So it is time to design your seal, but what will you choose for your sealing ring? There are multiple types of sealing rings, as well as complementary fittings that extend the life of your seal or improve its function. Deciding what is right for your application can be daunting, but it does not have to be.
In this guide, we’ll break down how to choose the right o-ring (or other sealing ring) to prolong the life of your seal and maximize functionality.
O-Ring
First and foremost, there is the tried and true o-ring, which also covers micro or miniature versions.
O-rings are incredibly versatile and offer a wide range of solutions for almost any application and industry. These sealing solutions can also be paired with complementary fittings that help them function better in your application.
Pros
- O-rings are incredibly versatile, they come in a large array of materials, colors, sizes, etc. and are very customizable.
- They are one of the most common sealing solutions, making them readily available in a wide range of standard sizes and materials along with customization options.
- Because they are so widely available, o-rings are often a very cost effective solution.
- If you are using o-rings in large quantities, you can purchase o-ring cord, which can be used to splice and vulcanize custom o-rings on site.
Cons
- O-rings can sometimes be problematic in dynamic applications (twisting, rolling, etc.).
- They have limited high pressure resistance, thus back-up rings may be needed depending on your application pressure conditions.
Applications
- Almost anything! O-rings are the go-to answer for a reason, but…
While o-rings are often a solution, they might not be the best solution for your application.
X-Ring (or Quad-Rings®)
X-rings (or quad-rings®) have a similar shape to o-rings, but their cross section forms an X, with four contact points. These are an alternative to o-rings and recommended for low speed reciprocating or oscillatory motions where they are twisting, rolling, or bunching.
Pros
- X-rings provide less friction than o-rings.
- They are interchangeable with o-ring sizes and gland design, making them an easy substitute.
- These o-ring alternatives are available in the same standard sizes and custom sizes as o-rings, while being readily available in USA AS568 standard sized NBR Buna-N and FKM.
Cons
- X-rings are not recommended for pressures >500 psi.
- As they are more specialized, x-rings may not be available in all compounds.
- They are also a little more expensive than standard o-rings.
Applications
- X-rings can be used anywhere an o-ring is used, but they are best utilized for reciprocating applications. For example, x-rings are often used effectively in syringes, where the reciprocating action of extracting and moving the liquid would cause an o-ring to twist.
U-Cup Lip Seals
U-cup lip seals are in the same general shape as an o-ring, but the cross section is a U. U-cups can function on their own, but they also have the unique option of being “loaded.” A loaded u-cup has an o-ring or spring energizer nestled into its internal groove.
U-cups are designed for dynamic reciprocating applications up to 1250 PSI, but loaded u-cups can handle up to 5,000 PSI.
Pros
- U-cups have longer sealing life than o-rings because they experience lower levels of friction.
- These seals are also available in non symmetrical rod and piston configurations, which are common applications that use u-cup seals.
- Polypaks® use an o-ring to provide sealing force at a low pressure.
- For non-standard existing grooves, we can design custom lip seals.
Cons
- Unfortunately, u-cups are more difficult to size than o- or x-rings.
- They are available in a limited array of materials and standard sizes.
- U-cup seals are a more expensive solution than other options.
Applications
U-cup seals have a more limited range of applications than o- or x-rings but they are highly suited for use in:
- Dynamic applications,
- Rod and piston seals,
- And hydraulic applications.
Glyd Rings®
Glyd Rings® combine the power of a Turcon based slipper seal and energizing o-ring to extend the life of an o-ring in dynamic, reciprocating applications. They use an interference fit that couples with the extra tightness of the o-ring to ensure a quality seal at lower pressure.
Pros
- Glyd Rings® are typically suitable for slow and fast reciprocating speeds running dry or lubricated.
- They can withstand pressures up to 3000 PSI in most applications.
- They operate at low friction with no stick-slip effect.
- Glyd Rings® are compatible with all o-ring materials.
- With a high wear resistance, they also offer minimal break out force.
Cons
- Glyd Rings® cannot be stretched more than 5% during installation.
- They are not recommended for oscillating applications.
Applications
- Glyd Rings® are most commonly used for piston seals in dynamic applications.
Back-up Rings
Back-up rings are installed alongside o-rings in the extrusion gap to protect the seal from extrusion at high pressures and temperatures. They are flat, split, spiral, or contoured to fit snugly like a washer. As they block the extrusion gap, they prevent the o-ring from extruding.
Back-up rings can prevent damage to the o-ring, resist extrusion, improve performance, and stop leaks. Ultimately, they improve the performance and life of your seal!
Pros
- Back-up rings are available in elastomeric and PTFE compounds.
- PTFE back-up rings can be solid, split, spiral, or custom to help make installation easier.
- PTFE back-up rings are readily available in standard sizes, such as AN6244, AN6246, MS27595, MS28774, MS28782, and MS28783.
- Elastomer back-up rings easily fit standard o-ring sizes.
Cons
- Due to the nature of having two o-rings in the groove, back-up rings require a wider gland to accommodate them.
- While very beneficial, they are an added expense.
- A standard PTFE size back-up ring will not work in a standard size static o-ring groove. It will prevent the hardware from assembling.
- Solid back-up rings do not stretch for installation.
Applications
- Back-up o-rings best work in high pressure applications where the original o-ring will be tested, such as in high pressure valves and hydraulic systems.
The Ultimate Way to Choose Your Sealing Solution
As you can see, o-rings are often a solution but are not always the solution for your application. Depending on the temperature, pressure, and dynamic nature of your application, another type of seal might be the solution for you.
Before you design your seal around an option that might not be optimal for your application, consider talking to a seal professional.
These experts can help you:
- Identify the unique trigger points in your seal that could cause a failure.
- Develop a custom or standard solution so you save your time, energy, and effort for other parts of the design.
- Feel secure that you are getting the most out of your seal.
- Avoid downtime, expensive redesigns, and hazardous messes.
You have a lot of tasks on your plate, and becoming a sealing expert does not have to be one of them. Our experts can quickly identify a viable solution for your application so that you don’t have to go back to the drawing board if your seal does not function properly.