Industry News

Problems with the design of the wound gasket

2019-02-15
Wound gasket is a composite flat gasket made of metal and non-metal material. It is made of V-shaped or W-shaped steel strip and non-metal strip alternately wound. It has good compression resilience and is especially suitable for stress relaxation, temperature and pressure fluctuation. Or the sealing of medium and low pressure flanges under impact and vibration conditions.



  1, selection. Wound gaskets A, B, C, D A total of 4 types of type A is a basic type of wound gasket without inner and outer rings, suitable for the groove surface flange. Type B is a wound gasket with an inner ring and is suitable for convex and concave flanges. Type C is a wound gasket with an outer ring, and Type D is a wound gasket with an inner and outer ring. These two types of gaskets are suitable for protruding flanges. The most common type of error is the use of Type A or Type B wound gaskets for flanged flanges. Since these two types of gaskets do not have an outer ring, there are two problems in use. First, the gasket is not easy to be centered. Even if the pre-tightening force generated by each bolt is evenly equal when pre-tightening, the pre-tightening seal pressure generated on the gasket sealing surface will be different because the gasket is not centered. Affect its sealing performance. Second, the pre-tightening force is larger. According to the standard winding gasket with the same nominal diameter and nominal pressure and the same type, the design is carried out after considering a certain margin. The most important thing is to determine the sealing surface width of the wound gasket. When some designers replace the original non-metallic gasket with a wound gasket, the width of the sealing surface of the wound gasket is determined according to the width of the sealing surface of the non-metallic gasket, so that the width of the sealing surface is larger than that of the corresponding standard wound gasket. The sealing surface is several times wider, resulting in a multiple increase in axial stiffness. In the case of normal preload, the amount of compression and rebound is greatly reduced compared to the corresponding standard gasket, the initial sealing is difficult, and leakage is likely to occur during operation. In order to increase the amount of compression and rebound of the gasket, it is necessary to increase the pre-tightening force abnormally, but the pre-tightening force excessively deforms the flange, so that the uneven force of the gasket causes leakage. When the solder joint is easily collapsed, the pressing force applied during the production of the gasket is drastically lowered, thereby causing a leak.

  2. Formed steel strip design. In the standard of wound gaskets at home and abroad, the geometrical dimensions of the formed steel strip are not given, and are generally determined by the manufacturer according to experience. Tests have shown that the larger the angle of the V-shaped steel strip, the smaller the compression amount, when the thickness of the wound gasket and the load to be applied are constant. The longer the bevel, the greater the amount of compression. Since the amount of compression is an important indicator affecting the sealing performance of the gasket, the two parameters should be optimized to achieve the best sealing performance.

3. Non-standard gasket design. The design of non-standard winding gaskets should be based on standard wound gaskets with the same nominal diameter and nominal pressure and the same type. After considering a certain margin, the most important thing is to determine the sealing surface width of the wound gasket. Some designers use the wound gasket to replace the original non-metallic gasket. The sealing surface of the sealing gasket according to the non-metallic gasket is several times wider, which causes the axial stiffness to increase exponentially. In the case of normal preload, the amount of compression and rebound is greatly reduced compared to the corresponding standard gasket, the initial sealing is difficult, and leakage is likely to occur during operation. In order to increase the amount of compression and rebound of the gasket, it is necessary to increase the pre-tightening force abnormally, but the pre-tightening force excessively deforms the flange, so that the gasket is unevenly stressed and causes leakage.