U- Seals Application in Engineering Machinery Hydraulic Systems

1. Main Application Positions

U-type seals are widely used in reciprocating motion components of construction machinery hydraulic systems, mainly including:

Core Sealing of Hydraulic Cylinders

Piston Sealing: Installed in the piston groove of hydraulic cylinders of excavators, loaders, and cranes. It is used to isolate the rod chamber and rodless chamber of the cylinder, preventing internal leakage of hydraulic oil

Piston Rod Sealing: Installed in the end cover groove of the hydraulic cylinder. It prevents the hydraulic oil inside the cylinder from leaking outward, and blocks external dust, mud and water from entering the cylinder

Auxiliary Sealing of Hydraulic Actuators

In the reciprocating parts of small hydraulic motors and hydraulic push rods (such as the auxiliary device hydraulic system of small excavators), small-sized U-type seals are also used for sealing

2. Core Advantages for Hydraulic Systems

The hydraulic systems of construction machinery are generally of high pressure, large flow, and complex working conditions, and the structure and performance of U-seals match well:

High-pressure Adaptive Sealing

The lip structure of the U-seal will automatically fit the sealing surface as the pressure of the hydraulic system increases. The higher the pressure, the better the sealing fit, and there will be no sealing failure under high pressure. It is suitable for the conventional working pressure of 10-35 MPa of construction machinery hydraulic systems, and U- seals made of some special materials can withstand higher pressure

Compatibility with Hydraulic Oil Media

U- seals made of commonly used nitrile rubber (NBR)，FKM and polyurethane (PU) materials are well compatible with mineral oil-based hydraulic oils commonly used in construction machinery hydraulic systems, without swelling or accelerated aging

Strong Pollution Resistance

The lip of the U- seal can scrape off a small amount of dust and mud attached to the surface of the piston rod during reciprocating motion, reducing the probability of pollutants entering the hydraulic system and reducing the failure probability of the hydraulic system

3. Precautions for Application

Groove Design Matching

The corresponding installation groove needs to be designed according to the specifications of the U-type seal to ensure that the U-type seal has a proper pre-compression amount after installation. Excessive pre-compression will accelerate wear, while insufficient pre-compression will cause sealing failure

Material Selection Matching Working Conditions

For conventional hydraulic systems of excavators and loaders, PU materials are sufficient

For construction machinery operating in low-temperature environments, cold-resistant NBR materials are required.

Installation Protection

During installation, avoid scratching the U-type seal by the sharp edges and threads of the cylinder. It is recommended to use installation tools for auxiliary installation