The role and important knowledge of seals

In the hydraulic system and its components, the design and placement of the sealing device and sealing elements of the role: to prevent the leakage of the working medium and the invasion of foreign dust and foreign bodies. The utility model is characterized in that a sealing element is arranged in the sealing device.

Seal can be divided into two types of static seal and dynamic seal. There are three main types of static seal gasket seal, sealing and direct contact seal. Based on the working pressure of distinction, and can be divided into static seal sealing in low and high pressure static seal, seal pressure mainly by the gasket material is soft and wide sealing, and high pressure sealing with metal gasket material, hard contact width narrow. Dynamic seal can be divided into rotary seal and reciprocating seal.

In general, the requirements of the hydraulic system on the sealing ring or the choice of the main elements of the sealing ring to consider the following points:

1 in the condition of pressure, temperature range has a good sealing effect

2 when there is relative motion, the friction force caused by the seal should be as small as possible, and the friction factor should be as stable as possible.

3 corrosion resistance, good wear resistance, not easy to aging, long service life, after wear to a certain extent, automatic compensation.

4 simple structure, easy disassembly and assembly, low cost.

One of the most commonly used is the rubber seal gasket and combination seal gasket.

Rubber seals are mainly O ring, Y ring, etc., in which the most widely used O ring.

O shaped ring: O ring is formed in the mold vulcanization; its role is the role of two-way sealing elements. Due to the initial compression in the radial or axial direction at the time of installation, the O ring has the capability of initial seal. Due to the pressure generated by the system and the initial sealing force together with the total sealing force, and it will increase with the system pressure increases.

General installation for the overall groove design, can reduce the cost of parts design. The utility model has the advantages of simple installation, low error rate, large material selectivity and strong applicability.

O type ring can be used as the main sealing element, can also be used for sliding shoe seal and dustproof ring of force components, so almost no industry is not using O.

In the mechanical design manual has been the size of the O ring standardized serialization

GB GB1235-76 meaning is: the diameter of the outer diameter of the format to represent the O coil specifications

GB recommended standard GB/T3452.1-1992 meaning is: the use of the diameter of the inner diameter of the format to represent the O coil specifications.

Technical data:

Pressure range: no less than 20Mpa when the ring, when the ring is less than 40Mpa. Temperature: depending on the O type ring material properties in general: -30 C ~+110 C / C in the use of special consideration must be given to the use of the working conditions of the occasion. For example: the mold cylinder in the O ring will generally use FKM (fluorine rubber) material, can withstand high temperature.

The disadvantage is: as a dynamic seal, the starting friction resistance is larger, can not automatically compensate for wear, short service life.

O type ring installation: it can be used in the end of the installation can also be used in radial installation. Installation should be equipped with the corresponding trench, generally have about 20% of the compression margin, and the installation can not be allowed to distort it in the trench. Avoid the use of threads, with sharp edges and other sharp edges when the surface of the seal. After installation, if placed for a long time, should be wrapped with plastic wrap.

Application example of O ring:

1 we commonly used welded joint is to rely on O ring seal, in the welding can not be installed. Joint JB970-77 welding straight through the outer diameter of phi 32 specification is GB1235-76 30*3.1 O ring.

Combination pad: this ring is made of soft seal and metal ring, the role of the middle seal, the outer ring plays a supporting role. Sealing performance of the combined gasket is good, the connecting force is small, the pressure is high, and the utility model can be used for the static sealing of working pressure 40Mpa. Installation does not require special trench, easy to replace the installation. It is also widely used in the hydraulic system, so the Ministry of machinery launched its standard code JB982-1977.

The combination of the use of the main occasion of the joint seal, the installation of the screw and screw on the inner ring to apply the initial sealing force.