Sealing performance of hydraulic fittings: Ensuring system stability


The critical role of fittings for system stability

Hydraulic couplings are a vital component of hydraulic systems, they are used to connect and disconnect different hydraulic components and pipes. The importance of hydraulic couplings lies in the fact that they ensure the reliability, efficiency and safety of the hydraulic system.

The sealing performance of hydraulic couplings is crucial for the stability of hydraulic systems. In hydraulic systems, the pressure is very high, so it is important to ensure that the connections are well sealed to avoid any leakage. A poorly sealed hydraulic fittings will result in pressure loss, system leakage, fluid leaks and reduced system performance. This will not only reduce the efficiency of the system, but will also lead to system failure and safety risks.

To ensure efficient and reliable hydraulic systems, hydraulic fittings must have good sealing performance. This is often achieved through the use of sealing materials such as O-rings, conical seals and metal seals. When designing and selecting hydraulic fittings, pressure, temperature, media and other environmental factors must be considered to ensure that they will operate consistently and provide reliable sealing performance.

Evaluation criteria for sealing performance

Common fittings sealing performance evaluation indicators

  • Leakage: The leakage amount of a hydraulic fittingsis the amount of fluid that leaks out from the fittings. The less the leakage amount, the better the sealing performance of the fittings.
  • Working pressure:The working pressure of a hydraulic fittings is the maximum pressure that the fittings can withstand. The higher the working pressure of the fittings, the better the sealing performance.
  • Durability:The durability of a hydraulic fittings refers to the service life of the fittings. The better the durability of the fittings, the better the sealing performance is maintained in long-term use, reducing the cost of repair and replacement.
  • Temperature adaptability:The temperature adaptability of hydraulic fittings refers to the maximum temperature range that the fittings can withstand. A fittings with good temperature adaptability can maintain good sealing performance under different temperature conditions.
  • Compression deformation:Compression deformation of hydraulic fittings refers to the deformation of the internal structure of the fittings under high pressure. fittings with small compression deformation have better sealing performance.
  • Corrosion resistance:The corrosion resistance of hydraulic fittings refers to the ability of the fittings to corrode the medium. A good corrosion resistance fittings can maintain a good sealing performance in a harsh media environment.
  • Selection and use of sealing materials:The sealing material of hydraulic fittings is an important factor to ensure the sealing performance of the fittings. The selection and use of suitable sealing materials can effectively improve the sealing performance of the fittings.

The above indicators are common indicators for evaluating the sealing performance of hydraulic fittings, which are important guides for the design, selection and use of hydraulic fittings.

Test method of fittings sealing performance

  • Leak test:Leak test is a common method of testing the sealing performance of hydraulic fittings The test is performed by adding pressure to the specified value and immersing the fittings in the liquid to observe whether the fittings is leaking or not.
  • Pressure test: Pressure test is to test the sealing performance of the fittingsby adding pressure inside the hydraulic fittings and observing whether the fittings can withstand the specified pressure.
  • Temperature test:The temperature test is to test the performance of the fittings by observing whether the fittings can maintain good sealing performance under different temperatures.

Compression deformation test: The compression deformation test evaluates the sealing performance of a fittings by measuring the deformation of the internal structure of the fittings under high pressure.

  • Seal material durability test:The seal material durability test is conducted to evaluate the durability and suitability of the seal material by observing the performance changes of the seal material under long-term exposure to different media.

Factors affecting the sealing performance of fittings

Choice of materials

The selection of hydraulic coupling material requires consideration of several factors, including media, operating pressure, temperature, operating environment and cost. Common hydraulic fittings materials include the following:

  • Steel: Steel is a commonly used material for hydraulic fittings with high strength and durability for high pressure, high temperature, strong corrosive media and harsh environment applications.
  • Copper:Copper is a good conductive, thermal and corrosion resistant material, suitable for low pressure, low temperature, high conductivity requirements of the application scenario.
  • Cast iron: cast iron is an inexpensive material for hydraulic fittings, suitable for low pressure, general temperature, and economical demanding application scenarios.
  • Stainless steel: Stainless steel has excellent corrosion resistance and high temperature performance, suitable for use in strong corrosive media, high temperature environment.
  • Aluminum alloy: Aluminum alloy has high strength and good thermal conductivity and is suitable for low pressure, high temperature and light weight applications.

In addition to the above common hydraulic fittings materials, you can also choose other materials, such as plastic, rubber, etc., according to the requirements of specific application scenarios.

Influence of processing process

The fittings processing process has a significant impact on the performance and quality of the fittings. The following are the effects of fittings processing on the performance and quality of the fittings:

  • Processing accuracy: the processing accuracy of the fittingsdirectly affects the connection performance and sealing performance of the fittings, and the higher the processing accuracy, the better the connection performance and sealing performance of the fittings.
  • Processing surface quality:the processing surface quality of the fittings affects the sealing performance and corrosion resistance of the fittings, and the better the processing surface quality, the better the sealing performance and corrosion resistance of the fittings.
  • Processing process selection: Different processing processes will have different effects on the performance and quality of the fittings, such as casting, forging, cold extrusion and other processing processes, the performance and quality of the processed fittingsare different.
  • Processing tools and equipment:The precision and quality of the tools and equipment used for fittings processing will also have an impact on the performance and quality of the fittings, and the higher the precision of the processing tools and equipment, the better the performance and quality of the fittings.
  • Processing materials: The quality and performance of processing materials directly affect the performance and quality of the fittings.

O-ring selection and installation

O-rings are a common sealing element used to prevent fluid or gas leakage. In the selection and installation of O-rings need to pay attention to the following points:

  • Choose the right material: choose the right material according to the medium, temperature, pressure and other conditions, generally you can choose buna, fluoroelastomer, silicone rubber and other materials.
  • Choose the right size:the size of the O-ring should match the size of the seal, choosing an inappropriate size may lead to leakage or poor sealing.
  • Check whether the O-ring is damaged or aging:Check whether the O-ring is scratched, deformed, hardened, etc. If it is damaged or aging, it should be replaced in time.
  • Apply lubricant before installation: Before installing O-ring, apply a small amount of lubricant to improve sealing performance and avoid damaging O-ring.
  • Avoid over-stretching or squeezing:When installing O-rings, avoid over-stretching or squeezing to avoid deformation or damage to the O-ring.
  • Do not flip or twist the O-ring when installing: When installing the O-ring, do not flip or twist the O-ring to avoid deformation or damage to the O-ring.
  • Pay attention to the position when installing:O-ring should be correctly installed in the groove of the seal and ensure the correct position of the O-ring to ensure the sealing performance.

Measures to improve sealing performance

Optimized fittings design to reduce leakage points

  • Material selection of the fittings:choosing materials with good corrosion resistance and pressure resistance, such as stainless steel and copper alloy, can effectively reduce the risk of leakage of the fittings.
  • fittingsstructure design: The structure of the fittings should be reasonably designed to ensure a close combination with the seal. Special structural designs such as spherical structure and conical seal can effectively improve the sealing performance of the fittings.
  • Surface treatment:Special treatment of the fittings surface, such as chrome plating, polishing, spraying, etc., can improve the smoothness and corrosion resistance of the fittings surface and reduce the leakage point.
  • Lubricant selection:Choosing the right lubricant can effectively reduce the wear and friction of the fittings and improve the sealing performance of the fittings.
  • Installation techniques: Correct installation of the fittingsis the key to reducing leak points. Care should be taken to avoid excessive stretching or squeezing, not to flip or twist the O-ring, and to choose the correct tightening strength, etc.
  • Regular inspection and maintenance:Check the fittings regularly for damage or aging, and replace or repair them promptly if problems are found to avoid leak points.

Improve fittings machining accuracy to reduce surface defects

  • Selecting the appropriate processing equipment: Selecting the appropriate processing equipment is a prerequisite for improving processing accuracy and reducing surface defects. To choose the appropriate processing equipment according to the shape, material and processing requirements of the fittings, such as lathe, milling machine, drilling machine, etc.
  • Choose the right tool:choosing the right tool can ensure the processing accuracy and surface quality of the fittings. According to the fittings material, processing requirements and cutting conditions, choose the appropriate tool type, cutting edge angle, cutting speed and feed amount and other parameters.
  • Control the machining process parameters: control the machining process parameters can effectively reduce surface defects and improve machining accuracy. Pay attention to the control of machining speed, feed, depth of cut and other parameters, and also pay attention to the selection and use of cutting fluid to ensure the stability of the machining process and surface quality.
  • Detection and correction of machining errors: the machining accuracy and surface quality of the fittingsshould be tested regularly, and if machining errors are found, they need to be corrected in time. Optical measurement, coordinate measurement and other techniques can be used to detect and correct the size, shape and surface quality of the fittings.
  • Pre-processing treatment:The fittings should be processed before processing, such as deburring, rust removal, polishing, etc., to reduce surface defects and improve processing accuracy.

Strengthen the installation and maintenance management of fittings

  • Consider the working environment: The selection of sealing materials and O-rings should be determined according to the working environment of the hydraulic system, such as working temperature, pressure, medium, etc. Different working environments require seals of different materials to ensure sealing performance.
  • Selecting suitable materials: sealing materials are generally divided into two categories: elastic materials and non-elastic materials, commonly used materials are rubber, polyurethane, fluorine rubber, nitrile rubber, etc. Different materials have different characteristics, such as elasticity, hardness, corrosion resistance, etc. Suitable materials should be selected to ensure sealing performance.
  • Choose the right type of O-ring:There are also many types of O-rings, such as inner circle O-ring, outer circle O-ring, square O-ring, etc. The suitable type should be chosen to ensure the sealing performance.
  • Precautions during installation:When installing seals and O-rings, care should be taken not to damage the seals and O-rings, and an appropriate amount of lubricant should be applied during installation to avoid wear due to dry friction.
  • Maintenance management:The wear of seals and O-rings should be checked regularly and replaced in time if there is wear to avoid leakage due to degradation of sealing performance.


By choosing suitable sealing materials and O-ring types, strengthening the fittings processing process, ensuring the quality of fittings installation, regularly inspecting and replacing seals, and doing a good job of hydraulic system maintenance management, we can effectively improve the fittings sealing performance and hydraulic system stability, thus ensuring the normal operation of the hydraulic system.

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