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
NPT/NPTF BSPT (JIS-PT) Metric Taper SAE Straight Thread ISO 6149 JIS-B2351 DIN Metric BSPP (JIS-PF) 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