Can O-rings be used in rectangular or non-circular groove patterns? This question comes up weekly, and the answer is a resounding “Yes!” however there are definite guidelines we want to follow. A non-circular face seal footprint might also be called a racetrack groove, a wandering groove or a custom plan view. When using an O-ring, the main design consideration is the corner or smallest radius (shown “r” in diagram). The inside radius should be at least three times the O-ring cross sectional diameter. In a perfect world, six times greater is even better. What we want to avoid is over-stressing the O-ring around the bend, or causing a corner crease which increases likelihood of corner leakage. Designing the radius at six times the cross section will minimize the bending stress, resulting in increased service life.

Ideal design: r > 6 x W diameter but no less than r > 3 x W diameter

To minimize installation difficulties arising from stretch or OD compression on the seal, the centerline perimeter of the groove should match the centerline circumference of the O-ring. The rectangular cross section of the groove will follow the suggested guidelines in the O-Ring Handbook. 

The substances used in the food and in the chemical process industries are identical in many cases, whether they are of natural origin or synthetically produced.   Irrespective of their type and occurrence – be it in process media, in raw materials for products or in finished products – the materials for seals and engineered components used in production equipment coming into contact with diverse chemical substances have to meet specific purity requirements and be resistant to chemicals under the given process conditions. Purity and stability are therefore basic prerequisites for materials in the chemical process industry and the food industry. The challenge lies in selecting the proper sealing material for an application.

Consumer health and safety are of paramount importance in food, beverage and pharmaceutical production processes. Therefore, the materials have to comply with specific legal requirements and standards, depending on their application. The harmlessness of the materials for the intended uses, such as applications involving contact with foodstuffs and drinking water, must have been certified by relevant approvals and conformities. Equally important to consumer safety is that the materials are free of polycyclic aromatic hydrocarbons (PAH), phthalates, mineral oil based plasticizers and animal derived ingredients (ADI). 

In addition, qualitative aspects such as neutrality with respect to taste and odor generally have to be ensured whenever materials are utilized in food and beverage production. In the production process, the sealing compounds must not release any components which – even if not harmful to human health – would affect the quality of the final product in any way that could be perceived by the senses or otherwise.  
 

As particularly the processes in the food and beverage sector are as wide and varied as the products themselves they make special demands on the seals and sealing compounds used in them as well – be it in terms of resistance against chemical substances and various process media, temperatures, pressures and mechanical loads or special sanitary requirements. Of particular relevance here are CIP/SIP processes for cleaning and sterilization involving disinfectants, superheated steam and acids. The reliable functionality and durability of the seals has to be ensured even in harsh application conditions.

This wide range of requirements can only be covered by a wide range of materials and material groups. The appropriate selection from Parker Prädifa’s extensive portfolio of sealing compounds is made based on the required properties profile in combination with the necessary approvals and conformities existing for the respective material. With pure to ultra-pure materials optimized for the respective applications in the material groups of EPDM, NBR, FKM, FFKM, TPU, PK, PTFE and metal Parker Prädifa offers precisely this diversity of possible choices and combinations, for example:

• EPDM
  compounds for highly sensitive production processes in the food and beverage industry, biotechnology and medical device technology
  Properties: very good media resistance in hot water, steam, lyes and acids, in polar CIP/SIP media and resulting long life even in cleaning and sterilization processes
  Approvals/conformities: FDA, USP Class VI, 3A, (EC) No. 1935/2004

• EPDM
  compounds for drinking water applications
  Properties: very good mechanical properties, outstanding compression set, good low-temperature performance down to -50 °C
  Approvals/conformities: FDA, WRAS, W270
   
• NBR
  compounds for food applications
  Properties: very good media resistance in media containing oil and grease, very good wear resistance
  Approvals/conformities: FDA, (EC) No. 1935/2004.
   
• FKM- and HiFluor®
  compounds for the food and beverage industry, biotechnology and medical device technology
  Properties: excellent media and temperature resistance
  Approvals/conformities: FDA, 3A USP Class VI, (EC) No. 1935/2004, BNIC
   
• Parofluor® FFKM
  compounds for the food/beverage and pharmaceutical industries
  Properties: pure high-performance compounds with extended service life and suitability for extreme chemical and thermal requirements
  Approvals/conformities: FDA, (EC) No. 1935/2004, USP Class VI.
   
• Ultrathan® TPU
  compounds for food industry applications including food gases and household appliances
  Properties: high wear resistance, good hydrolysis resistance and good permeation properties
  Approvals/conformities: FDA, (EC) No. 1935/2004.
   
• Polon® PTFE
  compounds for the food industry
  Properties: best media resistance and widest temperature range, excellent friction behavior
  Approvals/conformities: FDA, (EC) No. 1935/2004, USP Class VI.
   
• PK compound nobrox®
  for sealing elements and other engineered components in the food industry
  Properties: outstanding wear resistance, chemical resistance and resilience
  Approvals/conformities: FDA, (EC) No. 1935/2004, USP Class VI.
   
• Metal
  seals for harsh application conditions, outside the application range of polymer materials.
   

A new brochure from Parker Prädifa provides comprehensive information about the various material families for seals and engineered components in the aforementioned industries, their property profiles and applications, plus the national and international standards and regulations on wich the approvals and conformities are based.

Download PDF

Article contributed by

Christine Stehmans
Marketing Communications Manager
Engineered Materials Group Europe

Modular Seal Kit for Pneumatic Cylinders Covers All Kinds of Applications

New Material nobrox Increases Design Freedom for Seals and Engineered Components

Selecting the right EMI shielding material for your application can be challenging. A new Conductive Elastomer Engineering Handbook published by Parker Chomerics offers detailed technical explanations and helpful advice on choosing solutions for EMI shielding. Available as a free download in PDF format, this guide aims to help design engineers in selecting the optimum EMI gasket for the task in hand.

The handbook is an essential design companion for any engineer tasked with delivering EMI shielding solutions. As well as a thorough look at the theory behind EMI shielding, it covers corrosion resistance, with particular emphasis on design guides for corrosion control.

One of the numerous informative sections in the Conductive Elastomer Engineering Handbook focuses specifically on gasket design, where there are many areas of principal emphasis. Other chapters include seal cross-section selection, fastener requirements and designing a solid-O gasket-in-a-groove. A further section on gasket mounting techniques shows designers cost-effective choices in both materials and assembly.

The handbook also examines the performance data associated with conductive elastomers, including compression-deflection, stress relaxation, compression set and shielding effectiveness. Also covered are EMP survivability, vibration resistance, heat ageing, outgassing and lightning strike resistance.

The Conductive Elastomer Engineering Handbook includes details on the following product ranges.

Once used mainly to shield critical defence and aerospace electronic systems, Parker Chomerics conductive elastomers have become the progressive choice for packaging designers of consumer, telecommunications, automotive, industrial equipment, medical devices and much more.

Conductive elastomers are reliable over the life of the equipment. The same gasket is both an EMI shield and an environmental seal. Elastomer gaskets resist compression set, accommodate low closure force, and help control airflow. They’re available in corrosion resistant and flame-resistant grades. Their aesthetic advantages are obvious.

Almost any elastomer profile can be extruded or custom-moulded with modest tooling costs for either prototypes or large orders. Parker Chomerics can also take a customer-supplied design and deliver finished parts.

Parker Chomerics offers hundreds of standard moulded and extruded products. Moulded products provide moisture/pressure sealing and EMI/EMP shielding when compressed properly in seals, flanges, bulkheads, and other assemblies. Extrusions provide similar benefits and are also readily lathe-cut into washers, spliced, bonded, kiss-cut, or die-cut to reduce installation labour and to conserve material, resulting in a cost-effective alternative to other methods of EMI shielding and environmental sealing.

Parker Chomerics CHOFORM automated EMI gasketing system is ideal for today’s densely populated electronics packaging, particularly where intercompartmental isolation is required to separate processing and signal generating functions. CHOFORM is directly dispensed on castings, machined metal and conductive plastic housings. It provides excellent electrical contact to mating conductive surfaces including printed circuit board traces.

ParPHorm is a family of non-conductive, thermal and moisture cure, form in place, elastomeric sealing compounds.  These silicone and flurosilicone materials provide environmental, fluid and dust sealing of small enclosures.

Parker Chomerics CHO-MUTE elastomer based absorber materials are designed to offer a user friendly approach to the reduction of unwanted electromagnetic radiation from electronic equipment as well as minimize cavity to cavity cross coupling, and microwave cavity resonances. Comprised of a silicone elastomer matrix with ferrous filler material, these materials provide RF absorption performance over a broadband frequency range from 500 MHz to 18 GHz.

Parker Chomerics can supply a complete single source solution to your EMI shielding needs in plastic housing. If the device requires a display filter, Chomerics can design and supply using the latest technology. The filters can provide EMI shielding and improve view ability in any environment. The display filter may be incorporated into the housing or bezel, ready for assembly. EMI shielding gaskets can be added as an integral part of the housing using Chomerics in-house supply of all gasket technologies. If thermal management materials are needed, Chomerics can supply heat sinks with thermal interface materials integrated into the housing. Finally, non-conductive thermoplastics are available with secondary EMI coatings which may be more suited to certain applications.

To learn more about Chomerics' EMI shielding products, click here.

This blog was contributed by Melanie French, marketing communications manager, Parker Chomerics Division Europe. 

Related content:

EMI Shielding Caulk Delivers Superior Performance in Military Radar Systems

Interesting New Developments in Commercial Aerospace Gaskets 

Improved EMI Shielding Consistency of Single Pellet Conductive Plastics

With the desire for renewable energy sources, coupled with dependence on foreign oil, Americans are becoming increasingly interested in alcohol/fuel blends.

There are nearly 20 million flex fuel vehicles on U.S. roads today, and over 2,900 ethanol fuel stations. With the increased use of alcohol/fuel blends there is also an increased demand for seals that are compatible with alcohol/fuel blends. Parker offers a variety of compounds to meet this crucial need in the automotive industry.

The combination of alcohol and fuel creates a significant conundrum from a sealing standpoint, as you need a compound that is compatible with both alcohol and fuel. For conventional gasoline, we typically recommend A-type fluorocarbon, or GLT-type fluorocarbon if you need to seal down to -40˚F (-40˚C). These perform extremely well in gasoline, but in alcohol, they can swell to more than twice their original size, as shown in Figure 1.

To solve this issue, Parker offers a number of specialized grades of fluorocarbon, which are also compatible with alcohol/fuel blends. Of these, one of our most cost-effective options is V1263-75. It is an F-type fluorocarbon with a temperature rating of -15˚F to 400˚F (-26˚C to 204˚C).

When colder temperatures are desired, Parker also offers V1163-75, which is a GFLT-type fluorocarbon, which has a temperature range of -35˚F to 400˚F (-37˚C to 204˚C).

Compounds V1163-75 and V1263-75 will continue to be the low cost solutions for sealing flex fuel. In fact, these materials have been used successfully in ongoing multi-year customer field trials without fuel leakage. However, Parker’s low temperature (Type 3) fluorocarbon compounds VG286-80 and V1289-75 offer an additional safety factor for low temperature function.

For more information, visit the Parker O-Ring & Engineered Seals Division and speak online with our experienced applications engineers

This article was contributed by David Mahlbacher, applications engineer, O-Ring & Engineered Seals Division.

Related content:

3 Global Trends Driving Seal Innovation in the Automotive Industry

Seal Materials for Biodiesel

O-Rings and Seals for Automotive Transmission Fluid

Parker Hannifin Engineered Materials Group has developed a wide variety of metal seals which can be formed or machined. A metal seal is a highly engineered sealing solution which provides elastic recovery or spring back to maintain good sealing, despite separation of mating surfaces due to effects of thermal cycling, flange rotation, applied mechanical or hydrostatic loads or creep. 

A metal seal is used when the application conditions are outside the specification limits of a polymer. For example, when:

Metal Seals are primarily used in static applications for temperatures as high as 1000°C/1832°F and pressures as high as 6825 bar/99000 psi for select applications. At low cryogenic temperatures and low pressures, such as vacuum seal applications, metal seals are far better than polymers since they do not become brittle and lose elasticity. Metal seals also have a low leakage rate down to 1 x 10-12 cc/sec per mm circumference which in comparison to high load O-rings is almost 100x better. 

Unlike elastomer seals, metal seals are very highly resilient to corrosive chemicals and even intense levels of radiation. With this resilience coupled with the right material selection/coating for an application, a metal seal can be a very durable seal performing dependably year after year.

Parker has a variety of in-house developed coatings which are used based on the application conditions and base material. The chart on page D-59 of the Metal Seal Design Guide (shown below) shows examples of some of the coatings based on the base material.

Metal seal x-sections can vary from a solid O to a Hollow O and from a C Ring to an E Ring depending on the application load and allowable leakage rate as shown in the figure below. Each x-section has benefits based on the application use and cost as indicated in the chart below.

Page A-10 of the Metal Seal Design Guide (shown below) shows some common applications in the industry and the type of metal seal used in those applications. These are examples of applications where the application conditions exceed beyond what an elastomer is capable of handling.

One of the most important and critical aspects of using a metal seal is surface finish of the mating hardware. The required surface finish co-relates to the seal free height as shown in the chart below. Since metals don’t compress or are not as elastic as some of the elastomers, it is very important to have a tighter surface finish. Most of the metal seal applications require surface finish of 32 u inch RA or better. Anything over 32 u in RA will not be bubble tight sealing (leakage rate of 1x10^4 cc/sec) which could be okay for certain applications.

In certain applications, higher surface finish can be negated with the help of coating applied to the metal seal. The picture below shows how coating helps navigate through the peaks and valleys of the hardware surface hence creating sealing.

• Independent optimization of functional components means each discrete function including load, spring back and outer sealing layer ductility/hardness can be optimized to ensure highest seal performance in every situation.

• Directly bonded electroplatingonto the load bearing substrate eliminates unnecessary parts and failure modes.

• Pressure energizationuses internal hydrostatic pressures beneficially to supplement the self-energization forces from the tubing, jacket or spring. This becomes particularly helpful at high pressures over 3,000 psi (21 MPa) enabling metal seals to seal at 25,000 psi (170 MPa) and beyond, without risk of blow-by during proof or burst testing.

• Total metal seal servicecovers custom and standard sized seals from 0.250" to 300" (6 mm to 7,60 m), including circular and non-circular shapes. We also offer the complete range of MS metal O-ring sizes, all AS1895 E-ring sizes, and the fastest delivery of C-rings from our preferred size list.

• Rapid response and JIT(just-in-time) deliveries are assured due to design, testing and all manufacturing processes (including roll and die-forming, machining, welding, heat-treatment, electroplating) being performed within our own facilities. 

Download the Metal Seal Design Guide.

For additional information on metal seals, please contact our engineers or visit our website. 

This blog was contributed by:

Vivek Sarasam, heavy duty mobile Sr. application engineer

Jeffrey Labonte, market manager

Related content:

High Performance Seals for Extreme Aerospace Environments 

O-Ring Sealing for Maximum Service Life in Aggressive HTS Turbine Oils

New Low-Temperature Compound Improves Jet Engine HTS Oil Sealing Performance

Parker Engineered Materials Group has developed a wide range of materials for liner seals to meet the demands of the ever increasing temperature requirements in liner seal applications. The new materials exhibit excellent coolant resistance, coupled with design capabilities to provide you a reliable, easy to assemble and efficient product. 

Parker has been one of the first in the market to develop a coolant resistant FKM (Viton). Over two decades, these materials have been used in multiple applications providing excellent chemical resistance to coolant, gear lubes, ATF and diesel. 

In applications where the seal is prone to coolant attacks at higher temperature, a coolant resistant FKM is needed. As you can see in the picture below, a coolant resistant FKM will not be as susceptible to cracking and degradation as opposed to a standard FKM. 

Parker has strived to develop the material over the years and has been successful in achieving coolant resistance at higher temperatures. As shown in the chart below, three generations of material development can be seen along with their performance at the higher temperatures. 

Some of the common liner seal cross sections are O-rings, D-rings and double chamfer seals. Each x-section has an advantage based on application conditions and production costs. 

• Excellent functionality

  • O-rings are industry standard for high pressure sealing

• Standard sizes

  • AS568 through metric sizes available for easy sampling

• Easy installation

  • O-rings are easy to install on standard grooves – constant profile no way to install incorrectly​ (watch our videos on Male Groove Installation and Female Groove Installation for a quick demo). 

• Gland design software inPHorm

• Lowest cost tools

• Flat ID adds stability

• Standard and custom sizes readily available

• ID and OD feature combinations

• Flat ID adds stability and can eliminate rolling and spiral failure

• Can be used in reciprocating or oscillating and dynamic or static applications where better gland stability is desired

• Standard and custom sizes readily available

• ID and OD feature combinations

• Parts twisting during assembly

• Difficult to identify on a large part

• Problems during installation of seals

• Paint - clear visual after assembly to show correct installation

• PTFE coated parts for ease of installation and Poke-Yoke

• In addition, seals can be provided with chamfered or radius edges

For assistance with materials or which liner seal is best for your application, please contact our Applications Engineers via our live chat service on Parker O-Ring & Engineered Seals Division's website.

Seals and the Quest for MPG

3 Guidelines to Ensure Proper Seal Installation

Proper Installation of an O-Ring: Standard Male Gland

A common problem I hear in the heavy duty industry today is sealing T-Joint applications effectively without the use of RTV Silicone (Room Temperature Vulcanization). Although RTV may be effective at times, most joints where this would be used are serviceable joints, which becomes an issue. When servicing these joints, the RTV needs to be scraped off hardware and re-machined, which causes issues as first fit (production) parts are often not reusable. Also there are issues where there is a multi-piece T-Joint assembly and only one segment needs to be serviced, but the technician needs to spend more time disassembling all parts before servicing due to the use of RTV. Additionally, there is always the concern of overfilling and negating the primary seal function or possibility of leak path in a joint with RTV.

To counter such issues, Parker has developed a proprietary solution - ParFab, a process which uses PIP (Press-in-Place) seals and in-house splicing technology to come up with a solution. Parker has developed a proprietary manufacturing process which uses the base elastomer (rubber compound) to splice, hence making the splice a lot better than most of the competition.

A T-Joint is a location in an assembly where you have three pieces of hardware coming together at right angles to each other forming the letter T in two planes. For example, in the picture shown above, the planes highlighted in blue and red form the T-Joint. It is often an issue sealing those locations as there is usually no overlap in sealing across both planes, therefore the use of RTV is used to fill the gaps. 

Parker uses in-house splicing technology to create the ParFab series of seals. It is this technology that has enabled Parker to provide a PIP seal with additional pieces of rubber spliced to it to create a T-Joint sealing system with no leak paths. Since this design technology eliminates gaps between seals from the three different planes, it eliminates the use of RTV. 

As shown in the FEA snapshot, the block of rubber that is spliced to the vertical plane compresses and extrudes into the PIP seal grooves in the horizontal plane, thus generating compression between the block and the PIP seal. The spliced pieces on the PIP seals in the horizontal plane help support the PIP seal when being compressed. 

Parker has been able to incorporate its design experience and knowledge of PIP seals and ParFab technology to create this solution. With this solution, an RTV-less sealed T-joint is created, which can be serviced, replaced without any machining involved and is easy to install. Some key benefits are:

• Eliminates use of RTV: No RTV is needed for this solution. Hence saving time during installation both on the production lines and at dealer facilities providing aftermarket opportunities.
• Reduces installation time: When compared to competitive technology which includes multiple seals and RTV, in addition to using more fasteners, PIP Seals are easy to install and require far less load to compress, hence reducing installation time and saving money.
• Provides value add: Single out of the box solution compared to using multiple seal technologies from multiple suppliers in addition to using RTV.
• Improves serviceability due to multiple PIPs: Easy to service multi-piece T-joint sections. Disassembly of the entire T-joint is not required, hence saving time and money. 

For assistance with materials or which liner seal is best for your application, please contact our Applications Engineers via our live chat service on Parker O-Ring & Engineered Seals Division's website.

Related content:

Sealing Fundamentals | Face Seal

Environmental Seal Enclosure 101

Racetrack Grooves: Can O-Rings be used in Non-Circular Groove Patterns?

Be it in the production of food, pharmaceuticals and cosmetics or medical devices coming into contact with the human body, excellent purity and media resistance combined with a wide range of robust properties is always required of the materials used for the components in the manufacturing processes. Specifically for these challenging applications, Parker has developed a new sealing compound with very good mechanical properties and excellent permanent elasticity: HiFluor® FB V8991.

Fluoroelastomeric materials have proven their viability in chemical and food processing, cosmetics, pharmaceutical and life science applications involving non-polar solvents, aliphatic compounds, greases, oils and aromatic substances whenever the resistance of standard materials such as hydrogenated nitrile butadiene rubber (HNBR) and ethylene propylene rubber (EPDM) is no longer sufficient.

As a compound and seal manufacturer, Parker Prädifa, in the light of the growing demands made on sealing elements in the aforementioned markets, has developed a HiFluor® FB compound with very good mechanical properties and excellent permanent elasticity. 

With its properties profile shown in Table 1, HiFluor® FB V8991 proves to be the compound of choice in hygienic and aseptic applications.

 Test

 Standard

Dimension

V8991-75

 Elastomer base

FKM

 Color

ocher

 Hardness

 DIN 53505

Shore A

75

 Specific weight

 DIN EN ISO 183-1

g/cm3

1,94

 Tensile strength

 DIN 53504

N/mm2

18,5

 Ultimate elongation

 DIN 53504

%

273

 Modulus (100 %)

 DIN 53504

N/mm2

6,8

 Low-temperature properties TR10

 ASTM D 1329

°C

-7

 Compression Set (70 h / 200 °C)

 DIN ISO 815

%

30

Table 1: Physical data of HiFluor® FB V8991

O-rings and molded parts made of the newly developed HiFluor® FB compound V8991 are also particularly well suited for use in direct contact with the food or pharmaceutical products. In addition, Parker Prädifa always attaches major importance to compliance with the laws and regulations in target markets when developing new compound solutions for chemical and process engineering. Particularly in processes requiring a high level of purity of the final product, the meantime between failure (MTBF) of the component used is very important. A sealing element that has been attacked by chemicals will release particles that may enter the food product or batch of pharmaceutical ingredients, making them unfit for consumption. This may result in major financial losses. Due to its proven very good media resistance, the HiFluor® FB compound is superbly suited for use in many food, pharmaceutical and life science applications.

• Outstanding resistance in use with alkalis, acids, greases, oils and aromatic substances
• Good resistance in use with CIP/SIP media, steam up to 150 °C
• Wide temperature application range from -25 °C to 200 °C
• Very pure material, free from phtalates and mineral oil based plasticizers
• Approvals/conformities
• FDA Section 21 CFR177.2600
  - USP Class VI
  - 3-A Sanitary Standards Class I + II
  - Free of animal-derived ingredients
  - BNIC
  - Regulation (EC) No. 1935/2004
  - Regulation (EC) No. 1907/2006 (REACH)
  - RoHS Directive 2011/65/EU
   

After using seals made of HiFluor® FB V8991, customers in the food, beverage, pharmaceutical and life science sectors have confirmed that they were able to increase MTBF for repaired units by 300 percent. In addition to improving their process quality, customers were able to considerably increase their productivity and the safety of their products which, not least thanks to the sealing compound, are fully traceable.

Smoothies have literally been on everyone’s lips in recent years. The pureed fruit or vegetables offered in small containers have become a staple on supermarket cooling shelves. Easy to consume on the fly, smoothies cater for our modern lifestyle while giving us the reassuring feeling of getting plenty of vitamins and strengthening our immune system.  

Unlike fruit juices, smoothies are produced from the whole fruit which may even include the skin. Bananas are often a basic ingredient, although juices, water, green tea, milk, other dairy products or coconut milk are used as well, depending on the recipe. Some smoothies even contain chocolate or peanut butter. The wide variety of fruit acids, aromatic or flavoring substances and dairy products, combined with abrasive components, poses a major challenge to the entire processing chain, particularly the seals in the production and bottling lines. Many standard sealing compounds no longer meet these demands.

More Information:

EMG Report Edition November 2016, Page 18

Brochure: Materials for the Chemical Process and Food Industries, Page 12

Article contributed by

Elke Vöhringer-Klein
Market Manager Chemical Processing Industry
Engineered Materials Group Europe, Prädifa Technology Division

A Guide to Selecting the Proper Sealing Material for Food Applications

New Material nobrox Increases Design Freedom for Seals and Engineered Components

For several years, one of the biggest drawbacks of “chemically resistant” FFKMs, or perfluoroelasters, has been their relatively poor compression set resistance. Typically, compounding these materials to be extremely resistant to many different chemical environments comes with the drawback of having to give up their ability to resist taking a set after being under high temperatures for an extended period. Parker's solution to this industry challenge is ULTRA FF156.

Compression set refers to a common failure mode of elastomers where a seal permanently flattens out while in application and the joint begins to leak. A material's resistance to this permanent deformation can be easily tested in the lab. To do so, a seal’s thickness is measured, then that seal is compressed about 25% before being heated in an oven at a particular temperature for a predetermined amount of time. That seal is then removed from the oven and the thickness is remeasured.

The value reported is “% seal height not recovered”, therefore a lower value would imply a higher compression set resistance. Figure 1, seen below, shows how FF156 compares to other chemically resistant FFKM offerings within the same hardness range and class. As you can see, FF156 vastly outperforms both in compression set resistance which implies longer seal life in application.

When looking at relative value and cost of material, FF156 is an excellent choice within the FFKM material family. It demonstrates a higher temperature capability and broader chemical resistance compared to FKMs, silicones, and AFLAS. The higher temperature capability of FF156 allows it to be used for applications in aerospace, heavy duty mobile, chemical processing, and semiconductor industries where temperatures can routinely exceed 400°F. A snapshot of FF156’s chemical resistance is shown in Figure 1, with the low volume swell in an Ethylene Diamine fluid immersion. Ethylene Diamine is a very aggressive base and is used as a common benchmark to test fluid for FFKM chemical resistance. Additionally, FF156 demonstrates above average hot water and steam resistance for an FFKM compound. Outside of FF580 and FF582, Parker’s explicit “steam resistant FFKMs”, it has the best steam resistance within the material family. Finally, FF156 can be manufactured into a variety of custom molded, extruded, spliced, O-ring or lathe cut products.  This versatility allows a uniform compound offering for the Parker ULTRA FFKM family of products.

FF156 offers a wide variety of features, including high compression set resistance, broad chemical resistance, and steam resistance, at approximately 60% of the cost of FF580, widely considered to be one of the top-performing 75 duro FFKMs in its class. Coupled with the ability to be extruded, spliced, or molded into complex shapes, FF156 is Parker’s newest solution to your sealing needs.

For more information or to speak with an engineer about your specific application, use our Live Chat tool or give us a call. 

This article was contributed by Tyler Karnes, applications engineer, Parker O-Ring & Engineered Seals Division.

Related content:

Perfluoroelastomer Materials Tailored for Your Needs

Reduce Standard Groove Size with Parker Diamond Seals

Chemical Compatibility: A Critical Component in Seal Design

Every design engineer should know that an EMI gasket must be installed between mating flanges to prevent electromagnetic radiation (EMI) from entering or leaving an electronic enclosure. But what if your equipment will be used in humid or tempest environments? How confident are you in your design that corrosion protection will be addressed? Not so much? Well, then read on. Here’s our top three design tips for ensuring corrosion resistant EMI protection.

1. Choose the correct EMI gasket. Sounds simple, right? But oftentimes, design engineers think they’re picking the right EMI gasket when in fact, they’re not. Correct gasket selection can minimize the difference in electrochemical potential relative to the structural metal, which in turn will slow down corrosion by ensuring a lower galvanic current. 
    
   You’ll want to select an elastomeric EMI gasket, such as the Chomerics CHO-SEAL® family, that contains conductive filler particles which will provide a combination of EMI shielding and corrosion resistance when in contact with metal. Pure silver, silver-plated copper, silver-plated aluminum and nickel-plated aluminum are among the particle types which have an important influence on corrosion resistance.

    
2. Don't forget to choose a surface treatment. To maintain aesthetics and stop oxidation and corrosion, you’ll probably plate or paint your metal enclosure and finish flange surfaces to ensure protection against corrosion. But what you might not know is that you’ll want to select an additional coating system that prevents surfaces from corroding in those high humidity or marine environments.
    
   CHO-SHIELD® 2000-series coatings from Parker Chomerics are three-part, copper-filled urethane coating systems, which minimize the effects of galvanic corrosion due to the soluble chromates they contain. When paired with the fluorosilicone binders of CHO-SEAL® 1298, the combination delivers elevated resistance to galvanic corrosion. 

    
3. Secondary sealing might be necessary. So you’ve got your elastomeric EMI gaskets and your corrosion resistant coatings, think you’re all set? Maybe not. Best design practice also indicates that an additional moisture seal should be considered if there is a requirement to exclude salt fog or spray that could act as an electrolyte and lead to corrosion.
    
   For example, in aircraft applications, a seal-to-seal design may be used. Here, gaskets of identical material are applied to each mating flange and edge-sealed using a non-conductive sealer to prevent moisture from entering.

So what have we learned? When you deploy a carefully selected combination of EMI gaskets, conductive coatings and secondary sealing, design engineers are able to minimize or limit corrosion to deliver sufficient EMI shielding performance for the service life of the equipment.

Are you ready to start choosing your EMI gasket? Download our Conductive Elastomer Engineering Handbook today and you'll learn: 

• EMI shielding theory
• Corrosion resistance principles
• Conductive elastomer gasket design
• Parker Chomerics elastomer product guides
• Industry organizations and standards
• Parker Chomerics capabilities and offerings

For more information on the Chomerics Conductive Elastomer Engineering Handbook and other Chomerics offerings, please visit our website or contact us. 

This blog was contributed by Tim Kearvell, elastomer product manager, Chomerics Division Europe.

Related content:

New Essential Handbook for EMI Shielding Applications

Interesting New Developments in Commercial Aerospace Gaskets

Improved EMI Shielding Consistency of Single Pellet Conductive Plastics 

Parker is revolutionizing part identification technology with a multitude of options. Customers are able to benefit from various identification methods such as non-permanent and permanent part markings by selecting their part number and company logo on the seal. For more advanced identification, a customer may opt to use the Parker Tracking System or utilize our RFID seals for tracking purposes. These identification methods ensure product authenticity and reduce seal installation errors by providing visual indicators for the assembly process.

Non-permanent markings are applied to the surface of the seal and can be in the form of a company logo, unique part number, barcode, or other seal information. Non-permanent markings ensure Parker’s part origin, enables part level traceability, and provides an easily visible cue to operators. This value added feature helps reduce installation errors in addition to protecting customers against counterfeit seals. 

As shown in the image to the left, adding the part number and company logo to a seal is a good way to ensure the consumer authenticity of the part they are purchasing. Part marking the seal using Parker’s proprietary process also helps catch any counterfeit parts in the market. This value added service is inexpensive and in most instances, is offset by the gain in the aftermarket sales it provides.

This method has additional uses in production to provide poka-yoke by helping differentiate similar parts and ensures the correct part is used in today’s fast paced integrated production lines and dealer facilities.

Parker Hannifin Engineered Materials Group has been instrumental in developing a permanently marked surface modification to use on various types of seal products. Unlike non-permanent markings, where the part marking could eventually wear off due to friction or use, a proprietary surface modification is used to place the customers name or logo on the seal without compromising seal performance. Some examples are shown in pictures below.

Our patented technology integrates RFID technology into seals, providing a multitude of benefits:

• Unique electronic identification for each seal

A proprietary method is used to integrate the RFID chip into the seal, which means that the RFID cannot be removed without damaging the seal. This, in conjunction with our PTS system, provides positive authentication with the use of a scanner or a smart phone, making it convenient for users across the world to verify the authenticity of the product. Any information (for example What, When, Where etc…) stored in this RFID chip can be read when the product is scanned, which means the information stays with the product even after it is removed from its original packaging and installed. 

• Eliminates mixed seals of similar size/color

Since the seals contain an RFID chip, it ensures the correct part is installed onto the product. It is also possible to scan the final assembly to determine that the seals have been installed, eliminating human error. This decreases downtime caused by line delays and quality issues resulting from installation errors. 

• Eliminates counterfeit / fraudulent seals in the supply chain

With the proprietary technology of Parker, the customer can rest assured that any counterfeit part has been eliminated from the market. Since the information on the RFID chip is tracked and stored in the database, it becomes very difficult for other manufacturers to make counterfeit parts.

• Aftermarket product verification

The consumer is able to authenticate the seals and protect his warranty by scanning the part and ensuring that the seal is from the OEM of the product, thus helping the company capture the aftermarket business.

Additionally Parker offers PTS (Parker Tracking System) for companies who do not have their own database or software. PTS is a web based service for customers to verify and identify Parker products by using Radio Frequency Identification Technology (RFID).

For more information on Parker's part identification technologies, please contact our Applications Engineers via our live chat service on Parker O-Ring & Engineered Seals Division's website.

Related content:

Seal Identification Methods: Part Printing | Sealing Fundamentals

Sealing Fundamentals | Seal Identification Methods: Color Coding

Making Strides Towards Liner Seal Technology

Parker's metal seals are used in the most extreme environments that demand extreme temperature and pressure solutions. Metal seal technology is used in cryogenic, high temperature, hard vacuum, high pressure, and corrosive applications. The ability to choose the correct sealing technology as well as the correct part number for the application can be challenging. Metal seals perform differently than polymers in application, so standard polymer practices should not be applied to metal seal design. This guide is intended to be used when you are in the process of selecting the correct part number for your application.

The simplest part number structure is shown in Figure 1 and is broken down into six segments. The first segment identifies the metal seal type, followed by the seal size, the cross section, material, temper and then the plating.

There are over 73 million possible part number combinations not including the diameter of the seal as shown in Figure 2.

In order to determine the correct part number for an application, follow the steps below:

Step 3. The diameter of the seal is identified numerically in the next six digits. If an English part number is being created, the first three out of six digits will be the whole inch value, and the last three digits will represent the remaining decimal. For a Metric part number, the first four out of six digits will represent the whole mm value, and the last two digits will represent the remaining decimal. Please note that the decimal shown in Figure 4 is imaginary and is not printed in the actual part number. For Internal pressure seals the diameter of the seal is measured off of the outer diameter, and for External pressure seals the diameter of the seals is measured off of the inner diameter.

Be it in the food processing industry, restaurants or residential kitchens: components with food contact in industrial equipment and household appliances are subject to strict legal and exacting technical requirements.

Due to its technical properties and possibilities for component integration and reduction of the need to use diverse materials, nobrox® W6101, as a versatile material for seals and engineered components, enables new approaches to solving engineering challenges and saving costs in the food industry.

Delivering top performance in terms of wear resistance, chemical stability and resilience, reliability and service life, ease of installation and economy, Parker’s compounds from the nobrox® family are equally well suited for use as sealing elements and other engineered components with and without a sealing function. Due to their properties profile, they open up opportunities to reduce the need for using diverse compounds and enable the integration of several functions in a single component. Parker Prädifa is now presenting W6101 as a variant from the nobrox® family that meets all the requirements for food applications.

Compound Versatility Beats Compound Diversity

In food processing machines, polymeric components such as tubes, covers or housings, as well as highly stressed engineered elements such as seals, wipers, guides and pistons are increasingly used. As a cost-efficient alternative the utilization of plastic materials as a substitute for metal makes sense in many areas as well. The technical requirements in terms of temperature resistance and structural strength can be met by selecting appropriate plastic compounds. Typically, various tailored materials are utilized to cover diverse component-specific demands. In addition, every one of these materials has to conform to legal requirements for food applications, which entails high documentation and testing requirements.

nobrox® W6101 offers new possibilities to meet many market-specific challenges and to thus limit the variety of required materials and associated expense. The material is resistant against media commonly used in the food industry, FDA-conformant and meets the requirements of Regulations (EG) No. 1935/2004 and (EU) No. 10/2011 as well as NSF 61 (U.S. drinking water approval).

Due to its mechanical properties profile, nobrox® can be classified to range between thermoplastics such as polyamides and PEEK as well as their derivatives. However, in food industry applications, it offers crucial benefits compared with conventionally used polymeric compounds. A substitution of PEEK, PA, POM, PTFE, UHMW-PE, TPE U or other elastomers commonly used in the industry makes technical and economic sense in a wide application window.

nobrox® is suitable for use in dynamic seals or wipers and a wide variety of engineered components such as pistons, guides or gearbox components. Functional integration – for instance of a seal, wiper or guide in a piston – and the associated reduction of the number of components is possible as well. 

As the number of components decreases, so do installation requirements as well as splices and joints in the design, which pose the greatest risk of contamination and accumulation of food resides or micro-organisms. The typically difficult accessibility of narrow gaps (e.g. in front seal of grooves, splices and joints) is reflected in long and costly cleaning cycles. Consequently, instead of fighting contamination by excessive cleaning with increasingly aggressive media, the appropriate approach to be used here is to counteract the causes and risks with materials expertise and intelligent seal or component design. Particularly in domestic appliances, component reduction results in ease of use. The frequently necessary partial dismantling of the devices for maintenance and cleaning is facilitated, saves time and is more convenient.

Machine elements like seals, wipers and guides typically operate under high tribological loads in dry running or low-lube conditions. Therefore, high lifetime requirements make the use of wear-resistant materials indispensable. The utilization of lubricants is often impossible or should be avoided. The excellent wear and creep resistance of nobrox® has been confirmed by test results.

• Suitable for versatile uses
  - in sealing technology: as a sealing element, guiding element, anti-extrusion element, diaphragm, …
  - outside sealing technology: as a material for engineered components

• Mechanical properties comparable to PA 12 with approx. 40 K higher melting temperature of 220 °C

• Permanent service temperature of up to 150 °C

• Good resilience and low creep

• High chemical resistance / good barrier properties

• Very short cycle times (fast recrystallization)

• Low moisture absorption of 0.4 % at 23 °C, 50 % relative humidity

• Extremely high ultimate elongation

• Very good tribological properties / good sliding properties combined with low wear

• Good impact resistance at -40 °C

• Flame-protected without halogens and red phosphor

• Very good weldability (laser welding, vibration welding, etc.)

• Gamma sterilization possible

• Outstanding reproducibility of dimensions and tolerances 

More information:

• EMG Report 06/2017 Page 10, Universal Material nobrox for Food Applications
• EMG Report 04/2015 Page 7, Universal nobrox Material in Professional Coffee Machines
• Brochure "Materials for the Chemical Process and Food Industries"
• www.nobrox.com - Food Applications

Article contributed by

Matthias Buchfink, Application Engineering, and
Michael Erwerle, Compound Technology

Engineered Materials Group Europe,
Prädifa Technology Division

A Guide to Selecting the Proper Sealing Material for Food Applications

New Sealing Material HiFluor FB for Hygienically Sensitive Applications

New Material nobrox Increases Design Freedom for Seals and Engineered Components

Reducing the environmental impact of operating a passenger car has long been a request from the environmental community, and that demand continues to spread. But how can something as small as a seal influence vehicle emissions?

The most obvious way to reduce the environmental impact of a vehicle is to burn less fuel while doing the same job, and to burn it more completely. In a previous blog, I mentioned several ways in which state of the art seal materials help improve overall vehicle efficiency. These include VG286-80 and VG109-90 used in gasoline direct injection fuel systems and VG292-75, VG310-75, and FF400-80 used in turbocharger coolant applications. But these are not the only ways that seals impact vehicle emissions.

Another critical source of emissions – and one that is directly impacted by seal material – is fuel vapor escaping from the vehicle’s fuel system. This happens whether the car is running or not, and it’s much worse in hot weather. Gasoline evaporates quickly, and that fuel vapor can be hard to control. Not only are vapor leaks much harder to prevent than liquid leaks, but fuel vapor can permeate through most rubber and plastic materials and escape into the environment  When it does, those unburned hydrocarbons contribute to smog and ground-level ozone pollution.

Fortunately, Parker has decades of experience in solving these types of sealing challenges.

Fuel vapor permeation rates can be measured directly through fuel vapor permeation tests such as the Thwing-Albert method, but this is a very slow process and it takes weeks to reach equilibrium. As a result, it’s not a good screening test for quick comparison. It’s much easier and faster to measure the volume swell with a liquid fuel immersion. While it’s not a perfect, it does provide a quick, “down and dirty” evaluation of different types of seal materials.

Table 1 shows the volume swell of various fuel-resistant materials after being fully immersed in two laboratory reference fuels. Using reference fuels eliminates the variability inherent in using actual pump gasoline from different manufacturers, refined at different times of the year, and from different batches. Fuel C is a little more aggressive to seal materials than regular American gasoline. CE-10 is a blend of 10% ethanol and 90% Fuel C, which makes it similar to most gasoline sold in the US. As you can see, there is a significant difference among different types of seal materials. Clearly, high fluorine fluorocarbon materials offer the best resistance to both fuels.

Table 1: Volume swell of various seal materials in fuel, 70 hours at 23 C per ASTM D471.

High ACN nitrile

Fluorosilicone

Traditional fluorocarbon

Low temp fluorocarbon

High fluorine fluorocarbon

Fuel C

16%

15%

3%

5%

2%

CE-10

21%

18%

6%

11%

4%

Because reducing the weight of a vehicle also helps with fuel economy, many fuel system components have changed from metal to plastic over the years. Not only does this increase the opportunities for fuel to permeate out of the fuel system, but it also increases the sealing challenges. Sealing plastic components brings three challenges not seen when working with metal components: parting lines, rigidity, and creep. Plastic components are almost always molded, meaning they have mold parting lines. Those parting lines frequently pass through the seal groove, and the seal must be able to conform around that imperfection to form a vapor-tight seal. Second, plastic components aren’t rigid like metal components; they move when a seal is pushed against them, so the amount of seal load force that can be applied is limited. Third, plastic components move over time in response to these load forces in a process called creep, which means the amount of squeeze applied to a seal reduces over time.

To get the best performance when sealing against plastic components, softer materials are key. Compounds in the normal 70 to 75 Shore A range generate so much load force that they deform the plastic and dramatically increase the creep rate of the plastic. In addition, harder compounds don’t seal well around plastic parting lines, so softer compounds are preferred over harder ones.

However, there’s a limit to how soft a compound can be. Hardness is controlled by the use of reinforcing fillers, and these fillers also help to reduce the fuel vapor permeation through the elastomer. Softer compounds usually have higher permeation rates. Also, extremely soft rubber compounds with no fillers tend to have poor resistance to compression set and compressive stress relaxation, which reduces the effective service life. The ideal balance tends to be in the 60 to 65 Shore A range.

Based on these two design criteria, the ideal compound for minimizing fuel vapor loss is a 60 to 65 Shore A, high fluorine fluorocarbon elastomer. For nearly 20 years, that exact solution, Parker’s VW252-65 compound, has sealed the fuel tank of almost every passenger car assembled in North America.

Now, Parker has taken another evolutionary step forward by improving the compression set resistance, low temperature performance, and fuel vapor permeation resistance with VW313-65, our next generation fuel system seal material. A comparison is shown in Table 2. Still a high fluorine fluorocarbon compound in the ideal 60 to 65 Shore A range, VW313-65 was also designed to be manufactured in all corners of the globe. This means seals can be made locally to best suit our customers’ needs to localize manufacturing and optimize logistics.

Table 2: Comparison of VW313-65 and VW252-65.

Hardness, Shore A

Compression Set, 336 hours at 200°C

Compressive Stress Relaxation, 1500 hours at 150 C

CE-10 volume swell

CE-10 fuel vapor permeation

TR-10

VW252-65

66

60%

42%

6%

24

-5°C

VW313-65

69

50%

72%

4%

18

-8°C

VW252-65 has long been the preferred material for minimizing fuel vapor loss from a vehicle fuel system, and VW313-65 offers further performance enhancements to provide for the next generation of vehicles.

For more information, please contact our Applications Engineers via our live chat service on Parker O-Ring & Engineered Seals Division's website.

This article contributed by Dan Ewing, senior chemical engineer, 

Parker Hannifin O-Ring & Engineered Seals Division.

3 Global Trends Driving Seal Innovation in the Automotive Industry

Seals and the Quest for MPG

Mobile cranes perform a wide variety of tasks, typically of the heavy-duty kind. The work they do and the locations at which they operate are frequently exposed to harsh climatic conditions in places with insufficient infrastructure. This means that the sites at which the cranes are positioned and the environment in which they move is often not entirely suitable for  this kind of heavy construction equipment. Accordingly, there are high loads acting on the components, which often wear out prematurely as a result. A new sealing solution for swivel joints in cranes subjected to high loads, which combines a polyurethane O-ring with a nobrox® back-up ring, has effectively remedied this issue.

Swivel joints are generally used for swiveling and/or rotating hydraulic connectors. The type of ball bearing mounted swivel joint from Parker Ermeto, which specializes in a wide range of industrial components, is unique in this form and features a particularly robust design. In addition to applications in booms or cranes, these swivel joints can essentially be installed in excavators, drill units or diverse stationary applications as well.

Aside from a ball bearing mounted race made of bearing steel, which transmits rotary movements even under extremely high interior pressure loads of up to 420 bar with nearly no losses, such high-performance swivel joints require a seal that encloses the hydraulic fluid while permitting relative rotary movements in its seat under maximum contact pressure without abrasion or extrusion. Drag-in of the hydraulic fluid into the ball guide must be prevented – even after an extremely cold night when the mobile crane after an eight-hour period of rest with unheated units is set up, i.e. started up again. Furthermore, a sealing ring as atmospheric protection is provided against external dirt and drag-in of dust or condensate.

The ball bearing mounted swivel joints utilized in mobile cranes posed the problem that the NBR O-rings and back-up rings used for sealing could extrude into the gap between the ball bearing mounted pivot and the surrounding housing after a relatively short period of time. Consequently, the back-up ring was practically pulverized, resulting in wear of the O-ring. The extremely high contact pressures and the simultaneous slow rotating movement were identified as the causes. As a result, the sealing elements were pushed into the gaps induced by the manufacturing process, which ultimately led to seal wear. This effect can be observed during the controlled lowering of the jib under high operating pressures and simultaneous occurrence of extreme flow velocities, i.e. above those established by the engineering design criteria.

Thanks to its excellent wear resistance and good anti-frictional properties, Parker Prädifa’s new thermoplastic sealing material nobrox® (PK) was taken into consideration as a material for the back-up ring at an early stage. Another objective was to enhance the robustness of the O-ring as well by utilizing a material with higher wear resistance. Therefore, instead of the previously used NBR material, an Ultrathan® (TPU) compound from Parker Prädifa’s portfolio was selected.

In the physical laboratory, the swivel joint with the new sealing set was tested in a wide range of extreme operating conditions exceeding those of the application and simulating the operating parameters actually prevailing on the vehicle with maximum realism. These tests run over 10,000 cycles were successfully passed, revealing that the maintenance-free operating period of the swivel joint far exceeds the typical frequency and operation sequences of a jib.

More Information:
www.nobrox.com
O-ring Praedifa series V1, Ultrathan®
Ermeto DIN Ball Bearing Rotary Fittings

Article contributed by

Michael Dillmann, Account Manager,
Engineered Materials Group Europe

Carsten Schippers, Research & Development,
Fluid Connectors Group, Tube Fittings Division Europe

Optimum Sealing Performance, Even in Low-Pressure Conditions With the HL Rod Seal

New Material nobrox Increases Design Freedom for Seals and Engineered Components

Tandem sealing system enhances performance of mini excavator actuators

Frequently, our team in Applications Engineering receives a question along these lines: “Is your compound E0740 peroxide cured?” Usually, these questions are asked because an end customer specifies cure system as a requirement on the drawing for the part. Parker considers the ingredients used in our manufacturing process as a trade secret and are not at liberty to directly disclose what cure system is used for any given compound. However, there is a valid and scientific basis behind why customers are concerned with the cure systems of the O-ring material, but is it as critical as it seems?

When uncured rubber is subjected to high temperature and pressure, the polymer chains that make up the rubber material are being locked into place due to cross-linking. Cross-linking is when chemical bonds are formed between individual polymer chains and is what allows rubber to go from a sticky, soft playdough-like material to a solid, sturdy seal. To facilitate this reaction, cure agents are added into the raw compound. These substances form the cross-links while the parts are being molded. The key result of curing the rubber is that curing drastically affects the material properties for a given compound. Two compounds could theoretically be the same up until the point of curing, but once the rubber is cured, these two compounds would have very different material properties.

Depending on the base polymer, there are different options for what cure system can be used during manufacturing. In general, each polymer family has at least two options for cure, each providing a different set of finished material properties. In addition to final material properties, cure systems can also differ in cost, with the costlier cure system typically resulting in a more desirable set of final properties for seal applications. Often when customers are specifying a cure system, their intended end-result is to obtain a material with a particular set of properties. A common example of this was laid out above, when a customer may ask whether “E0740 is peroxide cured.” In practicality, what they likely want to know is “Does E0740 have a high resistance to compression set, high tensile strength, and better-than-average high temperature resistance?” These are the properties that result from an EPDM material being peroxide cured. If, in some crazy advancement of science, we discovered that barbecue sauce provided EPDMs with material properties superior to that of peroxide while being less expensive, specifying a “peroxide cure” would no longer be beneficial, as the finished material properties of a peroxide-cured-compound would be inferior and more expensive than those obtained through barbecue-sauce-curing. While that is certainly a silly example, one day in the future, a new technology will be developed and rubber materials will be cured with different substances than what is currently considered to be “mainstream” technology.

When someone asks about the cure systems of a compound, our protocol is to understand more about the customer’s application. Each option for cure system of a rubber family has its advantages and disadvantages. Understanding each customer’s specific application tells us what properties are going to be critical in the material selected for their application. For nitrile compounds, many customers prefer peroxide curing, which typically provides increased compression set resistance, higher temperature performance, higher ultimate tensile strength, and increased chemical resistance. However, there are other customers who, maybe in the case of dynamic sealing, would prefer sulfur cure, which would provide better wear resistance, is more cost effective, provides higher ultimate elongation, and improves the ability to withstand repetitive bending. When it comes to sealing, it’s not always about how you got there, but whether or not you get the right material that gets the job done! 

For more information or to speak with an engineer about your specific application, use our Live Chat tool or give us a call. 

This article was contributed by Tyler Karnes, applications engineer, Parker O-Ring & Engineered Seals Division.

Related content:

Chemical Compatibility: A Critical Component in Seal Design

Perfluoroelastomer Materials Tailored for Your Needs

New CPI FFKM Extends Seal Life, Solving Long Time Industry Challenge  

Frequently, our team in Applications Engineering receives a question along these lines: “Is your compound E0740 peroxide cured?” Usually, these questions are asked because an end customer specifies cure system as a requirement on the drawing for the part. Parker considers the ingredients used in our manufacturing process as a trade secret and are not at liberty to directly disclose what cure system is used for any given compound. However, there is a valid and scientific basis behind why customers are concerned with the cure systems of the O-ring material, but is it as critical as it seems?

When uncured rubber is subjected to high temperature and pressure, the polymer chains that make up the rubber material are being locked into place due to cross-linking. Cross-linking is when chemical bonds are formed between individual polymer chains and is what allows rubber to go from a sticky, soft playdough-like material to a solid, sturdy seal. To facilitate this reaction, cure agents are added into the raw compound. These substances form the cross-links while the parts are being molded. The key result of curing the rubber is that curing drastically affects the material properties for a given compound. Two compounds could theoretically be the same up until the point of curing, but once the rubber is cured, these two compounds would have very different material properties.

Depending on the base polymer, there are different options for what cure system can be used during manufacturing. In general, each polymer family has at least two options for cure, each providing a different set of finished material properties. In addition to final material properties, cure systems can also differ in cost, with the costlier cure system typically resulting in a more desirable set of final properties for seal applications. Often when customers are specifying a cure system, their intended end-result is to obtain a material with a particular set of properties. A common example of this was laid out above, when a customer may ask whether “E0740 is peroxide cured.” In practicality, what they likely want to know is “Does E0740 have a high resistance to compression set, high tensile strength, and better-than-average high temperature resistance?” These are the properties that result from an EPDM material being peroxide cured. If, in some crazy advancement of science, we discovered that barbecue sauce provided EPDMs with material properties superior to that of peroxide while being less expensive, specifying a “peroxide cure” would no longer be beneficial, as the finished material properties of a peroxide-cured-compound would be inferior and more expensive than those obtained through barbecue-sauce-curing. While that is certainly a silly example, one day in the future, a new technology will be developed and rubber materials will be cured with different substances than what is currently considered to be “mainstream” technology.

When someone asks about the cure systems of a compound, our protocol is to understand more about the customer’s application. Each option for cure system of a rubber family has its advantages and disadvantages. Understanding each customer’s specific application tells us what properties are going to be critical in the material selected for their application. For nitrile compounds, many customers prefer peroxide curing, which typically provides increased compression set resistance, higher temperature performance, higher ultimate tensile strength, and increased chemical resistance. However, there are other customers who, maybe in the case of dynamic sealing, would prefer sulfur cure, which would provide better wear resistance, is more cost effective, provides higher ultimate elongation, and improves the ability to withstand repetitive bending. When it comes to sealing, it’s not always about how you got there, but whether or not you get the right material that gets the job done! 

For more information or to speak with an engineer about your specific application, use our Live Chat tool or give us a call. 

This article was contributed by Tyler Karnes, applications engineer, Parker O-Ring & Engineered Seals Division.

Related content:

Chemical Compatibility: A Critical Component in Seal Design

Perfluoroelastomer Materials Tailored for Your Needs

New CPI FFKM Extends Seal Life, Solving Long Time Industry Challenge  

The utilization of suitable materials based on specialized engineering and manufacturing know-how makes it possible to integrate several parts and/or functions in a single assembly component. In many cases, this can shorten the process chain and reduce logistics and assembly requirements. In the case of hygienically sensitive applications such as those in the food industry, a reduction of the number of components enhances hygiene and ease of use, as the number of interfaces and joints decreases as well. As a result, the need for long and costly cleaning cycles is eliminated and the frequently necessary partial dismantling of equipment for maintenance and cleaning can be accomplished with much greater ease and in less time.

The brew unit is the centerpiece of any fully automatic coffee machine. This is where the key parameters of the coffee’s quality are determined, such as the compaction level of the grounds, water pressure and filtering of the coffee product.

The brewing chamber, the metallic micro-strainer and, last but not least, the brewing piston with the associated sealing and wiping system are the key components of the brew unit. 

Conventional brewing piston systems in professional fully automatic coffee machines frequently consist of complex, metallic brewing pistons with sophisticated geometries and failure-prone sealing systems with an average expected lifetime of approximately 50,000 brewing cycles. Afterwards, the brewing piston and the related sealing system have to be exchanged in a time-consuming and costly process.  

The sealing system not only has to withstand a pressure of up to 20 bar at temperatures of 95 °C, but also resist the highly abrasive coffee powder and the acidic coffee extract.

• The newly developed brewing piston system features two major components: the brewing piston and the portafilter with integrated sealing, wiping and filtering function. Easy connection of the components can optionally be achieved by a threaded connection or snap fitting for ease of assembly and servicing.

• The fully integrated design of the nobrox® brewing piston reduces the geometric complexity and number of single componens while increasing ease of assembly and servicing.

• The piston attachment combines various functions, which helps reduce the complexity and component diversity of the brew unit. This where the non-reinforced nobrox® material can display its advantages. Its high wear resistance makes it possible to combine the sealing and wiping function in a dynamic sealing system. The sealing/wiping lip is preloaded by a TPU O-Ring and ensures consistently good sealing performance between the brewing piston and the brewing chamber across the entire lifetime.

• Service life extended on average by 50 to 100 % or to an average expected life of > 100,000 brewing cycles.

• Lower heat loss compared with metallic pistons saves heating elements.

• Manufacturing cost benefits due to injection molding technology compared with machining of metallic brew pistons.

• Unlike solution concepts that enclose the seals in a groove on the outer piston diameter the fully integrated system permits absolutely no dead space. This avoids coffee deposits that impair functionality or flavor. Due to the outstanding tribological properties of the nobrox® material, there is no need for additional lubrication. 

More information:

• EMG Report 04/2015 Page 7, Universal nobrox Material in Professional Coffee Machines
• EMG Report 06/2017 Page 10, Universal Material nobrox for Food Applications
• Brochure "Materials for the Chemical Process and Food Industries"
• www.nobrox.com - Food Applications

Article contributed by

Stefan Reichle
Market Unit Manager Industry
Engineered Materials Group Europe, Prädifa Technology Division

Universal Material nobrox® for Food Applications: Compound Versatility Beats Compound Variety

A Guide to Selecting the Proper Sealing Material for Food Applications

New Sealing Material HiFluor FB for Hygienically Sensitive Applications

New Material nobrox Increases Design Freedom for Seals and Engineered Components

Electric vehicles are developing fast in line with growing demand. However, only by selecting proven, reliable, high-quality products for the effective thermal management and EMI shielding of batteries, is it possible to maximize performance.

Although electric vehicles represent a greener and cleaner future, they come with a number of technology challenges, including within the battery pack. When large batteries need to provide as much power as possible to supply energy to the car, they generate a considerable amount of heat that must be dissipated. Left unchecked, excessive heat can cause faster battery wear, reduced performance and reduced charge efficiency, not to mention the obvious safety hazards associated with thermal runaway of the battery packs.

Effective thermal management is therefore critical to optimize battery performance and longevity with improved safety and reliability, allowing vehicles to travel greater distances and increasing the achievable run-time on a single charge. 

1. High volume thermal dispensable gels, such as the THERM-A-GAP GEL family, can be dispensed between the coils and the aluminum chassis of the battery to deliver long-term thermal stability and performance. These gels are particularly suitable in volume markets such as automotive due to the ease of dispensing using robotics or automation, thus reducing cycle times and costs considerably. 
2. Thermally conductive gap filler pads are an alternate solution depending on the design of the battery packs. Products such as the THERM-A-GAP gap filler pad family are perfect for assemblies that might require some additional support and higher electrical isolation. 

In addition to effective thermal management, another technology challenge presented by the growing demand for electric vehicles is the need to shield against electromagnetic interference (EMI). The cables that travel between the battery and engine, as well as the battery and charger, see high current produced at low frequency. This produces a large magnetic field that can negatively affect other electronics within the vehicle. High shielding attenuation is also required to protect the battery and its circuits from any incoming EMI.

3. Conductive elastomers can be used to overcome these issues. These elastomers, such as the CHO-SEAL family of elastomer gaskets, are filled with conductive particles and connect interfacing components to reduce the air gap and create a Faraday Cage that blocks EMI fields. Oftentimes, batteries also need to be sealed against environmental dust/fluids. Here, it is possible to deploy combined solutions to support EMI and environmental shielding/sealing. 

4. Form-in-place (FIP) conductive gaskets can be used for battery applications which require shielding of the electric traction elements. FIP can be robotically dispensed directly onto castings making it a low cost option. 

5. Electrically conductive plastic, which can replace the metal housing of the battery ECU, can eliminate 35% of the housing weight, and provide cost reductions of up to 65% by eliminating secondary operations. PREMIER PBT-225 is a single pellet electrically conductive polybutylene terephthalate that offers many comparable properties to those of aluminum, along with weight reduction which helps improve the performance of electric vehicles. 

Learn more about Parker Chomerics' EMI shielding and thermal management technologies for electric and hybrid vehicles. 

This article was contributed by:

Tiberius Recean - sales manager, automotive

David Beresford, marketing and technology manager, Chomerics Division Europe.

Related content:

Top Three Design Tips for Corrosion Resistant EMI Protection

New Essential Handbook for EMI Shielding Applications

Improved EMI Shielding Consistency of Single Pellet Conductive Plastics

Precision O-rings are manufactured by vulcanization in a closed mold using compression or injection molding. This makes it possible to produce O-rings in relatively small manufacturing tolerances and with good surface quality according to ISO 3601-1 and ISO 3601-3. Due to defined vulcanization parameters, precision O-rings exhibit consistently high mechanical properties across the entire circumference. This high quality level is an indispensable prerequisite for achieving consistently good sealing effects over a long period of time.

However, up to now, this production technology has been regarded in the sealing industry as not being economically feasible for O-rings in very large dimensions due to the enormous work and related costs involved in making extra-large molds. In addition, such large molds are extremely difficult to handle and therefore cannot be accomplished by many seal manufacturers.

The innovative manufacturing technology of continuous vulcanization used by Parker Prädifa, which does not involve failure-prone joints, enables the cost-efficient production of precision-quality O-rings with high mechanical load resistance in nearly any desired diameter. The technical properties of continuously vulcanized O-rings are comparable with those of O-rings produced by conventional compression molding. As a result of being molded, these XXL O-rings are quality products for challenging applications.

The surface qualities and tolerances correspond to those in ISO 3601:2012. However, this standard only covers cord thicknesses of up to 8.4 mm. To ensure that customers receive reliable and consistently high-quality O-rings where cord thickness is >8.4 mm, Parker Prädifa has developed an in-house standard based on ISO 3601:2012.

In addition to precision-quality XXL O-rings, Parker Prädifa offers the development and production of customer-specific geometries in large diameters. A wide range of materials is available according to the application requirements.

The challenge >> In the large-scale industrial production of semi-synthetic antibiotics, up to 500,000 liters of antibiotics are produced per batch. For such large-scale production to be economically feasible equipment of corresponding dimensions is required. In addition to large fermenters with diameters of several meters in which the biotech antibiotic is bred, centrifuges of similar dimensions are utilized to separate the antibiotic from process agents. Leakage must be prevented at all cost for safety and economic reasons. A leaking centrifuge might contaminate the antibiotics, resulting in high financial losses or, worse yet, in health and environmental hazards.

The solution >> Parker Prädifa was involved in the project at an early stage to develop a reliable sealing solution. The utilization of continuously vulcanized, i.e. jointless precision O-rings ensures the requisite reliability. Besides the seal design, the compound properties, particularly temperature and media resistance, play a key role. In addition to permanent temperatures of 250 °C, the seal has to withstand the aggressive media used in antibiotics production. The Parofluor® (FFKM) compound V8920 was selected as the suitable material for this application.

The challenge >> The development of a new lithography system for semiconductor manufacturing posed the challenge of sealing two halves of a housing. Due to the tolerance situation in producing the respective housing halves, there was a risk of a gap of up to 0.5 mm occurring between the two halves in the assembled housing.

The solution >> In sealing technology, the gap dimensions to be bridged are typically between 0.05 mm and 0.25 mm. As larger gap dimensions available for sealing in the groove in this application could not be reliably sealed, or only by entailing a higher risk of leakage, with a solid seal such as an O-ring, a conventional O-ring sealing solution was not selected here, but a profile seal featuring a lip design. This seal was developed using Finite Element Analysis (FEA) to ensure reliable sealing of large gaps and tolerance variations in the seal groove between the two halves of the housing. In addition, the shape of the seal prevents twisting during installation and reduces the required assembly forces.
In the selection of the seal compound, high purity requirements had to be considered. Due to specific post-curing processes, the FKM compound V0747 with low outgassing properties achieves outstanding results.

More information

EMG Report 07/2017, Page 22
Brochure: XXL Size Seals and Molded Parts

Article contributed by
Stefan Reichle, Market Unit Manager Industry
Engineered Materials Group Europe, Prädifa Technology Division

New Sealing Material HiFluor FB for Hygienically Sensitive Applications

Optimum Sealing Performance, Even in Low-Pressure Conditions With the HL Rod Seal

New Material nobrox Increases Design Freedom for Seals and Engineered Components