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| What are the commonly used non-metallic materials for valves? |
| 发布日期：2020-05-30 15:54:00 点击数：558 次 |
| Nitrile rubber Buna-N The rated temperature range of nitrile rubber seat is -18 ℃ ~ 100 ℃. Usually also called NBR, NITRILE, or HYCAR. It is an excellent general-purpose rubber material suitable for water, gas, petroleum and grease, gasoline (except gasoline with additives), alcohol and ethylene glycol, liquefied petroleum gas, propane and butane, fuel oil and many other media . It also has good abrasion resistance and deformation resistance. Food grade (FG) nitrile rubber seat rated temperature range is -18 ℃ ~ 82 ℃. Its composition complies with Section 177.2600. Of Part 21 of the CFR Standard. The scope of its use is the same as that of conventional nitrile rubber but requires FDA (US Food and Drug Administration) certification. EPDM The rated temperature range of the ethylene propylene rubber seat is -28 ℃ ~ 120 ℃. EPDM is an abbreviation of its components, that is, a terpolymer of ethylene, propylene, and diene, and is also commonly called EPT, Nordell, and EPR. Excellent ozone resistance and weather resistance, good electrical insulation, good resistance to polar agents and inorganic media. Therefore, it can be widely used in HVAC industry, water, phosphate ester, alcohol, glycol, etc. Ethylene propylene rubber seats are not recommended for use in hydrocarbon-based organic solvents and oils, chlorinated hydrocarbons, turpentine, or other petroleum greases. Food grade ethylene propylene rubber valve seat rated temperature range is -28 ℃ ~ 120 ℃. Its composition complies with Section 177.2600. Of Part 21 of the CFR Standard. The scope of its use is the same as that of conventional nitrile rubber but requires FDA (US Food and Drug Administration) certification. PTFE Teflon valve seat rated temperature range is -32 ℃ ~ 200 ℃. Excellent high temperature resistance and chemical resistance. Because PTFE has high density and excellent anti-permeability, it can also prevent the corrosion of most chemical media. Conductive polytetrafluoroethylene is an improved polytetrafluoroethylene product that allows current to pass through the lining and thus cancels the insulating properties of polytetrafluoroethylene. Because of its conductive properties, conductive PTFE cannot use spark to check its quality. Reinforced polytetrafluoroethylene RTFE RTFE is a modified body of PTFE material. Although the friction coefficient of pure PTFE is very low (0.02 ~ 0.04), the wear is extremely large, and because of its easy creep, poor mechanical properties, low bearing capacity, poor dimensional stability and other characteristics, it has great limitations as a friction material. Only modified to meet the special requirements for wear-resistant sealing materials in various industries through the method of material compounding. In order to improve the wear resistance of PTFE, some wear-resistant substances such as glass fiber, carbon fiber, graphite, molybdenum disulfide, Bronze powder and some organic compounds make them form network nodes in the PTFE layered structure to improve stiffness, thermal conductivity, creep resistance, and greatly improve wear resistance. Viton The rated temperature of the fluoroelastomer seat is -18 ℃ ~ 150 ℃. Viton is a registered trademark of DuPont, and Fluorel is a registered trademark of 3M equivalent to fluoroelastomer. This material has high temperature resistance and excellent chemical resistance. It is suitable for hydrocarbon products, low concentration and high concentration of mineral acid, but cannot be used in steam medium and water (poor water resistance). UHMWPE UHMWPE Ultra high molecular weight polyethylene valve seat rated temperature range is -32 ℃ ~ 88 ℃. This material has better low temperature resistance than PTFE, but still has excellent chemical resistance. UHMWPE also has good abrasion resistance and corrosion resistance, and can be used in high-abrasion applications. Silicone rubber Silicon copper rubber is a polymer composed of silicon and oxygen atoms in the main chain, with organic groups. The rated temperature range is -100 ℃ ~ 300 ℃. Has good heat resistance and temperature resistance, excellent electrical insulation performance, and large chemical inertness. Suitable for organic acids and low concentrations of inorganic acids, dilute alkalis and concentrated alkalis. Disadvantages are: low mechanical strength. Post-curing treatment is required. Graphite Graphite is a crystal of carbon. It is a non-metallic material with silvery gray color, soft quality and metallic luster. The Mohs hardness is 1 ~ 2, the specific gravity is 2.2 ~ 2.3, and the bulk density is generally 1.5 ~ 1.8. It has unique physical and chemical properties such as high temperature resistance, oxidation resistance, corrosion resistance, thermal shock resistance, high strength, good toughness, high self-lubricating strength, thermal conductivity, and electrical conductivity. It has special oxidation resistance, self-lubricity and plasticity at high temperature, and also has good electrical conductivity, thermal conductivity and adhesion. It can be used as filler or performance improver for rubber, plastic and various composite materials to improve the wear resistance, compression resistance or conduction performance of the material. Graphite is usually used to make the valve gasket, packing and valve seat. Graphite has a very high melting point, and it only begins to soften under 3000 ° C under vacuum. At 3600 ° C, graphite begins to evaporate and sublimate. The strength of general materials gradually decreases at high temperatures, while graphite is heated to 2000 ° C The strength is doubled compared to normal temperature, but the oxidation resistance of graphite is poor. The oxidation rate gradually increases with the increase of temperature. |
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