The metal sheet replaces the asbestos sheet or asbestos rubber sheet, avoids direct contact with the medium, avoids the asbestos fiber strength decline, overcomes the leakage phenomenon, and thus expands the use of asbestos rubber sheet.
The general metal-clad asbestos mats use temperature is 450 ℃ (individually up to 600 ~ 700 ℃, such as in flue gas at atmospheric pressure ~ 0.16MPa), the use pressure is 4MPa, up to 6MPa. If the pressure is increased again, the gasket is prone to cross flow and the core material expands from the overlap.
Since metal-clad asbestos pads require the tightening force of broken bolts, even when the operating pressure is lower than 2.45MPa, flanges below pg25 kg cannot be used. Otherwise, the rigidity of the flange and bolts is not enough, and the deformation will cause the seal to be fundamental. Some people do not think that because the core material becomes soft, the fastening force is absorbed by the core material, and the metal plate cannot be provided. In addition, in the medium doped with chloride ions and acidic medium, crevice corrosion is likely to occur at the overlap between the stainless steel pad and the iron sheet pad.
If the temperature is higher than 450℃, ceramic fiber or carbon fiber can be used for the core material. A steel plant uses metal-clad ceramic fiber gaskets for high temperatures of 1100°C and has not been damaged for two years. Flexible graphite is the most suitable core material. At present, domestic production of metal-clad flexible graphite mats has been mass produced. Its use effect is continuous metal wrapped asbestos pad.
The metal cladding can be made into various shapes, and is widely used in various resonators, large covers of reactors, loading and unloading holes, manhole flanges, etc. I have produced iron-clad pads with a diameter of 2m in China, which are in good use.