contamination.

Parker Composite Sealing Systems Division offers a multitude of sealing options so let us help you with your next project. For more information on our unique sealing solutions, contact the experts at the Composite Sealing Systems Division.

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For obvious reasons, product safety is increasingly subject to legal provisions. As the industry’s first manufacturer to do so, Parker-Prädifa is now implementing the requirements of the German Product Safety Act, which is based on EU law, for seals and other polymer products, thus playing a pioneering role.    

According to the Product Safety Act (ProdSG), which has been in effect in Germany since the end of 2011, manufacturers have to provide their products with appropriate user instructions if, for the protection of health and safety, specific requirements (such as warnings) have to be complied with during usage, maintenance and repair of the products. These instructions must be available in local language and visible to the end user on the product. 

legal requirements entail two tricky challenges. As our products, for one, are sold around the world, this raises the question about the appropriate language to be used. For the other, the size of our products does not provide a sufficiently large surface for such information. Added to this is the demand that the instructions must be visibly available to the user of the products. Hence a reference to a website printed on the packaging label is not an option. A case in point would be the repair of an agricultural machine in the middle of a forest where it can be assumed that the user has no internet access.

Even though to date the relevant national organizations and bodies have not reached any agreement on how to precisely implement the Act with regard to seals, an internal team has now developed an effective and feasible solution for Parker-Prädifa’s products. To satisfy the requirement of providing information in the relevant languages, the team selected appropriate pictograms with pictorial pointers regarding misuse or mishandling. The pictograms (largely according to DIN ISO 7000) refer to the typical criteria for suitability in the application and the required appropriate storage. In the interest of our end customers and in line with our obligations under applicable law, a responsible and practical solution has thus been found.

The following pictograms will be found on all product labels of the Parker Engineered Materials Group Europe, starting in January 2016:

For more information, please read our article “New Product Labels for more Safety” in the Dec. 2015 issue of the EMG Report (page 9).

Article contributed by
Thomas Braun,
Marketing und Engineering Manager,
Engineered Materials Group,
Packing Division Europa

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Are you uncertain of what to look for when comparing material data reports for various elastomers?  Ever wonder about the impact a seal’s durometer has in the application? Have you asked, ‘What is compression set and why is it important?’ These are the types of questions and concepts covered in the O-Ring Elastomers chapter of Parker’s O-Ring eHandbook. 

Since its debut in 1957, the Parker O-Ring Handbook has become a fixture on the reference shelves of engineers and seal specifiers worldwide. According to Steven Weinzierl, Ph.D., Parker's Global e-Business Customer Support Manager, "Parker's O-Ring Handbook is one of the world's most complete reference books for everything and anything related to the technology and application of O-Rings. It is downloaded thousands of times a month from www.parker.com, making it one of Parker's most downloaded knowledge assets." By creating an interactive, digital version of this resource, Parker is expanding it's customer base and utilizing various forms of multi-media to provide visual explanations and demonstrations that further enhance an industry staple.

Seal manufacturers compile material data sheets of physical properties, compression set, and a myriad of other combinations of testing; all intended to demonstrate the seal material’s capability. But what are these characteristics, and how does one relate the results to an application? 

The Physical and Chemical Characteristics chapter explains the lab testing behind each data point on a test report. Video snips of laboratory equipment testing O-rings illustrate how data is generated. Animations create a visual explanation of testing such as TR-10. Brief summaries of each characteristic explains how data can be applied to an O-ring in service. Photographs and vibrant charts help to put context around the data, in order to bring to light how each bit of information should be interpreted.

Perusing the Physical and Chemical Characteristic chapter will allow you to evaluate rubber test reports with a greater understanding than ever before.

Further subsections of the Material Selection Guide feature a compound family overview including a description of compound advantages, typical temperature maximum/minimum, and compatible fluids. A list of incompatible fluids are also detailed, allowing the user to receive a concise summary of the most common, and even the more obscure elastomer types.

Check out the Parker O-Ring eHandbook sections highlighted above or visit the Parker O-Ring Division website for further information and useful tips on how to select an O-Ring.

This article was contributed by:

Dorothy Kern
Applications Engineer Lead
O-Ring Division

Samantha J. Sexton
Marketing Communications Manager
O-Ring Division

Other blogs from Parker O-Ring Division:

A Simple Guide to Selecting an O-Ring

New O-Ring eHandbook Provides a Premier User Experience

New O-Ring Materials for Jet Fuel Lengthen Maintenance Cycles and Reduce Costs

Automotive fuel systems harbor the risk of electrostatic charging which may lead to arcing. The objective, therefore, is to engineer fuel systems using conductive components. Parker-Prädifa effectively supports this aim in a new generation of FKM sealing compounds delivering significantly increased conductivity combined with excellent media resistance. Compared with standard FKM materials for fuel applications, the new Parker compound V8918-75 improves conductivity by a factor of 1,100,000 on the component (O-ring).

As the FKM elastomers generally used in fuel applications are very good insulators per se, the utilization of standard elastomers would result in an electrical isolation of the fuel system components. Therefore, Parker-Prädifa developed a new generation of FKM sealing compounds with significantly increased conductivity combined with excellent media resistance. Standard FKM compounds for fuel applications have a conductivity of 2.1E+11, whereas the conductivity of Parker’s new FKM compound V8918 is 1.83E+4, equating to an improvement by a factor of 1,100,000.

The development of the new FKM compound generation involved a number of criteria to be observed. The physical properties of the FKM had to be on a high level, electrical conductivity was to be significantly increased, media resistance to fuel, biofuels and flexfuels had to be exceptionally good, and cold flexibility had to be ensured. Table 1 summarizes the properties profile of the newly developed compound V8918.

In addition to significantly enhanced conductivity, the utilization of a material in modern fuel systems requires excellent media resistance. Table 2 reflects the storage results of V8918 in FAM B and E85. The storage tests were conducted according to VW 2.8.1 A at 23 °C for 168 hours. After re-drying the samples at 85 °C for 22 hours, only a marginal change of the original properties can be observed in both test media.

The new Parker-Prädifa compound V8918-75 exhibits a well-balanced physical profile, significantly increased electrical conductivity, very good media resistance, as well as very good suitability for low application temperatures. Consequently, it is predestined for sealing solutions to minimize electrical charging in fuel Systems.

For more information and detailed test results, please read our article “1,100,000 Times Better Conductivity” in the Dec. 2015 issue of the EMG Report (page 13).

Article contributed by
Dr. Heinz-Christian Rost
Technology and Innovation Manager,
Engineered Materials Group

New Material nobrox Increases Design Freedom for Seals and Engineered Components

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Have you ever taken a component off the shelf, only to discover that the O-ring on it is full of cracks? Have you ever wrapped some pencils in a rubber band, only to have the rubber band develop cracks and eventually break? You may have witnessed ozone cracking, or “ozonolysis”.

We use O-rings every single day, and most of us don’t even know it, until one of them starts to leak. One common cause of leakage in O-rings is ozone cracking. On a manufacturing floor, ozone cracking can be a source of aggravation. In the field, it can cause leaks, which may lead to serious injury or death. Fortunately, this is a very preventable phenomenon. In this blog, you will learn about the causes of ozone cracking and how you can prevent it.

Ozone cracking occurs mostly with O-rings made from nitrile rubber. If you have previous experience with O-rings, you may recognize this material as nitrile, buna, or buna-N. This material is called a polymer, which is Greek for “many units”. Each molecule consists of long chains, of individual units, which are bonded together into a long chain. In the case of nitrile rubber, the repeating unit, or link, is shown in Figure 1.

Figure 1. Repeating unit for nitrile rubber

The C, H, and N represent carbon, hydrogen, and nitrogen, while the dashes represent single, double, and triple bonds. Of particular interest is the double bond between the second and third carbon atom. This double bond is a "weak spot" within the molecule. Ozone can "donate" an oxygen atom and break this chain, as shown in Figure 2.

Figure 2. Ozone cracking at the molecular level

The two oxygen atoms are connected to the carbon atoms on either side, but they are not connected to each other. Because of this, the polymer chain is literally cut, forming a tiny crack in the O-ring. As more of these polymer chains are cut, the cracks get bigger and bigger, until they can be seen with the naked eye.  

Figure 3. Ozone cracking in nitrile O-ring

Oxygen is present in the air that we breathe, and is necessary for life on Earth. Oxygen atoms typically join up in pairs, forming dioxygen. This makes up the vast majority of oxygen in the atmosphere. Occasionally, oxygen atoms join in groups of three. This creates a substance called ozone.

As a general rule, ozone is good up high, but bad nearby. In our stratosphere, ozone concentration is between 2 and 8 parts per million. This forms the fantastic blue ozone layer that protects us from the sun’s harmful rays. However, in the troposphere, or the air that we breathe, concentrations above 75 parts per billion can cause health problems, according to the EPA (even though their own scientists recommended 60 parts per billion). Even very tiny concentrations such as these can cause ozone cracking in nitrile O-rings.

In general industrial applications, the primary drivers of ozone concentration are ultraviolet light, electrical arcing, and electromagnetic fields (which are the main reasons for higher ozone concentrations in the stratosphere).

• Keep O-rings away from ultraviolet light. The most common sources are direct sunlight, and fluorescent light bulbs.
• Do not store O-rings within 6 feet of an electric motor, or other potential sources of electrical arcs.
• Do not store O-rings in a stretched state. O-rings typically need to be stretched for ozone cracking to occur.

• When using nitrile O-rings on fittings, we recommend installing them into the mating part within 24 hours of installing the O-ring on the fitting. If O-rings must be stored in a stretched state, store them in an airtight bag until ready to use.
• Assemble nitrile O-rings wet with a grease to protect from ozone.

In applications where long-term environmental exposure is inevitable, we recommend using an ozone-resistant material, such as HNBR, EPDM, or fluorocarbon.

If you have any questions, please feel free to contact Parker applications engineering or check out our interactive O-Ring eHandbook.

This article was contributed by

David Mahlbacher, Parker O-Ring Division, Applications Engineer

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O-Ring Squeeze - More is Not Always Better

A Simple Guide to Selecting an O-Ring

How to Avoid Critical Component Failure in the Oil & Gas Industry

Designing the proper gland for a seal is usually a straightforward, easy process.  Not only does the Parker O-Ring Handbook outline recommendations for stretch, squeeze, and volume fill necessary to achieve a good design but the Parker inPHorm design tool can be used to directly output the recommended dimensions making the design process quick and painless for most situations. 

While most may be straightforward, there are certain applications, like those which experience high pressure, that require special consideration to ensure a robust design is achieved.  Parker O-Ring Division defines a high pressure seal as one that may see 500 psi or greater.  When an application pressure exceeds these limits, critical parameters like modulus of elasticity and diametral clearance become vitally important.  If these factors are not considered, the design may run the risk of extruding seal material which can result in leakage, equipment downtime, equipment recall, or even injury to personnel.  In the following paragraphs, I will help identify what modulus of elasticity and diametral clearance are, how they are impacted by pressure and how you can determine the pressure rating of a system. 

Modulus of elasticity, often abbreviated as modulus, is defined as a material’s resistance to elastic deformation. A rubber material’s modulus is the ratio of stress over strain and can be measured experimentally by pulling samples on a tensometer.  Modulus is difficult to express numerically because of rubber’s non-linear behavior.  Oftentimes modulus at 100% elongation is given on a material test report.  This value is the ratio of stress over strain after a material has been stretched 100% of its original length.  Modulus can also be reported at other percentages of elongation with the expectation that the value may not be exactly the same as modulus at 100%.  Because of the non-linear behavior of rubber and the destructive nature of tensile testing, we choose to focus on material hardness as an easy measure of how an O-ring will perform in relation to pressure.  When comparing two materials of the same hardness, we then utilize modulus at 100% elongation as a way to indicate which material will resist extrusion better.

In the world of O-rings, we measure material hardness using the Shore A durometer scale, which runs from 0 to 100.  On the scale, 0 represents the softest materials and 100 represents the hardest materials.  For example, a typical rubber band has a Shore A durometer of 20, while a plastic hard hat would measure 100.  As the Shore A durometer hardness of a material increases, the modulus of elasticity also increases.   

The standard O-ring material hardness is about 70 to 75 Shore A.  These materials can handle most application pressures, but when pressure increases the force exerted on the material can become great enough to deform and push the O-ring.  Parker O-Ring Division has specialty compounds designed with a hardness of 90 to 95 Shore A, making the seals more suitable for higher pressure. 

While hardness governs how the material reacts to pressure, diametral clearance governs the size of the gap that an O-ring can extrude out of.  Diametral clearance is the total gap between the bore diameter and the piston diameter.  Figure 1 identifies the radial clearance in both a male and female radial seal application.  To convert radial clearance to diametral clearance, just multiply the radial clearance by two. 

Figure 1

To understand how diametral clearance affects pressure rating, it is easier to think about an example outside of O-rings.  If you have a piece of metal with a pinhole and you push Silly Putty™ through the hole, you’ll find that material does not push through to the other side.  If you slowly increase the size of the hole, you’ll find that eventually, at a certain size, the material will begin to “extrude”.  This helps show that the size of a gap plays an integral role in how likely it is for material to be forced out. 

In light of the effect that clearance and material hardness plays in extrusion, Parker has provided baseline recommendations to help determine the likelihood of extrusion in a given application.  The “Limits for Extrusion” chart, shown below and published on page 3-3 of the O-Ring Handbook, gives guidelines for pressure, clearance, and material hardness.  The “Limits for Extrusion” chart was generated from actual testing performed by Parker Engineered Materials Group. 

Interpreting the “Limits for Extrusion”chart can be done in two ways.  When given gland design information (including clearances) and material choice, a pressure rating can be obtained.  For example a gland design with a 0.010” clearance gap utilizing a 90 durometer material can potentially see 2,000 psi before extrusion would occur.  If given a required pressure, then the required clearance can be found for a given material hardness.  For example, an application at 1,000 psi would require a 0.018” clearance gap for a 90 durometer material, a 0.013” clearance gap for an 80 durometer material, and a 0.008” for a 70 durometer material.  As you can see, the softer the material gets, the smaller the clearance needs to be to prevent extrusion.

       Figure 2

By following the design recommendations outlined per the O-Ring Handbook and “Limits for Extrusion” chart, a robust design can be achieved which helps eliminate the risk of seal failure.  This helps give you the safety and peace of mind needed when designing critical components utilizing sealing materials.  

For additional assistance you can contact Parker’s Application Engineering department for detailed recommendations on applications which fall outside the scope of this post. 

This blog was contributed by Eric Uehlein, O-Ring Division Applications Engineer

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Answers to Your In-Service Rubber Properties Questions

Are you designing an enclosure to help keep your critical components or internal fluid free from environmental exposure?  The good news is that Parker Engineered Materials Group has experience designing seals for use in environmental enclosures and has the material technology necessary to provide the most robust seal to meet your enclosure requirements.

In the coming weeks we will share this experience by providing in depth discussions on the important aspects of a good environmental seal.  This particular blog will provide an overview of these factors, including the importance of good seal design, the certifications that provide confidence in the seal’s capability, and the available seal profiles useful for many different application constraints.

Keeping the environment outside your enclosure starts with proper seal design.  Squeeze is the most important factor of this design.  When you squeeze solid rubber material, the internal cross-linking of the elastomer resists deformation and pushes the rubber against the assembly allowing conformance to the surface.  When good squeeze is achieved, the rubber provides an environmental barrier and the resiliency of solid rubber ensures the seal will last.  The second most important factor of proper seal design is material selection.  Many enclosures utilize cellular or foam rubber to achieve a cheap seal.  While this may be an inexpensive option in the short term, cell and foam rubber do not have the same long term resistance that you find in solid rubber parts, which can cause leak paths to develop over time.  Solid rubber, on the other hand, can provide a long term solution ensuring good reliability of your enclosure. 

Your environmental enclosure may reside outdoors in a hot, arid desert or a wet, muddy swamp.  Or, the enclosure could be placed indoors in an environment housing flammable chemicals or requiring a high degree of cleanliness.  In order to ensure your enclosure works as intended, it is best to choose material that is suitable for a wide range of conditions.  Industry certifications help provide assurance that your design keeps the environment out and provides a long lasting solution.  ASTM G21-96 helps measure a polymer’s resistance to fungal growth in this type of environment and UL 94 helps determine a material’s resistance to fire exposure.  UL also has approvals for larger electronic boxes under the UL50E certification.  Using select Parker materials, which are certified to UL50E, can help bypass additional testing that may be needed on other material in the marketplace.  Parker also has experience with end-use certifications like IP65 and IP67. By working with Parker Application Engineers during the design process, you can be assured that the chosen seal will help your enclosure meet the necessary certifications your customers require.

Seal configuration can often be the most challenging aspect of the design process.  Real estate for cutting or molding a groove can be limited, part tolerances can be large, or available compressive force can be low.  Fortunately, Parker has developed solutions for each of these cases.  If available room is low or geometry is constrained, Parker can cut and splice seal material to the dimensions you require.  In the event that enclosure tolerances are large or available compressive force is low, Parker engineers can design a custom hollow seal to help absorb large tolerances while providing very low compressive force compared to solid cord.  The continuous, solid nature of the rubber material allows hollow sections to be added to the seal with lower compressive force without compromising material integrity over the life of the product.  The Parfab design guide shown below contains a sampling of the custom options we can provide.  

For those not familiar with seal design, developing the proper seal for use in an enclosure can often seem like a daunting task.  Parker Application Engineers can assist with the design process to help ensure all of your requirements are met. 

Please keep on the lookout for our follow ups to this blog with more in depth information on the UL 94 approval process and Parker UL 94 approved materials coming next.  For more information on additional products visit the Parker O-Ring Division Website.

This article was contributed by Michael Sobeski, Product Engineer, O-Ring Division.
 

Sealing for Harsh Environmental Conditions in Telecommunications Applications

A Simple Guide to Radial Seals | Sealing Fundamentals

Selecting the Right O-Ring Seal Squeeze Ratio

After successive years of unprecedented growth, the tank car industry is facing numerous challenges. New regulations for stricter tank car standards have been mandated, estimated to cost $2.9 billion to retrofit the current fleet. According to the Association of American Railroads (AAR), crude-by-rail saw a 17% decline in 2015. At the last AAR meeting in Colorado Springs, CO., the Department of Transportation (DOT), unveiled drastic new measures of accountability. Starting this year, shippers and terminals are going to be held accountable and responsible for NARs.

Shippers at risk

No official figures have been released for 2015, but as of June 2015, NARs increased by 19%. The most common culprit being the manway, with the four leading issues being loose bolts, missing gaskets, deteriorated gaskets and misaligned gaskets.

AAR guidelines

The AAR does not approve any gaskets nor does it approve facilities that manufacture them. AAR Pamphlet 34 (Recommended Methods for Safe Loading & Unloading of Tank Cars) only has the following to say on gaskets:

a.2.1.16.3 - The manway gasket is in place, intact, has not taken a permanent compression set that interferes with sealing ( … )

b.3.4.5 – If the manway was opened during the operation, be sure to inspect the manway gasket for damage, deterioration and proper alignment ( … )

c.Section 4 (Reprint of AAR Manual Appendix D) – 6.2 – Install a new gasket compatible with the commodity to be transported ( … )

Lack of standards

Gaskets take a compression set after first use. It is compression set/ creep that results in loose bolts, accounting for over 50% of manway related NARs. Whether you are using a rubber (BUNA, Viton, etc.) gasket or a PTFE (Teflon) gasket, all will take a compression set. Suppliers advise or recommend that you not use their gasket more than once. Some recommend that you wait 24 hours after torqueing their gaskets and apply a final retorque before using. 

Finding a solution

Recognizing that the answer was not one of material selection, but rather inadequate seal design, Parker’s Integrated Sealing Systems Business Unit took on the challenge of offering a sealing solution that completely eliminated all the leading causes of NARs, as well as offering a gasket that could be reused. In developing a solution, Parker sought feedback from a variety of industry experts with extensive experience using manway gaskets, including petroleum/chemical companies, as well as the AAR and DOT. With their input, Parker designed and patented its Sure Torque gasket, featuring a stainless steel (primary seal) insert and over-molded elastomers. To verify its design, Parker then tested its Sure Torque gasket with the four most popular gaskets in the industry. Results can be found below.

Test Parameters:

• Test used a heavily used manway fitting at room temperature
• Secured using the recommended star pattern over three passes to 250 ft-lbs
• Pressurized in 10 psi increments up to 165 psi and monitored for 24 hours
• Repeat steps 1-3 until test gasket failed

An engineered solution

Sealing and maintaining bolt torque is not a unique challenge for tank cars. The Parker Sure Torque Manway Gasket incorporates an integrated stainless steel ring that specifically resolves the four leading issues that cause manway NARs. It is the only gasket that can be reused, while only needing to be torqued once, can’t fall into the manway, greatly simplifies installation and minimizes maintenance procedures.

To learn more, view our video on the Parker Sure Torque Manway Nozzle Gasket below.

Summary

Much is being done to improve the safety of the existing fleet of tank cars as well as the specifications for new builds. Although expensive to retrofit, the AAR has been thorough in overseeing the necessary changes to ensure the best outcome for all parties.

Similarly, although traffic is down for the tank car industry, especially crude-by-rail, it’s not all doom and gloom. The Enbridge and Sandpiper pipelines have been delayed subject to environmental reviews. Existing pipeline networks do not extend to East Coast refineries and Canada’s oil production is forecast to grow faster than pipelines can be built, making crude-by-rail the only viable alternative.

As the industry moves forward with safer technologies, more inspectors and changes in who is accountable for NARs, now is the time to take a long hard look at how tank cars are sealed.

For more information, contact the sealing experts at Parker. 

This article contributed by Emanuel Guerreiro, Industrial Market Development Manager, Parker Hannifin Integrated Sealing Systems Business Unit.

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Material certifications play a vital role in determining whether a chosen seal material is suitable for your service. In a continuation of our series on environmental seals for enclosures, we will be discussing a specific certification, UL94 V-0. Parker Engineered Materials Group has found that UL94 V-0 certified material is crucial for customers operating in the Renewable Energy, Telecommunications, Power Generation, Chemical Processing, and General Industrial markets due to interest for flame retardant materials. These customers want to ensure their connectors, instrumentation, or equipment enclosures are capable of withstanding a certain degree of fire exposure without compromising the integrity of their assembly. I will go into detail about what the UL94 V-0 certification is, how the test is conducted, and what Parker materials are available with this certification. 

Underwriters Laboratories (UL) standard 94 outlines test methods intended to measure the flammability properties of polymeric materials in response to small open flame or radiant heat sources in a controlled laboratory condition. UL94 is performed on the individual components giving the end-user a high degree of confidence that fire testing will be successful on the final product. 

The UL 94 standard has methods for both a horizontal (HB) and vertical (V) burn test. Of the two, the vertical burn test can be the most destructive, as it provides the highest degree of flame and material interaction. The diagram below shows a comparison between how the UL94 HB and UL 94 V are tested. 

Within the vertical burn test there are several classifications that you will see: UL 94 V-0, UL94 V-1, and UL94 V-2. Each classification calls for a specific degree of exposure and guidelines (refer to the chart below) for how long an after flame or afterglow may be present when the flame is removed. An after flame occurs because even though the fire was removed, the remaining material is still combusting. For instance, if we look at the UL94 V-2 classification in the chart below, we see that an initial flame is exposed to the material for 10 seconds. After the burner is removed, the flame may be present on the material for up to 30 seconds. The material is then subjected to a second application of the burner and after removal the material may continue burning for up to 60 seconds. During the burner process, a cotton indicator is located below the material and flame to catch any flaming drops of material. Under UL94 V-2 the cotton indicator is allowed to catch fire, while under UL94 V-1 and V-0 the indicator must not ignite. The flame application process is continued for five samples and the total after flame is measured and must meet the requirement of 250 second maximum for V-2 rating. As the rating moves from V-2 to V-0 you can see that the requirements become more stringent and the total time of after flame decreases dramatically. 

Parker Engineered Materials Group has found that the stringent requirements of the UL94 V-0 material certification provide the safest and most reliable solution for customers with fire safety concerns. We have developed our silicone material, S7395 to meet the UL94 V-0 requirements. S7395 is also resistant to fungal grown per ASTM G21-96 and is available in a wide variety of shapes and cross-sections to allow for custom configurations in many types of applications.

Be sure to keep on the lookout for our next follow up blog on enclosures and environmental sealing. For more information on additional products visit the Parker O-Ring Division Website.

This article was contributed by Michael Sobeski, Product Engineer, O-Ring Division.

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Modern high-performance engines require seals and sealing systems that deliver top performance in terms of operating reliability and service life as well. The new Parker Prädifa HNBR material N9192-80 meets the challenging requirements in these applications in an outstanding manner. Due to intelligent formulation of the peroxidically linked HNBR compound, the seal’s strength values, abrasion performance and restoring rate could be improved to yet another higher level. For high-load dynamic applications, this means an enormous gain in reliability. In addition, thanks to its gray color, the risk of confusing the seals with commonly used black seals can be excluded.

In N9192-80, Parker Prädifa is offering a new universally usable HNBR compound for challenging demands. The material that is particularly suitable for automotive applications is characterized by good cold flexibility down
to -35 °C and resistance against commonly used hydraulic media, specifically in automobiles. In addition, N9192-80 exhibits very good resistance to coolants and engine oils. Wear resistance has been improved by 30% compared to standard HNBR compounds.

HNBR polymers are produced by hydrogenation of NBR, which results in higher temperature resistance and better protection against oxidative attacks. Compared with conventional HNBRs, the new N9192 compound was improved once more by skillful selection of the raw materials and formulation. Due to the material´s gray color, a mix-up of the seals with black seals (e.g. based on EPDM, FKM, AEM and ACM) in automobiles can be excluded. As mix-ups harbor the risk of seal failure in important technical components that may result in high costs up to and including recalls and the associated risk of major image loss to the manufacturer, this is a significant gain in reliability and safety.

N9192 is resistant against mineral oil based hydraulic fluids and fully synthetic transmission fluids. Its improved dynamic properties qualify the compound for reliable utilization in challenging hydraulic applications. Additional fields of application for N9192 are opening up in refrigeration engineering and in the coolant circuit as the compound has very good resistance in coolants.

Furthermore, N9192 is suitable for use as a sealing material in diesel exhaust gas technology as the compound exhibits no significant changes in mechanical properties, particularly volume swelling, in 32.5 % urea solutions (AdBlue®). The aqueous urea solution is used in the catalytic reduction of environmentally toxic nitrogen oxides that are produced in the combustion process of diesel engines. 

N9192 is a new high-performance compound that additionally satisfies two further requirements in terms of health and environmental protection. Naturally, the compound complies with legal requirements (REACH, SVHC, RoHS, etc.). In addition, N9192 is free from polycyclic, aromatic hydrocarbons (PAHs) which have been proven to be carcinogenic as well as having a major adverse effect on the environment. Measurements obtained according to ZEK 01.4-08 (GS) QMA 2001.1284 are below the limit of quantitation (LOQ) of 0.2 mg/kg, as confirmed by the DEKRA Laboratory for Environmental and Product Analytics in Stuttgart.

• Good low- and high-temperature performance
• Very good resilience in high-load applications
• Wear and abrasion resistance, extended service life
• Very good media resistance
• Resistance against engine oil
• Contains no prohibited substances or substances requiring declaration according to GADSL, SVHC, PFOS
• RoHS-, WEEE-conformant
• PAH-free

Article contributed by

Dr. Maria Fleischer
Compound and Process Development
Engineered Materials Group,
Prädifa Technology Division

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Parker Diamond Seals are designed to be a compact, robust axial seal alternative to standard cross section seals. Their unique design allows for reduced compression forces, making them ideal for small, lightweight housings in aerospace and military applications. 

With a tall and narrow diamond-like cross section, the diamond seal groove is 60% narrower than traditional grooves for comparable seal heights. The narrow cross section of the seal allows it to be used in tight corners and around small holes. The groove width savings allows housing to become thinner, reducing the weight assemblies and is less expensive to machine when compared to standard grooves. 

The Diamond Seal has two types of beads located around the profile of the seal. The stabilizer bead prevents the seal from tipping into the groove. The retention bead provides the interference with the groove wall providing exceptional retention.  

Diamond Seals are ideal for the following military and commercial aircraft applications:

• Actuator
• Cockpit control panels
• Electrical control bowes
• Fuel management units
• Fuel pumps
• Guidance modules
• Hatch cover seals
• Housing seals
• Hydraulic motors

Parker Engineered Seals Division has obtained Qualified Product Listing (QPL) for many standard aerospace compounds in several material families. These compounds can be found in the below table. 

Parker is not limited to the use of these materials. Diamond Seals can be molded in almost all of the compounds available in Parker's material library. Parker Diamond Seals material can be tailored to target the right balance of seal load, compliance, chemical resistance, and temperature range. 

Parker Diamond Seals are a cost effective sealing solution providing easy assembly, and excellent retention for the most demanding applications. 

For more information on additional products, visit the Parker Engineered Seals Division website. 

Article contributed by Ben Bennett, Aerospace Market Specialist, Engineered Seals Division

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Incorrect O-ring installation can lead to assembly damage causing leakage during the first pressure test. If the system does not pressurize properly, the entire piece of equipment should be disassembled and seals must be replaced. Depending on when this test occurs, multiple manufacturing steps could be in between the seal installation and the first step where leakage can be identified. If O-ring damage happens with high frequency, you could be wasting time and money on seal replacement. Luckily, there are some easy steps that can be followed to help prevent this from occurring. Parker’s recommended guidelines for installation include always using lubrication, good gland design, and ensuring correct sizing.

Using lubrication is an essential facet of proper installation. Lubrication reduces surface friction between the O-ring and mating surfaces, allowing the O-ring to seat in the groove with very little difficulty. In male and female radial seals, lubrication will reduce installation force and create a smooth transition as the piston is inserted in the bore. 

Choosing the proper lubricant requires careful consideration of your system. You must ensure the lubricant choice is compatible with the O-ring material being used, suitable for the temperature range of the application, compatible with the system fluids, capable of producing a high surface tension film, and does not clog system filters. 

Parker offers two lubricants, O-Lube and Super-O-Lube. The O-Lube is an outstanding general-purpose grease intended for O-ring and elastomer seal types used in hydrocarbon service. O-Lube has a recommended service temperature of -20°F to 180°F (-29°C to 82°C). On the other hand, Super-O-Lube is an ideal all-purpose O-ring lubricant. Rather than a grease, the Super-O-Lube is a high viscosity silicone oil. It is an extremely effective seal lubricant, useful from -65°F to 400°F (-54°C to 204°C). 

For more information on Parker O-Lube and Super-O-Lube and how to choose a lubricant, refer to section 3 of the O-Ring Handbook. 

One of the easiest ways to ensure care-free installation is by following good design practice as recommended in the Parker O-Ring Handbook. The dimensions listed in the O-Ring Handbook put good compression on the O-ring while preventing the groove from exceeding 100% fill. In radial seal applications Parker recommends using a lead in chamfer at an angle of 15-20 degrees with an opening which exceeds the maximum height of the O-ring in the groove. 

Want to know more about installation of specific groove types?  Parker has produced easy to follow videos showing how to install O-rings in dovetail grooves, face seals, and male and female radial seals. 

Putting the wrong sized O-ring into an application can also lead to damage, making it important to verify O-ring sizing to ensure the right O-ring was selected. Unfortunately, measuring O-rings in the field or in a warehouse is not easily done without the proper tools. Parker offers a unique solution to this problem by offering measuring cones and circumference “Pi” tape to help provide quick and easy O-ring sizing information. These tools will help ensure that the proper Parker standard size is chosen during assembly.

By following the above recommendations you can be at ease during manufacturing your product. If you do encounter issues during your assembly that fall outside our recommendations, Parker can help troubleshoot your situation. Parker O-Ring Division application engineers can assist with your particular application. Our engineers can be reached a variety of ways, via telephone, email, and even online chat. With this additional help you can be sure that you will find success using Parker O-Rings. 

This article was contributed by Eric Uehlein, Applications Engineer, Parker Hannifin O-Ring Division

Be sure to check out our video demonstrating the various ways to apply Parker lubricants in your applications.

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Today’s sealing challenges demand innovative solutions, and nobody knows innovation better than Parker. That’s why Parker develops and manufactures engineered sealing solutions – technologically advanced sealing devices and materials that can keep pace with aggressive chemicals, temperatures, and pressures.

Our sealing products are designed with a unique combination of experience, innovation and support to ensure superior product performance, reliability and safety. Our on-site research laboratories evaluate performance through comprehensive testing processes to meet specific customer needs. And our world-class facilities allow us to formulate and design products to meet the most stringent industry standards (MIL, AMS, UL, and many others) to address aerospace applications calling for extreme high/low temperatures, fluid/pressure resistance, and fire resistance.

See the chart below to see some of the products that Parker's Engineered Materials Group offers to meet your sealing and shielding needs in the aerospace market. 

Diamond Seals

Tadpole Tapes

 FlexiSeals - Spring-energized PTFE Seals (Air Management Systems)

Custom Rotary Shaft Seals For Aerospace

Custom Expansion Joints

VX065

FF200

 Metal Seals (Jet Engines)

VMQ, PVMQ Extruded Profiles

For more information on how Parker can assist with your aerospace needs, visit our website or give us a call at 800-854-5350. And for more blogs pertaining to the aerospace market, see the "Related content" section below.

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Faster, Better, Stronger Sealing

There are three global trends driving innovation in the automotive industry: the desire to drive farther and release fewer emissions from every unit of fuel, the need to last longer without maintenance, and less tolerance for evaporative emissions caused by minor leaks, particularly at low temperatures. All three priorities have driven significant change in vehicle and component design in just the last 10 years, and these trends will only continue. These trends are readily apparent in ever-more-demanding requirements for fuel injector seal materials, and Parker compound VG286-80 offers unmatched benefits in all three areas.

For many years, the incumbent technologies in automotive fuel injection have been low temperature fluorocarbon compounds. With the newer fuel systems, VG286-80 offers several improvements that make it the material of choice for fuel injector applications.

Injecting high pressure fuel directly into the combustion chamber has driven up the mileage that can be squeezed from each drop of gasoline or diesel. In the days of carburetion, gasoline was delivered under vacuum. With fuel injection, fuel began to be delivered to the intake manifold at close to 100 psi of gauge pressure. With direct injection, fuel line pressures are reaching several thousand psi and are projected to continue increasing. This has multiplied the mechanical demands placed upon fuel injector seals to the point that extrusion failure can now be observed during testing. While this is new for the automotive industry, Parker has a considerable amount of history combating this failure mode in the fluid power and oil and gas industries. We have incorporated knowledge and experience from working on extreme pressure applications in the oil and gas industry into the development of VG286-80.

One of the things we “cross-pollinated” from oil and gas to automotive was pressure testing. Pressure testing in a fuel injector is difficult because of the size of the fuel injectors. Rather than trying to duplicate a fuel injector, we developed an extreme pressure test rig that allowed us to compare different material for pressure resistance. This test rig can pressurize an O-ring gland up to 15,000 psi (103.4 MPa) at temperatures up to 150°C. To accelerate the failure process, the clearance gap is substantially larger than is typically seen in fuel injector applications. If the material reaches the full pressure without extrusion failure, the pressure is held for 10 minutes before depressurizing and cooling to room temperature. This cycle is repeated until the seal fails (defined as sudden system pressure loss.) Most seal materials extrude and fail prior to achieving the full 103.4 MPa. This provides a numerical basis for comparing the pressure resistance of different materials.

When we tested VG286-80 side-by-side with a common GFLT compound of similar hardness, VG286-80 showed a 25% improvement in pressure resistance.  In fact, VG286-80 almost got to the full 15,000 psi test pressure before it extruded. Unfortunately, we weren’t able to test a GLT compound in this test rig.

VG286-80

GFLT

GLT

Pressure to failure

101.4  MPa

75.2 MPa

Not Tested

One of the key drivers for fuel injectors is low temperature seal performance. As I mentioned before, fuel injectors have been using low temperature fluorocarbon compounds for many years. Those in the GLT family have a TR-10 of -30°C, and those in the GFLT family offer a -24°C TR-10 coupled with excellent resistance to alcohol-containing fuels. VG286-80 beats both incumbent materials by a significant margin.

VG286-80

GFLT-type

GLT-type

TR-10, Low Temperature evaluation

-36°C

-24°C

-30°C

Being better for the sake of being better isn’t important unless it means something in the application. In most applications, O-rings can seal down to about 8°C below their TR-10 value in static applications such as fuel injectors. The goal in the automotive industry is to seal at -40°C without leakage. For the GLT-type compounds, that’s realistic, but just barely. The GFLT-type compounds don’t really get there, and that can cause small leaks during low temperature fuel injector tests. Ten years ago, this was considered acceptable, but with increasing scrutiny of leakage, these results are becoming more problematic. In comparison, VG286-80 has room to spare at -40°C.

Another phenomenon comes into play in high pressure gasoline direct injection systems. Just like high pressure causes the boiling point of water to shift upward, high pressure also causes the TR-10 and the glass transition point of elastomers to shift upward. For approximately every 750 psi (5.2 MPa,) the freezing point of an elastomer increases (gets worse) by 1 degree Celsius. In a 15 MPa (2,175 psi) gasoline direct inject fuel injection system, the elastomers in the fuel system can experience a 3°C upward shift in their low temperature performance. Under high pressures, this is enough to cause GLT type O-rings to leak at high pressures. In comparison, VG286-80 still has some additional safety factors in terms of low temperature flexibility.

Another notable area of development has been in the use of bio-derived renewable fuels. Supplementing gasoline with bio-sourced ethanol or methanol provides emission credits for a vehicle manufacturer, but it can wreak havoc on legacy seal materials. GLT-type fluorocarbon seal materials degrade quickly in methanol fuel blends and those with high ethanol concentration. VG286-80 has chemical resistance that’s more like the GFLT-type materials.

VG286-80

GFLT

GLT

Fuel C swell, 70 hrs @ 40°C

13%

10%

12%

CE20 swell, 70 hrs @ 40°C

20%

18%

23%

Methanol swell, 24 hrs @ 23°C

16%

6%

77%

Today, a good number of new cars come equipped with powertrain warranties that cover 100,000 miles, and some vehicle warranties are good for up to 10 years. In addition, the average age of all cars on the road in the United States is 11.4 years, and expected resale values – which are strongly influenced by vehicle longevity and repair histories – drive both lease and purchase deals. This gives manufacturers a strong incentive to ensure vehicles remain functional and leak-free for at least a decade.

Unfortunately, the wizards of computer modeling haven’t figured out how to predict exactly how long a seal will last in a particular application. (When they do, I’ll be blogging on that momentous development.) In the meantime, we have to make do with relative comparisons of expected service life based on compression set and compressive stress relaxation.

There is a lot of debate in the industry about which is better, compression set or compressive stress relaxation (CSR.) Compression set is a lot easier to run and more repeatable, and the two tests tend to go hand in hand. A compound that is good for compression set is also good for CSR. Both tests have their place, but for a quick comparison of materials, compression set offers a good snapshot. VG286-80 offers compression set resistance (and, by extension, expected service life) that’s on par with GLT compounds and significantly better than GFLT compounds.

VG286-80

GFLT

GLT

Compression set, 168 hrs @ 175°C

24%

30%

19%

Traditionally, seal material selection for fuel injectors came down to a choice of two less-than-ideal options: use a GLT fluorocarbon and suffer poor resistance to alcohol-containing fuels, or use a GFLT fluorocarbon that is great in the fuels but leaked a little at low temperature and didn’t last as long. Adding the high pressures of gasoline direct injection made this choice even more difficult. Not only does it cause seal materials to extrude and fail, but it also makes low temperature leakage worse.

VG286-80 solves all of these issues. It has even better low temperature flexibility than the GLT type materials, the same resistance to alcohol-containing fuels as GFLT, similar compression set to GLT, and more than enough pressure resistance to handle the mechanical demands of injecting gasoline directly into the combustion chamber.

For more information on this or other Parker materials, visit the Parker O-Ring Division and speak online with our experienced applications engineers.

This article contributed by Dan Ewing, Senior Chemical Engineer, Parker Hannifin O-Ring Division.

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