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How does hydraulic oil affect the performance of seals?

by:ORK      2022-10-14
I believe that everyone is no stranger to lubricating oil.“Hydraulic oil”Well, that's understandable. What is hydraulic oil? Hydraulic oil is the hydraulic medium used in the hydraulic system that utilizes liquid pressure energy, and plays the role of energy transmission, system lubrication, anti-corrosion, rust prevention and cooling in the hydraulic system. For hydraulic oil, first of all, it should meet the requirements of the hydraulic device on the viscosity of the liquid at the working temperature and the starting temperature. Since the viscosity change of the oil is directly related to the hydraulic action, transmission efficiency and transmission accuracy, the viscosity-temperature performance and the transmission accuracy of the oil are also required. Shear stability should meet the various requirements presented by different applications. It can be seen that the role of hydraulic oil cannot be ignored. So what effect does hydraulic oil have on seal performance? Let me give you a brief analysis: No matter what kind of material, it should have the following properties: 1. It has certain mechanical and physical properties: such as tensile strength, constant elongation strength, and elongation; 2. It has certain elasticity and hardness 3. Compatible with the working medium, it is not easy to swell, decompose and harden; 4. Wear-resistant, with a certain tear resistance; 5. It has high temperature and low temperature aging performance. The properties mentioned above are not possessed by any sealing materials. It is necessary to select suitable sealing materials according to the working environment, such as temperature, pressure, medium and movement mode, and to meet certain requirements by formulating the matching formula of materials. Or use two or more materials in the form of composite or combined structure to exert their respective strengths to achieve a more comprehensive effect. Formation of sealing effect: dynamic sealing is divided into non-contact sealing and contact sealing. Non-contact seals are mainly various mechanical seals, such as: graphite packing rings, floating ring seals, etc.; Block leakage channels to obtain sealing effect. The seals used in hydraulic systems are mostly static seals (face seals), reciprocating dynamic seals (piston, piston rod seals) and rotary seals.  Factors affecting the sealing effect: the selection of the sealing structure and the oil film formation, pressure, temperature, compatibility of materials, material, hardness, geometry, surface finish, etc. of the working surface contacted by the dynamic seal. Compatibility of sealing material and hydraulic oil (liquid) One of the sources of particle pollution of hydraulic oil is the incompatibility between sealing material and hydraulic oil.“crumbs"or“Wear debris". seal due to“swelling"caused by damage“crumbs"or be“extraction"The unbonded inorganic substances and filling and reinforcing materials that come out will damage and fail the seals, and at the same time contaminate the oil, causing the hydraulic oil to deteriorate and fail.  Vane pumps are widely used in hydraulic systems. When the working pressure is greater than 6.9MPa, the wear problem becomes prominent, so anti-wear agents are used in hydraulic oil; in order to adapt to the hydraulic system near high temperature heat sources and open flames, use Fire-resistant phosphate esters, water-glycol hydraulic fluids, oil-in-water and water-in-oil emulsions, etc. and should“use"And there are a wide variety of hydraulic oils (liquids) for different purposes configured with various types of composite additives such as anti-oxidation and anti-rust. The seal is produced“swelling"or“extraction"The reason is that the various chemical elements and their concentrations contained in the additives in the hydraulic oil, according to“Similar compatibility"It has different effects on different sealing materials, and it is also the medium resistance performance of the sealing material. For example: ShellOmala320 gear oil and ShellOmala460 gear oil show a polar phosphorus (P) element concentration of about 300ppm, so nitrile rubber is polar because of the acrylonitrile group, and has excellent oil resistance, but it is not suitable for this Media conditions for the type of oil. Company website: https://www.orksealing.com/
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