1. Flat welding flange is commonly abbreviated as flat plate and also called slip-on flange. The flat welding flange and the pipe are connected in the way that the pipe is first inserted into the inner flange hole properly before slip-on welding. 2. The flange is suitable for pipe systems with low pressure level and slight pressure fluctuation, vibration and shock. The flange strength is that it is easy to align for welding and assembling and inexpensive, having been widely used.