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Rubber lining: A rubber lining is achieved by directly attaching corrosion-resistant rubber sheets to the surface of a metal substrate, thereby creating a continuous and complete protective layer. There are many types of rubber, and the ones commonly used for linings include natural rubber, styrene-butadiene rubber, neoprene, butyl rubber, nitrile rubber, EPDM rubber, chlorosulfonated polyethylene rubber, and others. Rubber possesses excellent plasticity, adhesiveness, workability, as well as unique processing properties such as vulcanization molding. Rubber lining is generally produced by bonding sheets of unvulcanized rubber compound to the surface of equipment and then vulcanizing them ； Some use naturally vulcanized adhesives applied to vulcanized rubber sheets, or they are lined with special pastes or rubber sheets and then vulcanized naturally. Rubber lining is suitable for conditions with a pressure of less than 1.6 MPa and a vacuum level of less than or equal to 0.1 MPa. Under normal conditions, the allowable operating temperature for vulcanized rubber sheets is -20 to 85°C; some heat-resistant rubber linings can withstand temperatures up to 120°C. The volume of rubber-lined equipment can reach 10,000 m3, with storage tanks having a diameter of over 20 meters and a height of over 20 meters as well. Rubber can also be used as a lining for small pumps, valves, stirrers, impellers, pipes, etc., and as an impermeable, corrosion-resistant isolation layer in brick-lined systems. In fact, rubber lining can be applied to any area that can be reached by hand or tools. The corrosion resistance of various types of rubber sheets is specified in HG/T 20677-2013 “Design Code for Rubber-Lined Chemical Equipment”. The structural design and construction acceptance of rubber-lined equipment can be carried out in accordance with standards such as HG/T 20678-2000 \"Technical Specifications for the Design of Lined Steel Vessels\", HG/T 20677 \"Design Code for Rubber-Lined Chemical Equipment\", and GB 50727-2011 \"Code for Acceptance of Construction Quality of Anti-Corrosion Works for Industrial Equipment and Piping\". The vulcanization methods for rubber linings typically include the following: ① In-vessel vulcanization. This is the most common vulcanization method, in which the equipment lined with rubber is placed inside a high-pressure vulcanization tank, and saturated steam is introduced directly to provide heating. The pressure of the saturated steam is controlled to meet the temperature and time requirements of the vulcanization process, thereby ensuring proper vulcanization of the rubber lining. ②In-situ vulcanization: When the external dimensions of the rubber-lined equipment are large enough, and it can be sealed to withstand the pressure of vulcanization steam (usually 0.3 MPa), it is possible to carry out the vulcanization process by introducing saturated steam directly into the interior of the equipment. ③Hot water or atmospheric pressure steam vulcanization: For large-scale equipment lined with rubber at atmospheric pressure, when such equipment cannot be placed inside a vulcanization tank and its structure cannot withstand the pressure of vulcanization steam, special rubber compounds should be used for lining. Afterwards, water is injected into the lined equipment to heat it up (this is known as hot water vulcanization or open-vessel vulcanization), or steam is introduced into the equipment so that the temperature inside reaches 90–95°C under atmospheric pressure, thereby enabling vulcanization. ④Room-temperature vulcanization (also known as natural vulcanization or cold vulcanization) is a method of lining with rubber using special compounds that can be vulcanized at room temperature, by employing vulcanizing agents and vulcanization accelerators. After the device has its adhesive sheet applied, it can undergo the vulcanization process spontaneously after being left at room temperature for 3 to 4 weeks. Currently, only special materials such as natural soft rubber, neoprene, and butyl rubber can be vulcanized at room temperature. Quality inspection: Rubber-lined equipment must have adequate quality assurance. After the rubber is applied and vulcanized to the equipment, the following items should be inspected: ① Visual inspection – Use visual inspection to check the completion status of the lining, its bonding condition, the presence of bubbles, the condition of the joints, and any mechanical damage ； Use measuring tools to check the dimensional specifications of the lining. ②Pore detection: A probe from an electric spark tester is used to scan the surface of the rubber-lined layer; by observing the discharge sparks, pinhole defects in the rubber lining can be easily identified. Spark testers come in high-frequency, low-frequency, DC, and pulse types. For lining materials with low insulation resistance, the different types may sometimes pose a risk of insulation failure in the normal areas of the lining; therefore, careful selection is necessary when using such testers. ③Thickness detection: The thickness of the adhesive layer can be measured non-destructively using electromagnetic or permanent magnet type magnetic thickness gauges. Key areas where the rubber lining is prone to stretching and thinning during application, as well as after processing post-vulcanization, require special attention during inspection. ④Hardness testing: The Shore A hardness tester is used to test soft rubber linings, while the Shore D hardness tester is used for hard or semi-hard rubber linings. Evaluation is carried out by comparing with the specified hardness standard values for each rubber layer, in order to determine the degree of vulcanization of the rubber-lined layer. ⑤Tap test: Gently tap the rubber-lined layer with a special metal rod, and determine the adhesion between the rubber layer and the substrate by listening to the changes in sound ； For soft rubber linings, the finger press test can be used for inspection. This inspection is generally used as a follow-up check for suspicious areas identified during a visual inspection (such as delamination).