The main design disadvantage of dual phase steel flange is no leakage. This is a deficiency in that design. The connection is dynamic, stainless steel flange, and periodic loads such as thermal expansion fluctuation will cause the movement between flange faces, affect the function of flange, damage the integrity of flange and lead to leakage.

Because of its good comprehensive performance, elbow is widely used in chemical engineering, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire protection, power, aerospace, shipbuilding and other basic projects. It is required to control the curvature radius of the elbow. For example, if the radius length is 1.5D, the radius