Category Archives: Fluoroelastomers

How to Choose the Best Sealing Materials Based on Chemistry & Strong Oxidizers

Strong oxidizers can damage metal, causing pitting or rust and treating possible safety concerns.

In chemistry, strong oxidizers are substances (like chromic acid) that can cause other substances (like seals and gaskets) to lose electrons. So, an oxidizer is a chemical species that undergoes a reaction that removes one or more electrons from another atom.

This causes a change in mass. Metals will turn into their respective heavier oxides, and the carbon in graphite will oxidize into carbon dioxide—which, although molecularly heavier, is a gas at room temperature.

This happens in pumps, valves, pipelines or any other equipment that have seals and gaskets carrying a strong oxidizer. It will cause pitting or rust and, depending on your choice of seal material, may require shorter service intervals. Ultimately, you may have to look for a more suitable material that can handle strong oxidizers.

More importantly, an oxidizing agent can cause or contribute to the combustion of another material.

The U.S. Department of Transportation defines oxidizing agents specifically. DOT’s Division 5.1(a)1 means that a material may enhance combustion or quickly raise pressure causing a rapid chemical reaction. A fire may start or, even worse, create or facilitate an explosion.

There have been instances of fires or explosions in mining, chemical process and even fertilizer factories where strong oxidizers were used.

Deadly Force

A West Texas fertilizer company storage and distribution facility caught fire on April 17, 2013. As firefighters attempted to extinguish the blaze, the plant exploded with the force of 10 tons of TNT, killing 15 people and injuring 200. It destroyed 60 nearby homes and left a 93-foot-wide crater where the plant once stood.

All said, it is important to choose the right sealing material for strong oxidizers. There are multiple products on the market for the chemical processing, oil and gas, mining and aerospace industries.

Gasket Selection - PTFE
PTFE (Polytetrafluoroethylene) Molecule

A fluoropolymer, such as polytetrafluoroethylene (PTFE), can handle most strong oxidizers, as long as the temperature is below 260 C (500 F). This is also true with a modified PTFE because they are chemically inert and stable.

Strong oxidizers will weaken most other material to various degrees. Much of a material’s capability to withstand a strong oxidizer depends on the used concentration, the service temperature and the service pressure. Therefore, consult with the sealing material manufacturer to ensure compatibility.

How Graphite Handles Strong Oxidizing Environments

Graphite starts as natural mineral flake and is mined in various parts of the world. The flakes form a layered structure of completely crystalline graphite, which is essentially elemental carbon. In this form, it is used for products like powdered lubricant and lead in pencils. It has excellent lubricity in this form.

Expanded graphite is produced with the use of strong oxidizing agents such as sulfuric and nitric acids. The acids weaken the bonds between the graphite layers, the flakes are then rinsed, dried and exposed to high heat.

The heat causes the layers to separate and expand dramatically to form expanded worm-like macro structures. The structures can then be recompressed into flexible graphite forms.

Graph Lock Flexible Graphite Garlock
Garlock’s Flexible Graphite, GRAPH LOCK

Flexible graphite is a soft material that is resistant to many strong chemicals and high heat. It has a low coefficient of friction and is proven to be advantageous over braided carbon or graphite fiber packings mainly as it is a better conductor of heat—a plus on moving shafts.

Flexible graphite is also naturally lubricious, conformable and resilient. It has good corrosion resistance and is compressible, allowing it to conform to most mating surfaces or valve cavities.

The chemical compatibility of flexible graphite can be enhanced with a blocking agent like PTFE. However, flexible graphite’s temperature limit will be restricted by PTFE’s limit of 260 C (500 F). If high temperature is an issue, this configuration will not work.

Flexible graphite, in combination with PTFE, is an extremely effective material in sealing fugitive emissions or volatile organic compounds (VOCs). VOCs have been targeted by several government agencies as a source of air pollution. Although, flexible graphite alone has a long way to go in stopping all fugitive emissions, it is a trusted sealing material for valves, flanges and stems in the chemical process, power generation, and oil and gas industries.

Flexible Graphite Pitfalls

Flexible graphite may be susceptible to chemical attack in the presence of strong oxidizing fluids, including air at extremely high temperatures. These include liquids such as 20 percent concentration of nitric acid or a 98 percent concentration sulfuric acid, the same chemicals that are used to break down mined graphite into expanded graphite flake.

Some flexible graphite compositions include oxidation inhibitors or are physically structured to extend temperature capability when exposed to these extra strong oxidizers.

The class of organic chemicals that should not be used are those that are highly oxidizing like nitrates, persulfates, perbenzoates and peroxides. Unacceptable compatibility for inorganic chemicals includes molten sodium, potassium hydroxide and chlorine dioxide.

However, many of the chemicals depend on the concentration, and some engineering groups can create an inhibitor that is right for a specific oxidizer. For instance, a 704 stainless steel cladding provides the user with protection against strong oxidizers while still providing the benefits of flexible graphite.

When in doubt, do a test loop using a pump to pressurize the strong oxidizer exposing it to flexible graphite. The pressure, temperature and concentration of the oxidizer must be exact as used in service, as to provide some idea of how the material will react to a given chemical.

It is easier to list the chemicals that are not compatible with flexible graphite (about 50) than those that are (more than 600 tested). A list of incompatible materials are listed below:

Strong Oxidizers for Flexible Graphite

  • Aqua Regia
  • Bromine (dry)
  • Calcium Chlorate
  • Calcium Hypochlorite
  • Calcium Nitrate
  • Chlorazotic Acid
  • Chlorine Dioxide
  • Chlorine Trifluoride
  • Chloric Acid
  • Chloroazotic Acid
  • Chloronitrous Acid
  • Chromates
  • Chromic Acid
  • Chromic Anhydride
  • Chromium
  • Chromium Trioxide
  • Dichloropropionic Acid
  • Dichromates
  • Hydrogen Dioxide
  • Hydrogen Peroxide
  • Lime Nitrate
  • Lime Saltpeter
  • Molten Alkaline
  • Nitrates
  • Nitric Acid
  • Nitric Oxide
  • Nitrocalcite
  • Nitrohydrochloric Acid
  • Nitromuriatic Acid
  • Norge Niter
  • Norwegian Saltpeter
  • Oleum (Fuming
  • Sulfuric Acid)
  • Oxygen (above +600 F)
  • Ozone
  • Perchloric Acid
  • Permanganate Solutions
  • Persulfates
  • Perbenzoates
  • Perborates
  • Peroxide Potassium
  • Bichromate
  • Potassium Chlorate
  • Potassium Chromate
  • Potassium Dichromate
  • Potassium Nitrate
  • Sodium Chlorite*(over 4%)
  • Sodium Hypochlorite
  • Sodium Peroxide
  • Sulfuric Acid
  • Sulfur Trioxide

For more information about which materials would be the best fit for your specific chemical application, contact Gallagher Fluid Seals today.

This original article was featured on the Pumps & Systems website and was written by Mark Freeman.

Freudenberg Announces New Seals and Materials for the Aerospace Industry

Freudenberg Sealing Technologies introduced several new material and sealing innovations at the 2019 International Paris Air Show.

These new products are designed to help aerospace customers address ever increasing safety and performance requirements in the industry.

During the June 17-23 event in Paris, Freudenberg showcased a new high temperature, fireproof material; an Omegat OMS-CS cap seal; and new ethylene propylene diene monomer (EPDM) and a fluoroelastomer (FKM) developmental material.

“Our aerospace customers strive continuously to be faster, safer and more efficient, which in turn requires us to innovate to help them reach those goals – a challenge we enthusiastically embrace,” said Vinay Nilkanth, vice president, Global Mobility Sector, Freudenberg Sealing Technologies. “The launch of several new products aimed at improved performance underscores Freudenberg’s commitment to being a global leader and development partner to the industry.”

Freudenberg’s new proprietary fireproof sealing fabric is made to withstand the extremes. Tested on standard aerospace bulb seals and passing AC20-135 fireproof requirements, the fabric acts as a barrier, providing up to 15 minutes for necessary corrective action. The fabric performs as well as other industry standard solutions but is much more cost effective.

Omegat Cap Seal

For use in dynamic, reciprocating applications where low friction is required, the new Omegat OMS-CS cap seal is a two-piece rod seal set consisting of an engineered polytetrafluoroethylene (PTFE) ring and an O-ring energizer. The seal offers low breakaway and running friction, and is chemically compatible with aerospace fluids and greases. It also provides excellent wear and extrusion characteristics, and has angled blow-by notches and lubrication grooves.

Freudenberg’s new EPDM LM426288 material is for use in low pressure static sealing to -77°C (-106°F) and has excellent resistance to, and swell behavior in, AS1241 phosphate ester hydraulic fluids. The material offers high temperature compression set resistance and short term resistance to 150 °C (302°F) for high temperature hydraulic systems such as hydraulic braking.

The FKM LM426776 material for use in low pressure static sealing to -67°C (-88°F) shows excellent resistance to several aerospace media, including jet turbine and gearbox lubricants, high and low aromatic content jet fuels, and fire resistant hydrocarbon hydraulic fluids. The material offers short-term high temperature resistance to 270°C (518°F) and long-term compression set resistance at 200°C (392°F).


The original article can be found on Freudenberg’s website.

Gallagher Fluid Seals is a preferred distributor of Freudenberg Sealing Technologies. To learn more about Freudenberg products, speak to a Gallagher representative today by calling 1-800-822-4063

The Rise of Metal Detectable O-Rings

Food Safety Modernization Act (FSMA)

Every year, nearly 1 in 6 people in the U.S. get sick (~48 million people), 100,000+ are hospitalized, and 3,000 die from foodborne illnesses or diseases, according to data from the CDC. Though this is largely a preventable problem, it still poses a significant public health burden.

The FDA Food Safety Modernization Act (FSMA), enacted by Congress in 2011, is “transforming the nation’s food safety system by shifting the focus from responding to foodborne illness to preventing it.”

Although one might think the relevancy of the FSMA isPastries on a Conveyor Belt more geared towards the food or beverage product itself, this act is actually vital to the processing operations in food, beverage, and pharmaceutical industry.

Over time, exposure to continuous vibration, volatile temperatures, and corrosive chemicals can cause O-rings in processing operations to become worn and eventually fail. When this occurs, particles of rubber from seals and gaskets can shear-off and migrate through sanitary systems, piping mechanisms, or by other means, eventually entering the product stream.

In some cases when a problem is discovered, equipment must be shut down and visual inspections conducted to find the source of contamination. This leads to downtime, lost production, and lost revenue. If the contaminant ends up in the supply chain, even more risk is assumed due to recalls or litigation.

Enter the metal detectable O-ring.

Continue reading The Rise of Metal Detectable O-Rings

Elastomer Seals for Instrumentation: Seal/Groove Design

Seal Design: Instrumentation IndustryGallagher recently released our High Performance Elastomer Seals for the Instrumentation Industry White Paper.  This was written by Russ Schnell, an Elastomer Consultant contracted by Gallagher Fluid Seals, and a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont.  This white paper is now available for download on our Resources page.

Below is the third and final section of the white paper, which will discuss the importance of proper seal and groove design.


Proper Seal & Groove Design

Elastomer Seal: Perfluoroelastomer PartsProper seal design is a necessity for elastomer seals to perform reliably over the long term. Many of the instrument applications mentioned above use o-ring seals. The suggested compression for an elastomer o-ring seal to perform properly is typically a minimum of 16%, and a maximum of 30%. However, this range must also take into account the thermal expansion of an elastomer at elevated temperatures as well as any swell due to chemical exposure. Many of the elastomer seals used in instruments are small o-rings, which can create design issues. This is especially true for perfluoroelastomer parts which have a relatively high coefficient of thermal expansion (CTE). Fluoroelastomers have a lower CTE, making seal design easier at elevated temperatures.

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Elastomer Seals for Instrumentation: Laboratory Equipment

Elastomer Seals for Instrumentation: Laboratory EquipmentGallagher recently released our High Performance Elastomer Seals for the Instrumentation Industry White Paper.  This was written by Russ Schnell, an Elastomer Consultant contracted by Gallagher Fluid Seals, and a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont.  This white paper is now available for download on our Resources page.

Below is the second section of the white paper, diving into applications where the measurement is made in analytical laboratories which employ numerous solvents in a wide range of analyses and test equipment.


Laboratory Equipment

The final set of instrumentation is laboratory test equipment. As opposed to the laboratories in chemical plants, which often perform the same routine analyses on plant process streams, general analytical labs employ numerous solvents in a wide range of analyses and test equipment. As such, the ability of seals to resist a breadth of chemicals without degradation or leaching contaminants into a sample is of great importance. Although instrument seals are easily replaced in a laboratory environment, this operation still takes a technician time. It is always easier if the system can be flushed with a cleaning solvent and then be ready to run the next sample versus having to change out an elastomer seal due to incompatibility with a solvent.

Continue reading Elastomer Seals for Instrumentation: Laboratory Equipment

Elastomer Seals for Instrumentation: In-Line Process

High Performance Elastomer Seal for InstrumentationGallagher recently released our High Performance Elastomer Seals for the Instrumentation Industry White Paper.  This was written by Russ Schnell, an Elastomer Consultant contracted by Gallagher Fluid Seals, and a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont.  This white paper is now available for download on our Resources page.

Below is the first section of the white paper, diving into applications where the measurement is made at the process and the results then transmitted to a control system.  This section will review the four types of in-line measurement devices, all involving slightly different elastomer sealing applications.

In-Line Process Applications

Flowmeters

Flowmeter - Elastomer Seal for InstrumentationFlowmeters are used to measure the flow of liquid. In this section we will only consider the measurement of liquid flow in a closed piping system. Several examples of flow measurement devices include: flowmeters, Venturi tubes and orifice plates.

Note that these devices are “in-line” and require isolating the process line to remove and repair, or replace the measurement device. Shutting down a process to remove a device is time consuming, involves loss of production, and may require specific procedures to protect the operators and environment when a line is opened. All of these devices require seals to prevent leakage of the process to the environment and the elastomer seals should last the life of the flowmeter. For aggressive chemicals or high temperature applications, FKM or FFKM seals are an excellent choice. These products offer a long service life and resist deterioration in harsh environments.

Continue reading Elastomer Seals for Instrumentation: In-Line Process

[VIDEO] How to Choose a Fluoroelastomer

Fluoroelastomer Basics - Consideration When Choosing a FluoroelastomerGallagher Fluid Seals recently posted our new Fluoroelastomer Basics webinar on gallagherseals.com.  This is the third and final section of our webinar, focusing on Considerations When Choosing a Fluoroelastomer. The full video is now available on our Resources page.

This video discusses considerations when choosing a fluoroelastomer, including temperature performance range, performance in harsh chemical exposure, and the need to take caution when using fluoroelastomer blends.

[VIDEO] Fluoroelastomer Materials

Gallagher Fluid Seals recently posted our new Fluoroelastomer Basics webinar on gallagherseals.com.  This is the second section of our webinar, focusing on Fluoroelastomer Materials. The full video is now available on our Resources page.

This section of the video discusses different fluoroelastomer materials, along with their mechanical and physical properties, and in which applications they’re normally found.

[VIDEO] Basic Understanding of Fluoroelastomers

Fluoroelastomer Basics - DOWNLOAD VIDEOGallagher Fluid Seals recently posted our new Fluoroelastomer Basics webinar on gallagherseals.com.  This is the first section of our webinar, focusing on the Basic Understanding of Fluoroelastomers. The full video is now available on our Resources page.

In this snippet, learn the differences between elastomers and fluoroelastomers, and how the amount of fluorine in an elastomer affects it’s chemical resistance and properties.

 

NEW! Fluoroelastomer Basics Webinar

Fluoroelastomer Basics - DOWNLOAD VIDEOGallagher Fluid Seals recently made our Fluoroelastomer Basics webinar available on the website.

This webinar will discuss:

  • Differences between an elastomer and a fluoroelastomer
  • The important role fluorine plays
  • Types of fluoroelastomers and their features and benefits
  • Material performance comparisons
  • Chemical resistance of fluoroelastomers
  • Temperature ratings of fluoroelastomers
  • Considerations when choosing the right fluoroelastomer for your application

What is an Elastomer?

Fluoroelastomer - Elastomer CrosslinksAn elastomer is made up of long chain polymers which are connected by crosslinks.  Crosslinks are analogous to springs and provide an “elastic” (recovery) nature to the material.  The crosslinks are relatively stable, but can break down under extreme temperatures and pressures.

Continue reading NEW! Fluoroelastomer Basics Webinar