As one of the most common, effective and important link forms in petrochemical plants, various pipelines, pipe fittings, valves, instruments and equipment, flanges have unique performance and advantages. In the vast majority of cases where flanges are used, the sealing is achieved by the cooperation of flanges, bolts and gaskets. Any problem with one of the components will cause the leakage of the entire sealing system.
The sealing principle of the flange: through the pre-tightening force of the bolt, sufficient pressure is generated between the gasket and the flange sealing surface, and the gasket is plastically deformed to fill the tiny gap between the flange sealing surfaces and block the medium leakage channel to achieve the sealing effect. Gaskets are actually the most important part of flange sealing.
The gaskets used for flange connection include flange insulation group gaskets, graphite gaskets, PTFE gaskets, non-asbestos soft gaskets, rubber gaskets, spiral wound gaskets, metal composite gaskets, etc. Select suitable sealing materials for temperature, pressure and sealing medium.
The main factors affecting flange sealing:
Influence of actual working conditions: pressure, temperature, physical and chemical properties of medium, temperature and pressure change too much and too frequently, the possibility of seal failure is greater.
Influence of bolt pre-tightening force: Increasing the bolt pre-tightening force can increase the sealing performance of the gasket, but it should not be too large, otherwise the gasket will be easily crushed and the gasket cannot be guaranteed to have sufficient sealing performance.
Influence of gasket performance: The material performance of the gasket itself is the most important key to determine the sealing performance. It is necessary to select the appropriate gasket according to the actual use situation.
Influence of flange stiffness: Insufficient flange stiffness will cause excessive deformation, which is also one of the main reasons for seal failure.
Influence of the sealing surface: The shape and roughness of the flange sealing surface need to be consistent with the gasket. Generally, the sealing performance of the gasket with good rebound rate is better.
Flange insulation group gasket:
The insulating group is composed of a large insulating gasket, a bushing for each bolt, an insulating gasket for each nut and a steel gasket. The insulating group is used in two different pipeline flanges to prevent corrosion and corrosion. For fully conductive insulation protection, suitable for offshore insulation, seawater environments, hydrocarbon, chemical insulation, oil refineries and pipelines. Usually made of G10, G11, phenolic and other insulating materials, it has corrosion resistance, high temperature resistance and good sealing performance, which can better prevent leakage.
Graphite Gasket:
It is composed of pure graphite plate or reinforced graphite and metal. It has excellent thermal stability, self-lubrication, corrosion resistance, and excellent compression rebound rate. It can be used in most sealing systems such as pipelines and valves.
Metal wound gasket:
Generally, it is made of high-quality metals such as SUS304 and SUS316, and graphite, PTFE, non-asbestos and other materials are alternately overlapped and spirally wound, with excellent resilience, especially suitable for uneven load, periodic changes in temperature and pressure, shock and Vibration occasions.
Metal Clad Gasket:
It is a composite gasket that uses non-metallic materials inside and a metal sheet covered by a specific cold working process on the outside. It is suitable for flange sealing of pressure vessels with large diameters, and is generally used in medium and low pressure conditions.
PTFE Gasket:
Polytetrafluoroethylene gasket (PTFE) has excellent properties such as anti-aging, corrosion resistance, insulation, etc. It maintains good mechanical strength between -100 ° C and 100 ° C, and will not pollute any medium. It can be widely used in food, in the pharmaceutical and other industries.
Asbestos-free rubber gasket:
Asbestos-free sealing materials synthesized from aramid, glass, inorganic, carbon fiber, etc., and rubber, have different properties and uses according to different formulations and processes, and are generally suitable for most occasions.
