Threaded flanges are widely used in low pressure piping systems, as no welding is involved while connecting the flanges to pipes or other equipment. However, the flange may be welded around the joint after assembly, but it is not considered a satisfactory method of increasing its applications. Threaded flanges are also known as screwed flanges and are similar to slip-on flanges, but the bore is threaded to enable assembling without welding. Threaded pipe flanges are usually used with pipes that have external threads.