Hydraulic hose fittings can be one of two types – permanent or reusable. Permanent or crimped hydraulic fittings are widely used in the fluid power industry because they are easier and quicker to attach than reusable fittings. Crimped fittings are also more reliable. To attach a crimped fitting, you will need crimping or swaging equipment. These fittings are squeezed onto the hose at assembly and are discarded when the hose assembly fails.
Reusable or field attachable hydraulic hose fittings are not commonly used today since they are considered "old technology." A reusable fitting is easily identifiable because it fits right onto a hose by using only a wrench and a vise. Reusable fittings typically cost more than crimped fittings and are more time consuming during the assembly process.
Accurate identification of ports and connectors in a hydraulic system is necessary before the correct hose or tube assembly can be assembled and installed.
30⁰ Flare (Metric)
24⁰ Flareless (SAE)
24⁰ Flareless (DIN)
30⁰ Flare (BSPP)
O-Ring Face Seal (ORFS)
60⁰ NPSM Swivel
60⁰ Cone (BSPP)
60⁰ Cone (Metric)
Types of hydraulic fittings vary depending on their sizes, configuration, and thread types. The three most common types of hose fittings are O-ring, mated angle and threaded. However, there are several more types of hydraulic hose fittings available.
O-Ring: The three types of O-ring seal designs are O-ring boss, flat face O-ring seal and O-ring flange. With these types of couplings, there is an O-ring seal that is the main component in creating the seal.
Mated Angle: An example of a mated angle is SAE 45° or JIC 37° but there are others as well. Fittings with an angle seat have straight or parallel threads for sealing. When the male and female counterparts are threaded together, the threads themselves do not actually form the seal. Instead, they function mechanically to bring the two mating angle seats together which ultimately forms the seal.
Tapered Threads: These types of fittings have two types of threads: male or female. Male fittings feature their threads on the outside and female fittings have threads on the inside. When the male and female counterparts are threaded together, the tapered threads deform which applies pressure on the couplings ultimately making a tight seal. Tapered threads can be imprecise but never use Teflon tape to ensure the seal. Teflon tape is often banned in hydraulic and pneumatic systems because of its tendency to shred and contaminate sensitive areas. Its lubricity has also been known to induce over-torquing.
After you have determined the sealing method, visually look at the location of the O-ring, nose seat, seat angle and fitting termination. You can visually see the O-ring location as well as the type of nose seat. However, you will need to use a seat gauge to determine seat angle.
|Inside||Inverted||60⁰ Inclusive||British Standard Pipe Parallel|
|Inside||Inverted||24⁰ Inclusive||DIN 24⁰ Cone|
|In Flange Groove||Flat Face||N/A||SAE O-Ring Flange (Code 61 or 62)|
|Outside||Flat Face||N/A||SAE O-Ring Boss|
|At Nose Seat||Flat Face||N/A||O-Ring Face Seal|
|None||Standard||37⁰||JIC 37⁰ Flare|
|None||Standard||45⁰||JIC / SAE 45⁰ Flare|
|None||Standard||30⁰||Japanese Industrial Standard & Komatsu|
|None||Inverted||N/A||Metric Stand Pipe|
|None||Inverted||30⁰||National Pipe Straight|
|None||Inverted||45⁰||SAE Inverted Flare|
|None||Inverted||24⁰||InclusiveFrench Gaz 24⁰ Cone|
|None, except -20||Standard||24⁰||InclusiveFrench Gaz 24⁰ High-Pressure Flange|
|N/A||N/A||N/A||National Pipe Tapered|
|N/A||N/A||N/A||British Standard Pipe Tapered|
With the caliper, measure the thread diameter of the largest point (Outside Diameter (O.D.) of male threads; Inside Diameter (I.D.) of female threads). Using the thread gauge, determine the number of threads per inch. Comparison of gauge and coupling threads against a lighted background will ensure an accurate reading.