O-rings are highly versatile and widely used as a sealing solution due to their efficiency, affordability, and ease of use in both static and dynamic applications. They are crafted from a wide range of elastomer materials, capable of sealing practically any liquid or gas.
Designing and producing O-rings requires careful consideration of several factors, including quality, quantity, application environment, cost-effectiveness, chemical and pressure compatibility, longevity, and lubrication requirements.
O-rings are versatile seals, typically elastomeric but also available in materials such as PTFE or metal, exhibiting a bi-directional, circular design. They function by deforming their material under installation and media pressure to effectively seal gaps between mating components.
However, these seals are not impervious to issues. High system pressures can lead to a phenomenon known as extrusion, where the seal material deforms into the gap, resulting in seal failure. This issue can be mitigated by employing harder seal materials or introducing back-up rings for support.
The strength of an O-ring lies in its ability to behave like a highly viscous fluid under pressure, creating a positive barrier against the medium it's designed to seal. This unique attribute, coupled with its capacity to revert to its original shape post-deflection, makes O-rings invaluable in sealing applications.
Additionally, the O-ring's elastomeric nature allows it to adapt to unit tolerance variations, maintaining a sealed condition. The squeeze, or the degree of compression, is a crucial factor in the design of O-ring seals. For O-rings with smaller cross sections, a higher degree of squeeze is needed to counterbalance larger groove dimension tolerances.
O-rings can be successfully used in static as well as dynamic applications. A seal that does not move, except for pulsation caused by cycle pressure, is called a static seal.
There are four varieties of static applications: axial, radial, dovetail and boss seals.
The O-ring cross section is squeezed axially in the groove similar to a flat gasket.
The O-ring cross section is squeezed radially in the groove between the inside (ID) and outside (OD).
The O-ring is also axially squeezed in a dovetail groove.The groove design allows the O-ring to be retained in the face seal during assembly and maintenance.
This is beneficial for special applications where the O-ring has to be fixed by the groove e.g. a lid which opens regularly.
Bosstail The O-ring is used for sealing straight thread tube fittings in a boss.A boss is a cylindrical projection on a casting or forging. The end of that projection is machined to provide a flat, smooth surface for sealing.Straight threads used with an O-ring provide a better seal than tapered threads used alone.
Seals that are subjected to movement are dynamic seals. These are further defined as reciprocating (seals exposed to linear motion), rotary (stationary seals exposed to a rotating shaft) and oscillating.
Seals used in applications that slide back and forth.This motion introduces friction, which creates design considerations different from those of static seals.
The O-ring may be housed in a groove (rod seal) in the cylinder wall instead of a groove in the piston surface (piston seal) without any change in design limitations or seal performance.
Oscillating applications are those seeing both rotary and reciprocating movement.
A valve spindle is an example of an oscillating application.
Rotary seals refer to seals used in applications that rotate.
Calculating O-ring groove and size
It is important to know how deep and wide the groove is into which the O-ring will go. Otherwise, an O-ring size cannot be determined properly. Usually, you have already calculated the groove for the O-ring before choosing an O-ring.
The following is important to consider when calculating the O-ring size & O-ring groove:
Make sure the width of the groove is greater than the depth, i.e. your groove is rectangular and not square. This is because an O-ring is usually pressed into the groove from above (axially). Since an O-ring is not compressible, but deformable, it must be able to release its volume. Free space in the groove is therefore essential. If the groove is not wide enough, the O-ring is pressed squarely and the material loses sealing capacity.
The diameter of the O-ring should be at least 15% smaller than the space of the groove. If this margin is smaller, the risk of damage to the O-ring increases.
Read more about Determining the right o-ring dimensions for your application
Are you calculating the depth of the O-ring groove? Your groove depth determines the compression of your O-ring. Always include the gap space (clearance gap) in your calculations. An O-ring groove should be rectangular.
Do you want to calculate the O-ring and groove size yourself?
The O-ring calculator will help you calculate O-ring and groove sizes.
An important consideration when choosing the right O-ring is the indentation, or compression ratio. Too high a compression ratio can lead to damage, while too low a compression ratio will cause the O-ring to seal inadequately.
Incidentally, compression rate should not be confused with the term Compression Set. The compression rate indicates the deformation of the O-ring, while the Compression Set indicates the elastic memory of the material.
The recommended indentation is 15 to 25% in static applications. In vacuum applications, pressures can be even higher. Pressing at more than 25% creates additional stress for an O-ring. This can lead to premature damage.
In dynamic applications the recommended compression rate is 8 to 16%. Due to friction and wear, smaller cross-sections are compressed by up to 20%.
Rubber materials or elastomers used in sealing applications are often described as compounds; meaning that they are a mixture of ingredients manufactured under specific conditions. A compound typically comprises a polymer, cross-link system, fillers and other ingredients used to achieve specific manufacturing-, application- or cost requirements.
The basis of compound design is a selection of the polymer type. To the elastomer, the compounder may add reinforcing agents, such as carbon black, colored pigments, curing or vulcanizing agents, activators, plasticizers, accelerators, antioxidants or antiradiation additives. There may be hundreds of such combinations.
Different circumstances demand various compound properties. That is why so many compounds have already been developed. We have categorised our compounds in standard- (general purpose), specialist-(industry or application specific) and high performance grades.
One of the most frequently named properties regarding polymer materials is hardness. Hardness is the resistance of a body against penetration of an even harder body of a standard shape at a defined pressure.
There are two procedures for hardness tests regarding test samples and finished parts made out of elastomer materials:
Shore A / D in accordance with ISO 868, ISO 7619-1, ASTM D 2240 Most elastomers are measured on the Shore A scale. Shore A hardness of 35 is soft; 90 is hard. Shore D gauges are recommended where the Shore A rating is greater than 90.
Durometer IRHD (International Rubber Hardness Degree) in accordance with ISO 48 , ASTM 1414 and 1415
The softer the elastomer, the better the seal material conforms to the surfaces to be sealed and lower pressure is required to create a seal. This is particularly important in low pressure seals that are not activated by fluid pressure. The softer the elastomer, the higher the coefficient of friction.
In dynamic applications however, the actual running and breakout friction values of a harder compound with lower coefficients of friction are higher because the load required to squeeze the harder material into the O-ring groove is much greater.
The softer the elastomer the more risk that at high operating pressure the elastomer of the O-ring will extrude into the clearance gap between the mating seal surfaces.
The harder materials offer greater resistance to flow. With an increase in temperature, elastomers first become softer and then eventually harder as the rubber curing process continues with the application of heat.
This information is only a guideline. Chemical compatibility lists should be consulted, such as the ERIKS Rubber Chemical Resistance Guide
Whenever possible the fluid compatibility of the O-ring compound should be rated "A". For a static seal application a rating "B" is usually acceptable, but it should be tested. Where a "B" rated compound must be used, do not expect to re-use it after disassembly. It may have swollen enough that it cannot be reassembled. When a compound rated "C" is to be tried, be sure it is first tested under the full range of operating conditions.
It is also particularly important to test seal compounds under service conditions when a strong acid is to be sealed at elevated temperatures because the rate of degradation of rubber at elevated temperatures is many times greater than the rate of degradation at room temperature.
Important to consider when selecting the right seal material:
Rubber is a commonly used material for O-rings. The material's flexibility allows it to take many different shapes. And its diverse properties make it suitable for use in all kinds of applications. Proper selection of the rubber material is essential to prevent leakage or other possible damage. There are four factors that are very important in this: medium, pressure, temperature and time.
Proper assembly prevents O-ring damage. Therefore, always pay attention to the following aspects during assembly:
Using (assembly) grease makes fitting an O-ring easier in many cases. It reduces the friction between the O-ring and the parts it sits between. This makes it easier to fit the O-ring into the groove.
Lubrication also extends the life of the O-ring, as it forms a protective layer. A thin layer of mineral oil, grease, silicone oil or application fluid is often sufficient. Make sure that the type of rubber used is resistant to the grease used. For example, a VMQ (silicone) rubber is not compatible with silicone grease. Since both the rubber and the grease have the same structure, the oil can be absorbed by the O-ring and cause swelling and damage.
In any case, never glue an O-ring into the groove. An O-ring should move and set freely in the groove.
An O-ring is sometimes smaller or larger than the groove in which it is placed. Since rubber is an elastic material, this is not necessarily a problem. It may even be a deliberate choice because of the groove or availability of the O-ring. Quiet stretching or compression of the inner diameter (ID) can solve this and is also allowed. However, the stretch of the ID should never exceed 5%. Stretching should not exceed 3%. For both margins, this is the fitted condition.
During assembly, an O-ring may be stretched. The recommendation is to stretch the O-ring in a gentle manner to a maximum of 50%. Subsequently, do give the O-ring time to return to its original shape before putting the application into service. This depends on several factors, including the material, application and environmental influences (such as temperature). Furthermore, some materials are more elastic than others, an example of an elastic material is VMQ.
The wrong tool will cause assembly damage. Avoid sharp parts that can damage the O-ring. Use an O-ring mounting kit when installing or removing O-rings. This allows you to install and remove O-rings more easily, without causing damage. Also be careful not to stretch or twist the O-ring too much during installation.
Storage life is the maximum period of time, starting from the time of manufacture, that an elastomeric seal element, appropriately packaged, may be stored under specific conditions. After this period of time the O-ring is regarded as unserviceable for the purpose for which it was originally manufactured. The time of manufacture is the cure date for thermoset elastomers or the time of conversion into a finished product for the thermoplastic elastomers. Shelf life of elastomers when stored properly is especially determined by the specific compound.
The storage life of different elastomers differs according to ISO 2230, indicating an initial and an extension storage period for unassembled components.
Factors that can influence the storage life of O-rings:
Proper storage prevents damage to your O-ring. ERIKS recommends the following storage parameters:
Besides proper storage, it is also important to regularly check the function of fitted O-rings. And that they are cleaned intensively to maintain optimum function. Periodic maintenance of your machines should therefore include O-rings. If this does not happen, chances are that the O-rings within your application will have a shorter lifespan.
If you do clean your machines regularly, you need to be sure that the cleaning process is suitable for your O-rings. This is because not every rubber seal can withstand the chemicals found in cleaning agents. Machines and appliances are also often cleaned with steam cleaners. In those cases, too, you need to be sure that the steam does not damage the O-rings.
Selecting the right size O-ring, using an O-ring that suits the application and professional assembly usually prevents damage. Nevertheless, it can happen that the O-ring gets damaged. It is then important to know what causes it so that you can fix it in a targeted way.
O-rings are manufactured in accordance with a variety of standards for different countries. Standards say something about the size of the O-ring: internal diameter by cord thickness. For most O-rings from ERIKS, the standard AS568 applies. AS stands for 'Aerospace Standard'.
The ISO 3601-1 standard defines the quality requirements, such as tolerance of the material of an O-ring. Production and control of dimensions and imperfections also follow the ISO 3601-1 standard.
The O-ring is by far the most commonly used seal. Yet there are applications for which alternative seals are better suited, for example the X-ring:
Preventing early leakage in a dynamic, sliding (piston/rod sealing) application - An O-ring may twist in a sliding application, creating a possible leakage path. This twisting will not happen with an X-ring due to its stability.
Longer life in a dynamic application - An X-ring requires less contact pressure, has more contact surfaces and can be better supplied with grease than an O-ring.
Lower deformation force - The X-ring is good to use in applications where the materials or housing are not as strong, for example thin-walled plastic cylinders or housings. The housing must be strong enough to deform the seal and not the other way around.
Our present article aims to explain the concept of rubber o-rings. By reading the current entry, you will also learn about other technical seals operating on our Polish market.
When answering the above question, it is worth quoting the available definition of o-rings:
O-ring, also called O-ring.
A type of ring-shaped gasket.
Practical part: O-rings
So let’s go back to more useful information about o-rings than defining them.
As is commonly known, o-rings are the most popular technical seals.
In order to answer this question, we will break it down into the following components:
If we have already had contact with rubber O-rings, we know that their installation is one of the simplest activities. This is largely due to their flexibility, which is much appreciated nowadays.
A wide range of O-ring sizes
The wide availability of sizes, from any internal diameter to the cross-section (commonly known as the O-ring thickness), allows you to quickly find the right size, according to our needs.
Here it is also worth adding about the wide range of rubber compounds available, which allow to increase the service life of these basic technical seals, although we will write about this part in one of the next sections.
Due to the fact that we are Poles, the price does matter for us. Also in the case of O-rings valuations – the price has a positive effect on their demand. The cheapest gaskets can be purchased from PLN 0.39 (in words: thirty-nine groszy) per piece in retail sales. The prices at the POWER Rubber O-ring wholesaler are even lower! It is worth sending inquiries by e-mail: power@powerrubber.com
In this section, we will devote time to providing, or rather recalling the basic information, features related to rubber O-rings.
O-rings and their markings
There are several ways of marking O-rings on the market. One of the easiest for the user is the designation we use (POWER Rubber – the Editor reminds us).
What is the marking for o-rings?
The o-rings in POWER are marked as follows:
Inner Diameter to Thickness (be it, as we mentioned earlier, the section or the height).
Would it be nice to see an example of the marking for the o-ring on POWER Rubber?
Of course it is! Here is a simple example of an O-ring with an inner diameter of 5 and a height of 2. With us, such an O-ring has the following designation:
Here you can buy Rubber O-rings – manufacturer
Following the markings and the dimensioning of O-rings, the best source of knowledge on this subject is our dedicated technical article:
How to dimension O-rings We invite you to read
What other basic information about the O-ring should be known? What will be useful for most Users?
What we should pay attention to are the compounds of which the O-rings are available.
Here we have two options:
Rubber O-rings – Everything you need to know
The NBR O-ring is a technical seal made of synthetic rubber, officially acrylonitrile-butadiene rubber, intended for contact with hydraulic oils.
Temperature range: -20 ° C to + 90 ° C
Example of use: common places of the cheapest O-rings, e.g. seals for oil containers.
Attention! POWER Rubber does not recommend the use of NBR O-rings on the inside of motors. For this type of application, it is worth choosing Viton® o-rings – details can be found in the next section of this article.
An example of a fluorine blend which is a superior model of NBR blend. It has greater chemical resistance and a higher temperature range than NBR. Recommended for contact with mineral oils.
Temperature range: -14 ° C to + 250 ° C
Application example: Seals inside motors.
O-rings made of hydrated acrylonitrile-butadiene rubber, HNBR for short. The material is designed to work with oils and greases or ozone.
It is worth mentioning here that the material has a higher resistance, especially to abrasion, than NBR.
Temperature range: -21 ° C to + 150 ° C
Example of use: O-rings in contact with oil, requiring frequent disassembly.
EPDM O-rings are gaskets made of a mixture of ethylene-propylene-diene rubber. Seals made of this material are intended for operation in conditions related to weather, contact with water, exposed to solar radiation.
Temperature range: -41 ° C to + 125 ° C
Temperature range for the supernatant mixture:-50 ° C + 150 ° C
Example of use: sealing in steam boilers and compressors, or in contact with ozone.
Neoprene o-rings are one of the newest technologies on the market. They show a combination of EPDM and NBR blend features.
What does it mean?
This means that they can be exposed to UV radiation while maintaining their resistance to contact with oils.
Temperature range: -40 ° C to + 100 ° C
Resistant to contact with freon and ammonia.
O-rings made of a silicone compound have two markings:
VMQ O-rings with working environment:-55 ° C to + 225 ° C and
FVMQ flurosilicone O-rings, the scope of which is from -20 ° C and up to + 300 ° C
Silicone O-rings can have FDA certification, i.e. certification that allows the use of O-rings in the food industry.
Application example: food line seals with liquid application, silicone rubber seal for contact with drinking water.
The silicone oring is usually a FDA (Food and Drug Administration) certified seal – approval for the contact of rubber products with food
(in accordance with EU directives https://ec.europa.eu/food/)
O-rings made of FFKM or FFPM compound. Officially Perfluorinated rubber known as Kalrez®
FFKMrings are characterized by very high chemical resistance and a wide temperature range. Depending on the model, the temperature range is from -42 ° C to + 325 ° C
Basic models are marked as: 0040, 0090, 1050LF, 3018, 4079, 6221, 6375, 6380, 7075, 7090, 9100. You can read about everything here: Kalrez
PTFE o-rings are gaskets made of a rubber mixture most closely related to plastic due to the fact that they are made of Teflon®. This allows to obtain O-rings resistant to heat, cold, corrosive chemicals and to be used in places where a low coefficient of friction is required. Certified for contact with food.
Temperature range: -200 ° C to + 260 ° C
Compression and friction resistant.
These are O-rings covered with a Teflon layer to increase chemical resistance.
Temperature range: -60 ° C to 260 ° C
Example of use:
As you can see, we have presented the basic rubber compounds from which technical seals are produced. Now let’s ask ourselves:
Is there anything else he should know about seals?
We answer: Yes, there is one key topic worth mentioning, namely:
O-ring hardness is one of the most overlooked aspects of these flat seals. Many specialists forget about the consequences of incorrect selection of the correct hardness of O-rings.
O-rings, and more precisely their hardness, is determined on the Shore A scale.
Example?
O-ring 5×2 70 Shore A means: O-ring which has a reading of 70 on the Shore A scale (abbreviation: ShA).
The standard O-ring value is 70 ShA. It is a universal value. Below this value, O-rings or other seals are softer: e.g. 50 ShA, and above 70 ShA, e.g. O-rings 80ShA or O-rings 90ShA are harder variants.
And the whole thing: hardness affects the pressure resistance.
What does it mean?
This means that with increasing pressure in the equipment where the seal is to be installed, the seal should have a higher hardness.
Are these all the topics? Due to our vast knowledge, we will be happy to share information about colored O-rings.
Each of us gets used to the colors, be it the color of clothes or accessories in everyday life. We know that for outfits where we want to look elegant, we put on a white shirt, and for casual outings, we can allow ourselves a little deviation from this rule. Despite the hard rules, there are soft rules in life, especially about colors.
Best example:
Red is always faster
Why is it so accepted? – we will ask
This is because most sports cars in the previous years had just such a color, a color that at the same time made us aware of the vehicle brand.
Is it not possible to have a fast car nowadays, but a color other than red?
After a moment of reflection, each of us will answer: you can have a fast car in a different color. The current development of technology allows for all sorts of variety, including the possibility of choosing any color from the RAL palette (international color chart). It all depends on the cost.
The same is true for O-rings and other seals. In fact, we are able to offer any color of o-rings for any purpose, but it is worth considering whether we can use standard colors such as black or green for o-rings, which are the common color for each of the mixtures. Additional advantages are the lower target price due to the use of standard color.
So what is the purpose of using colored O-rings?
Here we can give you some examples from our experience in consulting technical seals.
In Poland, we have assumed that each color is a different material. As it was explained above, we can use seals of any color and its properties, although the Oldest Highlanders have the following applications remembered for each color of the o-rings. And so we can assign:
Black o-rings – any of the available mixtures can be hidden under this name. The most common are NBR rings or Viton® seals, but also EPDM O-rings.
In most common places where O-rings are used. At the battery sink, on the bike, or in basic functions, where rubber seals perform sealing functions.
The brown color for O-rings is the color used in rings made of a mixture of Viton®, FPM and FKM.
Red o-rings are commonly used silicone o-rings made of the VMQ compound.
Green O-rings are the color assigned to a mixture of EPDM and HNBR. O-rings for use in air conditioning.
The White O-rings are silicone rings. They come in two versions as standard: transparent and milk white. This color is also assigned to Teflon products, the abbreviation of which is often marked PTFE.
Blue o-rings are a rarer sight. However, such non-standard gaskets are also available in our offer.
Another, still rare, color for technical seals is Yellow. However, we also offer a Professional Approach here as a manufacturer of rubber products.
Advice for people looking for yellow O-rings: please contact us to agree on dimensions and use.
Even less common seals are those in silver, but the most important thing is to satisfy the customer.
Back then, we had the opportunity to deliver silver-colored gaskets.
It must be admitted that it is a very unusual color for rubber products. Much more related to steel alloys, therefore the use of this color was needed: Reducing the visibility of the use of O-rings in the outer layer of the device.
We are glad that another production company joined the group of satisfied customers of POWER Rubber.
However, there will always be a Person who will ask:
When we want to explain the differences between green and black O-rings, then we can help others:
As you can see, the colors of the O-rings are optional according to the customer’s needs. The manufacturer of rubber O-rings and products can advise on the use of appropriate mixtures. You can choose from the following types of rubber: NBR, FKM, FPM, EPDM, HNBR, Silikon or FFKM, and o-rings in a seamless cover, most often known as FEP o-rings.
Check here: norms and standards adopted for O-rings
Due to our experience and contact with customers, we will present the most common places of use for seals. Our extensive experience helps us in this, which consists not only in selling gaskets as a rubber shop with o-rings, but also as professionals who select technical seals for their machines and devices. We adjust rubber seals to the grooves we already have, but we also design grooves thanks to our knowledge of how to choose the O-ring for the groove. So let’s check where we can most often find our rubber gaskets with a cross-section of
Computer keyboard – an element of equipment in almost every house, apartment or office. Both acting as an external keyboard, but also as a keyboard that is included in our laptop. Of course, we are not talking about touch models here, but those with keys.
As it turns out, the rubber rings are just below the keys. It is worth noting that you should carefully disassemble the keyboard buttons to install the O-rings.
Here it is worth using a special tool for extracting the keys. It is easy to damage them. For this purpose:
And this is the correct O-ring assembly instruction for a computer keyboard.
What is the function of o-rings in the keyboard? We answer this simple question with the example of a short story:
Imagine that you come to your home after a hard day at work at your computer. A house with peace and quiet. Imagine that, right after leaving your stuff at the door, you take off your shoes and rush to the chair just to relax. You sit down and relax, and then suddenly: in all the silence, you hear a gentle tap on the keyboard. Initially soft sound, turns into a bothersome sound, and so the moments of relaxation passed.
What was missing in the given situation?
There are no O-rings for the keyboard.
As you can see in the story description above, the o-rings on the keyboard mute the sound of the keys. They increase the comfort of work by reducing the noise occurring when writing and using a laptop and a desktop computer. Thus, it is worth investing in for inner peace.
As it turns out, there are plenty of uses for these gaskets. This allows you to discover them in various places. And so we can meet them both in passenger cars, water vehicles and even airships.
Let us ask ourselves: what does this result from?
This is due to:
green
,red
,blue
or transparentFollowing this lead, our rubber seals can be found in many places of these vehicles and ships:
Our list is growing! Feel free to submit your ideas in the comments!
Who among us does not remember a situation when our faucet – whether it’s the kitchen faucet or the one in the bathroom – started to leak? Drop by drop, until complete damage and a steady stream of water.
What is the cause of a leak in the bathroom faucet?
What causes the seals on the washbasin faucet to leak?
Most often, the cause is damage to the battery seal.
To stop repairing a battery leak, just make the following action plan:
If, after our replacement, unfortunately, the battery continues to leak, we have two options:
For the second case, we have two solutions:
We invite you to take advantage of the opportunities available online in our online store with mail order sale. Usually with delivery by courier on the next working day.
Our high inventory levels allow us to provide express deliveries. They also allow wide access to metric and inch O-rings.
Where to buy rubber O-rings?> POWER Rubber <-
For the convenience of our customers, we have launched a stationary store in Pruszków – close to the capital of Poland Warsaw – at ul. Domaniewska 5A. The store is located close to the S8 A2 junction, Pruszków exit. It is equipped with the most common sizes and rubber products such as:
Best regards,
Team POWERRubber.com