Sealing is a mechanism that prevents leakage (internal and external) of working media and prevents foreign objects (such as air, dust, and water) from entering hydraulic components and systems.
Although seals are auxiliary components in hydraulic equipment, the quality of seals and sealing devices is one of the key factors directly affecting the normal operation of hydraulic systems. The quality of seals has to some extent constrained the improvement of the performance and reliability of hydraulic components and hydraulic systems, the length of their service life, and the key factors affecting the grade and level of hydraulic equipment and participation in international competition. This is also one of the main factors affecting the quality differences of hydraulic components at home and abroad. Often, the losses caused by the failure of individual seals can be tens of millions of times the value of the seal itself.
Dust Seal
Installed on the inner side of the hydraulic cylinder end cover, the main sealing lip is exposed to the air, and the sealing medium is dust, sand, rainwater, frost and other dirt attached to it, preventing external dust and rainwater from entering the sealing mechanism, affecting the viscosity of the hydraulic oil and scratching the sealing lip of the internal seal.
Dust sealing rings are available in various types, sizes, and sizes, including polyester and outer metal frames. Therefore, their range of use and target objects are more extensive.
Advantages: Excellent wear resistance, extrusion resistance, impact resistance, minimal compression deformation, wide adaptability, and easy installation. OTH-A11 dust sealing ring
OTH-A11 dust sealing ring
Piston rod seal
Installed inside the dust seal on the inner side of the hydraulic cylinder end cover, its function is to prevent hydraulic oil leakage. It is one of the main pressure bearing components, with one-way pressure bearing and direct contact with hydraulic oil. Require good pressure holding performance in a static state, high pressure bearing during movement, good sealing performance, low friction coefficient, strong resistance to extrusion, etc.
There are many cross-sectional forms and materials for piston rod seals, and different cross-sectional forms and materials should be selected according to different working environments. OTH-S24 type pull rod seal
OTH-S24 type pull rod seal
Guiding belt and support ring
support ring
Installed on the inner side of the hydraulic cylinder end cover, its main function is to support the piston rod; Prevent poor sealing effect and short service life caused by uneven pressure on the rod seal due to non vertical force on the piston rod.
Guidance tape
Installed on the piston, its main function is to guide the piston to move in a straight line, prevent the piston from deviating due to uneven force, and reduce the service life of the seal.
The service life of the guide belt and support ring directly affects the effectiveness and service life of the piston seal and piston rod seal, so the requirements for the guide belt and support ring are also high, such as low friction coefficient, high hardness, and long service life.
There are many forms of guide belts and support rings, as well as those used in combination with the main seal (OTH/K09). OTH-F01 type guiding support ring
OTH-F01 type guiding support ring
piston seal
Installed on the piston, its main function is to seal the gap between the piston and the cylinder, preventing hydraulic oil leakage, etc. The piston seal is the main seal inside the hydraulic cylinder, which can withstand pressure in both directions and is one of the most important seals that the hydraulic cylinder can withstand. The main requirements for piston sealing include good sealing effect, good pressure holding effect in static state, strong pressure bearing capacity during movement, resistance to extrusion, low friction coefficient, and long service life.
There are various forms of piston seals, and the most suitable form should be selected according to different usage environments. OTH-K09 piston seal
OTH-K09 piston seal
Static sealing
The static sealing ring of the end cover is installed at the contact position between the outer circle of the end cover and the inner wall of the hydraulic cylinder; The piston static seal ring is installed between the piston and the piston rod.
They are all static sealing rings inside the hydraulic cylinder. The static sealing of the end cover is to prevent hydraulic oil from leaking out of the gap between the end cover and the cylinder barrel, with single-sided pressure bearing, requiring strong anti extrusion ability and good sealing effect; Piston static seal is a bi-directional pressure bearing device that prevents hydraulic oil from leaking between the piston and piston rod. It requires strong anti extrusion ability and good sealing effect.
The common static sealing ring is an O-ring with a retaining ring. OTH-K35 type static sealing ring
OTH-K35 type static sealing ring
rotary seal
Installed on the shaft of the hydraulic pump and hydraulic motor to prevent the working medium from leaking out of the housing along the shaft and external dust from entering the interior of the machine. The ability of general oil seals to withstand pressure is poor, generally ranging from 0.2-0.3 MPa. Fluorine rubber pressure resistant oil seals have a pressure bearing capacity of 0.25-0.7 MPa, and the highest pressure bearing capacity of OTHELLO high-pressure oil seals is 40 MPa. OTH/A/A02 type skeleton oil seal
OTH/A/A02 type skeleton oil seal
The main cause of seal leakage
Installation issues
The incorrect installation direction of the seal resulted in leakage.
During installation, foreign objects, dust, etc. may enter the sealed chamber and cause leakage.
Poor assembly caused damage to the sealing components, resulting in leakage.
Scratches on the surface of the sealing component caused leakage.
5 piston rods are not concentric, causing leakage due to biased load.
Selection of sealing components
1. The pressure is too high and the hardness of the seal is too low, causing it to be squeezed out of the metal groove.
The sealing material and medium are compatible, and the sealing element is softened or dissolved.
Three seals are used in high-temperature conditions, and the sealing material is carbonized.
Low temperature causes the sealing material to harden and shrink, leading to leakage.
Using a line speed that is too high can cause the seal to overheat, dry grind, and carbonize, resulting in leakage.
Poor lubrication under operating conditions resulted in seal wear and leakage.
The cavity used by 7 is leaking due to vibration.
8. Leakage caused by seal wear due to dust.
The hardness of the 9 seals is too high to completely fill the metal grooves, causing leakage.
The size of the 10 seals does not match the metal groove, causing leakage.
11. Using seals that have been stored for too long or have aged can cause leakage.
Sealing structure design and assembly issues
Improper selection of supporting materials for cavity 1 results in wear and tear on the cavity and piston rod.
The size of the friction pair is not suitable, causing wear and tear.
Improper chamfering of the threads at the end of the 3-cylinder cylinder and piston, resulting in worn seals.
4. Inappropriate chamfer during seal installation and wear of seals.
5. The surface of the cavity and piston rod is rough, with scratches and worn seals.
Precautions for installation of hydraulic seals
1. Check the surfaces of the piston, cylinder, and installation guide sleeve, ensuring they are clean, free of burrs, and edges.
The installation tool should be smooth, without edges or sharp corners, to ensure that the seal will not be damaged in any form during the installation process (it is recommended to use Othello's OTH-0003 hydraulic seal special installation tool).
During installation, a small amount of lubricating grease can be applied to the sealing components and cylinder related surfaces to facilitate installation. However, residual lubricating grease is not allowed between the rubber elastomer and the sliding sealing ring, otherwise it will affect the sealing performance.
Whether installed vertically or horizontally, the coaxiality between the piston and cylinder should be maintained, as excessive eccentricity may damage the seals.
The installation speed should not be too fast, otherwise it may damage the sealing components. OTH-0003 type pull rod seal installation tool
OTH-0003 type pull rod seal installation tool
OTHELLO Mold free Sealing Technology
1. Advanced mold free processing equipment and technology can process high-quality seals of any specification, material, cross-section, and quantity, with a diameter of up to 4000mm;
We can customize sealing solutions for you and provide a series of services from design, production to after-sales service;
3. The sealing components for turning have no mold or standard restrictions. The thickness can be changed according to the overall wear condition of the oil cylinder, and tolerances can be reasonably configured to produce more personalized and suitable products;
4. Common problems with molded parts such as missing glue, rotting, uneven parting surface height, difficulty in trimming edges, and difficulty in controlling key dimensions;
5. The installation of turning seals is not easily deformed, resulting in better sealing effect;
The fast delivery speed greatly reduces the downtime for equipment maintenance.
Sealing materials and their properties
Sealing materials mainly use rubber and synthetic resin, and their uses vary due to the different performance characteristics of various materials. When selecting, appropriate choices should be made based on different usage requirements and conditions.
The compatibility between a sealing material and hydraulic oil refers to the fact that the sealing performance of a certain material is relatively good for a certain working medium being sealed, but extremely poor for another medium.
