Introduction to the Characteristics of Large Flanges and the Connection between Gaskets and Flanges
Introduction to the Characteristics of Large Flanges:
Metal-clad gaskets are made by wrapping thin metal sheets (such as white iron sheets or stainless steel) around asbestos and other non-metallic materials. They can also be made by wrapping asbestos with thin steel strips to create wrap-around gaskets. In high-pressure equipment and pipelines, large flanges are used, which can be made of materials like copper, aluminum, No. 10 steel, stainless steel, and have a lens shape or other forms of metal gaskets.
One of the key features of large flanges is that they have a narrow contact width (line contact) with the sealing surface, and the sealing surface and gasket have a high level of finish. Large flange connections are primarily used to connect cast iron pipes, lined rubber pipes, non-ferrous metal pipes, and large flange valves. Large flange connections are also used for connecting process equipment with large flanges.
The main characteristics of large flange connections are easy disassembly, high strength, and excellent sealing performance. When installing large flanges, it is essential to ensure that the sealing surfaces of the two flanges are parallel, free from any damage, and are thoroughly cleaned. The gaskets used in large flange connections should be selected as per the designated specifications. Large flange connections play a vital role in pipeline construction.
Large flange connections are divided into threaded large flange connections and welded large flange connections. The thickness of large flange plates and the diameter and number of connecting bolts vary depending on the pressure levels. The gaskets used for large flange connections also differ based on various pressure levels, ranging from low-pressure asbestos gaskets to high-pressure asbestos gaskets and metal gaskets.
The Connection between Gaskets and Flanges:
Based on the provided information, pure aluminum has a maximum operating temperature of 425°C and should provide reliable sealing. However, it is observed that shortly after a heat exchanger starts operating, it begins to leak, and the leakage persists for only a short time even after re-tightening. Upon inspection, it's found that the inner diameter of the gasket has deformed significantly. This is because pure aluminum has excellent plasticity. Its yield strength at 250°C is only about 15% of that at room temperature, and its elongation can reach 4-5 times the original length.
In other words, aluminum sheets are highly susceptible to pressure creep and deformation at high temperatures. Therefore, it's necessary to replace the gasket material or use a grooved-surface flange and a flange with two grooves as a solution. The flange sealing surface is composed of one grooved surface and one groove, and the gasket is placed in the groove.
Applicable gaskets include metal and non-metal flat gaskets, metal composite gaskets, wrap-around gaskets, etc. Like the grooved-surface flange, gasket compression is minimal, and gasket stress is even. As gaskets do not come into direct contact with the medium, their exposure to corrosion and pressure effects is minimal. This sealing method is suitable for situations with strict sealing requirements, such as high pressure, flammable, explosive, and toxic media. Sealing surface gasket installation is advantageous but may be more challenging for neutral, machining, and gasket replacement.
In addition to the three sealing surface types mentioned above, there are also specialized sealing surface patterns for use with trapezoidal grooves, as well as with O-rings and lens gaskets.
SINO SPECIAL METAL supplies various types of pipe fittings, flanges, and pipes made from different materials. We are a reputable supplier, and we welcome inquiries and consultations.
