What are the Fitting Type Connections Used in Hydraulics?

Generally speaking, the fitting connections used in hydraulic systems around the world, follow regional preferences which have been in place for quite some time. There are some areas of crossover, where for instance Japanese manufacturers might use American fittings on some machinery, but for the most part, the regional usage prevails. For this reason, there are connectors specific to Japan and the Far East, parts of Europe, the United States, and many other countries of the world.

How Many Different Hydraulic Port Connections Are There?

To summarize, there are quite a few different hydraulic port connections in existence today, and they roughly follow geographic usage. That is to say that the different connection types tend to be used in specific areas of the world, where standards for usage were developed. It might be convenient if there were to be a world-wide standard, but that isn’t strictly necessary, given the fact that the equipment which is manufactured in a certain area of the world is generally used right in that same area.

Of course, it is true that Japanese equipment can be purchased and used for American applications, and in situations like this, the Japanese connections would have to be used for replacement parts. This isn’t particularly inconvenient however, since the Japanese fittings are readily available on the market, and can easily be purchased when needed.


The American connection types consist of NPSM, NPTF, SAE series, Ermeto fittings, and CAT fittings, and within these categories there are several individual types of hydraulic fittings. There are ISO connection types which are one of the few international fitting types. The German fittings are preceded by a ‘DIN’ designator, indicating that they are of the German National Standard, the British connections are usually designated with a BSP or similar acronym, and the Japanese connection types can be identified by their JIS designations.

Why Do So Many Port Connections Exist?

It’s not really surprising that there are so many hydraulic port connections available for use in the modern world. The reason it has developed this way is that most of these connections were developed in specific areas of the world and came to be accepted in those regions. That historical use has continued to the present day, and manufacturers simply prefer to use those same connections which were historically developed and used for decades.

There is some crossover usage on hydraulic port connections for instance the SAE straight thread and the 4-bolt flange fittings of American origin, which are often used in Japan. This came about after World War II, when a great deal of machinery was exported from the US to Japan, and it was necessary to adopt those port connections as standard for the incoming American equipment.

However, it is fair to say that by and large most usage of hydraulic port connections tends to be regional and tends to follow the preferences of manufacturers in that area. If you were to conduct a review of all the designs used globally for hydraulic fittings, you would find that there are 10 main tube and hose connections, and another nine main port connections. 

The individual port connections consist of the following: NPT/NPTF, BS PT (JIS–PT), metric taper, SAE straight thread, ISO 6149, JIS–B2351, DIN metric, ESPP (JIS–PF), and four-bolt flange. The specific tube/hose connections currently in use are the following: 37° flare, 30° flare (metric), 45° flare, 24° flareless (SAE), 24° flareless (DIN), 30° flare (ESPP), O-ring face seal (ORS), 60° NPSM swivel, 60° cone (ESPP), and 60° cone (metric).

List of Port Connections & Their Origins

The following is a listing of port connections currently use in various geographic regions of the world, along with a description of each:

  • NPTF (National Pipe Tapered Fuel) – still enjoys wide usage in America, but is not recommended for fluid applications by the National Fluid Power Association (NFPA).
  • NPSM (National Pipe Straight Mechanical) – sometimes used in fluid power systems, this connection features a male half with a straight thread and 30-degree internal chamfer, while the female half has a straight thread and inverted 30-degree seat.
  • SAE J1926 Straight Thread O-Ring Boss (ORB) – recommended by the NFPA for usage in controlling leaks for systems where medium and high pressure conditions are present.
  • SAE J514 JIC/37˚ Hydraulic – both male and female halves feature 30-degree seats, and this connection is recommended by the NFPA.
  • SAE J512 45°  – both male and female halves have 45-degree seats, and this connection is often used in truck piping, automotive, and refrigeration systems.
  • Ermeto® Flareless Tube Fittings SAE J514 – both male and female halves feature 24-degree seats, with the male having straight threads and the female half using a bite-type sleeve.
  • SAE J1453 O-Ring Face Seal – this connection is well known to provide the most effective possible leakage control on the market today.
  • SAE J512 Inverted – often used in automotive systems, this connection generally features 42-degree seats for both male and female parts.
  • SAE J518 4-Bolt Flange – frequently used in fluid power systems, this connection actually has two different pressure ratings, for Code 61 and Code 62.
  • ISO/DIS 6162 4-Bolt Flange – also used in fluid power systems, these connections include a medium-pressure rating and a high-pressure rating. 
  • ISO 6149 Port and Stud Ends with ISO 261 Threads and O-Ring Seal – very similar to the  SAE J514 Straight Thread O-Ring Boss connector, but this one uses metric threads.
  • DIN 7631 Series – often used in hydraulic systems, this connector uses metric threads for both male and female halves.
  • DIN 3902 Series – an unusual configuration, which features a single male half, which can be joined to one of three different female halves.
  • DIN 20066 4-Bolt Flange – frequently used in fluid power systems, this connector has two ratings, one for standard usage and the other for heavy duty usage.
  • DIN 3852 – Male Connectors and Female Ports – this whole series is controlled by Germany, but is frequently used by other countries in various formats.
  • Millimetrique and GAZ Series – a French connection with a single male half and two possible female halves.
  • British Standard Pipe (BSP) – similar to the American NPT, but with a slight difference in the threading.
  • JIS 30° Male (Inverted) Seat, Metric Threads – JIS parallel with threading according to  JIS B 0207
  • JIS Tapered Pipe (PT) – similar to the BSPT connection in dimensions, appearance, and design.
  • JIS 30° Male Inverted Seat, Parallel Pipe Threads – similar to the BSPP connection.
  • JIS 30° Female (Cone) Seat, Parallel Pipe Threads – very similar to the American 37-degree SAE connection.
  • JIS B 8363 4-Bolt Flange – frequently used in fluid power systems, with a rating for standard usage and one for high-pressure usage.
  • JIS 210 Kgf/cm2 4-Bolt Square Flange – similar to the SAE 4-bolt connector, except the flange is different and the bolt pattern is square.

Do you Need Help With Your Hydraulic Fittings?

If you are having trouble with your hydraulic systems, or need help replacing any of the parts that your equipment relies upon, you need to be able to hire a company that will not only be able to be onsite quickly, but also provide you with quality service that will meet your specific needs. Contact Sapphire Hydraulics today to have our technicians onsite. 

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