Sealing technology and development trend of hydraulic joints

The sealing technology of hydraulic joints is the core of confirming the excellent operation of hydraulic systems, and its performance directly affects system pressure maintenance, leakage control, and component life. With the development of hydraulic technology towards high pressure, high speed, and environmental protection, sealing technology is also innovating its services. The following are the key points and future trend analysis of hydraulic joint sealing technology:

1、 The core technology of hydraulic joint sealing

1. Sealing structure type

o-ring seal

Principle: Fill the sealing gap with the elastic deformation of the O-ring to form an initial sealing force.

Features: Simple structure, low cost, but limited high pressure resistance (usually ≤ 35MPa), requiring groove design to prevent extrusion.

Application: Low pressure hydraulic systems, general industrial equipment.

Flat seal (end face seal)

Principle: Sealing is achieved by adhering a metal or hard material plane to a sealing gasket (such as a metal gasket or PTFE gasket).

Features: High pressure resistance (up to 100MPa or above), anti vibration, but requires suitable precision for processing and confirmation of flatness.

Application: High pressure hydraulic valves, engineering machinery joints.

sphenecal mechanisam

Principle: By utilizing the automatic centering characteristics of spherical and conical surfaces, a line contact seal is formed under pressure.

Features: Good anti eccentricity ability, excellent sealing, but high processing accuracy requirements.

Applications: High pressure quick couplings, aerospace hydraulic systems.

Composite seal

Principle: Combining O-ring with wear-resistant (based on actual reports) rings (such as polyoxymethylene POM) and retaining rings (such as nylon) to achieve a combination structure that balances sealing and anti extrusion performance.

Features: High pressure resistance, wear resistance (based on actual reports), long service life, but high cost.

Application: Hydraulic systems for heavy machinery and injection molding machines.

2. Innovation in sealing materials

Fluororubber (FKM)

High temperature resistance (based on actual reports) (up to 250 ℃), chemical corrosion resistance, suitable for media such as hydraulic oil and fuel oil.

Hydrogenated Nitrile Rubber (HNBR)

Oil resistance is better than ordinary nitrile rubber, and it has good low temperature resistance (below -40 ℃).

Polytetrafluoroethylene (PTFE)

High temperature resistance (based on actual reports), resistance to almost all chemical media, but poor elasticity, requiring improvement in sealing through spring energy storage or filling modification.

Nanocomposites

By adding nanoparticles (such as silica and carbon nanotubes) to rubber, performance, tear strength, and aging resistance can be improved.

3. Surface treatment technology

Coating treatment

By plating hard chromium and nickel phosphorus alloys, the hardness of the sealing surface can be improved and wear can be reduced.

laser cladding

A higher hardness alloy layer is formed on the sealing surface, significantly improving the ability to resist particle wear.

Microtexturing

Processing micro grooves on the sealing surface through laser or etching to store lubricating oil and reduce friction coefficient.

2、 The development trend of hydraulic joint sealing technology

1. High pressure and higher pressure

Demand driven: The pressure requirements for hydraulic systems in industries such as construction machinery and aerospace are constantly increasing (such as from 35MPa to 70MPa, 100MPa).

Technical direction:

The combination sealing structure of equipment with high pressure resistance (such as double O-ring+retaining ring).

Use high-strength sealing materials (such as carbon fiber reinforced PTFE).

Optimize the geometric shape of the sealing surface (such as multi-stage spherical sealing).

2. Environmental Protection and Sustainability

Low leakage design:

By improving the sealing structure (such as zero leakage valve core design) and materials (such as low-permeability rubber), it meets environmental requirements such as the EU REACH regulation.

Compatibility of Biodegradable Hydraulic Oil:

The equipment is suitable for sealing materials of plant-based and synthetic ester hydraulic oils, avoiding environmental pollution caused by traditional mineral oil leaks.

3. Intelligence and self-monitoring

Embedded sensors:

Integrate pressure, temperature, or leakage sensors into the seal to monitor the sealing status in real-time and predict maintenance needs.

Self attentive service materials:

Research on sealing materials with microcapsule self attentive service function. When microcracks appear on the sealing surface, the capsule ruptures and releases the attentive service agent, automatically filling the defect.

4. Lightweight and miniaturization

Material lightweighting:

The joint body is made of lightweight materials such as aluminum alloy and titanium alloy, combined with high-strength sealing materials (such as PEEK) to reduce system weight.

Compact structure:

By using 3D printing technology to manufacture complex sealing structures, the number of parts can be reduced, and the joint volume can be reduced (such as the diameter of micro hydraulic joints can be less than 10mm).

5. Adaptability to extreme working conditions

High temperature resistance (based on actual reports)/low temperature:

Ceramic sealing materials with high temperature resistance (based on actual reports) (>300 ℃) or silicone rubber modified materials with low temperature resistance (below -60 ℃) for equipment.

Radiation and corrosion resistance (based on actual reports):

For scenarios such as nuclear industry and deep-sea exploration, we manufacture radiation resistant and seawater corrosion-resistant sealing technologies (such as Hastelloy coating+PTFE composite sealing).

3、 Future challenges and directions for response

Coexistence of high voltage and high frequency vibration

Challenge: Seals are prone to extrusion under high pressure, and fatigue failure is caused by high-frequency vibration.

Direction: Equipment dynamic sealing technology (such as floating sealing rings), optimizing material damping performance.

Multimedia compatibility

Challenge: The same system needs to be compatible with multiple media such as hydraulic oil, water-based fluid, and gas.

Direction: Design universal sealing structures or achieve quick switching through modular sealing components.

Balancing Cost and Performance

Challenge: The cost of stable sealing materials such as PEEK and nanocomposite rubber is relatively high.

Direction: Improve the performance of ordinary materials and reduce overall costs through material surface modification (such as plasma spraying).