The Fittings and Connections of Hydraulic Systems

When working with hydraulic fluid systems and apparatuses, it is important to always ensure that the fittings and connections implemented are secure and prevent any possible leaking. For applications such as aircraft, hydraulic fluid and power transfer units are crucial for the actuation of flight surfaces, landing gear systems, brakes, and other important equipment pieces. As such, proper hydraulic assembly is very important for pressure transfer and hydraulic power applications. In this blog, we will discuss the various fittings and connections common to hydraulics, allowing you to best manage such equipment for your applications.

When discussing piping systems and their connected parts, fittings refer to machine components that allow for two or more parts to be attached. If used to transport hydraulic fluids, fittings need to both connect components and ensure proper sealing at the same time. Generally, the most common hydraulic fittings are all-metal or O-ring types, and both provide their own characteristics that can make them beneficial for a specific use.

All-metal fittings are those that are tightened with metal-to-metal contact, and threading ensures that mating surfaces are pressed together to create a pressurized seal. With tapered threading on the male-end of the fitting, the female port may be attached and secured through the stress produced from tightening. As the hydraulic fitting threads are torque-sensitive, they can become warped and damaged if they are over-tightened. If threading becomes warped, fluids may begin to escape through created paths. As warping may even occur from repeated disassembly and assembly, thread sealant compounds may be used to strengthen the seal.

Flare-type fittings are another option, and they can achieve a positive seal by having a fitting drawn into the flared end of tubing with the use of an assembly nut. Flare-type fittings are most recommended for assemblies dealing with pressures below 3,000 psi due to the difficulty of producing flares for thick-wall tubing. Flareless fittings are more common for countries such as the United States, due to the fact that they need minimal tube preparation. As compared to other all-metal hydraulic fitting types, the flareless fitting is most optimal for withstanding vibrations.

As one of the most basic and simplistic methods for reducing leaking, O-rings are commonly implemented in many straight thread components and connections to prevent leaking. As torus shaped gaskets that are often produced from elastomers, the O-ring can be seated on the groove of a fitting and create a seal through its compression between two parts. Now widely accepted by many designers and manufacturers across the globe, O-rings come in the form of straight-thread O-ring boss fittings, O-ring flange fittings, and face seal or flare-face O-ring fittings. With all types, high amounts of pressure can regularly be managed due to their good performance characteristics.

When inspecting fittings and connections to ensure their correct assembly, torque wrenches and torque stripe indications can assist workers in making sure that large assemblies with many fittings are efficiently worked through. By labeling what connections are completed, it can be easier to ensure that leaking will not occur before turning on the system. As leaking may cause time delays in operations and may require cleaning and replacement, enacting proper connection checks beforehand can save both time and money.

Whether you are in search of hose components, auxiliary pump fittings, or tooling for specific fluids applications, there is no better alternative to Aviation Purchasing Platform. As a leading online distributor of aircraft parts, we are your sourcing solution for new, used, and obsolete items from top global manufacturers. When you are ready to begin the part procurement process, you may fill out and submit an Instant RFQ form as provided on our website and a dedicated account manager will reach out to you in 15 minutes or less with a personalized quote.


March 20, 2023

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