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Process of Elimination When Identifying Hydraulic Hose Fittings

- Jan 22, 2018 -

First, determine the type of fitting – is it permanent or reusable?

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.

Identify fitting ends and port connections

Accurate identification of ports and connectors in a hydraulic system is necessary before the correct hose or tube assembly can be assembled and installed.


Port ConnectionsTube/Hose Connections

Metric Taper
SAE Straight Thread
ISO 6149
DIN Metric
4-Bolt Flange


37⁰ Flare
30⁰ Flare (Metric)
45⁰ Flare
24⁰ Flareless (SAE)
24⁰ Flareless (DIN)
30⁰ Flare (BSPP)
O-Ring Face Seal (ORFS)
60⁰ NPSM Swivel
60⁰ Cone (BSPP)
60⁰ Cone (Metric)

Next, identify the sealing method

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.


Identifying Hydraulic Hose Fittings - Parker Hose Products Division - O-Ring SealsO-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.




Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Mated Angle SealsMated 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. Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Tapered ThreadsWhen 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. 

Then, look at the fitting design

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.  


Mated Angle Seat with O-ring:

O-Ring LocationNose SeatSeat AngleFitting Termination
InsideInverted60⁰ InclusiveBritish Standard Pipe Parallel
InsideInverted24⁰ InclusiveDIN 24⁰ Cone


O-Ring Face Seal:

O-Ring LocationNose SeatSeat AngleFitting Termination
In Flange GrooveFlat FaceN/ASAE O-Ring Flange (Code 61 or 62)
OutsideFlat FaceN/ASAE O-Ring Boss
At Nose SeatFlat FaceN/AO-Ring Face Seal


Mechanical Joint or Mated Angle:

O-Ring LocationNose SeatSeat AngleFitting Termination
NoneStandard37⁰JIC 37⁰ Flare
NoneStandard45⁰JIC / SAE 45⁰ Flare
NoneStandard30⁰Japanese Industrial Standard & Komatsu
NoneInvertedN/AMetric Stand Pipe
NoneInverted30⁰National Pipe Straight
NoneInverted45⁰SAE Inverted Flare
NoneInverted24⁰Inclusive French Gaz 24⁰ Cone
None, except -20Standard24⁰Inclusive French Gaz 24⁰ High-Pressure Flange


Thread Interface:

O-Ring LocationNose SeatSeat AngleFitting Termination
N/AN/AN/ANational Pipe Tapered
N/AN/AN/ABritish Standard Pipe Tapered


Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Visual Fitting Index


Lastly, measure the thread

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.

Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Male Pipe Thread Sizes Identifying Hydraulic Hose Fittings - Parker Hose Products Division - SAE Nut and Nipple Chart

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