Slippery PTFE Washers

PTFE is an excellent material for a wide range of sealing applications, including PTFE washers. Being chemically inert, it resists attack by almost all acids and alkalis. It’s soft, so it deforms readily to fill uneven gaps between surfaces, and it remains flexible and useable over a wide temperature range, (in comparison to other gasket materials). It’s a good thermal and electrical insulator, but it has one other useful attribute: low friction.

Low-Torque Tightening

Low friction means other surfaces experience almost no resistance as they slide over PTFE, (also known by its Chemours tradename, Teflon.) That’s advantageous when closing up a joint where one surface slides against the seal or gasket as it means all the applied force goes into the joint.

A product that exploits this behavior is the PTFE washer. Consider this a special type of gasket that benefits from low friction. Slippery surfaces help ensure the fastener fitted over the washer seals without moving or tearing the washer surface.

Applications for PTFE Washers

  • Plumbing — use PTFE washers under bolts and when fastening fittings to delicate or easily marked surfaces
  • Electronics — insulating properties and high-temperature resistance make PTFE washers a good choice for distributing screw loads in electrical assemblies
  • Mechanical assemblies — PTFE washers let bolt heads tighten down without putting and stresses into the surface underneath
  • Food industry – PTFE is available in food grades and withstands aggressive cleaning regimens

PTFE Washers:  Shapes, Sizes, and Forms

PTFE comes in sheet form and both filled and pure PTFE grades. It’s readily die-cut, water jet cut, and flash cut.

While there’s an assumption that washers are circular, they don’t have to be. Hexagonal shapes will utilize the PTFE sheet better while squares and rectangles may be more useful in some applications. Tabs can help resist rotation during fastening, although the slipperiness of PTFE means this is rarely an issue.

We are happy to provide a quote for PTFE washers custom fabricated to your specs.

When to Use EPDM Rubber Gaskets

EPDM is a soft, silicone-like material suitable for a wide range of gasket applications. It’s often molded into seals and ‘O’ rings but it’s also produced in sheet form of various sizes and thicknesses. This is ideal for laser, waterjet and die-cutting custom gaskets. Like all gasket materials though, EPDM does have some limitations. Here’s some guidance on when and when not to use EPDM Rubber Gaskets.

EPDM Gasket Material Basics

EPDM is an acronym for Ethylene Propylene Diene Monomer. The short version of the chemistry explained in, “Understanding EPDM Gasket Material,” is that this forms long interlocked molecular chains. This gives it an elastic behavior somewhere between neoprene and silicone.

Strengths of EPDM Rubber Gaskets

EPDM has characteristics that make it good for a wide range of gasket applications. Chief among these are:

  • Withstands attack by a wide range of chemicals including acids, alkalis and ketones
  • Good resistance to steam and caustic cleaners
  • Good resistance to UV light
  • Remains flexible at temperatures as low as -40°F (-40C)
  • Upper temperature limit around 225°F (107°C)
  • Good ozone resistance
  • Good dielectric properties mean it’s a good choice for electrical sealing
  • Good abrasion resistance
  • Excellent elastic recovery.
  • Won’t impart a taint to liquids or solids it comes into contact with

Limitations of EPDM Rubber Gaskets

EPDM should not be used with oils and fuels as these cause swelling. The upper limit to strength is around 1100 PSI.

Good Applications for EPDM Rubber Gaskets

EPDM works where the application needs a gasket material more robust than neoprene and less expensive than silicone. The three main classes of application are:

  • Food and drink processing equipment (mixer seals is a common application) as it’s available in food grades and withstands aggressive cleaning regimens.
  • Sealing outdoors, where it withstands low temperatures and exposure to UV.
  • Electrical cabinets and enclosures, where ozone may be generated.

More Information

If you have a gasket application that needs a more robust material than neoprene, EPDM might be the answer. Contact the specialists at Hennig Gasket to learn more.

Viton Washers for Fuel and Hydraulic Systems

Gasoline, diesel and hydraulic oil are some of the hardest fluids to seal against. They make most gasket materials swell, which increases pressure on the joint and leads to gasket failure. Nitrile rubber is one of the rare exceptions but its upper temperature limit is around 200⁰F. If you’re concerned that nitrile won’t be up to the job it’s time to move to Viton washers.

Viton™, FKM and FPM

The first thing to know about Viton is that it’s a trademark, (originally held by DuPont and now their spinoff, Chemours.) The technical term for this type of elastomer is a fluoroelastomer. In lay terms, it’s a synthetic rubber composed mostly of carbon and fluorine. In Europe fluoroelastomers are designated as FPM while here in the US we use the ASTM abbreviation of FKM. Whichever term you use, they’re essentially the same thing.

Properties of Viton and Other Fluoroelastomers

Viton and other fluoroelastomers are more expensive than almost any other gasket material, but three characteristics make them the preferred solution for the toughest sealing challenges:

  1. Excellent resistance to oil-induced swelling
  2. Highly resistant to most chemicals
  3. High-temperature strength (Viton goes to 400⁰F (204⁰C) and higher)

In addition, Viton has good UV and ozone resistance. Other points to note are that, while sufficient for most applications, tensile strength and resilience or elasticity are not high. Also, Viton is incompatible with acetone and many organic acids.

Applications for Viton Washers

High cost means Viton is reserved for difficult applications. Sealing pipes and fittings in fuel and hydraulic oil systems is a good example. Viton washers are a cost-effective way of minimizing the risk of potentially hazardous leaks and costly downtime in these situations. Likewise, it’s often the smart choice in systems handling corrosive chemicals where leaks must be prevented at all costs.

Viton Washers and Gaskets From Hennig

Viton comes in sheet form and a number of grades. We can water jet, flash or die cut the size and shape you need. Our specialists can help you decide what’s right for your application. Call (312) 243-8270 or 1-800-747-7661 or contact us.

Neoprene: It’s For More Than Wetsuits

Surfers and divers are very familiar with neoprene. It’s been the material of choice for wetsuits for decades. It’s also a versatile gasket material, although used in a different form to wetsuit material. Here’s what you should know about neoprene gasketing.

Synthetic Rubber

Neoprene is a DuPont tradename for polymerized chloroprene, which is one of the synthetic rubbers developed in the 1920s and 1930s. Chloroprene is composed of carbon, hydrogen, and chlorine which produce a clear liquid. Polymerization forms the molecules into long chains that interlock to create a soft, flexible material.

Neoprene is made as a solid, (described as homogenous neoprene,) and closed-cell foam. It’s this latter version that’s used in wetsuits with the pockets providing thermal insulation. Foamed neoprene provides good cushioning and is used for gasketing as it forms a soft, waterproof seal. (Pressure-sensitive adhesive applied to one or both sides makes it easier to fix in place.)

Neoprene is also used as a binder with Aramid fibers. This results in a higher-strength neoprene gasket.

Neoprene Properties for Gaskets

Being soft, (40 – 70 Shore A durometer,) and flexible with good elastic recovery, homogenous neoprene conforms readily to mating surfaces. It has excellent water resistance, (hence the wetsuit usage,) and also withstands oils, ozone, and some acids. Food grades are available.

The practical temperature range for neoprene gasketing is -20 to 180°F. This makes it unsuitable for sealing steam or other hot fluids. A bigger limitation is a lack of strength. Depending on grade, maximum tensile strength is 900 – 1,000 psi, meaning neoprene is not suitable on its own for high-pressure applications. Bound with Aramid though, it offers much higher strength.

Ask Us About Neoprene Gasketing

Homogenous neoprene comes in sheet and roll form up to 72” wide and in a range of colors. Thicknesses range from 3/32” up to 2”. We can waterjet, flash, or die-cut neoprene to the size and shape you need. If you’re looking for inexpensive gasket material and don’t need high strength, neoprene may be the gasket material for your application. Call us to discuss.

Heat Resistant Gaskets – What You Should Know

For gaskets, “If you can’t stand the heat, stay out of the kitchen,” becomes, “If it can’t stand the heat, stay out of the joint.” Using the wrong gasket material in a high-temperature application is the fastest route to failure. It could also be expensive and even dangerous. Here’s some advice for choosing heat resistant gaskets and gasket material.

Heat Resistant Gaskets:  Know the Application Conditions

When choosing gasket material always consider temperature, environment, media and pressure (remember them with the mnemonic TEMP), and temperature comes first. It relates mainly to the media that’s being sealed-in, which could be hot liquid, steam or high temperature gas, (exhaust gases for example,) but it can also refer to the temperature where the gasket is installed and used.

Heat and Gasket Materials

Elevated temperatures affect gasket materials in different ways, and the threshold at which the changes kick in varies widely too.

  • Rubbers (NBR, SBR,) harden and become brittle at temperatures over 300°F (149°C). They can also oxidize, which has the same effect.
  • EPDM and silicone will go to higher temperatures before losing the ability to seal. An upper limit for EPDM is around 400°F (204°C) while heat-resistant grades of silicone will go to 500°F (260°C).
  • For temperatures up to 600⁰F (316⁰C) PTFE is a good choice. It also has good chemical resistance, which makes it suitable for many process plant applications.
  • Compressed non-asbestos gaskets are an exception to the point about With an SBR or NBR binder that fixes a matrix of aramid fibers, these are suitable for 750⁰F (399⁰C) and some grades will go higher. (These have good resistance to steam, oil and fuels, but always check your application with us before buying!)
  • For resistance to really high temperatures, graphite is the answer. Available laminated, as a foil and also in spiral-wound gaskets, this will seal at 1,000⁰F (538⁰C) and higher. Other options are ceramic fiber (which tends to be brittle,) and fiberglass.

High temperatures will lead to sealing failure faster than almost any other factor. Always consider temperature when selecting gasket material, and ask for heat-resistant gaskets whenever temperature is a concern.

Contact Hennig Gasket & Seals for a free quote.

Thermoseal C4401: An (Almost) Universal Gasket Material

Gaskets seal everything from pipe flanges to manways but there’s no single gasket material that can do everything. However, Thermoseal C4401, (also known as Klingersil C-4401,) comes close. Here’s a quick review of how to select gasket material and an introduction to this versatile choice.

Factors to Consider

For every sealing application, a first step is to work out what material to use. This entails considering the temperature, environment, media, and pressure that the gasket will experience. (The mnemonic “TEMP” might help you remember this list.) Once those are known a gasket material can be chosen.

TEMP Compatibility Challenges

All gasket materials have a limited temperature range. Environmental concerns relate to things like exposure to ozone, UV light, and water. The media is the fluid being sealed in the pipe or outside the enclosure or man-way. And the pressure is the force the gasket will be exposed to.

Of these factors, media may pose the biggest sealing challenge. Every gasket material resists attack by some chemicals but is susceptible to others. EPDM for example is acetone-resistant but vulnerable to many fuels and oils. (Those examples are taken from “Gasket Material Compatibility Chart for Chemicals”.)

Meet Thermoseal/Klingersil C-4401

Thermoseal C4401 is one of a family of compressed fiber-reinforced gasket materials produced by KLINGER Thermoseal. These are made by mixing fibers into a rubber-like binder and then rolling it into a sheet. The fibers provide strength while compressibility and recovery come from the binder.

In Thermoseal C4401 the binder is a nitrile rubber and the fibers are aramid. Aramid is a light and strong synthetic fiber that resists abrasion and solvents. Nitrile is a form of synthetic rubber with excellent elastic behavior and good oil resistance. When combined the result is a gasket material that withstands temperatures as high as 750 °F (399 °C), and withstands a long list of chemicals.

Ask About Thermoseal/Klingersil C-4401

If you’re unsure about the media you’re sealing or just looking for a universal gasket material, C4401 is an excellent choice. Specialists at Hennig Gasket & Seals will be happy to tell you more.

Flexible Graphite Gasket Material – When to Use

If you need an alternative to PTFE gasket material, how about graphite? Produced as sheet material, flexible graphite gasket material withstands high temperatures while deforming easily enough to take up imperfections in flange surfaces.

Chemistry and Production

Graphite is a form of carbon. It’s used in pencils because it’s easy to slide the layers apart and spread them on paper. To produce a useful gasket material the graphite is first expanded and then passed through a machine called a sheeter.

Expanding entails exposing small pieces of graphite to sulfuric or nucleic acid. These force the atomic layers apart, making the graphite expand dramatically and forming what look like tiny worms. These “worms” are then fed into a sheeter that compacts them into a sheet of flexible graphite material.

For added strength, the graphite can be laminated onto either a thin stainless steel foil or a stainless tang.

Properties of Flexible Graphite Gasket Material

The practical upper-temperature limit is around 750 °F (399 °C) although some grades will go to 900 °F (482 °C). You may see claims that graphite can withstand temperatures as high as 5,400 °F (2,982 °C) but this is in an oxygen-free atmosphere, which few gaskets ever experience.

A limitation of sheet form expanded graphite is low tensile strength. Laminating onto 316 stainless raises this from around 700 psi to a much more useful 5,000psi. In terms of gasket applications, this means pure graphite sheet has very low resistance to pressure: foil and tang forms of graphite sheet are far more useful.

The downside of combining graphite with stainless is that this slightly reduces both compressibility and recovery behavior.

Graphite has excellent resistance to water, steam, hydrocarbons, and many acids and alkalies. However, sulfuric or nucleic acids will cause rapid decomposition. Note that graphite is not suitable for food, medical or pharmaceutical applications because there’s a possibility of releasing carbon particles into the fluid.

Flexible Graphite Gaskets Cut to Size

Hennig Gasket & Seals carries flexible graphite gasket material in a range of thicknesses. Gaskets can be cut to sizes up to 48” in diameter. Contact us for more information.

What’s Special About Food Grade Silicone Gasket Material?

Silicone makes excellent gaskets. It works over a wide temperature range, has a low compression set, high elongation, and is resistant to water, ozone, many acids, and UV light. If you’ve shopped for silicone gaskets or gasket material you probably noticed some formulations are specified as “food grade.” Here’s what that food-grade silicone gasket material means and why it might matter in your application.

Composition, Properties and Forms of Silicone Gasket Material

Silicone is an elastomeric polymer made from silica, (which is silicon dioxide, or sand), water and methanol. Silica is chemically inert and very stable, even at temperatures as high as 550 °F. It’s also an electrical insulator.

As a gasket material silicone has two weaknesses. First, it’s not oil-resistant and should not be used where it might be exposed to oil-based greases and lubricants. Second, it has poor wear and abrasion resistance so is best used as a static gasket rather than in applications where there’s sliding or dynamic contact.

Silicone gasket material is produced as a solid sheet in a range of thicknesses. It’s also available in foam and sponge form.

Food Grade and Non-Food Grade Silicone

Pure silicone is white. If it has no additives and is not ink-marked it will probably be suitable for use with foods. However, it’s important to check that it complies with 21CFR Part 177.2600 before using it in food or beverage-related applications. This is the FDA regulation that governs the purity of materials classed as food grade.

Some silicones are formulated with fillers, coloring, or both. This is to provide a particular appearance, improve wear behavior or reduce compression. However, some of these can leach out into the liquids or solids they come into contact with. If you need food-grade silicone gasket material with additives, check it meets FDA standards.

Ask Your Silicone Gasket Material Supplier

If you’re installing or replacing gaskets on food processing and preparation equipment they should be food grade, as defined by the FDA. Silicone is a good choice for food-grade gasket material.  Contact Hennig Gasket & Seals for various silicone gasket material options for your application.

When to Use a Full Face Flange Gasket

When you’re installing or replacing a gasket between pipe flanges correct alignment is important. If it’s misaligned, the part will protrude into the fluid flow while on the opposite side there’ll be a cavity. On both sides, there will be less gasket material trapped between the flange faces.

A full-face flange gasket avoids this problem because it’s located by the flange bolts. However, this design isn’t necessary for every application. Read on to learn more.

Full Face Flange Gasket vs. Ring Gasket

Flange Gaskets: Full-Face or Ring” explains the difference between the two types. Choosing which to use is largely a matter of clamping force needed and flange design.

A gasket prevents leaks by taking up imperfections between mating surfaces. This is achieved by firmly compressing the material so it conforms to both faces. This compression also helps the gasket resist the internal pressure within the pipe. The higher the pressure the greater the compression needed, (and it helps to keep the gasket as thin as possible.)

Ring-type flanges seal over a smaller area than full-face designs and apply higher compressive loads for a given bolt tightness. This needs to be considered when selecting a gasket material. Elastomeric gaskets can be crushed if over-tightened.

Because they seal over a larger area, full face flanges can’t achieve the same compressive load without tightening the bolts more than would be done for a ring face flange. Thus full face flanges, and also full face flange gaskets, are reserved for lower pressure and less critical applications. Conversely, most process plant piping systems use ring face flanges and gaskets.

Full Face Flange Gasket Versatility

A full-face flange gasket can be used in a ring face application. The material outside the faces won’t contribute to sealing but the bolt holes make it easier to position. Just be sure to get the right material properties and thickness for the task. However, don’t use a ring-type gasket in a full face application. You’ll be sealing over a smaller area and there’s a risk of bending or cracking the flange.

Contact us for a free full-face gasket quote.

When To Use Garlock Blue-Gard 3000

Garlock is one of the best-known brands in gasket materials and they have an extensive range of products. Here we’ll take a look at one of their materials that’s suitable for a wide variety of applications: Garlock Blue-Gard 3000.

Garlock Blue-Gard® 3000 Composition

The spec sheet tells us Blue-Gard 3000 is composed of aramid in an NBR binder. Here’s what that means.

The word “aramid” is a contraction of the chemists’ term, aromatic polyamide. It’s a generic term for high strength fibers produced from PPTA (poly-p-phenylene terephthalamide) polymer. You may recognize one of the widely used brand names: Kevlar.

In gasket material, these fibers need holding together. That’s the job of the NBR or nitrile rubber. NBR also provides the elasticity and compressibility we look for in a good gasket material.

Properties of Blue-Gard® 3000 Gasket Material

Aramid is very strong with excellent abrasion and creep resistance. It doesn’t melt or burn, even at very high temperatures, and it resists attack by solvents and oils. It will however degrade with prolonged exposure to UV light.

NBR is limited in the maximum temperature it can tolerate and is attacked by ozone as well as ketones, esters, aldehydes, and chlorinated hydrocarbons. Two examples of chemicals it should not be exposed to are acetone and benzene.

Where NBR excels is in resistance to oils, including those used in hydraulic systems, as well as fats and greases. When exposed to these oils it will swell. It also has good elasticity but will creep under load.

Garlock 3000 combines the most useful properties of aramid and NBR. It can tolerate 400°F (205°C) and has excellent creep resistance, which makes for good torque retention. Good strength means it withstands high internal pressures and it also resists attack from a wide range of oils.

When (And When Not) To Use Blue-Gard® 3000

Good uses are for sealing water, oils, and greases, even those being moved at high temperatures. Applications involving thermal cycling will benefit from high creep resistance. Applications to avoid are those with exposure to ozone, (such as high voltage electricity,) as well as perfumes and foodstuffs.

Hennig Gasket & Seals is the preferred vendor of Garlock Blue-Gard® 3000 and all other Garlock gasket material.  Contact us today for a quote on custom cut Blue-Gard® gaskets or sheets of Garlock gasket material.