In high-pressure or high-flow environments, how can the design of the End Fitting ensure its sealing and pressure resistance?

In high-pressure or high-flow environments, the design of End Fittings needs to pay special attention to its sealing and pressure resistance, because these properties directly affect the safety and reliability of the system. The following is a detailed analysis and solution:

1. Key points of sealing design
(1) Choose the right sealing method
O-ring seal
O-ring is a common dynamic and static sealing element suitable for high-pressure environments. By selecting high-pressure and high-temperature resistant materials (such as fluororubber FPM or perfluoroether rubber FFKM), the sealing performance under extreme working conditions can be ensured.
Metal seal
In ultra-high pressure or high-temperature environments, metal seals (such as copper gaskets or stainless steel gaskets) may be a more suitable choice. Metal seals can fill tiny gaps through plastic deformation to achieve high-strength sealing.
Cone seal
Cone seals use the compression force between the contact surfaces to form a seal, which is suitable for high-pressure pneumatic or hydraulic systems. This design has high pressure resistance and good self-sealing performance.
Card sleeve seal
Card sleeve joints squeeze the outer wall of the pipe through the deformation of the card sleeve to form a tight seal, which is suitable for high-pressure and vibration environments.
(2) Optimize the sealing surface accuracy
Surface finish
The roughness of the sealing surface will directly affect the sealing effect. In high-pressure environments, the sealing surface usually needs to achieve an extremely high surface finish (Ra < 0.8 μm) to reduce the possibility of leakage.
Geometric shape matching
Ensure that the sealing surface and the geometry of the mating part are completely matched (such as a plane, cone or sphere) to avoid leakage caused by shape deviation.
(3) Multi-stage sealing design
Under extreme conditions, a multi-stage sealing design (such as double O-rings or combined seals) can be used to improve sealing redundancy and ensure that the system can remain sealed even if the first-stage seal fails.
2. Key points of pressure resistance design
(1) Material selection
High-strength materials
Select materials with high tensile strength and yield strength (such as alloy steel, stainless steel or titanium alloy) to withstand the mechanical stress in high-pressure environments.
Corrosion-resistant materials
In high-pressure fluid environments, the fluid may be corrosive. Selecting corrosion-resistant materials (such as duplex stainless steel or Hastelloy) can extend the service life of end fittings.
Material fatigue performance
High-pressure environments may cause material fatigue. Select materials with high fatigue strength and further improve fatigue resistance through heat treatment processes (such as quenching and tempering).
(2) Structural design
Optimization of ribs and wall thickness
In high-pressure environments, the wall thickness of end fittings needs to be accurately calculated according to the pressure level. Use finite element analysis (FEA) to simulate pressure distribution and optimize wall thickness and rib design to enhance pressure resistance.
Rounded corner transition design

Using rounded corner transition design in stress concentration areas of fittings (such as thread roots or connections) can effectively disperse stress and reduce the risk of cracking.
Uniform force distribution
When designing, try to ensure that all parts of the fittings are evenly stressed to avoid deformation or rupture caused by excessive local stress.
(3) Connection method optimization
Threaded connection
In high-pressure environments, threaded connections need to use high-strength threads (such as NPT tapered pipe threads or BSPT threads), and further enhance sealing performance by applying thread sealant or using sealing tape.
Welded connection
For ultra-high pressure applications, welded connections may be a better choice. High-quality welding processes (such as TIG welding or laser welding) can ensure the strength and sealing of the joint.
Flange connection
Flange connection is suitable for ultra-large diameter or ultra-high pressure scenarios. By increasing the flange thickness, using high-strength bolts and optimizing the design of sealing gaskets, the pressure resistance can be significantly improved.
3. Fluid dynamics optimization
(1) Reduce fluid resistance
Flow channel smoothing design
The internal flow channel should be as smooth as possible, avoiding sharp angles or sudden changes in cross-section to reduce fluid resistance and turbulence.
Flaring design
The use of flaring design at the fluid inlet and outlet can reduce the impact of fluid impact on the accessories and reduce pressure loss.
(2) Prevent cavitation and erosion
Pressure balance design
In high pressure difference environments, designing a pressure balance device (such as a pressure relief valve or a throttle hole) can prevent cavitation caused by sudden pressure changes.
Erosion-resistant materials
In high-speed fluid impact areas, the use of erosion-resistant materials (such as ceramic coatings or cemented carbide) can extend the service life of accessories.
4. Testing and verification
(1) Pressure test
Static pressure test
The end fittings are subjected to static pressure tests to test their sealing performance and pressure resistance at rated pressure.
Burst test
A burst test is conducted to determine the maximum pressure bearing capacity of the fittings to ensure that they will not fail suddenly in actual use.
(2) Fatigue test
Cyclic loading test
Simulates pressure fluctuations under actual working conditions to evaluate the fatigue life of end fittings in long-term use.
(3) Sealing performance test
Air tightness test
Uses helium or other tracer gases to detect the sealing performance of end fittings to ensure that there is no leakage.
Liquid penetration test
Tests the sealing performance of fittings in a liquid environment to verify their applicability in different media.
5. Actual cases and technological innovations
(1) Aerospace
In the aerospace field, end fittings need to withstand extremely high pressures and temperatures. For example, end fittings in rocket engine fuel delivery systems are usually made of nickel-based alloy materials, combined with precision machining and surface coating technology to ensure their sealing and pressure resistance.
(2) Deep-sea oil extraction
End fittings in deep-sea oil extraction need to withstand pressures of up to hundreds of atmospheres. These fittings usually adopt a double-layer sealing design (such as metal + elastomer seal) and optimize the structure through finite element analysis to cope with complex deep-sea environments.
(3) Intelligent monitoring technology
Some high-end end fittings are integrated with sensors that can monitor internal pressure, temperature and sealing status in real time, thereby early warning of potential problems and improving the safety and reliability of the system.

In high-pressure or high-flow environments, the design of End Fitting needs to comprehensively consider multiple aspects such as sealing, pressure resistance, material selection, structural optimization and fluid dynamics. Through scientific design and advanced manufacturing technology, the reliability and safety of end fittings under extreme working conditions can be ensured.