Effect of materials on the performance of oil seal hydraulic seals

The leakage of lubricating oil from bearing. Requirements on the seal hydraulic seal is size (inner diameter, outer diameter and thickness) should be in accordance with the provisions; requires appropriate flexibility that the shaft can be properly stuck and plays a role in sealing; It would be heat-resistant, wear resistance, strength, good resistance to medium (such as oil or water), and long service life.

The first step in rubber formula design is the most important step that in order to select rubber substrate or raw material. Rubber is one kind of engineering materials, they have some common basic characteristics, despite of their composition. All rubber have elasticity, bending resistance, toughness, not easily permeable and air permeable properties. In addition to these common characteristics, each with a nature of its own, because each kind of rubber the different composition.

In order to use the oil seal hydraulic seals reasonably, you should pay attention to the following points:

Due to the reason of the structure and design t in the rotational ,the high speed of the shaft axes should use for high speed oil seal, low speed shaft for the low speed oil seal, cannot be low-speed oil seal for high-speed shaft.

Ambient temperature in the use of high temperature should choose polypropylene ester or silicon, fluorine, silicon and fluorine rubber. And should manage to reduce the oil temperature in the tank. In the use of low temperature, should choose the cold resistant rubber.

Oil seals in general pressure are poor with bearing the pressure, the oil seal will be deformed the when pressure is too large .when Under too much pressure ,should use the pressure bearing ring or strengthen the pressure oil seal.

Installation of eccentric and shaft with the degree of eccentricity are both too large, the seal will be poor. Especially in the high speed shaft, the situation is particularly serious.when the eccentric is too large, you can use the "W" - shaped section of the oil seal.

The smoothness of the surface in the shaft directly affects the service life of the oil seal, that is, the smoothness of the shaft is high, so the service life of the oil seal is long.

Pay attention that there should be a certain amount of lubricating oil in the lip of the oil seal.

The performance of seal lip material has an extremely important influence on the seal hydraulic seal. It determines the oil seal hydraulic seals’ the range of operating temperature, friction, wear resistance, dielectric properties and sealing performance etc. Therefore, as a rubber seal lip material, in addition meet the appropriate mechanical strength and hardness, temperature resistance, media work and other general requirements, but also must have good flexibility so that the shaft has good follow and irregularities in the shaft, eccentric vibration and have a good ability to compensate when the shaft runs. At the same time, highly flexible sealing lip on the radial force required for the shaft that to be sealed is also small, and that can reduce friction and friction heat.

The state of rubber O ring seal movement

Rubber O-ring is a circular cross section of the annular seal. It is the largest output and the standardization and serialization are highest level, also it’s the most mature of seal products in all seal products.

Rubber O-ring in the fluid state can be divided into static seal and dynamic seal according their work.

When the rubber O ring is used to seal the reciprocating motion, the sealing mechanism is self-sealing.

     The process is very complex because the rubber O-ring in motion and the fluid pressure from O-ring two sides alternately.Through the experiment of the piston rod seals,we’ve known the principle about the motion O-ring seal and the mechanism of leak.If we magnify the O-ring and shaft surface,it will uneven especially the connection.When the axial began to move to the right, due to the shaft and sticky liquid with O-ring and shaft between the wedge-shaped narrow area, make this part of the liquid pressure greater than the pressure of working fluid.If this pressure is greater than the contact pressure of the O ring, the rubber O ring will be pushed up, the liquid will be invaded into the recess, resulting in leakage. When axial movement in the opposite direction , because the opposite direction of the shaft and the motion direction of the pressure, leakage along the axial direction of motion will decreases.So the difference between the two formed reciprocating motion to external leakage.

The rubber O ring is placed in the sealing groove, one side or both sides are required to be sealed fluid medium.Regardless of the subject to mechanical pressure of the surrounding mechanical structure, or by transfer hydraulic fluid pressure and elastic body by variant (elastic or inelastic) to compensate the gap, into the "zero space", or stop by the sealing fluid flow.The elasticity of the rubber compensates for the manufacturing and tolerance, and the elastic memory inside the material is an important condition for maintaining the seal.

From a polymer point of view, the sealing behavior of the rubber O - ring material is similar to a highly viscous fluid, which has the characteristics of the pressure delivered to the surface.The rubber O-ring is installed in the groove to make the section to be compressed (usually 8%-25%), then it will generate an initial contact stress.In sealed fluid (air, water, oil, etc.) very low pressures or is zero, under the high pressure of the fluid, rubber O-ring is pressed to the trench corner opposite to the direction of the pressure and plugging fluid leakage path of the stress distribution, and plays a role in sealing.That mean under the high pressure of the fluid, the sealing contact pressure is the initial contact of rubber O-ring should force and the fluid pressure generated by contact forces. Contact pressure is slightly larger than the working pressure of the fluid, so greatly progress sealing effect.

Rubber is elastic hot melt hard setting body, plastic is hot cold setting.Rubber,due to the different types of sulfide, the temperature range of molding and curing, also has a considerable gap, and even can be affected by climate change, indoor temperature and humidity.Therefore, the production of rubber products, need to do at any time to adjust the appropriate, if not, then there may be differences in the quality of products.

Xinhuaxu high temperature rubber seal characteristics description.

High temperature resistant rubber seal ring is a high temperature resistance, oil resistance, ozone resistance, aging resistance and high gas tightness, is a high performance rubber.Commonly used silicone rubber, fluorine rubber, poly sulfur rubber, epichlorohydrin rubber, nitrile rubber, acrylate rubber, polyurethane rubber and butyl rubber, such as, mainly for the requirements of some characteristics of special occasions.

High temperature resistant silicon rubber sealing rings is refers to special properties (such as high temperature resistance, oil resistance, ozone resistance, aging resistance and high gas tightness, etc.), and application in special occasions , such as acrylonitrile butadiene rubber, butyl rubber, silicone rubber, fluorine rubber. Special rubber dosage is small, but in the special application occasions is indispensable.Acid alkali proof ring O sealing ring can be used to seal the original, but also can be used as a hydraulic sliding seal and dust ring of the force application .

FPM o ring seals are the synthetic rubber containing Fluorine atom., whose advantages are great hot resistant, oxidation resistance,oil resistance and chemical resistant. As sealing materials, resistant dielectric material and insulation materials, It mainly uses in aviation, chemical, oil, automobile and other industrial sectors. Fluorine rubber (FPM) is an organic elastomer which is formed by the co-polymerization of fluorinated monomers. Its high temperate resistant up to 300°C,  acid resistant , meanwhile, oil resistant are the best in all rubber of oil resistant. The performance of anti radiation and high vacuum resistant are both great. Electrical insulation, mechanical properties, chemical resistance, ozone resistance, resistance to atmospheric aging are excellent. The disadvantage is poor in productive process,expensive , poor cold resistant, low elasticity, low permeability. Temperature range: - 40 DEG C ~300.

    FPM o rings are the rubbers whose backbone is made up of silicon and oxygen atom, side-chain is made up of carbon bearing group. The most quantity of FPM is the silicon rubber whose side-chain is made of vinyl group. It is hot resistant, cold resistant, temperate between -100°C~300°C, and it is also weather resistant, ozone resistant, good at insulating property. The disadvantages are low strength, low performance in elasticity resistant, low abrasion resistant. Silicone rubber sealing ring is mainly used in aviation industry, electrical industry, food industry and medical industry, etc..

   How to choose o ring and hydraulic o ring correctly.

     hydraulic o ring extrusion is the rate of sealing````      .                 The elastomer matrix of ‘electrical’ cross section of deformed hydraulic o ring is like compression spring:inherent elasticity of rubber materials makes it back and against mating component. The contact force block liquid, gas and dry powder prevent them from flowing between the rubber seal and the hardware.

        The greater the pressure of the hydraulic O loop, the greater the force is applied on the hardware and the tight seal. But it doesn’t mean that designers always say it’s the most deformed.(Assuming they know why it’s that level, it called ‘the most’) It’s necessary to think about a great number of factors. If you add too much, it may can be potentially damaging to mating hardware, depending on the material and hardware design.

     Wear of o ring .With higher extrusion is also equipped with more friction and dynamic applications.This may be enough to affect the functionality of the device. For example, in a medical device involving manual adjustment, a o ring,whose excessive friction may prevent doctors from using the device correctly.

Hydraulic o ring damage, with a higher extrusion to make a higher risk. It occurred after installing o rings. Making the path to seal fluid or gas around. When o rings are deformed in 40% or 25%. The model description is fitted to the male (piston type) period. Hydraulic O type ring pinch damage O type ring seal. At the 40% level, the pinch is difficult to avoid, but the clamp is removed at a level of 25%.

Permanent compression deformation of hydraulic o ring. The extruded elastomer is applied by the matching hardware. The hardware’s seal always increase by the time. When these power all increase , the hydraulic o ring will be saved even though it cannot be deformed. The compression set is measured by this decay, expressed as a percentage. When the compression deformation is up to 80%, most of the hydraulic O circles are in danger of losing the sealing ability. Hydraulic o ring need long time to reach the level of 80% permanent compression deformation in a high level extrusion. So higher level extrusion generally translate into longer o ring life.

     Designers need to think about all factors except some specific factors, for example, the pressure of temperature and material are sealed. Before they decide how many o rings are applied to crush, they need to decide correctly . in order to ensure o rings cannot be twisted, don’t stretch o rings too much.