How To Identify Hydraulic Hose Fittings

When you have a damaged or worn-out hydraulic hose fitting, accurate hydraulic hose fitting identification is crucial for replacement. However, this can be a daunting task, as hydraulic hose fittings are available in a wide range of materials, sizes, connection ports, shapes, thread types, sealing methods, and configurations; it’s often difficult to notice the above variations at first glance, as most hose fittings appear very much alike.

Yet, when it comes to upgrading and repairing hydraulic hose components, every detail matters. Even a one-millimetre error in fitting size measurement can compromise the integrity of an entire hydraulic system, leading to fluid leakages, equipment damage, workplace accidents, and environmental pollution.

Nevertheless, identifying the best hose fitting for a specific application is easy with the right information and guidelines. This article details everything you need to know about identifying fittings for hydraulic hose assemblies.

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Understanding Hydraulic Hose Fittings

Hydraulic hose fittings are accessories used to connect hydraulic hoses to other elements of a hydraulic system, such as valves, actuators, and pumps. On one end, the hydraulic fittings feature a hose port that can be inserted into a hydraulic hose. Their other end is threaded, with either female or male threads, and is used to connect to other fittings or hydraulic system components.

In essence, hydraulic hose fittings are integral components that help contain and regulate fluid flow within a hydraulic system, preventing leaks and maintaining system pressure. They help ensure the smooth and safe operation of hydraulic systems. They also facilitate faster repairs and easier maintenance of hydraulic hose assemblies, consequently reducing downtime and increasing system productivity.

How to Identify Hydraulic Hose Fittings

The steps described in this section will help you identify the right fittings for your hydraulic hose. You can also watch the video below for tips and advice on hydraulic hose fitting identification.

1. Determine the Type of Fitting Connection

Hydraulic hose fittings generally include threads that come in different manufacturing standards. Common thread standards include British Standard, International Metric Thread System, and American Standard. This results in different classifications of hose fittings based on thread standards, e.g., British-thread-type fittings, American-type fittings, and metric fittings. Aside from thread standards, hydraulic hose fittings also differ in terms of sealing methods and may be country-specific or continent-specific.

In regard to those differentiating attributes, here are some of the most popular types of hydraulic fittings you’ll be likely to use in your hydraulic hose assembly:

JIC
Joint Industry Council (JIC) fittings are American-type hydraulic hose fittings machined with parallel (straight) threads and a 37° flare seating surface on both their external and internal thread cones. They are often manufactured in stainless steel, nickel alloys, carbon steel, and brass. These attributes enable high-strength, leak-free hydraulic connections.

JIC fittings also offer excellent sealing capabilities with metal-to-metal seals and can operate reliably under higher working pressures. This feature makes them ideal for high-pressure, heavy-duty fluid power and fuel delivery applications, like in John Deere’s hydraulic systems. They are also known for their ease of installation and are Europe’s most widely used American-type hydraulic fittings.

NPT/NPTF
National Pipe Thread (NPT) hose fittings include tapered external and internal threads that conform to the ASME B1.20.1 American Standard. The tapered threads incorporate a 30° chamfered internal flare, which enables the fittings to create a leak-tight seal for fluid transfer applications, particularly when used with Teflon tape. NPTF, a variation of NPT, is designed to provide a tighter seal without the need for additional sealing materials. NPT and NPFT threads are available in stainless steel and carbon steel for high-pressure hydraulic conveyance applications requiring vibration resistance and in brass or iron for low-pressure applications. NPT and NPTF are fittings very popular in Canada and the rest of North America.

BSP
British Standard Pipe (BSP) fittings include both BSPP (British Standard Pipe Parallel) and BSPT (British Standard Pipe Tapered) threads.

BSPP fittings feature parallel (straight) threads. They are not self-sealing; instead, they establish leak-proof hydraulic connections using either a combination of metal-to-metal sealing and an O-ring or angled metal-to-metal sealing surfaces.

On the other hand, BSPT fittings have tapered threads designed to provide a tighter seal as they are screwed in, often requiring a sealing paste or PTFE tape to help prevent leaks.

Highly versatile and adaptable, BSP fittings are manufactured from various materials, including high-grade stainless steel, brass, carbon steel, and even plastics. They are suitable for an extensive range of hydraulic applications in different industries, including shipping, manufacturing, chemical processing, and automotive. They are widely accepted and used in Europe and many other countries worldwide.

ORFS
O-Ring Face Seal (ORF) hydraulic fittings use an O-ring compression technique to create a tight seal between the mating surface and fitting. They include straight (parallel) threads and a machined groove in the face of the male-threaded fitting to allow for mounting an O-ring. ORF fittings are usually manufactured in nickel-plated stainless steel, carbon steel, or nickel-plated carbon steel.

Generally, ORFS fittings provide a leak-proof solution for high-pressure hydraulic applications that experience intense mechanical vibrations. They are typically used in OEM machines worldwide to provide leak-free hydraulic connections.

METRIC FITTINGS
These are hydraulic hose fittings featuring Metric Standard threads. They find application in various hydraulic machines and equipment in different regions across the globe. Listed below are some of the most popular types of metric hydraulic fittings:

• Metric Parallel Fittings: These are the standard metric hydraulic fittings. They feature a constant diameter throughout the threaded end. They are widely available and well-suited for low-pressure hydraulic applications.
• Metric Taper Fittings: These fittings are known for their precise conical external and cylindrical internal threads. They offer excellent self-sealing capabilities, eliminating the need for additional sealing methods like O-rings. Metric taper hose fittings are ideal for high-pressure hydraulic applications and are Europe’s most commonly used fitting type.
• JIS (Japanese Industrial Standard) Metric Fittings: These hose fittings are primarily designed for use in hydraulic machinery and equipment manufactured in Japan and some Korean-made equipment.

Note: JIS fittings do not technically include Metric Standard threads. Instead, they incorporate British Standard threads, which are similar to metric threads in many ways. They are also often used with standard metric fittings.

• Komatsu Metric Fittings: These are proprietary hydraulic fittings designed for use in Komatsu hydraulic machinery and equipment. They incorporate metric threads with a 30° flare.

SAE
Society of Automotive Engineers (SAE) fittings are known for their robust and reliable performance in hydraulic systems. These fittings have straight threads and create strong, leak-free connections using elastomeric seals like O-rings. They are available in materials such as stainless steel, carbon steel, and brass to suit various applications.

Standardized under SAE J514, these fittings include 37° flare, 45° flare, and O-ring boss (ORB) types. The 37° flare fittings, similar to JIC, use a 37° flare seating surface for a metal-to-metal seal, while ORB fittings use an O-ring seated in a groove for leak-proof connections.

Due to their high pressure-handling capabilities and reliable sealing performance, SAE fittings are versatile and widely used in automotive, industrial, and aerospace applications. Their ease of installation and maintenance makes them popular in demanding environments.

2. Identify the Fitting Size (OD’ ID)

After you have identified the type of hose fittings to use in your hydraulic hose assembly, the next critical step is determining the size of the selected fittings. This is done by measuring the fittings’ thread diameters using a vernier calliper. For male threads, you’ll need to measure the Outside Diameter (OD); place the Vernier Calliper at the extensive side of the male thread, ensuring it is close-fitted against the thread but not too tight to avoid distorting it.

For female threads, you’ll need to measure the Inside Diameter (ID); place the calliper inside the female-threaded hose fitting and expand its moving jaw until it touches the threaded wall, then tighten its screw and record the diameter measurements.

Thread diameter (OD or ID) is a prime factor in ensuring that the selected hose fittings are compatible with other hydraulic system components. Mismatched hose fittings in terms of thread diameter can lead to leaks, system inefficiencies, and even equipment breakdowns. Therefore, be sure to take several readings of the thread diameter and always double-check them. In hydraulics, even a 1-millimeter error can cause major issues.

3. Check the Thread Pitch

For Metric Standard threads, the thread pitch is defined as the distance between individual threads in millimetres (mm). For all other thread standards, thread pitch is considered the total count of threads per inch (TPI) along the length of a hydraulic hose fitting.

Differences in thread pitch can make two hose fittings with the same thread diameter incompatible, as their threads will not line up. Trying to force such fittings together may damage their threads or result in a loose hydraulic connection, causing leaks. As such, thread pitch is one detail you should never overlook during fitting identification.

Use a pitch gauge to measure the thread pitch of selected hose fittings. A pitch gauge, also known as a thread gauge or screw gauge, is a specialized reference tool with several inserts labelled with distinct TPI values. To use this tool, simply align its blades with the female/male threads of a hydraulic hose fitting until you find a perfect match. By doing so, you’ll be able to obtain the TPI value of the hose fitting.

Note: Before taking thread pitch measurements, you should match the manufacturing standard of your fittings’ threads to the pitch gauge you intend to use. For instance, if the selected hose fittings have metric standard threads, you’ll require an ISO-metric thread gauge to obtain accurate results.

4. Determine the Fitting Angle

Proper hose routing in hydraulic hose assemblies means considering the amount of angular offset between the hydraulic hoses and fittings to minimize the stress exerted on the two components. For this reason, elbow fittings with the correct offset angles should be used whenever a change in direction is needed in the hydraulic hose assembly. Using hydraulic fittings with incorrect offset angles may cause the connected hoses to twist, and a hydraulic hose pipe twisted as little as 7 degrees can start to leak or blow apart due to restricted fluid flow, especially in high-pressure systems.

Standard elbow hydraulic fittings come in three angles: 90°, 22.5° (although less common), and 45°. You can use a protractor to determine the elbow angle of a hose fitting.

5. Inspect for Sealing Method

Assessing the technical specifications and physical dimensions of a hose fitting will assist you in identifying the type of sealing method it utilizes. Common sealing methods for currently available hydraulic hose fittings include:

• O-Ring Seals: These are rubber/elastomeric rings placed in the machined groove of a hose fitting to create a leak-tight seal when compressed by the fitting’s mating part. They are well known for their effectiveness in preventing leaks in high-pressure hydraulic systems and can withstand extreme temperatures. However, for them to be effective, they should be adequately sized and compatible with the hydraulic fluid used in the system.

• Tapered Threads Sealing: In this sealing method, the hose fittings’ female and male tapered threads wedge together and compress to form solid and leak-proof hydraulic connections. You should apply a thread sealant to the male threads of selected hose fittings before assembly to create a more secure seal against fluid pressure and reduce the possibility of leakage.

• Metal-to-Metal Sealing: This sealing method uses a tapered thread and a machined face to create a leak-tight seal that can withstand high fluid pressure. The machined face controls the sealing, while the tapered thread helps hold the hose fitting in place. Essentially, metal-to-metal seals provide better sealing capabilities without the need for thread sealants.

• Mated Angle Seals: This sealing mechanism is used in hydraulic hose fittings with parallel or straight threads. A seal is formed when the female and male straight threads in the hose fittings tightly join together and their mating angles coincide. Compared to other sealing methods, mated angle seals are less effective at preventing fluid leakages and are prone to damage by misalignment or overtightening. Thus, they require additional thread sealants to ensure proper sealing.

Proper sealing of hydraulic fittings is critical because any leaks in a hydraulic system can lead to contamination of the hydraulic fluid and loss of system pressure. Therefore, be sure to match the thread types of selected hose fittings to the recommended sealing methods to ensure leak-tight hydraulic connections. This will not only help maintain the integrity of your hydraulic system but also help prevent potential accidents and equipment damage.

6. Use Reference Charts and Tools

As previously mentioned, to identify the correct fitting sizes for your hydraulic hose assembly, you should use a Vernier Calliper to measure the thread diameters of selected hose fittings, a pitch gauge to measure the thread pitch, and a protractor to determine the correct fitting angles for proper hose routing.

Once you have taken those measurements, cross-check the collected readings with hydraulic fitting reference charts provided by different fitting manufacturers such as Dixon. These charts often contain manufacturers’ technical specifications and dimensions of various hose fitting types, thread standards and sizes, recommended sealing methods, and other details. Cross-referencing your measurements helps ensure that the hose fittings you intend to install meet industry standards and your specific needs.

You can also seek professional assistance from hydraulic experts and hydraulic equipment vendors, like Marshall Equipment Ltd., whenever you need help identifying which type of hose fittings are ideal for your hydraulic system.

Download the following PDF for more technical information on hydraulic hose fitting identification.

Common Mistakes to Avoid

When it comes to identifying hydraulic fittings, there is very little room for inaccuracies or mistakes. Small errors in hydraulic hose fitting identification can lead to major issues in a hydraulic system. Listed below are some common mistakes to avoid:

• Overlooking the compatibility between hydraulic fittings and hose types: Ensure that the hose port of the selected fitting perfectly matches the port connection on your hydraulic hose. 
• Incorrectly identifying the type of threads in a hose fitting: To correctly match thread types, familiarize yourself with common thread standards (ISO Metric, NPT, BSP, etc.) and their distinct characteristics and applications. In addition to visual inspection, use Vernier Callipers and thread gauges to measure thread dimensions and cross-reference the collected readings with manufacturer-provided thread identification charts.
• Neglecting the compatibility between the hose fitting material and the hydraulic fluid conveyed: Determine the chemical properties of the fluids in your hydraulic system and select a hose fitting made of compatible materials.
• Failure to assess the intended operating environment: Evaluate the environmental conditions the hose fitting will be exposed to, including humidity levels, temperatures, UV exposure, etc., and choose a hose fitting that can function reliably in such conditions.
• Overlooking pressure ratings: Check the working pressure (WP) rating of the hose fitting you plan to install to ensure that it can handle the pressure requirements of your hydraulic system. 

Note: Incorrect hydraulic hose fitting identification can lead to improper connections, ineffective seals, accelerated fitting degradation, fluid leaks, system inefficiencies and downtime, and ultimately, catastrophic failures. This often necessitates costly repairs and replacements while posing significant safety risks to humans and equipment.

Ensuring Accurate Hydraulic Hose Fitting Identification for System Integrity

Accurate hydraulic hose fitting identification is essential to ensure the integrity and efficiency of hydraulic systems. The process can be complex due to the wide variety of materials, sizes, connection ports, shapes, thread types, sealing methods and configurations available. From thread standards to connection angles, every detail plays a crucial role in maintaining a tight, high-performance system. By identifying the right hydraulic hose fittings, you can avoid potential problems such as fluid leaks, equipment damage and system failure while ensuring your system’s smooth operation and longevity.

Fittings are an essential component of hydraulic hose assemblies. Marshall Equipment Ltd. provides a broad assortment of hydraulic hose fittings. Our experts can help you identify the correct fitting for your hose and even perform a complete hydraulic hose assembly for you. Please contact us for more information on our products and services.