The 4 Seal Types of Hydraulic Fittings

The 4 Seal Types of Hydraulic Fittings

In the world of industrial hydraulics, fittings are paramount. The system operates because they’re the key to keeping high-pressure fluids connected. And if you’ve ever seen a hydraulic system leak, you know exactly how unsafe that can be.

4 seal types of hydraulic fittings
4 seal types of hydraulic fittings

It pays to become familiar with the four seal types of hydraulic fittings. By doing so, you will ensure that your hydraulic system is as safe and efficient as possible. This guide will break down each seal type , help you choose the right hydraulic fittings you need and provide tips for maintaining your application’s performance.

So if you want to ensure your hydraulic system is airtight, come with us!

4 seal types of hydraulic fittings

Seals are essential components used to connect two pieces of equipment to create an airtight connection between them. Think of it like a zipper. Just like a zipper seals off your jacket against the cold wind outside, a seal will keep fluid and gasses within specific parameters.

As we all know, hydraulic system is a complete closed system with some specific pressure, seals must withstand the hydraulic fluid pressure against leakage, it highly relates to the temperature, pressure, and vibration of the system.

That’s why it’s essential to understand the different types of seals available in hydraulics before you get started. And we’ll cover that in the preceding section!

Tapered thread (NPT, and BSPT)

Tapered Seal Type hydraulic fitting( 60° cone seal combined)

One of the most common types of hydraulic fittings is the tapered thread. It’s also called a National Pipe Thread (NPT) in the US or British Standard Pipe Thread (BSPT) outside the US. These fittings have a tapered thread that compresses when tightened, creating a leak-proof seal between two surfaces.

Picture a nut and bolt to understand better how this works. When you tighten the bolt, you compress it on a surface to create a secure seal. The same principle applies to tapered thread fittings—when tightened, they compress and push against each other to form a tight seal.

Tapered thread fittings are easy to install with hand tools and great for medium-pressure applications like pumps, valves, and filters. They come in different sizes, and you can use them with virtually any fluid type. Just make sure that you check what size and thread type are suitable for your system—it’s essential for ensuring an effective connection!

Metal Seal Connector (60° cone, JIC 37° flare)

37° flare seal JIC fitting, Multiseal (sphere interface seal) fittings, 60° cone hydraulic fittings, 45° cone hydraulic fittings

Metal seals are the most common type of seal used in hydraulic fittings, and these connectors typically use either a 60° cone or a JIC 37° flare fitting.

  • 60° Cone

A 60° Cone seal connector is ideal for high-pressure applications, as it’s very secure and can handle up to 10,000 psi of pressure. It comprises two pieces: a male end and a female end. The metal connection won’t rust like other fittings, allowing you to easily connect flanges while maintaining a tight seal.

  • JIC 37° Flare Fitting

The JIC 37° flare fitting comprises stainless or zinc-plated steel for maximum corrosion resistance. Unlike the 60° Cone seal connector, these fittings can handle up to 15,000 psi of pressure – perfect for industrial settings that require additional strength and durability. The sealing cone has several ridges that create an airtight seal between the two connected parts, providing the ultimate protection against leaks.

Soft Seal Connector(O-ring)

O-Ring Flat Seat hydraulic fittings

O-rings, or Soft seal connectors, are a type of connector that uses an elastomeric seal to join two cylinders. These seal types of hydraulic fittings  are in the shape of the letter ‘O’, hence their name. O-rings are common seals used in hydraulic systems because they provide a tight, secure fit and long-term performance.


The benefits of using O-ring seals for hydraulic fittings include the following:

  • Easy assembly and disassembly: Since O-ring seals don’t require any lubricant or sealant to fit together, you can assemble or disassemble them easily.
  • Low maintenance costs: Because the O-rings require little to no maintenance, you can use them for extended periods without replacement.
  • Improved performance: By allowing oil to move freely through the system, these seals improve the overall functionality of your applications and reduce downtime.


Making them sit correctly in their grooves when installing O-rings is vital to ensure a tight and secure fit. In addition, you should also be sure that there is no dirt or debris on the sealing surfaces, as this could damage the seal and cause it to malfunction. Finally, check for leaks after installation by testing air and liquid pressure.

Compression Joint Fitting (inch compression)

You can use compression joints in hydraulics and pneumatic systems, and they typically have a threaded body and hardware that provides an air-tight seal. You made the seal when a nut tightened onto the body of the fitting compresses the insert against the tubing.

Compression joints are great for connections that handle higher temperatures or pressures than regular flare fittings. But here’s the thing: when using joint compression fittings, you don’t want to overtighten or reuse them; you can use them only once.

If you do decide to use these types of fittings, here’s what you should know:

  1. Make sure you select the correct type of fitting for your material tubing; there are various materials (such as copper and stainless steel) that require different types of fittings
  2. Determine if you will need any special tools; certain circumstances may require special tools like pliers or adjustable wrenches.
  3. Applying lube ensures proper installation by helping create a snug fit and preventing galling while tightening it.
  4. Don’t over-tighten – if you over-tighten a compression joint, it could lead to threads stripping or even the fitting splitting apart, so be extra careful not to make it too tight!

Banjo fittings and 24° cone o-ring fitting

Banjo fittings
24° cone seal hydraulic fitting with O-Ring seal

Why You Should Choose High-Quality Seal Types of Hydraulic Fittings

When it comes to hydraulic fittings, seals are everything. That’s because they help prevent leaks and protect the internal components of a hydraulic system from any possible contaminants.

But what makes one seal better than another? Let’s take a look at the benefits of a quality seal.


Quality seals are durable materials that can withstand pressure and temperature changes, making them less likely to wear out. This means you can use them repeatedly with minimal maintenance required.

Tight Seals

A quality seal also provides a tight fit that prevents outside contaminants from entering the system, keeping your equipment running smoothly. And because the seal is tight, you won’t have any leakage or loss of pressure in the system, which can have costly consequences if left unchecked.

Long-Life Performance

One of the most significant benefits of a quality seal is its long-life performance: you don’t have to replace your seals as often as you would with inferior quality products. This provides greater cost efficiency and peace of mind that your equipment will run smoothly for years.


There are four unique seal types of hydraulic fittings available. They all can do the job, but each type has unique features and benefits. Whether you need an O-ring, U-cup, V-ring, or flat face seal, it’s essential to know their differences.

For more information on determining the correct size and shape of seal for your hydraulic fitting and to take the guesswork out of installation and maintenance, consult us. With our help, you  are rest assured that your system is safe, reliable, and functioning correctly.


Table of Contents

instant chat



Welcome to scan name's whatsapp QR code!
I am glad to serve you!

Send us Message

Please feel free to contact us.