The O-ring is a type of sealing device. It has the shape of a ring, and it looks like an oval or tube divided into two portions. The o-rings are used in many applications including machine parts, electronic devices, the automotive industry and power plants among others.
These seals are mostly used as vibration isolators and gas seals due to their flexibility and good durability. They can also be found as edge sealings as they tend to resist heat, wear as well as chemicals such as acids and alkalis for longer periods. One other common use is to produce pressure barriers on steam turbines. An important application for this seal would be on pump ships where the seal is used to prevent oil spillage.
O-ring Design
The O-ring has some advantages, for example, an O ring is very flexible, durable and can resist wear as well as chemicals. One disadvantage of this sort of seal would be the fact that their use depends on the size. This means that you cannot find o rings in all sizes. However, if you need a specific size, you can request samples and test the effectiveness of the seal.
Other than that, o rings do not come cheap and their purchase could be well thought about. You need to consider whether you may find enough use for them so as to justify the cost.
How do O Rings Work?
They’re named for their shape, which is essentially a classic doughnut or torus form and simply refers to the creation of a more leak-proof seal between two other components. With the objective of preventing the undesirable emission of gases or liquids, they’re effectively a sort of gasket, however, rather than using o-rings in high-pressure situations where a normal cork, paper, or rubber gasket would be prone to failure, they’re used in lower pressure settings.
Simply put, an o-ring seal works by sitting in a groove or channel between two surfaces/components that may be mated or pushed together. The o-ring, which is usually made of some type of elastomer, sits in the gap between these two components and gets compressed to assist create a good seal. Some people may view an O ring as a life-saving component.
When the internal pressure is increased on this junction, the o-ring inside its groove gets deformed to a greater extent, which can improve sealing force up to a point. However, beyond a certain pressure or under more dynamic workloads, this might lead to seal failure. It’s critical to get the right balance between o-ring material, size, and operational environment in order to meet your needs.
Static and Dynamic Applications for O Rings
O-rings are a staple of any sort of machinery that depends on a tight seal, so it’s important to understand the difference between both static and dynamic applications.
In static applications, there is no relative movement between parts, thus a static o ring is used. When an o ring is used in static applications, the o-ring may be compressed into its groove/channel as far as it can go. If you were to use an o-ring in an application where there is moving or sliding between parts (such as within a pump with hydraulic fluids), then the seal might not hold up for very long due to issues like fatigue and other forms of wear and tear.
On the other hand, when using a dynamic o ring, the o-ring is placed in a pressurized environment where it may be stretched and stressed in some capacity. If you were to use an o-ring with a low durometer in this setting, you’d find that it would fail at a faster rate due to things like viscoelasticity and tear propagation. Having the right chemical compatibility of the O ring is crucial in this situation.
O Rings for Hydraulic Fluids
Take for example a hydraulic cylinder with an O ring seal. If the piston remains stationary within the cylinder then any leakage past the O ring may not vary from time to time, although after long periods of work or high operating pressures, there might eventually be some leak down due to creep.
If this piston is pushed into the cylinder, however, then it’s going to place more stress on both the cylinder and piston. In turn, there might be a greater amount of leakage past the O ring if a lower durometer was used in the seal. This is because it would have been too soft to withstand radial forces from external pressure, particularly for dynamic applications where high pressures are involved.
Another possible advantage of using an o-ring seal over other types of gaskets material is that it may generally add another level of redundancy into your system or application. By having two seals in play, you’re increasing the chances that one may not fail during operation. If one were to, then at least there’s another still intact which could hold up to normal operating conditions until service could be reached by qualified personnel.
O Ring Material
The following is a brief infographic on the types of o-rings available and their general applications. As for material selection, it’s up to you to consider both cost and performance, you can’t simply choose rubber or nitrile o rings for every application because they’re not all created equal in terms of chemical compatibility, heat resistance, compression set, abrasion resistance, etc. Extreme pressures may also affect your decision-making process when selecting an o-ring seal.
Once you’ve established basic use cases for each type of o ring, then it becomes easier to narrow down your choices based on industry standards (i.e. FDA) as well as applicable standards like ANSI/ASME/ISO which establish dimensions for certain parts like valves. If you intend to use a material that isn’t compatible with the o-ring that you’re trying to choose, then there’s a chance that you could ruin the machine entirely if these pieces aren’t fit together properly, so make sure to check all data sheets and physical properties before choosing any materials for your application.
O Ring Materials
There are many different o-ring materials in common use, and choosing the right kind for the task at hand is critical if you want it to perform consistently over time. In this part, we’ll examine some of the most frequent o-ring material types.
Silicone O Rings
Silicone o rings are the gold standard for many hydraulic applications, and they’re compatible with mineral oil, vegetable oil (such as dimethylpolysiloxane). They also offer good compression set resistance at medium to high temperatures, which means that you can expect excellent service life from them.
O-rings made of high purity silicone-like PVMQ or medical-grade silicone can be used in a variety of industrial applications, including food and beverage. However, it’s important to note that they’re not compatible with mineral oil since they may swell, but this could only affect performance when the o-ring is made from high hardness silicones.
Rubber O Rings
These are very common o-ring materials, particularly nitrile rubber (NBR). Properties for rubber o rings include resistance to compression set, ozone aging, thermal aging and cracking. They’re not as heat resistant as silicone, however, which may result in longer service life for applications that require continuous exposure to hot mediums.
Nitrile O Rings
Nitrile o rings are compatible with mineral oil and water, so they can be used for many different sealing applications. Nitrile is also pretty resilient to some chemicals like oils, greases, gasoline, pesticides and some acids.
O Ring Cross-Section
The cross-section of an O ring may generally determine how much force or load can be safely applied before it begins to leak. The greater the width of this X shape, the more reliable it may be under pressure because it may have been able to stretch further during operation without tearing from lateral forces. This is great for applications where load fluctuates as well as those which are dynamic in nature over time or space.
When choosing different metric o rings, the cross-section is usually in the form of a square, 90° circle, triangle (like in an equilateral triangle), or less frequently an X.
O Rings for Inner And Outer Walls
There are other types of O rings that can be used for inner or outer walls, depending on your application. For example, you might consider using an elastomeric seal or lip O-ring for external applications where it has the most exposure to the outside world over time. By contrast, an extruded O ring might work better when it’s placed inside a cylinder with high pressure moving through it because it may have been designed to handle these situations with a reduced risk of failure.
As with most things in life, there’s no one size fits all solution for every use case out there. Make sure that you read up on product datasheets from manufacturers before making any final decisions or purchases so that you don’t run into problems with service down the road.
This is also why it’s important to use custom o rings for your application instead of off-the-shelf parts. Engineers and researchers may often request that these be manufactured with specific dimensions, thicknesses, durometer ratings, chemicals, or other pertinent properties that the average consumer might not even know about.
Shapes for O Ring Seals
The shape and o ring design of your o rings may likely be the most important criteria for anyone desiring to find a new solution. There are plenty of shapes available, and you may get lucky by finding an ideal one off the shelf. However, many unique designs require special tooling or moulding services which can eat into profits or make custom products prohibitively expensive.
Reliable Seal Square Rings
When you see this shape, you could know that it’s designed to handle radial and axial loads, so they’re pretty versatile overall. Square rings are the most common type used in industry.
T Shaped O Ring Seals
T-shaped o rings can be either round or square and perform better than standard O rings under heavy loads like those found on conveyor belts.
Rectangular Rings
These can support lateral as well as a radial force for both static and dynamic applications. You may be able to find both static o rings and dynamic o rings in a triangle shape.
Round (or circular) O Ring Seals
This is the simplest shape and can be useful for applications where a fitting needs to have a tight seal. When you see a round O ring, it’s actually a rectangle with rounded edges.
What Causes an O Ring Failure?
O rings fail when they’re too small for their application. This can happen when someone uses an off-the-shelf o ring that isn’t designed to handle the maximum load or high pressure that might be applied in use. If you try to save a few bucks by cutting corners, you could end up paying more over time with many failures and malfunctions. O rings also frequently fail because of miscommunication between manufacturer and customer about the intended function and properties of these components.
Many problems in production can be avoided or at least mitigated by hiring experts. They’ll have all the tools, experience and expertise required to help you find better solutions than what your local machine shop might offer.
Goods can be replaced, but it’s much better to come up with a comprehensive solution that reduces failures and saves money over the long term. Before taking any other step, make sure you talk to experts first about what to expect from your custom O rings and how you could go about testing them for performance. This is one of those times where doing things right the first time around may save tons of headaches down the road so don’t wait too long before starting these discussions.
