As a result of exposure to high temperatures as well as vibration and corrosive clean-in-place chemicals, it is common for O-rings that are used in industrial processing operation to fail. When this happens, fragments of rubber from gaskets and seals can shear off and that can mean that they then find their way into sanitary systems and even enter the product stream.

In many instances, the issue does not need much more than a short stoppage of the process in order to replace the O-ring.  However, this can prove to be a problem because of the fact that products that are made for the food, beverage and pharmaceutical industries and for human consumption are highly regulated and so, this can come with further problems.

In situations such as these, it can mean that the machines must be shut down by operators to carry out a visual inspection in order to locate the part that has contaminated the system. This then leads to unscheduled downtime, production losses and a reduction in safety. Should a fragment of rubber lay undiscovered and it then manages to reach the supply chain, the issues that can arise from this are extremely problematic and costly, especially if the product must be recalled.

Therefore, metal/x-ray detectable elastomer O-rings and seals have been developed to ensure that they meet the challenging demand of the food and pharmaceutical industries. In other industries, where resistance is required against temperatures and chemical and forms part of the key seal selection criteria, in food and pharmaceutical applications have to adhere to strict cleanliness and regulatory guidelines. These help to keep the entire process safe for consumers.

Metal/x-ray detectable O-rings can help to speed up the process of identifying them should they fail and this can help to reduce the risk of contamination through early detection and containment. As a result, there is a reduction in the risk of polymers finding their way into the final product and the supply chain. Should the rubber from a standard seal fail and break down and then find its way into the product then this becomes almost impossible to detect while it is also very time-consuming.

Using conventional metal/x-ray detection techniques, metal/x-ray detectable seals can be easily detected and identified. Therefore, should a fragment of elastomer be identified, it is possible to halt the production line before efficiently removing the contaminated products to prevent them from entering the supply chain. Even pieces that are as small as 2mm can be identified.

Metal/x-ray detectable O-rings and seals can be manufactured in a range of compounds/colours and they all provide a feasible solution to a significant problem.

What Are The Benefits of Metal/x-ray Detectable O-Rings?

First of all, they are extremely easy to detect and that can help to prevent product recall and product loss. Therefore, it prevents the distribution of products that have been contaminated while they can be used in all standard OEM equipment. What’s more, they are also developed for both mechanical, microbial and high-temperature applications.

When it comes to seals, there might be a lot to think about, after all, it’s imperative that you get it right and that it works for your application. However, get it wrong and it could prove costly and cause a wide range of problems. Therefore, when it comes to static seals they are categorised as either axial seals or radial seals.

This categorisation is defined by the way in which compression is applied to the cross-section of the O-ring. So, what we aim to do is explain the difference between these two types of seals even though they might seem quite similar. The main difference between radial seals and axial seals essentially comes down to the direction in which compression is applied to the seal cross-sections. In the case of radial seals, compression is applied to the outside diameter and the inside diameter. In contrast to this, axial seals will have compression applied to both the top and the bottom of the cross-section of the seal. So, let’s delve deeper into the different properties and functions of both seals.

Radial Seal – What is it?

It is common to see radial seals used in bore, piston, cap and plug style applications. They then fall into one of two main categories known as dynamic radial seals and static radial seals. Dynamic radial seals are developed to be used in an environment where there is reciprocating, rotating or oscillating movements between two mating components. In contrast to this, static radial seals are traditionally used in those environments where there is very little or no motion between the mating surfaces that are being sealed. It is this specific reason that static seals are then considered to be more forgiving than dynamic seals. They have the ability to manage wider, larger gaps as well as surfaces that have a rough finish and higher pressures.

Axial Seal – What is it?

In applications where axial seals are used the top and bottom of the O-rings cross-section will be squeezed. Therefore, axial seals are the ideal solution for primary seals but also secondary seals in those applications where the primary seal is subjected to a significant amount of fluid or solid contaminants. This kind of seal is commonly used in face or flange type applications and they are a lot easier to manufacture when compared to static radial seals.

How Do You Pick The Right Seal?

As with any application, it is crucial that you choose the right seal. Therefore, it is imperative that you understand the different factors that might determine the seal that you need. It can also be of benefit to obtain professional advice and guidance as this will ensure that you get it right as if you fail to choose the correct seal then you are at risk of experiencing a wide range of problems depending on the industry that the machinery operates in. This highlights how important it is to understand the difference between seals and the benefits they offer.

If you have developed a piece of machinery that require seals, you are going to need to determine which seals are right for your chosen application. As a result, you should not overlook the process of designing in the right o-ring within an application.

If you choose the right o-rings, this will commonly help you to meet demands, some of which are often conflicting while they will help to improve performance as well as durability. What’s more, they will also help to reduce the risk of failure, but they are dependent on many different factors and so, we will explore these factors.

Choosing the O-Ring Material

It is vital that the compound material chosen is compatible with the working media that are used within the application. Therefore, if one or more of the following factors are incompatible then it can have a significant impact on the O-ring.

• The operating fluid can cause the seal material to degrade dues to chemicals. As a result, it can mean that the wrong compound against compatibility could result in the O-ring swelling. This could then lead to a reduction in performance and even the risk of failure.
• Temperature can also cause problems in the way in which an O-ring performs. Therefore, it is imperative that it remains with the optimum working parameters. If the temperature is too cold then this can reduce the elasticity, causing it to become brittle. This can then cause it to snap. If the temperature is too high then this can cause significant degradation.
• The operating pressure is also a vital consideration, especially in a static sealing application. Where other factors are taken into account, a material that has a 70 shore hardness will often do but once the pressure increases to 1500 psi, a back up ring should be considered as a way of preventing extrusion. Along with this, it might also be advised to consider a shore hardness of 80-90 to prevent any problems.

Housing Design or Seal Grove

The performance of an O-ring will be determined by the finish of the mating surface but also the seal housing surface finish. This is down to the fact that extremes of smoothness or roughness are not suitable when it comes to creating a good seal. A rough surface, over time, might cause small cuts in the material and that can cause the o-ring to weaken and eventually fail, significantly reducing its lifespan. In contrast to this, a surface that is extremely smooth can cause a similar effect to aquaplane and that can eventually lead to leaks.

As a result, the general rule of thumb or guideline that should be followed is that a seal grove surface finish of 16 rms is suitable for sealing gases while up to 32 rms is considered suitable for fluids. Anything from 8-16rms is considered to be more suitable for dynamic applications as this can help to minimise the risk of abrasion as well as the potential for spiralling.

Wind power is one of the most prominent energy sources of the future. As we look to greener alternatives for generating electricity, we are seeing more and more wind turbines being installed across the country. As it stands, there are over 7,000 turbines connected to the national grid in the UK and this is only going to increase. Therefore, wind power is proven to be the most developed alternative energy source.

Oil prices and an increase in the need for more energy has meant that energy suppliers are now looking to take advantage of the wind that blows across the UK. What’s more, as we aim to reduce carbon emissions, energy sources such as wind energy are going to become more prominent.

However, when it comes to seals, what seals are needed to ensure the operation of wind turbines can occur efficiently and effectively.

What Is Needed?

Rotary Seals – These are located in the main gear and it is here where the rotation of the blades is converted into a speed that is considered suitable for the generator. The seals are also used to hold the main shaft in the correct position.

When it comes to maintenance, the main brake will help to stop the turbine to a speed that is critical for maintenance. Here you will find scrapers, wear rings and rod seals while these seals will also be found in the Yaw brake. This break ensures that the nacelle is held in a steady position and facing the wind. All of the brakes, which includes the Yaw brake and the rotor locking system are fitted with critical safety-related functions within the turbine. Therefore, the sealing solutions used within the turbine must offer an enhanced level of reliability and so, they also have to be suitable for the environment which may involve both low and high temperatures.

Piston Seals, Static Seals and Wear Rings – These are all located in the accumulators and these work like hydraulic power batteries to enhance the efficiency of safety and energy. The angle at which the rotor blades face the wind is controlled by the pitch cylinder and actuators. Therefore, seals become an integral part of the system as they will need to withstand millions of strokes. Here you will find not just piston seals, static seals and wear rings but also rod seals and scrapers. These seals work to help control leakages but also improve the service life of the turbine.

The link between the blades and the generator is provided by the transmission. This is a crucial aspect of the turbine and its effectiveness while they are extremely efficient and require very little maintenance. Along with this, radial oil seals are perfect for sealing transmissions and so, they are made of a single lip that is bonded to a metal support using a garter spring although there are other variations to choose from.

So, it is clear to see that seals are a vital part of turbines and how they operate. Without the right seals, they would not work efficiently or effectively.

It is vital to understand that most elastomers have different formulas that can reduce the working temperature of the compound. In situations where a certain material has been deemed suitable as a result of its chemical compatibility or even its mechanical properties, there could be a version available for low temperatures. Here we give you a range of O-Rings that are ideal for low temperatures.

Why Does an O-Ring Fail at Low Temperatures?

The process of cooling results in rubber losing its elasticity and this is measured as the Compression Set of the elastomer. The compression set is a vital aspect of how an O-ring performs but it is crucial to ensure that a reliable seal is formed. This is defined by the percentage of material that does not return to its original size after it has been compressed.

Low-Temperature Nitrile O-ring

These have a temperature range of -45°C to 120°C.

Nitrile offers a moderate level of resistance against oils, chemicals and greases. However, it is worth noting that at low temperatures Nitrile is prone to shrinking and could lose chemical resistance.

Low-Temperature HNBR O-Ring

These have a temperature range of -45°C to 120°C. Along with this, they also have improved resistance to both chemicals and oils. However, like Nitrile, it can shrink at lower temperatures and lose its resistance to chemicals.

Low-Temperature Silicone O-ring

These come with a range of temperatures. The standard temperature range is -55°C to +200°C. However, the fluorinated temperature range is -60°C to +230°C while the special low temperature compound temperature range is -100°C to +230°C. They come with a high level of resistance to low temperatures although they are prone to wear while they have little chemical compatibility.

FFKM

Offering a temperature range of -42°C to +220°C, they also come with a high level of chemical resistance although they are considered to be an expensive solution.

FEP/PFA Encapsulated O-rings

These O-rings offer a temperature range of -60°C to +260°C. The elastomer is also suitable for use in a wide range of working conditions.

Astra Seals®

Astra Seals® have a temperature range of -250°C to +260°C. This offers the best low-temperature compression set. However, they are only recommended for use in axial sealing applications with no stretch.

To find out more at the NES Astra Seal®, visit https://www.nes-ips.com/astra-seals/

In the food industry, there are a wide range of applications that come with a number of challenging requirements. Hygiene standards and legislative manufacturing regulations are constantly changing and so, seals must also comply with these.

Elastomers that are used in pipes and pumps, as well as reaction vessels and process equipment have to be suitable to deal with the aggressive cleaning and sterilising processes. Along with this, the food industry also uses a wide range of flavours, preservatives and colours, all of which can have different effects on the materials that are used in sealing.

The Challenges of Water

The Water Regulation Advisory Scheme (WRAS) is a subscription membership company limited by guarantee. It was brought in during 2008 and the 26 water suppliers in the UK are subscribers of the scheme. The aim of WRAS is to ensure that public health is protected by preventing the contamination of public water supplies while also encouraging the use of water efficiently through promoting and facilitating compliance with The Water Supply (Water Fittings) Regulations. As a result, sealing materials that have been given approval for use in drinking water applications have to adhere to the requirements of BS 6920. Therefore, all non-metallic materials are required to undergo strict testing as a way of determining how they affect water quality. This approval will prove that the non-metallic material does not contaminate water and meets all relevant regulations.

FDA Approval

The Food and Drug Administration (FDA) will approve products that are used in applications in which food or consumables are manufactured and produced. This is especially true in food processing, dairy, beverage and pharmaceutical industries. Products that have FDA approval are found in most packaging equipment with one example being gable-top machinery. The FDA takes a thorough approach and so, the regulations have been adopted as an international control standard. However, the jurisdiction of the FDA is restricted to the USA only.

The FDA website contains CFR21.177.2600 and this makes clear the relevant regulations that are in place for rubber articles that are developed for repeated use. It details thoroughly which elastomers can be used for production, manufacturing, packing and processing. They also detail what can be used in preparing, treating, packaging, transporting and holding food.

The food industry is unlike many other industries out there and that is because all processes within it are developed to be safe. This is because any risk can be passed onto the public and with that could come significant problems if the regulations are not adhered to. Seals are an integral part of the process and they are developed to carry out a specific role but first and foremost, they have to be suitable for the role that they play in the food industry.

For more information on the Food & Beverage industry, visit https://www.nes-ips.com/food-and-beverage/

There is a distinct reason why many different industries would require the use of metal detectable and X-Ray detectable rubber materials and we aim to help you gain an understanding of where and why these would be used.

Regulations in the Food, Beverage and Pharmaceutical Industries

Specific government regulations stipulate that it is crucial that all food, beverage and pharmaceutical manufacturers ensure that all foreign materials are kept out of ingredients as this ensures that food and drugs are safe for consumers. It is a high priority to ensure that all foreign material is prevented from entering the processing stream, but this also means that the correct measures must be adopted in order to detect and identify any foreign material that might contaminate a product. This will enable them to quarantine it before it is distributed.

Through incorrect installation or excessive shear that is experienced throughout the operation, component parts that are used in the processing of food and drugs can break into fragments. Materials such as plastic, rubber or even metal can then contaminate ingredients. Some of the chemicals that are used for cleaning or the sterilisation of equipment can result in the degradation of rubber seals and that increases the chances of particles breaking off and finding their way into many of the products. When parts fail, it may cause product contamination but along with this, it can also lead cause downtime for machinery as well as the requirement to scrap products and even product recalls. All of this could come with legal issues and media attention that has a negative impact. All of these problems can then lead to a financial impact as well as a reduction in brand loyalty.

Hazard Analysis Critical Control Point (HACCP)

A vast majority of processing operations now use HACCP programs that require all parts to be metal detectable and X-ray detectable. This resulted in it becoming necessary for the development of special rubber materials that make it possible for food processors to carry out routine inspections for this form of contamination, making use of in-line metal detectors and X-ray machines. As a result, rubber must be compounded with specific additives that make it possible for detection to take place. Despite this, there are foods that have phase angles that are much like detectable rubber and so, it is vital that a full understanding of the rubber product’s application is in place as this will guarantee correct compound selection.

There are several metal and X-Ray detectable materials available that are manufactured using ingredients that are sanctioned under FDA Title 21 CFR 177 .2600. Some of these materials are 3A sanitary 18-03 approved and come in Silicone, EPDM, Nitrile, FKM and HNBR. All have a durometer range from 50 shore to 90 shore and come in blue which is the industry standard although materials can be coloured as per the requirements of the customer while any polymer can be manufactured to be metal detectable and x ray detectable.

For more information on Metal and X-Ray Detectable Seals, visit https://www.nes-ips.com/metal-detectable-rubber/

If you find yourself in a position where you have developed an application that requires seals, you need to ensure that you make the right choice. Finding the correct seals is imperative to the success of your application and as a result, choosing the correct O-Ring should never be underestimate. Along with this, the demands of that application will determine how you select your O-rings.

You should consider performance and durability as well as reducing the risk of failure when selecting O-Rings. However, choosing O-Rings will be determined by several factors and that is what we will aim to cover here.

Choosing O-Rings Material

To select the correct O-Ring, you will need to ensure that you choose the right material, ensuring it is compatible with all media that are working within your application. Therefore, if one of the following factors are considered incompatible then this can have a negative impact on the ring and how it performs.

Operating Fluid – The operating fluid that you use can chemically cause the seal material to degrade. Therefore, the wrong compound and fluid incompatibility can cause the O-Ring to swell. This will result in poor performance and it could even cause it to fail.

Temperature – Temperature can cause significant problems for your O-Ring and how it performs. It is important to keep the temperature within the optimum working parameters because should the temperature drop too low, it can cause the O-Ring to become brittle and lose its elasticity. In contrast to this, if the temperature is too high then this can cause significant degradation that could prove catastrophic.

Operating Pressure – The operating pressure is something that you need to seriously consider. Where a static sealing application is used and when other factors are taken into account, it is usually fine to use a standard 75 shore hardness material as this will usually be sufficient enough for the job. However, once the pressure increases to around 1500 psi, you should think about utilising a backup ring as a way of preventing extrusion. Along with this, it is important to consider a shore hardness of around 80-90.

Housing Design or Seal Grove? 

The performance of the O-Ring is underpinned by the seal housing surface being finished as well as the finish of the mating surface. This is down to the fact that a variation in extremes of smoothness and roughness will not result in a satisfactory sealing. If the surface is rough, then this could cause small cuts to appear in the O-Ring and this will cause it to degrade to the point where it fails and does not last as long as expected. In contrast to this, if the surface is especially smooth, then it can cause an aqua-plane effect and that can lead to leakage.

Therefore, a good guideline to follow is to use a seal grove surface finish of 1.6 Ra for sealing gases and as much as 3.2 Ra for sealing fluids and dynamic applications as this can help to reduce abrasion and the spiralling potential.

When developing seals for the food environment, there are many things that you need to consider, and these cover the development process and right through to the manufacturing process. The food industry and environment are unlike many others as it is one where hygiene is of significant importance and so when developing seals, there are several vital elements that you have to consider:

The Operating Conditions

When developing a seal, you will need to take the application into consideration. As a result, you will need to analyse the type of movement as well as the finish and type of equipment that is being sealed.

Along with this, the operating pressure is also a serious consideration while the speed and temperature also play a vital role. The maximum and minimum pressure will need to be considered while the speed and temperature that are present at this pressure will need to be determined. There will also be a maximum and minimum temperature along with a maximum speed and so, determining all conditions will feed into the development process

Fitting the Seal and Assembling the Equipment

An assembly drawing will make it possible to clearly identify the specific requirements. Many FDA seals have problems with fitting and with this comes an increase in costs and time if they are not actively managed at the start of the process. An example of this could be those seals that require an open housing as they can be damaged or become unusable if used in a closed gland.

Contact Media

Material choice is determined by the media that the seal will come into contact with. It is important to understand any potential changes throughout its operational life or if it is going to be required for a number of media. It can often be helpful to have one sealing option for multiple media and cycle changes.

Cleaning Method

In all food manufacture operations, hygiene is critical, and cleaning is an absolute must. Therefore, it is common for processors to do whatever it takes to make sure that the environment is safe and sterile. This could include extremely hard media or clean in place and steam in place methods. However, the chosen cleaning method could lead to the elimination of certain seal materials while it can also result in the need for replacements for each pass. Therefore, having the correct information from the outset can help to reduce costs and avoid errors that could prove dangerous.

For more information on seals for the Food & Beverage industry, visit https://www.nes-ips.com/food-and-beverage/