Identifying Hydraulic Hose Fittings

How do you identify hydraulic hose fittings when at first glance they can easily all look the same?

Fortunately, it's a lot easier than it looks by following the steps below.

Step 1: Reusable or permanent?

Is the fitting reusable or permanent? Permanent or crimped fittings are widely used in the fluid power industry for the ability to easily and quickly remove them. They are also more reliable than a reusable fitting.

A resusable fitting is easily identifable, since it only requires a wrench and vise to connect it to a hose. Versus a permanent fitting which is crimped, requiring a crimping tool.

In general, the majority of fittings will be permanent due to higher reliability and speed in replacing.

Step 2: Identify fitting ends and port connections

Use the chart below to properly identify the fitting ends and port connections.

Port Connections Tube/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)

Step 3: Identify the sealing method

Hydraulic fittings types vary depending on size, configuration and thread types. O-ring, mated angle and threaded are the most common, though several more types of hydraulic hose fittings are available.

O-Ring: O-ring seal designs have three types, O-ring boss, flat face O-ring seal and O-ring flange. With these types of couplings, the O-ring seal is the main component in creating the seal.

Mated Angle: SAE 45° or JIC 37° is one example of a mated angle, though more exist. Angle seat fittings have straight or parallel threads for sealing. When the male and female counterparts are threaded together, the threads do not form the seal. Rather, a seal is formed when the two mating angle seats are joined together.

Tapered Threads: Male and female are the two types of taper thread fittings. Male fitting threads are on the outside, while female threads are on the inside. When the two are threaded together, the tapered threads deform, applying pressure on the couplings which ultimately forms the seal. Tapered threads have a tendency to be imprecise, though never use tape to ensure the seal.

Step 4: Look at the fitting design

Look at the location of the O-ring, nose seat, seat angle and fitting termination. You can see the O-ring location as well as the type of nose seat. A seat gauge will be needed to determine seat angle.

Mated Angle Seat with O-ring:

O-Ring Location Nose Seat Seat Angle Fitting Termination
Inside Inverted 60⁰ Inclusive British Standard Pipe Parallel
Inside Inverted 24⁰ Inclusive DIN 24⁰ Cone

O-Ring Face Seal:

O-Ring Location Nose Seat Seat Angle Fitting Termination
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

Mechanical Joint or Mated Angle:

O-Ring Location Nose Seat Seat Angle Fitting Termination
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 Inclusive French Gaz 24⁰ Cone
None, except -20 Standard 24⁰ Inclusive French Gaz 24⁰ High-Pressure Flange

Thread Interface:

O-Ring Location Nose Seat Seat Angle Fitting Termination
N/A N/A N/A National Pipe Tapered
N/A N/A N/A British Standard Pipe Tapered