Basic safety requirements for corrosion and aging

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Basic safety requirements for anti-corrosion and aging performance of explosion-proof lamp materials

in explosive dangerous places, corrosive gases often exist. Under the long-term influence of temperature, UV radiation, humidity and corrosive gases, various materials of explosion-proof lamps have different applicability. 1. Plastics in lamps in the lamp structure, plastic parts have become important and proved to be practical components, which are applied to the internal parts of lamps, wires, translucent covers, protective covers, structural supports and other parts. The normal service life (aging) of these plastic parts is determined based on the "normal" use of lamps. Excessive use and destructive effects will reduce the aging resistance, as shown in Table 1. Table 1 destructive effect destructive effect cause result [1] high use temperature working voltage is too high ambient temperature is too high installation unreasonable deformation brittle discoloration ultraviolet radiation high pressure mercury lamp sterilization lamp yellowing brittle corrosive substance softener (Plasticizer) not 5.2zui large dynamic experimental force: 500kN correct cleaning method fracture reduction strength, external surface damage note: [1] all causes and results can be linked. Special attention should be paid to continuous working temperature, ultraviolet and visible radiation, static and dynamic mechanical collision, and air oxidation. A combination of these effects is particularly important and can make the material unsuitable for the intended use. For example, ultraviolet radiation plus heat can make the insulation of PVC cables produce green substances, which indicates that the insulation is reduced. The published characteristics of plastic materials named after general terms may vary due to different fillers or antioxidants, manufacturing procedures and designs. 2. Anti rust lamps used in normal indoor air can be made of various materials. The metal sheet parts of lamps shall be properly pretreated and surface coated, such as baking paint. For uncoated aluminum reflectors and grids, anodized aluminum should be used. Auxiliary parts of lamps, such as clips, hinges, etc., can be electroplated with appropriate materials, such as zinc, nickel, chromium or tin, and can be used satisfactorily in normal indoor air. 3. Anti corrosion lamps for outdoor use or lamps for indoor high humidity air shall have appropriate anti-corrosion performance. Although the lamp is not required to work under the condition of ground chemical gas, all the air contains a small amount of corrosive gases such as sulfur dioxide, so it may cause serious corrosion after long-term use in the moisture. When evaluating the anti-corrosion performance of lamps, the interior of closed lamps (even if the lamp has one or several drainage holes) is less corroded than the exterior of lamps. Improper use will cause the specimen to fracture at the fixture and lead to the failure of the experiment. The following metals or parts have sufficient corrosion resistance: ① copper and bronze, or brass with copper content not less than 80%; ② Stainless steel; ③ Aluminum (plate, extrusion or casting) and die cast zinc can prevent corrosion in the atmosphere; Flame retardant PP is still inferior in the appearance of household appliances. ④ cast iron or malleable cast iron, at least 3.2mm thick, with 0.05mm thick zinc on the outer surface and visible coating of this material on the inner surface; ⑤ Galvanized steel plate, with an average coating thickness of 0.02mm; ⑥ Polymeric materials, see section 3.5.1. Metal parts in contact with each other should be made of metals close to each other in the electrochemical sequence to avoid electrolytic corrosion. For example, brass or other alloy copper cannot contact with aluminum or aluminum gold; It is desirable for any of them to contact stainless steel. Polypropylene is usually selected as the plastic for outdoor use, and its characteristics have not changed significantly in a long working time. Cellulosic materials are generally not suitable for high humidity conditions, whether outdoors or indoors. Other materials, including polystyrene, are suitable for indoor use. If they are used outdoors, they are easy to be seriously damaged due to moisture and solar radiation. The plastic structure of lamps and lanterns intended to be used under high temperature conditions (indoor or outdoor) includes bonded joints, mainly because the adhesive used should be able to be exposed to moisture for a long time without damage. There is also a problem of processing tolerance. 4. In places where there is a considerable concentration of chemical corrosive gas or vapor, especially where condensation occurs, in addition to the preventive measures required by the above outdoor lamps, the following additional protective measures should be taken for the lamps used: ① generally speaking, lamps with anti-corrosion metal cast shells have better effects than lamps with metal plates. ② Where metal is used, the metal that can prevent existing specific corrosive substances should be selected as far as possible. Since most metals will be damaged by some corrosive substances, die-casting aluminum is satisfactory for most purposes. ③ Similarly, when selecting coatings or other protective methods, they should be selected according to specific corrosive substances or categories of corrosive substances. For example, coatings that are highly acid resistant cannot withstand the erosion of some alkalis. ④ Plastics such as polypropylene, PVC and polystyrene can well resist the erosion of most inorganic acids and bases. But they are easily eroded by many organic liquids and vapors. Because this effect depends on the type of plastic and specific chemical composition, the selected material should be suitable for the specific environment. ⑤ Enamel coating can prevent many chemicals. If you want to work satisfactorily in highly corrosive air, the enamel coating must not have broken places or cracks. 5. Influence of acid-base gases on electrical materials in places with acid-base gases, different corrosion-resistant materials should be selected according to their influence on electrical materials

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