What Are The Oil Seals And Common Styles of Oil Seals?
1.Introduction of Oil Seal
Oil sealsare mechanical components for sealing, also known as rotary shaft lip seals, the friction part of the machinery due to the mechanical operation of the oil into the oil, in order to prevent these oil leakage from the middle of the machinery and the use of oil seals.
2.Oil Seal Representation Method
Common Expression:Oil sealtype - inner diameter - outer diameter - height - material. For example: TC40*62*12-NBR means: double lip inner skeleton oil seal, inner diameter 40, outer diameter 62, thickness 12, the material is nitrile rubber oil seal.
3.Material of Skeleton Oil Seal
Nitrile rubber (NBR): wear-resistant, oil-resistant (can not be used in polar media) Temperature resistance: -40 ~ 120 ℃.Hydrogenated NBR (HNBR): wear-resistant, oil-resistant, aging-resistant, temperature-resistant: -40~200℃ (stronger than NBR temperature-resistant ability).Fluorine rubber (FKM): acid and alkali resistance, oil resistance (resistant to all oils), temperature resistance: -20 ~ 300 ℃ (oil resistance is better than the last two kinds).
Polyurethane rubber (TPU): abrasion resistance, aging resistance, temperature resistance: -20 ~ 250 ℃ (aging resistance is good and excellent).
Silicone rubber (PMQ): heat resistance, cold resistance, compression permanent deformation of small mechanical strength, temperature resistance: -60 ~ 250 ℃ (excellent temperature resistance).
Polytetrafluoroethylene (PTFE): good chemical stability, acid and alkali resistance, oil and other media, wear-resistant, high temperature, high mechanical strength, good self-lubrication.
Generally speaking, the skeleton oil seal often used materials nitrile rubber, fluorine rubber, silicone rubber, PTFE. Because of good self-lubrication, especially after adding bronze effect is better, are used in the production of retaining ring, Gryllis ring, Stefan seal, and so on.
4. Distinguish The Skeleton Oil Seal Type
C type skeletonoil seals for the inner skeleton oil seal can be divided into SC type, TC type, VC type, KC type, DC type of these five, respectively, is a single-lip inner skeleton oil seal, double-lip inner skeleton oil seal, single-lip unsprung inner skeleton oil seal, double-lip unsprung inner skeleton oil seal, double-lip double-spring inner skeleton oil seal.G type skeleton oil seal is out of the threaded shape, its type and C type the same, just in the process of modifying the outside into a threaded shape, similar to the role of the O-ring, that is, to play a role in strengthening the sealing effect, but also play a role in fixing the oil seal does not loosen.
B type skeleton oil seal is the skeleton inside with rubber material or skeleton inside and outside are no rubber material, no rubber material will make the heat dissipation performance better.
A type skeleton oil seal is assembledoil seals, the structure is relatively complex, characterized by better and more excellent pressure bearing performance.
They are different forms of oil seals. The common forms of general purpose oil seals are as follows：
| Outer DiameterDesign | Double Iron Shel | Housing Iron Case | Rubber Covered | Fully covered With Rubber | Fully Encapsulated With Inner And Outer Rubber | ||
| Inner Diameter Design | |||||||
| Spring | Lip Design | A | B | C | F | M | |
| Installed | Single Lip | S | on | SB | SC | SF | SM |
| Double Lip | T | FACING | TB | TC | TF | TM | |
| Not Installed | Single Lip | V | AND | VB | VC | VF | VM |
| Double Lip | K | THE | KB | KC | KF | KM | |
5.Common Styles of Simmerring Oil Seals
The rubber sealing bodies of TBG oil seals are usually made of materials such as nitrile rubber, hydrogenated nitrile rubber, acrylate rubber and fluoroelastomer, which have good oil resistance, high temperature resistance and chemical resistance. The metal skeleton is usually made of high strength materials to ensure the durability and reliability of the oil seal.
6.Sealing Principle and Application of Simmerring Oil Seal
The skeletonoil seals is divided into three parts: self-tightening spring, sealing body and reinforcing skeleton.
The sealing principle of the skeleton oil seal: due to the existence of the oil film controlled by the oil seal edge between the seal and the shaft, this oil film has fluid lubrication characteristics.
Analysis of sealing principle: Under the action of the skeleton oil seal, the rigidity of the oil film is just enough to form a crescent surface at the contact end of the oil film and air, preventing the leakage of the working medium and thus realizing the sealing of the rotary shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface, if the thickness is too large, the oil seal leaks; if the thickness is too small, dry friction may occur, causing wear of the oil seal and the shaft; if there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. Therefore, when installing, some oil must be applied to the seal, and at the same time ensure that the skeleton oil seal is perpendicular to the shaft centerline; if not, the sealing lip of the oil seal will drain the lubricant from the shaft, which will also lead to excessive wear of the sealing lip. In operation, the lubricant in the housing slightly oozes out a little.
7. The Role of the skeleton oil seal
General skeleton oil seal will drive parts in need of lubrication parts and force components isolated from the lubricant leakage, usually used for rotary shafts, is a rotary shaft lip seal. The skeleton is like the steel reinforcement inside the concrete member, which plays the role of strengthening, and enables the oil seal to maintain the shape and tension. According to the skeleton type, it can be divided into inner skeleton oil seal, outer skeleton oil seal, inner and outer exposed skeleton oil seal. The skeleton oil seal is made of high quality nitrile rubber and steel plate, with stable quality and long service life.
1.Preventing mud, dust, water and gas from intruding into the bearing from outside.
2.Limit the lubricating oil leakage in the bearing. Requirements for the oil seal is the size (inner diameter, outer diameter and thickness) should be in accordance with the provisions. Requirements for appropriate elasticity, the shaft can be properly stuck, play a sealing role. To be heat-resistant, wear-resistant, good strength, resistant to media (oil or water, etc.), long service life.
The selection ofoil seals should be based on the sealing medium and working conditions, the sealing medium needs to select the material of the oil seal, the working conditions mainly consider the use of pressure, working line speed, working temperature range.
When selecting the material of oil seal, the compatibility of the material to the working medium, the adaptability to the working temperature range and the ability of the lip to follow the rotary shaft when it rotates at high speed must be considered. The temperature of the lip of the general oil seal is higher than the temperature of the working medium by 20~50℃, which should be noted when selecting the material of the oil seal.
The use pressure of common oil seal is generally not more than 0.05MPa, when the working pressure is more than this value, pressure resistant oil seal should be used.
Under the condition of the same diameter, the oil seals made of different materials have different ability to adapt to the rotational linear velocity of the shaft surface. The range of linear velocity used by the oil seal is generally less than 15m/s.
The working range of the oil seal is related to the material used for the oil seal: -40~120℃ when the material is Nitrile Rubber (NBR), -30~180℃ when it is made of Alec Rubber (ACM), and -25~300℃ when it is made of Fluoroelastomer (FPM).
8.Design Requirements For Corresponding Shafts And Cavities
Design of shaft:
1. Surface Roughness:Due to the speed of the shaft and the oil volume is different, the general shaft roughness is too large or too small, will affect the leakage and wear of the oil seal. The allowable range of surface roughness of shaft is Rz1.0~5.0μm; Ra0.2~0.8μm. 2.5~1.6μmRz is taken for oil seal for rotary shaft.
2.Hardness:The surface hardness of the rotary shaft is generally taken as ≥ 35 HRC. when the medium is dirty, there are pollution impurities from the outside world, or the speed of the shaft table > 12m/s, the surface hardness of the shaft should be 55 HRC or more, the depth of the quenching layer on the surface of the shaft > 0.2mm.
3.Shaft chamfering, the recommended value of 15 ° ~ 30 °, in order to allow the oil seal is indeed loaded, do not damage the oil seal lip as a principle.
4.Shaft Processing:The correct shaft processing is to ensure the normal operation of the sealing system is a decisive factor, the appropriate oil seal shaft processing method is transverse to the fine grinding, emery paper grinding. Unsuitable processing method is on the lathe finishing, ultra-finishing, rolling processing, diamond paper grinding (sandpaper in the axial movement grinding).
5.Shaft Material:Mainly ordinary carbon structural steel, such as C35 and C45, in addition to cast iron, ceramic, resin plastic, but the latter three materials of the shaft on the oil seal seal are defective.
9.Installation of Oil Seal
1. Before loading the machine, the oil seal should be appropriately coated with lithium ester with molybdenum disulphide added between the lips to prevent the shaft from dry grinding phenomenon on the lips during the instantaneous startup, which affects the overload of the lips, and should be assembled as soon as possible, as soon as possible. The oil seal seat of the installed oil seal, if it is not immediately mounted, it is recommended to cover the top with a cloth to prevent foreign objects from adhering to the oil seal. The hand or tool for applying lithium grease must be clean.
2. The oil seal should be mounted flat, without tilting. It is recommended to use oil pressure equipment or socket tools to install. The pressure should not be too high and the speed should be even and slow.
3. The oil seal should be installed with oil or lubricant applied and the shaft end and shoulder rounded off.
4. When installing the oil seal, be sure to keep the lip end toward the side of the oil being sealed, and never assemble in reverse.
5. When the oil seal is inserted into the seat hole, it should be pushed in with a special tool to prevent the position from being skewed.
6. Various measures should be taken to prevent lip damage at threads, keyways, splines, etc., through which the lip of the oil seal passes, and assembly should be carried out with special tools.
7. Avoid touching the inner surface of the chamber and the surface of the shaft when disassembling the oil seal.
8. Used oil seals can not be reused even if their appearance is good, they must be replaced with new ones.
9. When there is bruise or rust on the surface of the shaft, it must be repaired.
10.When installing a new oil seal, in order to keep it away from the old lip contact area, shims should be used to avoid the original friction marks.
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