Apr. 07, 2025
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Hydraulic hose fittings are used to connect hydraulic hoses, tubes, and pipes to pumps, valves, cylinders and other parts of the hydraulic system. So what happens if you pick a wrong fitting? Unfortunately, something as small as a fitting can quickly decrease the efficiency of the whole hydraulic system and even pose a major safety issue. If you get too overwhelmed with the shapes, materials, threading, and sealing options to choose from, save your time, and check our guide on how to pick the right fitting best for your job.
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For many of us, the first time we have to decide on which type of hydraulic hose fitting to use is during the hose assembly. Crimping is the most popular method assembling the hydraulic hose. It is always a good idea to ask yourself five major questions about S.T.A.M.P. (size, temperature, application, materials/media, and pressure) before you get started with any hose assembly. Once the specifications have been defined, the hose assembly technician can get to work. The process can vary by crimper model, but typically the technician marks the insertion depth on the hose, applies lubricant to the fitting stem, pushes it inside the end of the hose, and inserts it into the crimper die. Finally, the technician secures the fitting permanently onto the hose by activating the crimper’s power unit to apply pressure. The hose assembly technician would be able to assist you in finding the best fitting and assist you with any questions.
Hoses, as well as fittings, come in many different types and materials. Importantly, the material used for the hydraulic hose fitting defines its properties. Most common fittings are made of plastic, steel, stainless steel, or brass.
Plastic fittings generally are considered more resistant to the corrosion but are weaker and less durable. Therefore, they are the least popular choice when it comes to hydraulic applications despite their low price. Due to the high-pressure ratings, metal fittings are a better fit.
Steel fittings come as a mix of iron with some other metals to make them more durable and improve the resistance to the heat. For example, carbon steel fittings made of the mixture of iron and carbon can withstand the temperatures from -65°F to 500°F.
Stainless steel fittings are used when the temperature range required for the job is -425°F to °F. They are an excellent choice for highly corrosive environments. Usually, they are rated up to 10,000 psi. Some of the stainless steel fittings with special designs can be rated up to 20,000 psi. However, the high price makes them less affordable, so other alternatives are usually considered.
Brass fittings are less strong and durable than stainless steel. They can provide a leak-free operation and meet SAE, ISO, DIN, DOT, and JIS standards. Brass fittings temperature range is -65°F to 400°F. They accommodate pressure up to psi, but lower pressure ranges are usually recommended.
Aluminum fittings are significantly lighter than steel and are corrosion-resistant. Due to their low weight, they are commonly used in the automotive industry.
The two main categories include:
Depending on the shape of the hydraulic fitting, they classified into:
Plugs
Unions
Elbows
Crosses
The Security of the Connection Including Sealing Type
Be careful if you use NPT (National Pipe Taper) pipe threads fittings. Even though it sounds easy to fix the leak with this type of fitting by tightening the connection, you increase the risk of getting a crack in the fitting. This is more likely to happen with repeated remakes (loosening and re-tightening the fitting). Use O-rings with the elastomeric seals such as DIN , SAE J to prevent the risk of unexpected leaks and switch to an untapered JIC fitting. If you use elastomeric seals, keep your temperature conditions within the recommended range. Unfortunately, even a single over-temperature event can damage all the seals and cause multiple leaks.
Pressure Rating
With the modernization of your equipment usually comes higher operating pressure. To address high operating pressure, more and more of our customers prefer to use O-ring seals. They are more resistant to cracks. O-ring seals also prevent the risk of over-torqueing and leakage. In terms of material stainless steel hose fittings have the highest pressure rating.
Vibration
Vibration affects hydraulic plumbing and can shift the torque and cause fatigue. Remember to inspect areas with high vibration for leaks and damage.
Temperature
The temperature range for tube fittings is defined by three factors: material, plating, and seal if used. For leak-free operation use O-ring seals if the operating temperature allows you. Check the table below for the temperature range for the most common fitting and seal materials.There are special options available if you need hydraulic hoses and fittings to work under extreme temperature conditions. Contact us to learn more.
Chemical Compatibility and Operating Fluid
A rule of thumb says that hose inner tube, cover, fittings and O-rings should be chemically compatible with each other. Pay extra caution when selecting a hose for gaseous applications, especially if there is a chance of permeation in order to avoid explosions, fires, and exposition to the toxic fumes. Always check with the manufacturer if the components of your hydraulic system are chemically compatible. Additionally, pay close attention to your seal being compatible with the type of hydraulic fluid used in a system. The Guide for Chemical Resistance Information from Parker can be found here.
Availability
It all goes great until you need a replacement fitting and the lead time is a couple of weeks, and you need it now. Usually, most NPT and JIC fittings are widely available and have many configurations to choose from. Hence, choose the fittings that are easier to find or stock up if you use any specific fitting with longer lead times.
Both SAE and ISO do not recommend mixing hose end fittings and hoses from different manufacturers. There are plenty of good reasons for this, but best reason to not do it is safety. Mixing a fitting from one manufacturer with another manufacturer’s hose could result in a failure or rupture at the crimp because the two products are just not compatible. The manner which the fitting is secured to the hose and the allowable tolerance for the hose crimp may differ. For example, the range for Parker’s allowable tolerance for a crimp can be as little as 0.02 inches and the range may not overlap with the other manufacturer’s product. Further, a manufacturer will not take responsibility for a failure. Therefore, if you intermix your hose and fitting from two different manufacturers, you should seriously reconsider.
It is important to remember to inspect your hoses and fittings for a secure connection and any leaks every couple of months. Even new fitting, if it was selected wrong, can cause problems. Although picking a hydraulic fitting sometimes feels overwhelming, if you follow our simple guide, it should not be a problem anymore.
If you want to learn more about selecting hydraulic fittings, contact us to speak with a fluid connector specialist.
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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.
Contact us to discuss your requirements of Hydraulic Hose Adapters. Our experienced sales team can help you identify the options that best suit your needs.
Featured content: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:
Quick links
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.
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.
Pressure – Check the maximum rated pressure needed. Components used with hydraulic tools are classified as high-pressure and typically rated for either or 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.
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.
First, look at the fitting from the side view to see if the thread is tapered or parallel. A tapered thread will get smaller in diameter towards the end. If you cannot tell this immediately, try using vernier calipers. The next thing you can do is check the thread pitch with a pitch gauge.
Finally, determine the nominal size by measuring the outside diameter or checking against a thread profile gauge. If you have a selection of known threaded fittings handy, checking to see how well these connect can also help.
A hydraulic coupler makes quick connections to your hydraulic system and typically includes male and female halves which can be connected by hand. For example, the C-Series Coupler is the standard on most Enerpac pumps and cylinders up to 10,000 psi (700 bar). You can buy them as a complete set or individually as male and female halves. Where multiple connections are needed, such as with split flow and other controlled lifting pumps, hydraulic couplers should be quick and easy to make a secure connection.
Common sizes of this type are ¼” – for use with small hydraulic cylinders and pumps. Some larger tools and medium-duty applications will most likely need a larger 3/8” coupler. Whichever you choose, the maximum flow capacity will be around 462 in3/min.
These are available in cone or flat face types. The cone type is less prone to back pressure than other types such as ball-style couplers. On the downside, they leak a little oil when disconnecting. The alternative solution is the more expensive flat face type click fit type, which is very much leak free.
These high-flow couplers feature a quick push to connect operation and also prevent spillage of hydraulic fluid. Although these are a simple push-fit design, users should not be concerned about their safety as they are recognized by the Hydraulic Tool Manufacturers Association for safety and performance. F-Series Flush Face couplers from Enerpac are 3/8” and allow a generous flow capacity of in3/min (40 l/min).
As the name implies, these are for use with hydraulic torque wrenches such as the Enerpac S-, W-, RSL-, DSX-, and HMT-Series. These are used with THQ-Series twin torque wrench hoses. They are usually ¼” unlike the large 3/8” couplers used for hydraulic cylinders and pumps.
Hydraulic adapter fittings are used to connect hydraulic hoses, tubes, and pipes of different sizes and types. Example uses are to connect different thread sizes or connector types, for example, from male to female threads or from NPT (National Pipe Thread) threads to SAE #4 (Society of Automotive Engineers).
A fixed coupling simply attaches two same-sized threaded components together using female threads. A hexagonal section in the center enables the coupling to be held while attaching.
Other fixed fittings for more permanent connections. Used for changing flow direction or adding an extra connection.
Dust caps for hydraulic couplers prevent dirt from entering the system which could cause the coupler to fail, or lead to premature wear of internal components. Types include push-fit plastic dust caps, (sometimes with a 2-in-1 configuration for both male and female haves), and also metal screw-on caps. Both types include a retaining strap or chain to keep it attached to the tool or hose fitting.
Considering the high pressures involved when using hydraulic tools, the risks of injury caused by projectile parts and under-skin hydraulic fluid injections are high if couplers are incorrectly used. A coupler bleed tool like the CT604 relieves hydraulic back pressure by safely bleeding the high-flow hydraulic coupler. The CT-604 is compatible with C Series couplers and works by slow hand rotation of the knob. This applies a force onto the ball or cone inside the coupler. Once the ball or cone is pushed from its seat the pressure is relieved. Read more about safe depressurization in this blog post.
If you are looking for hydraulic fittings to use with Enerpac tools you can get these from your nearest Enerpac distributor. If you’re based in the United States, you can buy hydraulic fittings online directly from Enerpac.
In summary, a ‘good’ hydraulic fitting is one that matches the application, with the most important selection criteria being operating pressure, thread/connector compatibility, flow rate, and material compatibility. If you select fittings and couplers from the same manufacturer or distributor that you got your hydraulic tools from this should be easier than shopping around.
Most importantly, to ensure safety, you must install and disassemble your fittings correctly, which means using the specified torque for threaded fittings and always depressurizing the system before removing any coupler or fitting.
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