O-ring seals and hydraulic fittings are popular in the hydraulic industry. However, to most people, it is just another type of hydraulic fitting. But it is more than that.
O-ring hydraulic fittings have specific advantages. For example, you can rely on such fittings for hydraulic applications that demand high pressures. Also, O-ring fittings are reliable in high-vibration systems as they are excellent shock absorbers.
All of this is possible primarily due to the O-ring design. Still, the design is not limited to the hydraulic industry. O-ring seals have other applications as well.
This begs the question, how do o-ring seals work, and what is the connection with hydraulic fittings? Read on, as we will be providing answers in this post.
What is an O-ring?
The definition of an O-ring, by Oxford Languages, is a “gasket or seal in the form of a ring with a circular cross-section.” This type of seal design is also known as a toric joint or packing. It is useful in dynamic or static applications.
The adoption of O-ring seals has a delicate history, which traces back to World War II. At the time, the US government classified the patent by Niels Christensen, a US-based Danish-born machinist, as a critical war-related item.
Due to their high performance in dynamic applications, it was not long before O-ring seals became commonplace in the hydraulic industry. The most popular type of O-ring application in the hydraulic industry is the O-ring Face Seal (ORFS).
The standard design for O-ring seals is circular, hence their name. However, other shapes, such as squares and Xs, are sometimes utilized.
Materials for O-ring construction vary widely depending on the intended use. In addition, they can be manufactured using different methods. Extruding, compression molding, injection molding, transfer molding, and machining are just a few.
How Do O-Ring Seals Work?
The O-ring seal design has gained popularity because it is easy to use and cost-effective. From pumps and valves to cylinders and connections, O-rings work to seal up leaks. How it works is simple.
One of the main reasons an O-ring is a reliable seal is that it can easily return to its original form after cross-section compression.
The initial compression of an O-ring seal is made by joining a circular cross-section into an O-ring groove. The dimension of the cross-section and its durometer determine the amount of force required to compress the O Ring.
In hydraulic system applications, O-ring face seals typically feature a straight thread and a machined groove on the male fitting’s face for the O-ring. Leak-proof connections are achieved by compressing this O-ring on the female fitting’s flat face.
As a result, the primary use of O-ring fittings in the hydraulic industry is to seal off fluid passages. This prevents leaks that can affect the system’s efficiency.
What O-Rings Come From?
As mentioned earlier, O-rings are manufactured using different materials. Some common materials used are polyurethane, nitrile rubber, fluorocarbon, silicone, and neoprene.
However, O-ring hydraulic fittings are majorly made from metal – carbon steel or stainless steel – and rubber. In particular, metal performs better in different conditions.
Consequently, choosing the right O-ring material and type is vital if you want it to do its job.
SAE Aerospace Standard With O Ring
O-ring seals come in different standard sizes. These standard sizes depend on different industry standards, including the SAE Aerospace Standard, British Standard, JASO Standard, and JIS Standard.
The SAE Aerospace Standard is the United States standard established by SAE International. The standard defines the cross-sections, diameters, dash numbers, and tolerances of O-rings.
One of the earliest applications of O-ring seals in the US was in the aerospace industry, hence the development of this standard. It is an inch-based size standard, which differs from the metric-based standard used in other parts of the world.
You would often see O-ring designations like AS568A, AS568B, and AS568C on the market. These are all SAE Aerospace Standard sizes with minimal differences.
O-Ring Seal Types in Hydraulic Fitting
There are two main types of O-ring seals in hydraulic fittings – the O-ring Face Seals (ORFS) and O-Ring Boss (ORB).
Flat sealing surfaces with an integrated seal distinguish O-ring face seal fittings. They are designed to connect to flanged tubing or hose connections. The secured seal prevents leakage, and the flat sealing surfaces lessen the likelihood of over-torquing.
On the other hand, O-ring Boss fittings are more or less an O-ring version of the 370 JIC straight thread Flare. Both fittings are interchangeable, as the ORB fittings typically feature an SAE straight thread.
However, ORB is superior in leak protection since it uses an O-ring rather than a metal-to-metal flare for its seal.
Final Notes
Now, you know the relationship between O-ring seals and hydraulic fittings. Simply put, O-rings seals help maintain a leak-proof hydraulic system in high-pressure and high-vibration applications. Wondering where you can get certified O-ring seals at affordable prices? Check out the different types of O-ring seals we have at Sinopulse today!