Thread Content
1. When selecting gaskets, a comprehensive analysis must be conducted of various factors such as the gasket’s sealing performance, operating pressure, operating temperature, properties of the working medium, as well as the type of flange sealing surface, the complexity of its structure, the ease of installation and removal, and cost considerations. Among them, dielectric properties, operating temperature, and operating pressure are the main factors affecting sealing, and they serve as the primary basis for selecting gaskets. 2. The type of gasket should generally be determined based on the operating temperature and pressure of the medium to be sealed. For high temperature and high pressure conditions, metal gaskets are commonly used ； For atmospheric pressure, low pressure, and medium-temperature conditions, non-metallic gaskets are commonly used ； For cases in between, semi-metallic composite gaskets are often used ； In applications with frequent fluctuations in temperature and pressure, self-tightening gaskets with good resilience are recommended. 3. There are many factors to consider when selecting gaskets; generally, while ensuring the fulfillment of the main requirements, it is advisable to choose gaskets that are inexpensive, easy to manufacture, readily available in the market, and simple to install and replace. 4. The thickness of the gasket depends on the specific circumstances. Generally speaking, if the sealing surface is well machined and the pressure is not too high, thin gaskets are preferable. However, when the internal pressure is high and the gasket is too thin, its rebound is insufficient in response to the elongation of the bolts, preventing it from achieving the necessary amount of recovery and thus leading to leaks; therefore, thicker gaskets should be used at high pressures. 5. The gasket coefficient m is independent of its width; therefore, the narrower the gasket, the easier it is to clamp. However, there is a limit on its minimum width; typically, the width should be greater than 5 mm. For metal gaskets, it is an important guideline to use a smaller width in order to avoid excessive bolt forces. 6. Since gaskets come into contact with the operating medium during use and are directly affected by factors such as the medium, pressure, and temperature, the material used to manufacture gaskets must meet the following requirements: (1) It should possess good elasticity and resilience ； (2) It should have appropriate flexibility to fit well with the sealing surface ； (3) It should possess high mechanical properties such as crack resistance, along with appropriate compressive deformation. (4) It must not contaminate the medium to be sealed, nor corrode the sealing surface; it should also not experience significant expansion or contraction as a result of the influence of the medium ； (5) It should be resistant to corrosion by the working medium ； (6) It should possess good physical properties, that is, it should not become hard and brittle at low temperatures, nor soft and malleable at high temperatures ； (7) It should exhibit minimal stress relaxation ； (8) It should have good workability, and except for special applications, the gasket material should be inexpensive and readily available on the market. Given that every material has its limitations, there are hardly any materials that can fully meet the above requirements. Therefore, when a gasket made of a single material fails to meet the requirements, two or more materials can be used in combination, such as wound gaskets or metal-clad gaskets. 7. Simplify specifications as much as possible and reduce the variety of products. For a piece of equipment, a pipeline, a device, or even a factory, the fewer the types of gasket specifications and materials, the easier it is to manage. Therefore, when selecting gaskets, in addition to ensuring they meet the required performance standards, it is also necessary to standardize specifications and materials as much as possible, avoiding unnecessary diversity. 8. Make the most of the advantages of various types of gaskets, that is, utilize their strengths. While wound gaskets possess good compressibility and resilience, as well as excellent sealing properties, enabling good sealing in most applications, they should not be used in every situation. In some cases, ordinary asbestos-rubber gaskets are sufficient to meet the requirements, so there is no need to upgrade to wound gaskets unnecessarily. However, in medium and low-pressure applications with stress relaxation and pressure/temperature fluctuations, wound gaskets are very suitable. 9. Special requirements must be taken into account; for example, if a certain medium does not allow trace amounts of fibers to be present, then asbestos rubber sheets and other fibrous gaskets should not be used. If certain areas experience significant vibration, gaskets with high vibration resistance should be used. For areas that are difficult to access for maintenance, durable gaskets should be used. 10. When using metal gaskets, they should be used in a fully annealed state. Whenever possible, softer metal materials should be selected; the hardness of the gasket should be 30–40 HB lower than that of the flange sealing surface. 11. Under corrosive conditions, select a gasket material that is compatible with the flange. The gasket gets corroded, thereby sacrificing itself to protect the flange ； Use gasket materials that give a positive result with flange gaskets; if the flange is corroded, use a sacrificial flange. Which one to use depends on the method of use and the type of gasket. 12. For highly toxic, explosive, strongly corrosive, highly polluting substances, and harmful gases, the use of asbestos rubber gaskets is not permitted. 13. When using metal ring gaskets or metal toothed combination gaskets, necked butt-weld flanges and studs (double-ended or fully threaded) should be employed.