Threaded flanges and weld neck flanges are two different kinds of flanges. Threaded flanges are suitable for low pressure and small diameter condition, while welded neck flanges are suitable for high and low pressure as well as large diameter condition. Flanges of different pressure and thickness have different requirements on the diameter and quantity of the connecting bolts. According to the different grades of pressure, flange seal rings are also made from different materials. According to materials, flange seal rings can be classified into carbon steel, cast steel, alloy steel, stainless steel, copper, aluminum, plastic, PPC, etc. According to the processes, they can be divided into pushing, pressing, forging, casting seal rings, etc. A-Type socket weld flanges generally only have flange ring, which are usually made from steel plate and can be forged if necessary.
In the high pressure equipment and pipes, we usually adopt metal seal rings made from copper, aluminum and stainless steel of len types or other shapes. The high-pressure seal ring and sealing surface have high finish after processing and the contact between them is line contact, with a very narrow line.
The valve clack of large flange has good rigidity and is not easy to deform during sealing. The seal ring of large flange can produce self-sealing force under the effects of the pressure in the opposite direction, resulting in increasing seal pressure and tightly pressing the seal ring on the valve seat. The larger the pressure in the opposite direction is, the greater the self-sealing force becomes, which makes the seal ring and the valve seat in close connection and helps achieve the effect of two-way seal.
A flange seal ring is a kind of product to prevent the leakage of flange by putting it between the two sealing surfaces of flanges and then tightening the flange with a bolt. In the case of replacing a seal ring of a large flange, it is not necessary to disassemble the valve clack when the seal ring need to be replaced. Simply fully open the valve next to the flange and remove the key from the operating device; turn the operation device into the closed state and then keep it connected with the main valve key; turn the hand wheel in the direction of opening until the seal ring is located on the opposite side of the valve body's sealing surface; finally, replace the seal ring.