Best Gasket Material for Nitrogen

Many industries use nitrogen. Some users even generate their gas on-site. If your company is among them you ought to be familiar with the best gasket materials to use.

Industrial Uses of Nitrogen

Liquid nitrogen is used when very low temperatures are needed. This is often for preserving biological samples or other organic material although other uses include cooling for superconductors and to aid in machining.

Applications for gaseous nitrogen include fertilizer production, food preservation, and annealing stainless steel. It’s also used in the production of electronic components like transistors and diodes.

Nitrogen Production and Storage

Nitrogen is produced by separation from air. (The air around us is approximately 78% nitrogen.) There are two methods:

  • fractional distillation
  • pressure swing adsorption (PSA).

Distillation entails chilling air until it becomes liquid, then raising the temperature slowly to let the individual components boil. In contrast, PSA is done at ambient temperature and in simple terms consists of pushing air through a membrane that separates the various constituents.

Distillation produces higher purity gas but is energy-intensive. PSA scales more easily for local or on-site gas generation, and this is the process most often adopted by manufacturers who don’t want to depend on deliveries and storage.

Suitable Materials for Gaskets in Nitrogen Systems

Nitrile and natural rubber gasket materials are good choices for gaseous nitrogen, although EPDM is generally considered best. EPDM gasket material has good heat resistance and a working temperature range of around -60 to 320°F (-50 to 160C). Resistance to oxidation, UV, ozone, and abrasion are all good and it also withstands water, acids, and alkalies along with ketones and alcohols.

Handling liquid nitrogen demands a gasket material with excellent low-temperature performance. If an elastomer is needed Santoprene® may be a good choice. A trade name for a class of thermoplastic vulcanizate (TPV) materials, this behaves much like EDPM but some grades remain flexible at even lower temperatures.

Consult a Materials Expert

Every gasket application is different so it’s always prudent to learn more about the material before purchasing. Specialists at Hennig Gasket are ready to help.

Gasket Material to Dampen or Attenuate Vibration

Yes, your next gasket should seal, but it could do more than that. A gasket is an excellent way of reducing the transmission of sound and vibration. That can extend equipment life and improve performance while creating a better environment for those nearby.

Gasket Material Properties for Vibration Dampening

The goal is to have the material acting like a spring: compressing and springing back in response to the excitation force. In other words, they need a combination of resilience and compressibility. Closed cell foams do this particularly well as the gas in each cell compresses and then expands.

Compressibility also depends on the nature of the material used. Softer elastomers like some grades of silicon or the urethane foam used in PORON® compress under relatively light loads. Others, like some nitrile rubbers, need more force to achieve a given level of compression.

For effective vibration dampening, compressibility, resilience and also thickness must be related to the excitation frequency and amplitude. Clamping force also plays a part as compression alters the material’s vibration response.

Vibration Dampening Gasket Materials

Silicone rubber and foam, nitrile sponge, and urethane foams can all attenuate vibration effectively. Less well known is that both felt and rubber-bonded cork material can also be used to cut or even eliminate the transmission of sound and vibration. Remember that the addition of a pressure sensitive adhesive (PSA) makes the material much easier to install or apply.

Situations benefiting from vibration dampening

Vibration-attenuating gasket materials are especially useful in HVAC systems where they can reduce noise significantly. Industrial machinery also benefits, with less vibration translating to higher quality output and longer equipment life.

Elastomeric gasket material is found in a growing number of electronics devices. Here it improves life by “ruggedizing” the equipment against knocks or drops. Recently a patented was granted for a vibration-attenuating camera mount that utilizes two gaskets for dampening. (US 9,654,692)

Next Steps

Gasket material selection is a complex field where every application is different. If vibration reduction is of interest ask for advice from a Hennig Gasket specialist today.

Why Steel Rule Die-Cut Gaskets are Disappearing

No one likes waiting for a gasket, especially when it’s for an urgent repair. No one wants to keep spare gaskets in inventory either. That’s why more gaskets are being water-jet cut. As tooling-free processes, they offer a faster turnaround than die cutting. Here’s more detail.

Steel Rule Die Lead Time and Storage

Each die is made to cut a unique non-metallic gasket. The sharpened blade is pressed into a slot cut in a backing board. Then ejection rubber is fitted around the blade to push out the cut gasket shape.

These take days or weeks to make so gasket manufacturers keep previously used tools in storage. At Hennig, we have thousands taking up space. If a customer wants a die cut gasket we check whether we have the tool needed. If we don’t, water-jet cutting is faster.

Tool Maintenance and Repair

Steel rule edges wear. That affects quality and accuracy, so they need sharpening and/or changing. Likewise, ejection rubber needs regular replacement.

In addition to faster order turnaround, these processes offer:

  • Better edge quality – no compression means straight and square edges.
  • Higher accuracy – water-jet machines can maintain tolerances as tight as +/- 0.0005” while die cutting struggles to beat +/- 0.010”. That’s because the machines are more precise and there’s no deflection or compression of the gasket material.
  • No tooling charges.

Die Cutting for Higher Volumes

Water-jet machines cut quickly, but not as fast as a tool in a press. (And rotary die cutting is even faster.)

Against that, the die cutting press takes time to set up. The breakeven point depends on gasket size, but water-jet and laser usually win for small quantity orders. Die cutting gets cheaper per piece for large quantities but don’t overlook tooling charges.

Speed Wins

With water-jet machines, gaskets can be cut to order. That enables a rapid turnaround that avoids holding spare gaskets in inventory. No wonder die cut gaskets are going away.

When to Use Felt Gasket Material

Most gasket materials are elastomeric or rubber-like in nature, but there’s another material that’s surprisingly effective in some sealing applications: wool. When compressed to a uniform density wool becomes felt. Felt has been used for sealing and gasketing for a long time and still has its uses.  Felt seals suppliers offer a variety of options

A “Non-Woven” Material

Most felt is produced by compressing wool into rolls of material. Wool fibers have a kind of “fish scale” surface that lets them hook together randomly. This creates a material that’s soft and compliant with a high level of resiliency. It can absorb and hold liquids even better than an open cell foam while resisting attack by oils and temperatures up to 200°F. An added benefit is that felt won’t unravel or fray like woven fabrics.

Industrial wool felt is specified by an SAE standard. This assigns grades from F-1 to F-55. Higher numbers indicate lower density, and these grades have less ability to absorb vibration and resist abrasion.

Felt is produced from other materials, most notably polyester fiber. Polyester felt will withstand temperatures up to 300°F but its properties and behavior are not addressed by the SAE standard.

Uses of Felt Gasket Material

  • Noise-deadening

Thanks to strong resilience, felt gasket material can absorb movement between surfaces that would otherwise cause rattles and squeaks. By preventing the transmission of vibration it’s also a good sound-deadening material.

  • Filtration

The random orientation of fibers in felt make it a very effective filtration medium. Filtration is further enhanced by soaking in oil. Wool fibers hold oil on their surface, which traps very small particles being drawn through.

This ability to retain oil also makes felt a good seal against moving surfaces such as shafts. The wool adapts to changes in gap while oil provides lubrication and simultaneously prevents fluid transmission.

Compliant but Durable

As a soft gasket material, felt is similar to an open cell neoprene, EPDM or silicone foam. Its upper-temperature limit is lower, but depending on grade, abrasion resistance can be higher. If you’re looking for a material that can lubricate as well as seal, ask about felt.

Custom Die Cut Gaskets

Practically every non-metallic gasket is cut from a sheet or roll of gasket material. Cutting methods include oscillating knife, laser, waterjet and steel punch dies although the most common process is steel rule die cutting. It’s cost-effective for medium quantity orders but needs special tools. Knowing a little about the process will help gasket buyers understand when this might be the one to use.

The “cookie cutter” process

A steel rule die is a steel strip bent to the profile of the part being cut. This is embedded into a plywood or phenolic board that holds it in shape. The exposed edge of the steel knife is sharpened so it can cut through the material. The board is then mounted into a press. Bringing the tool down into the gasket material cuts out the gasket.

To use the material efficiently gasket makers typically “nest” steel rule dies. This might mean cutting a small gasket from the center of a much larger one or combining a number of different gasket shapes in one tool.

For higher volume production a gasket maker might use a rotary die machine. Here the steel rule die is wrapped around a cylinder. Strip material is fed underneath and the die cuts out the gasket shapes as it rotates.

“Kiss cutting”

When cutting all the way through normal practice is to have a relatively soft sacrificial material underneath. This helps extend the life of the cutting edge. However, sometimes it’s better not to cut all the way through. This is “kiss cutting,” because the knife just “kisses” the backing material. It keeps the gaskets together in a single sheet while making them easy to separate when needed. This simplifies storage and is particularly useful when the gasket material has a pressure sensitive adhesive backing.

Dies for your gaskets

We’ve been cutting gaskets at Hennig for many years and have a lot of dies in inventory. If you want die cut gaskets it’s possible we already have the tools needed. Call or email to find out.

Yes, Cork is Still Used as a Gasket Material

Cork, the bark of the cork oak tree, has been used as a sealing material for centuries. The Romans “corked” wine bottles with it – something it still does today – and before modern elastomers were developed it was widely used as a gasket material. Cork gaskets are less common today, but they still have a role.

Properties of Natural Cork

Cork has a closed-cell structure that gives it excellent resilience. A layer can be compressed to around half its thickness and still recover when the load is removed. It’s also lightweight, flexible, and resists attack by water, many oils and even ozone. At around 275°F (135C) its upper temperature limit is lower than some elastomers, but that’s not its biggest weakness. Those are a vulnerability to mold, fungi and acid attack, and as an entirely natural material, its properties are somewhat unpredictable.

Composite Cork Gasket Material

Cork- rubber composites address these deficiencies. Typically these are 70% cork with a synthetic elastomer binder making up the balance. The elastomer imparts some of its own characteristics to the composite and is usually chosen to improve chemical compatibility and sealing performance. Processing also takes out much of the natural variability.

Composite cork gasket material is available that incorporates a number of different elastomers. EPDM, Neoprene, Nitrile and silicone are just a few. The material is produced as a sheet up to ¼” (6mm) thick and is easily die-cut. It readily takes a pressure sensitive adhesive coating, making it easy to apply in many gasketing and sealing applications.

The “Green” Dimension

Cork is cut from the cork oak tree once every nine years. The tree doesn’t die but instead grows a new layer of protective bark. This makes cork a renewable material, something that may be important in some applications and for some users.

There’s Still a Place for Cork Gaskets

Cork is waterproof and has great compressibility. Modern elastomers may offer better chemical resistance and a wider temperature range, but for sealing water and oil, don’t overlook this oldest of gasket materials.

Gasket Material and the PxT Factor

PxT stands for pressure times temperature. It’s a factor used more and more to characterize the performance of gasket material. The advantage is that it addresses how elastomers like silicone, EPDM and neoprene lose strength at higher temperatures.

An Inverse Relationship

Specifications for elastomers call out temperature limits. What’s rarely appreciated is that these values may not be good in all applications. Unlike metals where hardness changes very little as temperature rises, elastomers soften. For example, neoprene sheet material may have a quoted upper limit of 250°F but at this temperature it’s strength will be far lower than at say 68°F.

In many sealing applications pressure isn’t a concern. If the neoprene gasket only seals against warm air, that reduction in strength may not affect performance. However, if it’s sealing a pipe flange in a steam system reduced strength could be a problem. Even though the temperature might not exceed the upper limit, sustained pressure could extrude the material out through the flange.

Pressure AND Temperature

PxT shows how a gasket material performs under varying pressures and temperatures. Here are two examples.

Specs for a neoprene gasket material show the upper-temperature limit as 250°F and the maximum pressure as 250 PSI. However, the maximum PxT factor for the material is only 20,000 (°F x PSI). If used in an application with a continuous operating temperature of 250°F peak pressure is just 80 PSI. (20,000/250 = 80)

A sheet of EDPM gasket material has a maximum temperature of 300°F, a pressure limit of 250 PSI and a PxT factor of 30,000. In this case, the material manufacturer is saying that if sealing against media with a pressure of 200 PSI, the temperature should not exceed 150°F. (30,000/200 = 150)

If In Doubt …

Every gasket material has an upper-temperature limit. It may fail if taken beyond that, but it could also fail at a lower temperature if the pressure is high. The best approach is always to consult a material specialist like those at Hennig Gasket.

Sponge vs. Foam Gasket Materials

The terms sponge and foam are used interchangeably but they’re not the same. Buy foam for a gasket application and you may find the joint leaks. Use sponge material for cushioning and you may not get the protection you expected. Sponge and foam both have cellular structures, but there are important differences between the two.

Different Processes

Producing foam material is similar to baking bread. A chemical reaction in the liquid mixture creates carbon dioxide gas that leaves a very open structure.

Sponge materials also use a chemical reaction to create gas bubbles, but these remain self-contained cells, each one isolated from its neighbors. Some manufacturers can control the size and distribution of these pores to produce very consistent material with highly predictable behavior.

Open and Closed

The foam production process leaves an open structure more like a mesh than a solid. The stiffness or rigidity of this structure depends on the polymer used – typically that’s PVC, polyethylene or polyurethane.

In contrast, in a sponge the pores influence material behavior. Unlike a foam material, when sponge is compressed the gas in each pore has nowhere to go. That results in strong compression set resistance and good compression recovery.

Sealing Properties

Foam and sponge materials both have the advantage of low density but behave very differently when asked to act as a barrier. The open cellular structure of foam material lets fluid pass through readily, even when compressed. Sponge however blocks the movement of gases and liquids. That makes sponge material a good choice in HVAC sealing applications.

Cutting sponge will open up the edge pores. This allows a limited amount of liquid retention but the body of the material still acts as a barrier.

Materials for Sponge Gaskets

Practically all elastomers can be manufactured with a closed cellular structure. Consequently, neoprene, EPDM, nitrile and silicone gasket material are all available as sponges. As with their solid variants, these can be purchased with varying levels of temperature resistance and strength. Talk to a material specialist at Hennig Gasket if you need more advice.

Adding a PSA to Your Gasket Material

Not all joints hold the gasket in place. Electrical cabinet doors, food mixers and HVAC access panels are situations that often lack mechanical gasket retention features. In such cases the gasket must be adhesively bonded to the frame, cover or lid. Adhesives can be messy and awkward to use, and that’s why it’s worth asking about gasket material with a coating of pressure sensitive adhesive (PSA.)

The advantages of “peel and stick”

PSA is bonded to the gasket material before shapes are cut out. On the reverse side, (away from the gasket material) there’s a release film which is peeled off before the gasket is installed.

The advantages of PSA-coated gaskets are:

  • Easier to install.
  • Stay in place when the joint is opened.
  • Facilitates “kiss-cutting”. This is when the die cutter goes all the way through the gasket material but stops short of the PSA release film. Kiss-cutting holds the individual gaskets together in a sheet or roll, making them easier to handle.

Material compatibility

Most gasket materials will take a PSA coating. For example, both neoprene and silicone gasket material can be ordered with PSA. The major exception is PTFE gasket material as this is naturally non-stick.

PSA cautions

A PSA used on gasket material becomes part of the joint and experiences the same temperatures, pressures and chemicals as the gasket itself. Accordingly, the PSA must be matched to the application. Silicone gaskets are a good example. As these are used for both high and low temperatures the PSA must be chosen appropriately. In some cases the available PSA’s will limit the service conditions.

PSA selection is of particular importance when installing food grade or FDA gaskets. For these applications the adhesive must also be food grade.

Replacing a PSA gasket can be time-consuming. This is because the old adhesive must be completely removed from the joint faces before the new gasket goes on.

Make life easier

Depending on the gasket material and the nature of the application, a PSA can simplify gasket installation. If “peel and stick” gaskets would simplify your next sealing job, talk to Hennig.

Ketones and Gasket Materials

When selecting gasket material it’s important to look at the media being sealed. Some gaskets will not work with some chemicals. One example is the group known as ketones. Many gasket materials are not recommended for sealing these. If the product you are sealing contains ketones it’s important to know which gasket materials will work. Unless you’re a chemist it may not be obvious when a fluid contains or incorporates ketones. Here we’ll explain briefly how to recognize ketones and discuss which gasket materials to consider.

Ketone recognition

To chemists ketones, and the closely-related aldehydes, are a family of organic compounds containing a carbon-oxygen grouping. Products composed of ketones can sometimes be recognized by their name. The solvent acetone for example, is a ketone, as indicated by the suffix, “one.” Likewise, the term, “aldehyde” appears in many chemicals, such as formaldehyde.

As organic compounds, ketones and aldehydes occur frequently in nature and are generally liquid at room temperature. Examples include extracts of cinnamon bark, vanilla bean, lemongrass and the coriander herb. In addition, many fragrances gain their distinctive odor from various aldehydes.

In short, many food preparation processes, especially in baked goods manufacture, expose gaskets to ketones, as do a range of perfume and solvent processes.

Gasket materials susceptible to ketone attack

A long list of commonly used gasket materials are attacked by ketones and aldehydes. This includes:

  • Nitrile rubber/NBR/Buna-N
  • Neoprene
  • Hypalon® (chemically similar to neoprene.)
  • Silicon
  • Fluoro-silicones
  • Viton and other fluor-elsatomers

Gasket materials with some ketone resistance

Three materials stand out:

  • Natural rubber (rarely used due to its inconsistency and poor temperature properties.)
  • SBR/styrene butadiene rubber (not resistant to methyl ethyl ketone)
  • EPDM (not resistant to methyl ethyl ketone)

Consider the media

When selecting gasket material it’s essential to consider the media being sealed. Chemical incompatibility will lead to the breakdown of the gasket material and failure of the seal. Ketones, and their related organic compounds, aldehydes, present particular challenges because they occur widely and few materials offer good resistance. If ketone exposure is possible SBR and EPDM gasket materials should be your first choice.