Asbestos rubber sheet is made by pressing asbestos, rubber and fillers. According to its formula, process, performance and use, there are mainly high-pressure asbestos rubber sheet, medium and low-pressure asbestos rubber sheet, oil-resistant asbestos rubber sheet, acid and alkali resistance and other categories. Asbestos rubber sheet can be used as sealing material for pipeline flange, high pressure vessel flange and various mechanical joints. It can be used as washer with good sealing performance with acid and alkali resistance requirements. When used, gaskets of various shapes and sizes are usually punched according to requirements.
The asbestos materials for making asbestos rubber sheets are chrysotile asbestos and blue asbestos (blue asbestos).
1. Chrysotile asbestos belongs to serpentine asbestos. Its main component is magnesium silicate containing about 13% crystalline water. It has good heat resistance, alkali resistance, high tensile strength and poor acid resistance. Most asbestos rubber sheets are made from it.
2. Blue asbestos belongs to amphibole-like asbestos. Its main component is silicate containing 2.5-3.5% crystalline water. Magnesium oxide has very little component, and iron oxide accounts for 18-24%. Blue asbestos not only has good heat resistance, but also acid resistance, so it is mostly used to make acid-resistant asbestos rubber sheets.
The quality of asbestos fibers has a great influence on the properties of asbestos rubber sheets. Therefore, asbestos fibers are required to have high tensile strength, good heat resistance, appropriate length, flexibility and elasticity. Generally, high-pressure asbestos rubber sheets and oil-resistant asbestos rubber sheets above 400 are made of grade 2 and 3 asbestos fibers. Because of the limitation of asbestos rubber board, more use of three asbestos-free rubber board instead of the original asbestos board.
Asbestos rubber sheet has the characteristics of easy processing, low price, reliable sealing and simple operation, so it has a wide range of applications. In recent years, with the development of sealing fillers, packing seals have been greatly improved in material, structure and various characteristics, so packing seals have been widely used in mechanical industry, and good economic benefits have been achieved.
Asbestos rubber sheet is a filler sealing material used in flange or various mechanical joints. It should be punched into gaskets of various shapes. In the actual selection and installation of gaskets, gaskets of any type can play a sealing role for a long time in harsh environment. To ensure that gaskets can be sealed for a long time, the following eight important characteristics are required:
1. Gasket airtightness. For the medium of sealing system, gaskets do not leak during the recommended working time of temperature and pressure.
2. The compressibility of gaskets, the contact surface between gaskets and flanges should be well matched after the connecting bolts are fastened to ensure sealing.
3. Creep resistance of gasket. Under the influence of pressure load and service temperature, the gasket should have better creep resistance, otherwise it will cause the loss of bolt torsion, resulting in the reduction of surface stress of gasket and the leakage of hard gas system.
4. The gasket should be resistant to chemical corrosion. The gasket chosen should not be corroded by chemical medium and should not pollute medium.
5. Re-elasticity of gasket. Even in the stable condition of the system, the two flanges connected will surely have small displacement due to the influence of temperature and pressure. The elastic function of the gasket should be able to compensate for this displacement to ensure the sealing of the system.
6. Anti-adhesion of gaskets. Gaskets should be easily removed from flanges without bonding after use.
7. Non-corrosive gasket. Gaskets shall be non-corrosive to the flange surface of the connection.
8. Temperature resistance of gasket. The gaskets selected should be used normally at lower and higher temperatures of the system.
Asbestos rubber sheet has medium hardness, acid and alkaline resistance. It can work in acidic (alkaline) liquids with temperatures ranging from - 30 to + 60 degrees C.
When installing asbestos rubber sheets as seals, the following points should be paid attention to:
1. Do not damage the sealing surface or the sealing line on the surface of the seals.
The sealing performance of planar seals depends on the upper and lower ends; the sealing performance of hydraulic seals depends on lip lines matched with holes or shafts. These parts are made up of soft and resilient special materials, such as temperature-resistant, corrosion-resistant, aging-resistant graphite, rubber-plastic and fibers, which are vulnerable to damage. Therefore, special protection and preservation are needed in the process of handling, installation and storage. Care, once damaged, it often leaves a great hidden danger to the sealing parts.
2. No Forced Installation
Some seals are placed in groove-shaped filling letter, which needs to be installed tightly. They should not be rough and barbarous in construction. Forced loading with great action will certainly destroy the original prefabricated structure of seals, which is similar to the disaster caused by smashing prefabricated concrete and filling the required parts. Installation of such seals should be very careful and careful, and the insertion should be carried out step by step.
3. Pay attention to balance and symmetry in installation
Place the seals in the position where the effective sealing surface (or lip line) is tightly fastened. After the system is opened and used, further observation and the aftermath work of tightening seals are needed to prevent the breakdown caused by micro-leakage due to the change of working conditions (such as pressurization) during the operation of the system.
Seals shall be properly kept when not in use for the time being:
1. Anti-aging: avoid light, damp-proof, plain, away from cold and heat sources;
2. Do not apply pressure: Keep the seal relaxed naturally and do not apply external force to change its physical shape;
3. Classification and labeling: (same shape, different material, use location, applicable standard, purchase date, etc.).