The effect of hydraulic oil on seal performance in hydraulic breakers
Nov 10, 2022
Hydraulic oil of hydraulic hammer is used as working medium in hydraulic transmission system, which plays the role of energy transmission, conversion and control, and also plays the role of lubrication, anti-corrosion, anti-rust and cooling of the components in the hydraulic system. The seals in the hydraulic system play a role in preventing fluid leakage from the bonding surfaces, maintaining pressure, and maintaining energy transfer or conversion.
Most of the sealing materials used at home and abroad are polymer elastomers, and under some special conditions, plastics and various metals are also used. But no matter which material belongs to, should have the following properties.
1, has a certain mechanical and physical properties: such as tensile strength, fixed tensile strength, elongation;
2, a certain degree of elasticity, hardness, and small permanent deformation in compression;
3、Adapted to the working medium, not easy to produce swelling, decomposition, hardening;
4, wear-resistant, with a certain tear resistance;
5, with high temperature, low temperature aging performance. However, no seal material includes all of the above properties, it is necessary to select the appropriate seal material according to the working environment, such as temperature, pressure, media and movement, and to meet certain requirements by developing the material with the formula. Or use more than two kinds of material compound or combined structure to play their respective strengths to achieve a more comprehensive effect.
Formation of sealing effect: Dynamic seals are divided into non-contact seals and contact seals. Non-contact seals are mainly various mechanical seals, such as: graphite packing ring, floating ring seal, etc.; rubber-plastic composite seals and rubber-plastic combination seals are contact seals, relying on the pre-pressure force filled in the sealing cavity, blocking the leakage channel and obtain the sealing effect.
Most of the seals used in hydraulic systems are static seals (end seals), reciprocating dynamic seals (piston, piston rod seals) and rotary seals. Factors affecting the sealing effect: selection of sealing structure and oil film formation, pressure, temperature, material compatibility, material, hardness, geometry, surface finish of the working surface contacted by the dynamic seal, etc.
Several sealing materials with excellent media resistance and their characteristics.
1, nitrile rubber seals: nitrile rubber performance is affected by acrylonitrile content, with acrylonitrile content increases tensile strength, heat resistance, oil resistance, air tightness, hardness, but elasticity, cold resistance is reduced. NBR has poor ozone resistance and electrical insulation properties. Water resistance is better.
2, silicone rubber seals: silicone rubber according to its vulcanization characteristics can be divided into two categories of hot vulcanization type silicone rubber and room temperature vulcanization type silicone rubber. According to the different performance and use can be divided into general-purpose, ultra-low temperature resistant, ultra-high temperature resistant, high strength type, oil resistant, medical type, etc.
3、Fluoroelastomer seals: high temperature resistance, aging resistance, good insulation
4、Ethylene-Propylene rubber seals: oxidation resistance, ozone resistance and anti-erosion ability
5, polyurethane rubber seals: high hardness, good strength, high elasticity, high wear resistance, tear resistance, aging resistance, ozone resistance, radiation resistance and good electrical conductivity, etc., is the general rubber can not be compared.
6. Polytetrafluoroethylene (PTFE) seals: sealing, high lubrication and non-stick, electrical insulation and good anti-aging ability, excellent temperature resistance (can work under the temperature of +250 ℃ to -180 ℃ for a long time). PTFE itself is not toxic to humans.
