There are many models of hydraulic fittings. It is sometimes difficult to find your way around.
The hydraulic coupling has 2 ends:
Installation: The fitting is screwed onto a drilled block or onto a hydraulic component.
The adaptation: This is the part of the connection where the flexible or rigid hydraulic is screwed.
In Fig. A is shown a swiveling 90° elbow fitting. The implantation is in cylindrical gas and the adaptation is in JIC.
This type of fitting is called hybrid, meaning that each end is different. One comes from a French standard (AFNOR) and the other from an American standard (SAE).
A fitting is identified and recognized by:
its visual form. (74° cone, 24° cone, flat, nut shape...)
NPT installation: This is a conical thread on the inch side. Present in particular in nitrogen circuits. Sealing is done with sealant or Teflon.
JIC Adaptation: The fitting has a 74° external cone. Sealing is metal/metal.
ORFS adaptation (O'Ring Face Seal): The fitting has a flat surface where a seal is housed.
SAE 3000 PSI flange: This type of flange is very common. It is used in circuits where the pressure is less than 200 bars.
6000 PSI flange: This type of flange is very common. It is used in circuits where the pressure is greater than 200 bars.
B. English
(BSP : British Standard Pipe)
Installation and adaptation BSP: This is a cylindrical inch-size thread. The fitting has a 60° inside cone. Sealing is metal/metal.
Since the sealing cone is inside the fitting, the fitting can serve both as an adaptation or as an implantation.
The thread is identical to the gas fitting, it can perfectly replace a cylindrical gas fitting. For implantation, sealing is done with a BS ring.
C. French
(AFNOR : Association Française de NORmalisation)
Gas fitting: This is a cylindrical inch-size thread. Sealing is done by a seal present on the fitting or a BS ring. There is also the conical gas, it is to be avoided for the hydraulic circuits because the sealing must be done with joint paste.
The gas thread of the installation is identical to the BSP fitting.
Metric adaptation: The fitting has a 24° internal cone. Sealing is metal/metal. The adapter thread is metric.
The gas thread of the installation is identical to the BSP fitting.
D. German
(DIN : Deutches Institut für Normung)
Metric layout: This is metric cylindrical thread. Sealing is done by a seal present on the fitting or a BS ring.
Metric adaptation: The fitting has a 24° internal cone. Sealing is metal/metal or with a seal present on the tube connection.
There are 3 series of adaptations:
LL series: Very light series: It is a small dimension fitting often used for lubrication systems.
L series (Low): Light series: This is a fitting used for hydraulic circuits not exceeding 200 bars.
S series (Strong): Heavy series: This is a fitting used for hydraulic circuits exceeding 200 bars.
3. Identify a fitting
The table Fig. C makes it possible to identify the most common fittings by measuring the fitting.
4. Connections
The union makes it possible to connect 2 female connections between them.
Pictured: Union BSP
The sleeve fitting connects 2 male connections to each other.