Rubber seals such as O rings are designed and manufactured to last. We can select materials for optimal performance for the environment they’re going to be in, such as heat resistance or chemical compatibility. However, as all polymers are unique in their make up and structure, using the right material for the application is crucial.
Understanding what can cause chemical degradation, and how different materials react to certain chemicals, can avoid costly failures later down the line. Here’s what you need to know about chemicals and their effects on your rubber components and seals.
What causes chemical degradation?
Some chemicals will react with certain elastomers, if those materials are not resistant enough to the chemicals they are exposed to. This can cause a range of problems, from an increase in cross link density, leading to a hard, brittle seal, to chain scission, resulting in reduced strength.
In some situations, the chemical or elements of it can actually ingress into the seal itself. This is often caused by the chemical being too similar to the material used in the elastomer, effectively allowing the media to be soaked up by the seal.
Having the wrong type of seal for the job increases the risk of a chemical attack, and it’s not just a failed seal you may have to deal with. Seal failure and associated chemical ingress into other parts of the assembly, may lead to direct loss or damage to expensive machinery, not to mention process downtime within the operation.
How to know if your O ring has suffered a chemical attack
The first way to identify chemical degradation in O rings is to take a visual appraisal of the component. There are several tell tale symptoms of a chemical attack, including:
- Cracking and / or blistering
- A change in hardness
- Swelling, either localised or across the whole seal
Some of these symptoms can be caused by other issues, so it’s important to eliminate these or confirm chemical presence as soon as possible.
How to prevent a chemical attack
Choosing the right elastomer for the job is key to preventing any further chemical attack. Switch to an elastomer with proven resistance against the chemicals you know to be present in the environment.
Chemical attack is accelerated in elevated temperatures and when the seal is stressed, for example when its been stretched or squeezed excessively. This means that a material which, at first, seemed compatible suddenly becomes incompatible due to the forces it is placed under.
The best way to prevent chemical attack is to consult with an expert when making your material choice. To be sure that you’re getting the right elastomer for the job, chemical compatibility testing can be undertaken to help with your selection process.
Which elastomers offer the best chemical resistance?
The resistance of elastomers depends on the type of chemicals they will be coming into contact with. For example, if you’re using acetaldehyde in your operations, silicone and EPDM offer excellent resistance, whereas fluorocarbon, FFKM and polyurethane will fail. Nitrile and fluorocarbon would be a good choice for calcium bisulfide, whereas EPDM and natural rubber would not.
For help selecting the right type of material for your application, talk to our team.
Used in some of the harshest environments, where temperature extremes and chemical interactions are common, Viton™ rubber is one of the most hard wearing fluoroelastomers in the world. It’s high performance and excellent durability make it a top choice for many specialist applications.
If you’re looking for an impressively versatile material for difficult applications, you might be wondering ‘what is Viton™ and how can it help my business?’. We’re pleased to enlighten you with our complete guide.
What is Viton™?
Viton™ is a fluoropolymer elastomer and synthetic rubber compound, trademarked by DuPont under this brand name. It’s a fluorinated hydrocarbon rubber product with amazing capabilities, designed to withstand even the most challenging of environments.
In much the same way as Hoover has become synonymous with vacuum cleaners, so Viton™ has become the standard name for this type of material. However, there are differences within the Viton™ family which will affect their suitability for your application.
The standard grade for Viton™ is A grade, which has 66 percent fluorine content and is most commonly used in o rings and seals. Viton™ B offers better fluid resistance and Viton™ F is particularly good for resistance to fuel permeation. High performance grades are also available but do discuss with us if you’re not sure what you need.
Why use Viton™?
A Viton™ o ring will tend to be significantly more expensive than the equivalent nitrile component. This is because it simply does the job where other products cannot. In comparison to nitrile, Viton™ has a larger operating temperature range, better resistance to degradation from exposure to weather and ozone and is more chemically resistant too.
Choosing a Viton™ o ring for the toughest jobs means it will last longer. This means that you can enjoy extended service intervals, reducing maintenance costs and providing a more reliable seal. There is far less likelihood of unscheduled down time due to o ring failure, so your investment in a Viton™ product will pay back through better operational efficiency.
What is Viton™ good for?
Viton™ seals are an ideal choice in any environment where there are challenging factors to contend with. For example:
- High temperatures: A Viton™ o ring will withstand temperatures from -20°C up to 210°C
- Chemicals: Viton™ can withstand a range of chemicals, including oils, acids, silicone fluids and gasses as well as halogenated and aromatic hydrocarbons
- Environmental challenges: Viton™ can maintain a seal even in the presence of oxidation, UV exposure, weather, ozone, fungus and mould
So, what is Viton™ good for? Well, Viton™ is frequently used in appliance processing, automotive and chemical industries. We also supply Viton™ products to aerospace companies, oil and gas exploration industries and petroleum refining and transportation businesses.
Is Fluoroelastomer the same as Viton™?
When you’re thinking about what is Viton™ exactly, you can classify it as one of the many fluoroelastomers out there. It’s a trade name for a fluoroelastomers produced by DuPont, so yes, it is the same thing. Other brand names for fluoroelastomers include FKM and FPM.
What is the difference between Viton™ and EPDM?
The main difference between Viton™ and EPDM is the chemical resistance they exhibit. EPDM is a good product for use in steam environments and has a relatively good chemical resistance, but nowhere near as good as Viton™. EPDM should never be used with solvents or petroleum agents.
What is Viton™ seal?
A Viton™ seal is simply a seal manufactured from Viton™. These seals or gaskets are commonly used to seal leaks, valves, pumps and similar. Viton™ o rings are the most common type of seal, which we provide here at NES in a variety of sizes and profiles.
For more advice on Viton™ or any of our other products, get in touch with the experts at NES today.
Anyone who has grown up in the modern age has probably heard of Teflon™. Used in a variety of situations, from cooking to clothing, manufacturing to manicures, the amazing substance that we know as Teflon™ has proven itself to be an incredible addition to our modern lifestyles.
But have you ever considered what are the uses of Teflon™, and why is it such an incredible discovery? Let’s investigate.
What is Teflon?
Discovered by Roy. J. Plunkett in 1938, Teflon™ was identified almost by accident. While researching new refrigerants, Plunkett discovered an unusual by product which was exceedingly slippery and immune to many of the usual degrading factors.
Upon isolating this substance, Plunkett was attributed as the discoverer of Teflon™, a product used widely in numerous modern applications. What he had actually discovered was polytetrafluoroethylene, or PTFE, which is marketed by DuPont under the trade name Teflon™.
What are the uses of Teflon™?
So, you probably know of Teflon™ as a non-stick covering. It’s certainly put to good use in cookware, providing a non-stick surface for pans and pots worldwide. However, there are undoubtedly plenty of other places where you’ve come into contact with Teflon™, perhaps without even knowing it. For example:
- Nail polish: Teflon™ provides a smooth, crack free surface in many nail polishes
- Hair styling: Straighteners and curling irons are often coated in Teflon™
- Carpet protection: Is your carpet ‘stain resistant’? It’s probably infused with Teflon™
- Waterproof jackets: Do you own a Gore-Tex jacket? If so, you’re wearing Teflon™
- Paint and metal finishing: That nice shiny finish on your car paint? It’s probably Teflon™
- Solar panels: If your solar panels are classed as ‘self-cleaning’, that’s probably because they are coated in Teflon™ to let the rain wash the dirt away
Of course, there are many more examples of Teflon™ in practice, from door locking parts to drills, machinery and much more. Anywhere where you need to ensure a non-abrasive connection between two parts can benefit highly from the application of Teflon™.
Uses of Teflon™ coating
The most versatile element of Teflon™ is the fact it can be used to coat pretty much anything, without damaging the integrity or shape of the item it is being used to coat. When we’re thinking about what the uses of Teflon™ are, it’s important to realise that Teflon™ can be used as a coating on any other material you can imagine.
For example, Teflon™ can be used to coat dental fillings, to prevent them from sticking to adjacent teeth. It can also be used as a coating for pipes, to stop the metal from reacting to corrosive chemicals passing through them. It also makes an amazing lubricant where having wet oil present is just not practical.
It would be impossible to list all the places where you’ll come across this product, so when you’re considering what are the uses of Teflon™, it’s almost easier to think of where it is not used!
From food processing to automotive manufacturing, from your kitchen to your clothing, we rely on Teflon™ in so many ways it’s almost the unsung hero of our modern age.
In mechanical engineering, o-rings are a staple of a safe, functional assembly. In environments where high pressures or temperature extremes are common, they are the simplest and most effective way to create a reliable seal. Understanding how o rings are measured is a key skill for anyone who is responsible for the purchase or reordering of replacement gaskets for their facility.
You may have an o ring measuring tool or o-ring measuring gauge about your business, which is great. However, you still need to acquire the knowledge of how are o rings measured in order to accurately use these tools. Here’s what you need to know about getting the measurements of your o-ring right first time, every time.
Why do o-rings require accurate sizing?
Our o-rings are often used in sensitive environments, where pressures are extremely high or low, where temperatures are very high or low, or where chemicals or other dangerous liquids are in use. Failing to measure an o-ring correctly could result in a poor seal being made, risking failure and leaks within the system.
If you’re assembling an apparatus or machine for the first time, having the correct size and material of o-ring is crucial. Over time, your o-ring may start to wear or degrade, requiring replacement which, again, means knowing how are o rings measured in order to obtain the correct part. Having a poor fitting o-ring will decrease the lifespan of your seal and risks it failing unexpectedly.
How are o rings measured?
Here in the UK, o-rings are manufactured to specific sizes as specified by a British Standard (BS). Many rings will have a related BS number, which relates to the inside diameter, outside diameter and the thickness of the ring. These measurements can be taken in either inches or millimetres, although inches are the more common method used by o ring measuring tool products.
To measure your o-ring, follow these simple steps:
- Using a ruler, measure the distance between the outer edges, which will give you the outside diameter (OD)
- Using the ruler again, measure the distance across the inside of the ring, which will give you the inside diameter (ID)
- If you have a Vernier calliper, you can use this to measure the thickness of your o-ring. Place the gasket between the jaws of the calliper to take this measurement, but be careful not to compress the material at all otherwise you’ll get an inaccurate result
If the o-ring has been cut or damaged, or is not a solid ring, you can calculate the inside diameter using the thickness of the cross section (CS) measurement and the length (L) of the ring as follows:
- ID = circumference – CS
- Circumference = L / 3.142
- OD = ID + 2CS
Using these formulae, you should be able to find all the measurements you require in order to procure the correct replacement o-ring for your needs.
Using an o ring measuring tool
There are a number of tools out there to help you measure an o ring correctly. The two main types are the o-ring measuring gauge and the cone type o ring measuring tool. Here’s how to use them:
- The o-ring measuring gauge
This is a sliding tool with silhouettes of o-rings down its length. For smaller o-ring sizes, you simply match them up to one of the silhouettes on the body of the gauge. For o-rings of larger sizes, you can simply place them around the spindles at the top of the gauge and then extend the slider until the ring is taut. These measuring gauges can be found in both BS and AS (American Standard) configurations, and with both metric and imperial scales.
- The o-ring cone
These measuring cones have two measuring functions which aim to determine the thickness (CS) and the internal diameter. Around the bottom of the cone, slots will help you determine the CS of your o-ring by checking which one it fits in best. Once you’ve done that, you place the o-ring on the cone and see where it settles to determine the size.
Both of these products are relatively expensive for what they do and are probably an unnecessary investment unless you’re in the habit of measuring o-rings regularly. A Vernier calliper can be bought for a fraction of the cost and is useful in other elements of mechanical engineering too, for example when measuring the thickness of sheet metal, or the finer details of products.
If you are still not confident as to how an o-ring is measured, we’re here to help. You are welcome to send in your o-ring for measurement by our experts, or to contact us for help and advice on any of our products and their specifications. Getting the size of your o-ring right is crucially important, so don’t leave it to chance.
NES suggest that only o rings that have not being fitted into application are measured this way due to compressive force, temperature and groove dimensions. For further help on measuring o rings, please contact our technical team today.
You’ve probably come across numerous o-rings in your lifetime, whether you knew it or not. From cars to cameras, these little doughnut shaped parts are instantly forgettable but endlessly useful. They are probably one of the biggest revolutions in mechanical engineering to date, allowing us to develop new machinery, better products and safer working environments. So, what are o rings used for, and why are they so popular? Let’s find out.
Why are o rings used?
O rings have some amazing properties which makes them a crucial component of many precision engineered devices. Their natural propensity to return to their original shape when the cross section has pressure exerted on it means they are one of the most economical and reliable methods of making a strong seal possible.
The other reason o rings are so commonly used is down to the wide range of materials they can be made from. The majority of o rings are made from elastomers, which are a type of elastic polymer, but there are a huge variety of these elastomers available, each with different strengths, weaknesses and tolerances. The application that the o ring is destined for will determine which type of material is most suitable, for example:
- High and low temperatures: Silicone and fluorosilicone can cope with temperatures as low as -100°C. Cryogenic operations will require a seal that can cope with low temperatures such as the NES Astra Seal®. For very high temperatures, FFKM works at up to 316°C
- Chemical compatibility: Viton™, also known as FKM/FPM, o rings are resistant to many chemicals and work at high temperatures too
- Hot water and steam: Ethylene propylene o rings (EPDM) are resistant to steam and hot water, as well as to alcohol, strong alkalis and fluids found in automotive applications
- Grease and hydraulic fluids: Buna-N o rings, also known as nitrile o rings, are best to use where there is a lot of grease or hydraulic fluid around
As you can see, for pretty much any application you can think of, there will be an o ring which can handle that environment. This means they are useful in a huge range of applications, from appliances found around the home to gigantic machines used in manufacturing and even in the space shuttle!
What are o rings used for?
O rings are used to block a path which may otherwise allow a liquid or a gas to escape. The o ring is placed into a groove to secure them in place, and then compressed between two surfaces. By squeezing the o ring, there is no more clearance for it to move and it blocks the pathway of the liquid or gas you are trying to seal in place.
When the system comes under pressure, the o ring is squeezed against the opposite wall of the groove, maintaining a perfect seal even under very high or low pressures. The materials that o rings are made from (elastomers) are naturally springy and have a desire to return to their original shape, so when the pressure ceases, they spring back to their original position, maintaining a seal and readiness for the next cycle.
In a nutshell and to answer the question of what are o rings used for, they are used to seal in a liquid or gas and are the most effective way of ensuring a robust, reliable seal.
Where might you find o rings?
Because o rings are so good at keeping liquids and gasses from moving freely around, you’ll often find them in mechanical parts and processes, particularly where extremes of temperature or pressure are at work. Some applications that are almost certainly springing to mind already could include engines, boilers, refrigerators and compressors. But o rings are also found in some rather surprising places; for example:
- Scuba gear: O rings in scuba gear are a life saving component of the breathing apparatus. Before every dive, the diver will check the o ring in the neck of their air tank to ensure it’s going to provide a good seal and deliver air to their regulators, not sea water.
- Dental implants: In dental implants, liquid needs to be kept out of the implant to avoid the patient suffering with pain or infection. To do this, they use a biomedical silicone o ring, which forms a perfect seal and keeps the new tooth safe.
- Paintballing: Paintball guns use compressed air to shoot globs of paint at unsuspecting enemies. To keep the air sealed in and ensure a powerful shot, o rings are used throughout the gun.
- Your beer: If you enjoy a pint at the pub on the way home from work (don’t we all), o rings are contributing to your enjoyment and relaxation. Without an o ring, it would not be possible to transport the beer from the casket to the tap, or to carbonate it for that lovely bubbly refreshment.
Next time you’re down the pub, you can delight your friends with stories of what are o rings used for, and all the surprising places they might come across one.
For advice on o ring uses and materials, talk to our team of experts about our range of products including encapsulated seals, hot vulcanised o rings and moulded o rings.
Viton™ vs nitrile o rings
As two of the most commonly used elastomers, both Viton™ and nitrile o rings have some fantastic properties. Both offer excellent compression set and have a wide range of uses in industrial and domestic applications. However, not everything is equal between these two popular materials, and it’s important to know which is better for particular applications. Here, we’ll look at Viton™ vs nitrile o rings to see where each should be used, and why.
Also called NBR or Buna-N, nitrile o rings are probably the most economical and widely used elastomer out there. This material has a desirable set of properties including low compression set, high resistance to abrasion and good tensile strength.
- Temperature range: Effective from -40°C to 120°C
- Suitability: General purpose, particularly in areas where the seal will be exposed to hydrocarbons, oils, petrol, water and hydraulic fluids
- Benefits: Excellent abrasion and tear resistance, cost effective
- Limitations: Nitrile is not good at resisting degradation by ozone or weather
You’ll find nitrile o rings used in many applications, including where oil resistance is needed or where low temperature functionality is required. These include automotive, aircraft fuel systems, marine applications and more.
Viton™ o rings
The name Viton is a trademark, a bit like Hoover or Sellotape, and refers to fluorocarbon o rings, or FKM/FPM for short. This material has an excellent tolerance for high temperatures, resistance to oils, fuels and hydraulic fluids as well as aromatics and solvents.
Various types of FKM/FPM/Viton™ o rings are available, with varying amounts of fluorine additions which increase performance in specific situations.
- Temperature range: From -40°C up to 250°C
- Suitability: Good for use in high temperature situations or where chemicals are being used. As well as resisting oils, petrol and hydrocarbons, Viton™ is resistant to mineral acids, halogenated hydrocarbons and more.
- Benefits: Resistant to the majority of chemicals, as well as to degradation by UV, weather, ozone and mould.
- Limitations: Less tolerant of low temperatures
You’ll find FKM/FPM o rings in a huge variety of applications from aircraft engines to vehicle components, particularly where resistance to corrosive liquids and fuels is required. This material has low compression set characteristics, making it ideal for use in high temperature environments, as well as resistance to all sorts of chemicals.
Viton™ vs nitrile o rings – which is the right choice?
Viewing these two o ring materials at a glance, it’s easy to see some occasions where the decision of Viton™ vs nitrile o rings will be clear to see. For example, if you know your assembly works at more than 100°C, nitrile will not be suitable. If your assembly is likely to be exposed to the weather, to UV or to ozone, nitrile will likely degrade and risk failure.
Viton™ /FKM/FPM is superior to nitrile in almost all situations, excluding operation at sub zero temperatures.
If you’re not sure which you need in the case of Viton™ vs nitrile o rings, we’re here to help. We’ve worked alongside customers from all sorts of diverse industries to help match them up with the right o ring for their needs and can help you too. We want to make sure you get all the functionality you need, without spending more than is necessary. Talk to our experienced team today for advice and support.