Threaded (threaded) flange: the threaded flange is connected by screw thread. But the center of the product has a thread size corresponding to the pipe. Its main advantage is that it can be assembled without welding.
Sliding flange: the sliding flange has a lower hinge because the pipeline enters the single flange before welding. This is welded internally and externally to provide sufficient strength to prevent leakage. The sliding flange is the matching of the slightly larger outer diameter pipe. They are superior to the welding of neck flange. Due to the low initial cost, many users, but the final installation cost is probably not the same, because there are fewer welding neck flanges added.
Lap flange: the lap flange is actually identical to the sliding flange unless it has a radius between the hole and the flange race. It is necessary that the radius has a flange to accommodate the end of the lap stub. Usually, the lap flange and lap stub mate together at the end of the month to assemble the system.
The socket welding flange is a similar sliding flange unless it has a hole and counter hole size. Counter holes slightly beer than O.D. pipes match so that pipes are inserted into flanges similar to sliding flanges. The diameter of the smaller hole is the same as the ID of the matching pipe. The restriction is a built-in hole that acts as a shoulder sleeve for the pipe to stay at the bottom. This eliminates any flow restriction in the use of Socket Weld flanges.