O-rings are a crucial component and are vital to the overall performance of your application. Despite this, they are something that many take for granted without thinking about what would happen if they fail. Essentially, they become an afterthought.

However, O-rings are an integral part of your machine and application because, without them, things would become problematic quickly. The smallest fault, tear or nick in your O-ring could lead to leaks, damage to equipment or a complete failure. What’s more, they could also cause contamination issues in food or pharmaceutical manufacturing and that could pose a health and safety risk to the public. So, even if you might think that there is a problem with your o-ring or believe that it needs changing then it makes sense to do it because the implications of not doing so could be catastrophic.

The cost of a small replacement against the cost of the damage caused as well as downtime and man-hours that are lost cannot be compared. So, it’s simply not worth trying to use the same O-rings or continue knowing that there might be a potential problem or fault.

Regardless of the type of O-ring you are using, they all have a certain shelf-life. When you consider the likes of Polyurethane and Styrene Butadiene which have a short shelf-life and the likes of Viton, which has an unlimited shelf-life, it is clear to see that they are different. However, regardless of how different they might be, when they are put to use they both become just as likely to develop problems through becoming worn, torn or damaged.

Essentially, the main thing to consider is that you shouldn’t take them for granted. They serve their purpose but why avoid replacing them at a minimal cost when you face the risk of significant problems otherwise. So, it’s worth remembering that if your O-ring fails, your entire system could be brought to a standstill and that will always prove to be costly.

To find out more about NES O-rings, contact our Sales team at sales@nes-ips.com

With many types of fluoropolymers available, it can prove challenging to work out what is the best option. There are subtle variances in the structure of PTFE, FEP and PFA and they all offer something different but what are the main differences between these three materials?

PTFE

Polytetrafluoroethylene is also known as PTFE and was one of the first synthetic fluoropolymers to be made. It is ideal for creating coatings that have non-stick properties which makes it ideal in applications such as cooking or food manufacturing. As it is hydrophobic it has a high level of electronegativity which means that liquids will not affect it.

FEP

FEP is also known as Fluorinated Ethylene Propylene and it has different properties when compared to that of PTFE. However, it does have non-stick properties which again makes it suitable for use in applications where residues or oils are likely. FEP does have a softer makeup when compared to that of PTFE and that means that it can melt at a lower temperature which means that it is not suitable in applications that are exposed to high temperatures. Along with this, it is also transparent while it is resistant to sunlight and UV which makes it suitable for use in applications that are exposed to the elements.

PFA

Known as Perfluoroalkoxy, PFA has alkoxy substitutes that mean that the polymer can be melt-processed. However, it also differs from a molecular level as it has a smaller chain length than other fluoropolymers. It is extremely durable which makes it suitable for use in demanding application. It is also the preferred option when it comes to choosing a material that requires high chemical resistance as well as high purity and low stiffness while it is also extremely durable when it comes to resisting weathering. It has a lower melting temperature when compared to PTFE while it has great insulation properties and is UV resistant which also adds to its durability.

When it comes to compound deterioration, heat is one of the most destructive forces. Therefore, understanding “what is the best high temperature O-ring” is a crucial factor. If you are working with temperatures over 150°C then there are a number of materials you can consider such as FKM, FVMQ, and FFKM to name but a few.

O-Rings for Automotive Oils, Fuels And Gases

Viton is one of the best all-round materials available, particularly when used with oils, greases and fuels at high temperatures. An alternative to this is the Polyacrylate or ACM as it is known has resistance against mineral oils as well as engine, gearbox and transmission fluids. ACM O-rings have the ability to withstand temperatures of 150°C.

Hydrogenated Nitrile or HNBR has a top temperature of 140°C and again, this is compatible with automotive fuels, oils and gases although it is not suitable for use with chlorinated hydrocarbons or strong acids.

TFE/P or Aflas has the ability to handle the majority of chemical mediums that are used in automotive sealing. It has the ability to withstand a temperature of up to 204°C.

Silicone or VMP O-rings offer temperature resistance of up to 230°C and some variants of this material can handle up to 300°C. These are commonly used where there is high exposure to UV, ozone and weathering although they are not suitable for use in hot water, chemical or dynamic applications.

PTFE O-Rings have the ability to handle temperatures of up to 250°C and offer chemical resistance to acids, alkalis and solvents. In actual fact, it also has the ability to withstand temperatures as low as -200°C.

FEP comes from the same range of materials as PTFE. While it has many of the same characteristics, it can only work to a temperature of 204°C. These seals are both chemical and heat resistant, much like PTFE although they do offer an increased level of flexibility.

FFKM is also known under brand names such as Perlast, Perflour and Simriz. This is available for use in a range of applications and so, they are available in a range of material grades and this enables them to operate at temperatures that range from 230°C to 320°C.

In order to identify the biocompatibility of materials, USP Class VI testing is required. As one of the most widely used methods, VI forms part of six different classes with this being the most thorough. This form of testing is designed to certify that no harmful reactions or long-term issues are caused to the body by chemicals that are released or leached from plastic materials. The United States Pharmacopeia and National Formulary (USP-NF) determine the USP Class Testing standards, and so, this organisation is responsible for ensuring that medical devices and foods are safe. The testing is carried out frequently, especially those plastic materials that are regularly in contact with injectable drugs as well as a range of other fluids that are seen during the many steps involved in the drug manufacturing process.

What Are the USP VI Testing Methods?

Testing is carried out through producing an extract of the product using different extraction fluids which can include Polyethylene Glycol and vegetable oil. This is then injected into a specimen that is alive in order to see how it responds. This is carried out regularly and requires three forms of testing including systematic injections, intracutaneous and implantation.

Systemic Injection Test – During this test, test specimens are injected with the extract intravenously and monitored for 72 hours. They are monitored to identify any reactions that relate to abnormal toxicity level.

Intracutaneous Test – This test is carried out to identify whether any local skin reactions take place. The specimen is injected intracutaneously with the extract before being monitored for 72 hours. Any reactions are scored and averaged.

Implantation Test – The product materials implanted into the specimen to identify whether a reaction in the live tissue takes place after coming into direct contact with the product over a period of around five days.

What’s the Reason for Products Being USP Class VI?

Class testing is needed when manufacturing drugs to identify its low toxicity compliance while ensuring it meets all biocompatibility standards. Therefore, it is crucial to identify that any fluid contact surfaces will not leach harmful chemicals into the fluid during manufacturing. Class VI testing vigorously investigates where there is a reaction in the skin, body and living tissue, ensuring that a product is safe for use.

O-rings are a crucial element in manufacturing and the operating of machinery but when it comes to installing rings, it is important you know what to look out for.

When it comes to installing O-rings, it’s important that you get it right from the beginning as this will help to save time and money. Therefore, these installation tips can help you to avoid problems that could cause issues with applications further down the line.

Choose the Right Size – It’s crucial that you choose the correct size O-ring. If you go for one that is too small, then they tear and break while too big will not achieve the correct seal.

Don’t Overstretch – Every O-ring has a maximum stretch potential and if you overstretch them then they can break and tear during use. Therefore, it is crucial that engineers make  sure that the stretch does not go beyond that of the maximum elongation of the O-ring. What’s more, it is also crucial to stretch the O-ring evenly.

Don’t Roll It – When sliding an O-ring down a shaft for installation, it can cause the O-ring to spiral. When this happens it means that they cannot be installed correctly and that means that they will not do their job properly. This can then lead to leaks or damage. The O-ring should be slid into place as this helps to stop spiralling. If you are having problems, then lubricant can help.

Be Aware of Threads – O-rings are commonly fitted with threaded parts but these can commonly cause the O-ring to tear. When installing over a thread, cover the thread with masking tape as this will help the O-ring to slide over the threads without being damaged. If required, it is possible to use lubricant too.

Avoid Sharp Edges – Sharp corners and edges are often seen in manufacturing machinery and application and these can cause problems with O-rings. Some tears are small enough to go unnoticed which means that they can cause significant problems. So, don’t force the O-rings onto sharp corners or edges but instead attempt to use a lubricant to slide them into place if necessary.

An O-ring is a mechanical gasket that is shaped like a ring and they are placed within grooves and are designed to handle compression between two parts. This then works to create a seal, making them one of the most common seals seen in machine design.

The Purpose of O-Rings

The main purpose of O-rings is to prevent fluid or air from escaping as it acts as a sealing device. When the ring is squeezed between two surfaces, it takes up the clearance and then prevents any fluid or air from being released. They also retain their shape, so once they are released, they will naturally return to their previous shape. It is the memory that allows O-rings to seal under low or no pressure. When pressure is applied, the O-ring is squeezed against the wall of the groove and this causes expansion in the opposite direction.

What Material is Used?

They are made from a range of materials depending on the application they are needed for. Some O-rings will come into contact with chemicals or heat and so, they require different materials in order to deal with this. To name a few, O-rings can be made of:

• Polyurethane
• Fluorocarbon
• Neoprene
• Silicone
• Nitrile

What Applications Are They Used In?

O-rings are highly versatile which means that they can be used in an array of applications. They are cheap to manufacture while the installation is simple and replacements are cheap. When they are maintained correctly, they are highly durable too.

So, they can be used in applications where hydraulic cylinders move quickly and place pressure on the seals, but the O-ring has the ability to withstand this pressure. However, they can also be used in a range of other applications that can vary from the automotive and aerospace industry to inside computers.

The Benefits

They have the ability to withstand wear and tear while they require no specialist installation tools. Maintenance is simple and they are cost-effective too. They are highly resistant to heat and chemicals which means that they are suitable in a range of applications.

Contact our Sales team at sales@nes-ips.com to find out how our O-rings can benefit your application!

O-rings can fail for several reasons but there are more common reasons as to why this can occur. So, this article will help to identify the indications and causes of O-ring failure:

Extrusion and Nibbling

Indications of this problem appear as nibbles or nicks taken from the low-pressure side of the seal.

This is caused by high stresses as a result of high pressure, causing the ring to be pushed into the clearance gap.  As the O-ring becomes trapped, the sharp edges cause damage to the seal.

Abrasion

When abrasion occurs, the contact faces of the O-ring will have a grazed surface while lacerations might be visible.

The cause of this is down to repetitive contact between the O-ring and the housing whereby the friction is excessive between the two. If there is not enough lubrication then this can also cause failure due to abrasion.

Chemical Attack

The visible signs of chemical attack can be blisters, alteration in hardness, discolouration and cracking.

The cause of this is down to the way in which some chemicals interact with certain elastomers. This can often lead to cross-link density and that can cause the material to become brittle and hard.

Compression Set

A common sign of this problem is the way in which the o-ring changes its shape and becomes less circular while the surfaces appear flattened to the point where it has taken on the shape of the groove. This permanent appearance means that it is unable to return to its original shape.

The cause could be due to the elastomer being exposed to high temperatures causing the o-ring to set or poor-quality polymer formulation. As a result, the O-ring loses its elasticity, preventing it from returning to its shape.

Chemical Swell

The O-ring will look larger than its original design and this is likely to be consistent over the whole of the O-ring or in areas that have been exposed to chemical.

The cause is down to ingress of media within the elastomer which is down to a likeness between the compound and the media.

Rapid Gas Decompression (RGD)

The seal will show signs of blistering, cracking and could even have splits where it has ruptured.

High-pressure gas and elevated temperatures over long periods can cause this to happen. The external pressure reduces but the gas that is dissolved within the material is released and as it expands, it can cause the seal to fail if the rate of decompression and expansion is high.

O-ring failure is common when they are exposed to vibration and chemicals that cause corrosion. As a result, small fragments from seals can end up working their way into the product stream.

In most cases, this can cause production and processes to stop in order to replace the O-ring. However, when this occurs in industries such as food and pharmaceuticals, it means that there are bigger problems as these are products that are being manufactured for human consumption. As a result, this can lead to costly shutdowns while inspections take place to locate the problem part in the system. Downtime costs money and reduces safety and should the faulty part make its way into the supply chain then this can cause a wide range of problems.

One solution to help avoid or reduce this is to use metal detectable O-rings as they can help to keep the process safe and more efficient should problems arise. These O-rings can be detected quicker, reducing the risk of contamination while ensuring processes can begin sooner. What this means is that any failed components can be detected before they find their way into the supply chain. Standard seals can fail and find their way into the product, making it impossible to identify them and rectify the solution without costly interventions.

These metal detectable O-rings can be identified using standard metal detection methods and so, in very little time, they can be identified and removed. The production line can be paused allowing for an engineer to remove the contaminated products, so they do not enter the supply chain. Amazingly, it is possible to identify fragments as small as 2mm in size. These O-rings and seals can be made using a wide range of compounds and colours while they all provide a highly effective solution.

Essentially, metal or X-ray detectable O-rings can be easily detected, and this can help to minimise or completely reduce the need for product recalls which can help to reduce costs and the risk of further problems. They can be used in standard OEM equipment too, helping to prevent the distribution of products while they are also suitable for mechanical, high-temperature and microbial applications.

Used in a wide range of applications, O-rings are the most commonly used type of seal in a multitude of industries. O-rings come in many forms but the most common are rubber O-rings which come in a number of compounds that are designed to suit a variety of applications.

We provide a full range of standard sizes however, along with this, also have the ability to manufacture O-rings that not of a standard size.

If you are enquiring about O-Rings then please take a look at the table below to see all of the dimensions of BS O-rings.

Inflatable seals are designed to provide a solution when it comes to sealing against powders, gases, liquids, dust and granules. They are generally used to seal fabricated equipment where the sealing gap can vary while they are useful in instances where assembly and disassembly must take place quickly. They are also suitable for use where hygienic procedures exist.

But where are they used?

Marine Applications

These seals provide a watertight solution for door applications and sliding windows while they are also used in transom and salon doors on yachts. As they can be fitted into machined grooves, frog leg and channel fit profiles are commonly used.

The Handling of Powders and Solids

They are commonly used in food processes and pharmaceutical industries where powders are transferred and require an airtight seal. This can include the likes of bulk bag filler seals, hopper seals and seals for viscous pumping equipment.

Energy Generation Industry

Inflatable seals are used in the energy generation industry and in particular, nuclear power. They are suitable for meeting the tight tolerances as well as the tight quality control that needs to be put in place. They are used to seal pool gates in nuclear power plants while they are also used to seal airlocks, access door and equipment hatches.

Airtight Doors

Inflatable seals are ideal for ensuring a positive seal is achieved on doors that require an airtight seal. As they expand towards sealing, they can handle variations in the tolerances when the door is manufactured. While they create a positive seal, they also provide frequent access as they can be inflated and deflated. They are commonly found in chemical processing plants, laboratories and research facilities.

Aerospace, Transportation and Defence

All of these industries use inflatable seals for both bespoke and technical applications. Inflatable seals are used to deliver uniform pressure when bonding airframe components while they are also used to seal wind tunnels.

Inflatable seals can also be used to create watertight seals on military and other vehicles. In many cases, USP Class Vi and FDA certified, making it suitable for use in a range of industries. They can be developed to be heat and water-resistant, making them the perfect sealing solution across a variety of uses.

If you have an application that you think could benefit from an Inflatable Seal, contact the NES Sales Team at sales@nes-ips.com