Hydraulic Fittings

Hydraulic fittings refer to all components used to connect pipes and hoses that have at least one thread. Most hydraulic fittings feature two threaded sections for fast and secure connection. Conventional threads in these components range from M12 x 1.5 to M42 x 2.0. The dimensions are based on the diameter of the connected pipes or hoses.

In addition to hydraulic fittings, there are other connectors in hydraulic connection technology for various hydraulic applications:

• ORFS fittings
• Sealing cone fittings
• Weld fittings
• Check valves
• Cutting ring fittings
• Flange fittings
• Custom parts and individual fabrications

Cutting ring type hydraulic fittings

As an example of a typical hydraulic fitting, a specific type of hydraulic connection technology is discussed in more detail below.

Cutting ring fittings are a connection technology for pipes developed for very high pressures. They are also commonly known as Ermeto fittings. This name can be traced back to the Ermeto company, which developed this type of connection technology in the 1930s. The name Ermeto is derived from the Greek word for hermetically sealed, hermetos.

A connection with cutting ring fittings requires the cutting ring fitting body, a special union nut, the cutting ring, and the two pipes to be connected. These fittings are standardized according to EN ISO 8434 and DIN 2353 and are used particularly in hydraulics. The conical body is a metal clamping cone with a 24-degree sealing cone, which is connected to the nut with a metric thread.

Fittings of this type can withstand pressures from 350 bar up to 600 bar. The union nut, which is also tapered on the inside, compresses the cutting ring when tightened. This causes the wedge-shaped inner side of the ring to cut into the pipe wall, creating a fluid-tight positive fit.

Other Hydraulic Fittings

There are various ways to connect multiple pipes in a hydraulic system. For example, there is the option of a compression fitting. In a compression fitting, a conventional sealing or clamping ring is pressed onto the slightly conical body using a union nut.

This type of connection technology has the disadvantage that it can only withstand low pressures. Furthermore, the components cannot be reused. This type features two clamping rings. The front clamping ring is tensioned by tightening the thread, which creates the sealing effect. The fitting body is pressed against the surface of the pipe. At the rear clamping ring, the pipe is gripped just behind the point where the pipe is held by the nose of the clamping ring. The resulting radial holding or hinge effect ensures significantly better and long-term resistance to any vibrations.

The greatest advantage of this type of connection technology is that, compared to cutting ring fittings, disassembly and repeated assembly of the hydraulic fitting is possible without damage.

Another type of pipe fitting is the so-called flared fitting, which consists of a sleeve, a union nut, and a body with a spherical end. However, a disadvantage is that special flaring tools are required for assembly. Furthermore, it is possible for stress notches or longitudinal cracks to occur in thinner pipes during the flaring process. The assembly of the aforementioned hydraulic fittings is performed using an open-end wrench.