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.
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® 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.
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 designed 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 designed 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.
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.
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/
If you have the correct tools available to use, the process of measuring an O-Ring is relatively simple. All you need to undertake the measurement process is a clean surface that is level, an O-Ring and a device that you can use to measure such as a calliper although other measuring tools can be used such as size charts, gauges and cones.
O-Ring Measurement Process
In order to correctly measure an O-ring, you need to follow the process below:
- Put the O-Ring on a surface that is flat and is free of any debris
- Identify the inside diameter (ID) of the O-ring as well as the outside diameter (OD).
- Now you will need to measure the width of the O-ring or the cross-section (CS) of it. This can prove a challenge, but it can be measured by gently pressing the calliper ends onto the O-Ring.
It is possible to use just two dimensions to determine an O-Ring size; for example, the inner diameter and the cross-section measurements. If you know two of the three dimensions, then you can use the following formulas to calculate the third.
OD = ID + (2 x CS)
ID = OD – (2 x CS)
CS = (OD – ID) / 2
Rubber materials come with a range of qualities that all play into the sealing process and its complexity. There are tolerances, environmental factors as well as compression set but also, the hardness is also a vital component. The hardness is measured by Durometer and this will measure the hardness in materials such as polymers, elastomers and rubbers. It can prove a difficult property to ascertain as it is dependent on geometry and this will require thorough testing.
The Shore A scale is utilised for measuring how hard, a material is. Therefore, if a material has a Shore A “0” then this will mean that it is soft and has a gel-like appearance to it such as silicone. However, any elastomers that are rigid will often be at the other end of the scale and so, they will have a rating of around 90-95A.
Polyurethanes are often used at the 80-95A hardness range as they have the right blend of mechanical properties. As a result, they have the ability to flex and absorb any impacts while they can handle pressure and keep their shape. Therefore, they are perfect for applications such as shock absorbers.
Commonly, this scale is used for plastics. Those materials that have a hardness above 65D will be completely rigid and will not have the flexibility or surface flex that is commonly seen with A scale grades. These harder materials have a greater level of resistance to flex and that can mean that they are suitable for applications which includes impact protection or metal replacement. As a result, they are commonly used in mechanical products which can include gear wheels, castors and wheels.
So, the durometer scale is a way of measuring the hardness of a rubber material. The list below will provide you with an insight into the different hardnesses and where you can find them. As an overview, the majority of rubber materials will come under the scale of Shore A. However, with a variety of applications and requirements, material hardness can alter and measure on an alternative end of the scale. The list below will provide you with an idea of common materials are actively measured using the Shore Scale.
- Shore 20A – Elastic Band
- Shore 40A – Eraser
- Shore 60A – Car Tire Tread
- Shore 70A* – Sole of a running shoe
- Shore 80A – Leather Belt
- Shore 100A – Castor
In the basic sense, hardness relates to the way in which a material reacts to intrusion as well as permanent deformation from a harder body. When it comes to seals, it is a property that is a significant consideration, especially in relation to function and specification.
The hardness of seal materials such as rubbers, plastics and elastomers are measured in units of Shore or IRHD (International Rubber Hardness Degrees).
When comparing two materials, Shore hardness offers a reference point and there are 12 different scales that are used for measuring a range of substances. However, each scale will rank the hardness of a substance between 0 and 100. The higher the value, the harder the material.
The most common scales are the A and D scales, with the Shore A scale being used for elastomers and the Shore D scale is used to measure rigid plastics.
A durometer test instrument is used to measure shore hardness. The test method designation is ASTM D2240 while related methods include the like of ISO 7619.
So, the ASTM stipulates that the test method focuses on the penetration of a certain type of indentor when it is pushed into the chosen material under certain conditions. As a result, the indenter shape and the force that is applied will alter by scale and test.
The Shore Hardness gauge will have a needle mounted on a spring. This needle is then placed on the material before the pressure is applied. After the gauge has been placed against the material firmly and the needle has penetrated as much as possible, the needle will provide a measure of hardness that will relate to the Shore Hardness Scale
So, when it comes to seals, the Shore Hardness Scale will make it possible to determine which material should be used. The required hardness will be determined by the application
The Shore Durometer Hardness results are a great way of measuring the resistance of a number of materials. Despite this, the test is not used to predict a range of other property such as strength or resistance to scratches, abrasion or wear, and so, when it comes to design specifications, it should not be relied upon solely.
So, seal hardness is vital to fluid power system designers. The softer a seal is, the more easily it will stretch and that means that they will work their way into microfine surface imperfections while they will also provide a better seal on rough surfaces. This is ideal for lower system pressures. However, where pressures are higher, the hardness of a seal is important. A harder seal will have the ability to deal with abrasion and dynamic friction while it will also resist gap extrusion.
Therefore, the Shore Hardness Scale is imperative when it comes to ensuring the correct material is chosen for the application.
As far as manufacturing component goes, seals or o-rings are taken for granted. They have a history that dates back over a century but they are still needed in many industries. They are simple in how they look and the role that they play but despite this, they are extremely important.
While engineering, manufacturing and component design has altered significantly during this time, seals have pretty much remained unchanged. Despite this, they have altered in terms of their make up as technology and materials have improved throughout the years. However, seals are undoubtedly vital when it comes to the joining of two parts, as they will help to create a seal.
They can be used in a number of applications such as static and dynamic applications where there is movement behind the parts. Therefore, this enables the part to move and flex without the seal breaking. This is why the correct material has to be used when manufacturing the seal and choosing the seal.
They are required where the seal is needed to prevent the leakage of gases or liquids. Along with this, o-rings are especially suitable in high-pressure environments. Seals will sit in a groove or a channel between two surfaces that are pushed together. It then becomes compressed and that helps to form the tight seal. The more pressure that is applied internally, the more the seal will distort inside the groove and that will help to enhance the seal it creates.
These seals are often seen in pumps, connectors, valves and cylinders and they are seen in static, dynamic, hydraulic and pneumatic components. This makes them a versatile solution for a wide range of engineering problems.
In the same way as using any other form of gasket, a seal will be used in a similar way. It will sit across an engineered groove and this will bring with it a tight seal once it has been compressed. What’s more, many seals are simple to replace which makes them the ideal solution in a number of applications.
They also come in a variety of materials too. This makes them suitable for a wide range of requirement depending on a number of factors such as the industry and the equipment. Despite this, there is no doubt that seals have an important role to play regardless of the materials they are made of and the where they are used.
Metal detectable O-rings are essential for companies that use machines fitted with rubber seals that come into contact with the product.
In industries which have highly-regulated hygiene standards such as pharmaceutical, food, dairy and beverage, metal detectable elastomer O-rings will save you a significant amount of time, money and hassle.
Fitted with components that are identifiable by inline metal detectors or X-ray machines that are commonly used for safety procedures in a wide range of industries, when fragments made from metal detectable O-rings fall into a product, they are easy to locate and recover.
As a result, your productivity does not suffer. Metal Detectable O-rings can be identified in a fraction of the time it takes to conduct visual inspections. Therefore, you won’t need to shut down the production line until the contaminant is located.
Detectable metal O-rings also give companies the opportunity to improve safety measures at each stage of the production line. By doing so you can prevent the possibility of having to recall an entire batch.
Why use Metal Detectable O-Rings
When rubber polymer applications are exposed to volatile temperatures, continuous vibration and corrosive chemicals, they naturally weaken and degrade. Eventually, fragments of rubber from seals and gaskets sheer-off and fall into the end product.
Whereas traditional O-rings are made entirely of elastomeric substances, such as natural rubber, Viton™, Nitrile or Silicone, metal detectable O-rings and seals are a new breed of sealing material that have been developed in order to meet strict regulations imposed on food and pharmaceutical industries.
Metal detectable sealing materials are detectable by standard in-line metal detector systems which are already in operation in the food, beverage, and pharmaceutical industries.
Fragments as small as 2mm can be identified and removed either manually or by magnetic separators. By reducing the risk of product contamination, metal detectable polymers meet the legal requirements for hygienic design of machinery and complies with FSA regulations to help protect product safety, and eliminate downtime and product recall.
Because metal detectable O-rings are such a straightforward approach and a low-cost investment, there are no better means to ensure product and package integrity is not compromised.
Types of Metal Detectable Polymers
There is a range of metal detectable materials available that have been tested to the highest quality standards and are proven to be suitable for the food, pharmaceutical, dairy, manufacturing and processing plants that use corrosive chemicals.
- Nitrile Rubber (NBR)
- Silicone (VMQ)
- Fluoroelastomer (FKM/ Viton®)
Metal detectable sealing materials are a simple and cost-effective solution to prevent the contamination of products intended for human consumption.
NES supply a range of premium quality metal detectable and x-ray detectable rubber seals and O-rings.
There is a wide variety of sizes, colours and material specifications available so contact our friendly Sales team and we will advise you of the best products to meet your needs.