How to Identify Hydraulic Fittings?

Each country or industry has its own standard fittings. However, there are few fixed standards, and equipment installed on the same machine often has different standards. How to identify hydraulic fittings is crucial to choosing the right hose fittings.

When hydraulic hose fittings are damaged and need to be replaced, accurately identify hydraulic hose fittings is crucial for restarting the hydraulic system. This article will fully understand how to identify hydraulic fittings from the perspective of size, sealing method, connector model, etc.

How to Identify Hydraulic Fittings？

What are Hydraulic Hose Fittings?

Hydraulic hose fittings are used to connect hydraulic hoses. One end of a hose fitting has a hose port into which the hose can be inserted and used in a hydraulic system. The other end is a threaded end, either male or female, that can be used with other fittings or components. Hose fittings are available in bends ranging from 15 to 180 degrees to be used in a variety of applications.

Understanding Hose Fitting Types

Hydraulic hose fittings often include threads that are manufactured to different standards. Common thread standards include British Standards, International Metric Thread System, and American Standards. This leads to a variety of hose fittings. Below are the most common types of hydraulic fittings.

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American Standards Thread

American Standard threads have two notch marks on the outside of the fitting and marked with a “U”. There are many types of threads involved in the American Standard thread, including JIC, NPT, SAE and ORFS threads.

• NPT thread – National Pipe Tapered Thread: NPT threads are traditional tapered fittings used in hydraulic and pneumatic systems. They are a metal-to-metal sealing type that requires a pipe sealing like Teflon tape or pipe dope to make a leak-free connection. We do not recommend unmaking this connection, as it will leak upon reconnection.
  ● JIC thread – Joint Industrial Counsel Thread (37° Flare Type) – common in fluid power systems and can withstand higher working pressures. Both male and female fittings have 37° seats with a seal made at the flare of the male coupler and the coned seat of the female. Can be disconnected and reconnected without concern, although are susceptible to cracking when over tightening.
  ● SAE thread  – SAE 45 looks very similar to the JIC, the only difference  is that we have a different sealing angle; SAE thread at a 45 degree instead of a 37 degree. These are  commonly used on fuel system applications, air brakes, some refrigeration or air conditioning;  more found on our heavy trucks and automotive type applications, not typically with hydraulics.
  ● ORFS thread – O-Ring Face Seal – identified with an O-ring against the shoulder of the male on the face of the male thread. The O-ring on the face seals against a flat surface face on the female thread. This is a straight thread type, and the connection can be made and unmade without risk of leakage.

British Standards Thread

BSP fittings are marked with a notch on the surface and a “G” on the thread cap.

• BSP thread – British Standard Pipe: There are two thread types for BSP, BSPP and BSPT. BSPP stands for British Standard Parallel Pipe. These fittings come with parallel or straight threads. The pitch angle of BSPP fittings is always 55 degrees. BSPT is British Standard Tapered Pipe Thread. BSPT threads are tapered. This tapered thread provides a more secure fit and a better seal. Like BSPP fittings, BSPT fittings have a standard pitch angle of 55 degrees.

Metric Standards Thread

Metric thread is indicated as “M” and is one of the most commonly used threads in hydraulic fittings. There are three standard metric fittings in the world: DIN metric, JIS metric, and Komastu metric fittings.

• DIN – DIN metric fittings are commonly available in 24°, 45°, and 30° tapers. They include parallel threads and tarped threads. Straight thread fittings require sealants or O-rings to create a secure seal. Tapered metric fittings can be set up with a mechanical seal through both male and female threads.
• JIS – Japanese Industrial Standard: it is a Japanese thread and is commonly used in Asian countries. It includes tapered JIS hydraulic fittings and 30-degree cone JIS fittings.
• Komatsu Metric Fittings –These are proprietary hydraulic fittings designed for Komatsu hydraulic machinery and equipment. They feature metric threads with a 30° flare.

How to Identify Hydraulic Fittings?

There are 5 steps to identifying  hydraulic fittings type.

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Step 1: Is the thread male or female?

If the threads are on the outside of the fitting it’s a male thread.

If they are on the inside it’s a female thread.

Male or Female Thread

Step 2: Is the thread parallel or tapered?

If the diameter stays the same over the length of the threads it’s parallel,  also known as straight threads. Tapered threads decrease in diameter.

If you’re not sure, use a pair of calipers and measure the diameter at the top and bottom of the fitting.

Parallel threads include NPSH, NPSM and BSPP.

Tapered threads include NPT/NPTF, BSPT, and Metric tapered.

Parallel or Twpered Thread

Step 3: Is the sealing method flat seal, ball seal or cone seal?

A flat surface is a flat seal, a spherical surface is a ball seal, and an angled surface is a cone seal. If it is a cone seal, the angle must also be measured.

Step 4: What’s the thread pitch?

Thread pitch refers to the space between threads. Use a thread gauge pitch tool, caliper, or steel  rule to measure the distance between threads on the length of the fitting.

For metric threads the pitch is expressed in millimeters between each thread. For all other threads the pitch is considered the number of threads per inch.

Hydraulic Hose Fittings Size Code

Step 5: What’s the thread diameter?

Use a caliper or O.D. tape to measure the outside diameter of a male thread and the inside diameter of a female thread. You may see small variances between your measurements and the size charts due to different thread manufacturers. Each of our hydraulic fittings has detailed size data. If you have any questions, please contact us directly.

Step 6: Thread type standard

Measure these data to correspond with the supplier’s data and then select the corresponding connector. The measured data may be in error with the standard data. However, the measured diameter should not be larger than the standard data.

hydraulic fitting identification chart

Strongflex is a supplier of hydraulic accessories. We can supply various types of fittings for hydraulic systems. We have 20 years of industry experience and a professional sales team. If you encounter problems when ordering hydraulic hoses or hydraulic fittings, please feel free to leave us a message and we will solve it for you as soon as possible.

As a supplier of hydraulic fittings, we have prepared a hydraulic fitting thread test kit to facilitate identification for our customers.

hydraulic fitting thread test kit