Home>Bearing knowledge>The effect of hydraulic oil on seals and its application method

/*728*90 created on 2018/5/16*/ var cpro_id = "u3440131";

Influence of hydraulic oil on seals and its application method

---

/*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';

Hydraulic oil is used as the working medium in the hydraulic transmission system; it acts as the transfer, transformation and control of energy; together it also plays the role of smoothing, anti-corrosion, anti-rust and cooling of various components in the hydraulic system. Sealing in hydraulic system The piece plays a role in avoiding fluid leakage from the interface, adhering to pressure, adhering to energy transfer or changing.
At present, most of the sealing materials used at home and abroad are high molecular elastomers; some special conditions also use plastics and various metals. However, regardless of which type of data, they should have the following functions:
1. Has certain mechanical and physical functions: such as tensile strength, tensile strength, elongation,
2, has a certain elasticity, hardness is suitable; and tightening eternal deformation.
3, compatible with the working medium; not easy to swell, differentiate, harden,
4, wear-resistant; has a certain anti-shear function,
5, with high temperature, low temperature aging function.
However, there is no sealing material that contains all of the above functions; the requirements are based on the operating environment; such as temperature, pressure, media, and motion methods to select the appropriate sealing data; and the cooperative formulation of the proposed data to satisfy the required requirements. Perhaps more than two Data composite or combined layouts promote their respective expertise; reach a more comprehensive role.
The composition of the sealing function: the dynamic sealing is divided into non-touch sealing and touch sealing. The non-touch sealing is mainly various mechanical seals; for example: graphite packing ring, floating ring sealing, etc., rubber-plastic composite sealing parts and rubber-plastic composite sealing parts are attributed to Touch seal; relying on the pre-compression force loaded in the sealing cavity; blocking the leakage passage to obtain the sealing effect. The seals for the hydraulic system are mostly static seals (end seals), reciprocating seals (pistons, piston rod seals) and Rotary seal.
The factors affecting the sealing effect: the selection of the sealing layout and the composition of the oil film, the compatibility of pressure, temperature and data; the raw materials, hardness, several shapes and appearance of the surface of the touch operation of the dynamic seal.
First, the compatibility of sealing materials and hydraulic oil (liquid):
One of the origins of particle contamination of hydraulic oil is the “crush” or “wearing debris” that occurs when the seal data is not compatible with the hydraulic oil. The “crush” or “pumping” of the seal due to “swelling” is damaged. Lift out the unconnected inorganic matter and fill the reinforcement data; make the seal damaged and invalid; together with the oil constitutes the pollution of the hydraulic oil to cause failure.
The vane pump is widely used in the hydraulic system; in the state where the working pressure is greater than 6.9 MPa; the wear problem becomes outstanding; therefore, the anti-wear agent is used in the hydraulic oil, in order to adapt to the hydraulic system in the vicinity of the high temperature heat source and the open flame; Anti-combustion phosphate ester, water-glycol hydraulic fluid; oil-in-water and water-in-oil emulsion, etc., and various types of composite additives such as anti-oxidation and anti-rust which should be "used" A wide variety of oils (liquids), such as: zinc-free (ashless type) anti-wear hydraulic oil compounding agent in anti-wear hydraulic oil compounding type; hydrocarbon sulfide, phosphate, phosphite, etc.; A SPN extreme pressure anti-wear agent containing sulfur, phosphorus and nitrogen. In extreme pressure industrial gear oil; also based on PS type extreme pressure agent.
The reason for the "swelling" or "extraction" of the seal is the various chemical elements and their concentrations enriched by the additives in the hydraulic oil; according to the principle of "similar compatibility"; different sealing materials are different. The effect is also the dielectric resistance of the sealed data. For example: Shell Omala 320 gear oil and Shell Omala 460 gear oil exhibit a polar phosphorus (P) concentration of about 300ppm; so the nitrile rubber is rich in acrylonitrile The group has polarity; it has excellent oil resistance; it is not suitable for the medium conditions of this type of oil.
Followed by the continuous development of hydraulic oil (oil) types; various anti-wear, extreme pressure additives, metal deactivators, demulsifiers and anti-foam additives for improving oil (liquid) function; impact on the data of seals Verify by experiment.
Second, the sealing data is resistant to oil (liquid) function detection and identification:
The seals of the rubber data are resistant to oil (liquid); the standard test oil is usually selected; the temperature conditions and the experimental time are immersed according to the rules of the experiment; the test values ​​are compared before and after the immersion (such as the hardness change of the data, the change rate of the tensile strength, Elongation change rate, volume change rate, eternal deformation, etc.); evaluate its function.
The No1 specification oil is a “low volume addition oil”; the composition of this mineral oil mixture is extracted by solvent; chemically treated, dewaxed white wax residue and neutral oil,
The No. 3 specification oil is a "high volume addition oil"; consists of two smooth oils obtained by vacuum distillation through the selection of crude naphthenic products.
Different use of the index value of the data is not the same.
Third, the impact of hydraulic oil (liquid) on the function of the seal:
The theory of sealing is that there is an intact smooth film between a dynamic flexible seal and its cooperating surface. Under normal conditions, it is this smooth film that reaches the sealing intention and extends the life of the seal.
In the hydraulic system; the influence of hydraulic oil (liquid) on the sealing function of the seal except the compatibility of the medium/sealing data; the viscosity of the oil, the viscosity change with temperature, the speed of reciprocating (rotation) movement, the pressure and the shaft, the cylinder Or the material, hardness, shape, surface finish of the piston rod, and the layout of the seal, etc., which affect the composition of the smooth membrane and the characteristics of the membrane; all affect the sealing effect. Generally speaking, the smooth membrane forming the joint can achieve the ambition sealing effect. .
Japan's NOK company first used the latest image processing skills in the world to explain the sealing principle of the clear oil seal. The seal of the oil seal (rotating and sealing) is composed of two parts: smoothness and sealing principle. Smooth characteristics: the conflict characteristics of the oil seal are affected by The viscosity and sliding speed of the fluid are distributed; the relative sliding of the oil seal and the shaft moves in a smooth state in which the oil film is separated; thus adhering to the conflict resistance. The sealing principle: the oil sliding on the sliding touch surface moves from the atmosphere side to the oil side. The circulation from the oil side to the atmosphere side is smooth. The smoothness of the sliding surface is excellent; the wear can be avoided; thus there is no leakage.
When the speed of the system is too high; affects the composition of successive smooth membranes; incurs conflict heat addition; the temperature resistance scale beyond the sealing data constitutes the damage of the seal. When the pressure is too large; in addition to affecting the oil film composition; The seal has a "squeezing" effect; it is usually possible to use a "retaining ring" to improve it. Or to select a PTFE composite seal layout with a small coefficient of conflict and good self-smoothness will help to improve the smoothness between the conflicting pairs; High and low speed reciprocating motion and high pressure system cylinder piston and piston rod seal.
According to the conditions of the system and the medium environment, the seals and sealing materials, the correct device operation and the protection of the seals are reasonably selected; it is the key to obtain useful sealing effect, reliability and service life.

---

Recommend to friends comments close window

Bearing related knowledge

What are the advantages of ceramic bearings and all-steel bearings? Listed several common faults and low-noise bearings. Selection and pre-tightening of imported bearings Analysis of the dismantling performance of TIMKEN bearings

This article links to http://
Please indicate the bearing network http://

Previous: FAG bearing running track and loading method Next: Railway locomotive vehicle bearing (1)