How to Select the Right Hydraulic Fittings and Couplers

While hydraulic fittings and couplers may not be the most attention-grabbing products, they play a crucial role in maintaining the safety and efficiency of your hydraulic system. Choosing the right hydraulic fitting or coupler is vital, and with so many types available, it can be a challenge to identify the best fitting for your specific application

Hydraulic fittings are available in hundreds of configurations – in fact, there are too many types to cover in a single article. That’s why for the purposes of this blog post, we will focus on those most relevant to users of hydraulic tools; such as cylinders, cutters, and torque wrenches. We will look at the different types of fittings and couplers, what can go wrong, and things to consider when making your selection.

What are hydraulic fittings?

If you’re new to hydraulics, let’s define what we mean by a fitting. Simply put, hydraulic fittings connect hoses and pipes to other system components such as tools, valves, and pumps. If you use Enerpac hydraulic tools the most common types to be aware of are:

What makes a good hydraulic fitting?

Essentially, a good hydraulic fitting is one that’s appropriate for the specific application. This means choosing the right pressure rating, material, diameter, thread/connection type, and size.

A fitting should be easy to install and remove and should not require specialized tools or excessive force. If you’re choosing a coupler and your main priorities are a quick connection with minimal oil spillage it may be worthwhile paying extra for a flat face push-fit coupler.

Also, if the coupler doesn’t come supplied with a protective dust cap be sure to get one – especially if you work at dirty industrial/construction job sites.

What makes hydraulic fittings and couplers fail?

When used correctly, hydraulic fittings and couplers are unlikely to fail, but its worth taking extra care to avoid the following:

Improper installation: A poorly installed fitting can lead to leaks or even the complete failure of a whole hydraulic system. Over-tightening fittings beyond the recommended torque can cause damage to the fitting, leading to leaks. Don’t be tempted to use tools for couplers designed to be tightened by hand. In addition, if a coupler is not properly aligned with the hydraulic fitting this may also create stress and a risk of fatigue or damage.

Contamination: If dirt, dust, or other contaminants get into the hydraulic fluid, they can clog the coupler and prevent it from functioning properly. This is more of a potential issue for tool users out in the field and less so for factory-based hydraulic work-holding situations.

Impact damage: Physical damage to a coupler can cause it to become deformed, which can prevent it from operating correctly.

Vibration: Vibration over extended periods can cause fittings to loosen over time, leading to leaks or failure. Vibration can be caused by hydraulic pumps and cavitation within the hydraulic fluid.

Over-pressurization: If the pressure in the hydraulic system rises higher than what the coupler is designed to handle this may cause it to fail.

Corrosion: Over time, in harsh conditions, hydraulic fittings can corrode due to exposure to moisture, chemicals, or other environmental factors. This has the potential to weaken the fittings which could lead to leakage or failure.

Fatigue: Repeated cycles of pressure and stress can cause fatigue in the fittings, leading to cracks and failure.

Wear and tear: Over time, fittings and couplers that include seals may become worn and therefore lose their ability to maintain a tight seal.

Selecting Hydraulic Fittings: 5 Key Considerations 

Pressure – Check the maximum rated pressure needed. Components used with hydraulic tools are classified as high-pressure and typically rated for either 5000 or 10000 psi (350 or 700 bar). The fittings supplier should make this clear in their catalogs or on their website.

Flow Rate – The type and size of the tool will determine the flow needed. If you need a high-flow coupler, consider the Enerpac C (cone) type or F (flat face) type. These allow for up to 4 times more flow than many standard couplers.

Thread Type – These vary by region throughout the world, so make sure your fittings, tools, and hoses are compatible. If they’re not, an adapter or reducer may be available to solve the issue. Buying your hydraulic tools and hose connectors from a single manufacturer will help to avoid incompatibility issues.

Coupler Connection Type – Choose between the common type with a threaded sleeve to hand tighten, and “push to fit” flat face types that save time and minimize oil loss and spillage.

Material – The material of the fitting can influence its pressure rating and ability to withstand harsh and corrosive working environments. Also, bear in mind it’s not good practice to mix some metal types because of potential galvanic corrosion. 

What are the standard sizes?

Hydraulic fittings are available in many different sizes. However, if you are using Enerpac hydraulic tools the standard fittings and couplers will most likely be ¼”  or 3/8”, with NPTF or SAE thread types.

Identifying Hydraulic Fittings

A visual check of the type and size of the fitting is the first obvious step. However, when it comes to threads, at first glance these can all look the same. Fortunately, there are ways you can narrow down the possibilities. See more on the Parker blog here.