1、Relatively long plastic-lined steel pipes, usually 5-6 meters long small diameter pipe, the middle part is easy to leak, in the inspection because the electric spark detector can not reach in and can not detect, this problem can not be find.
A very simple way is to use a strong torch to illuminate the inner wall of the pipe, you can find out if there is a problem.

2、Plastic-lined steel pipes flange surface lining layer is prone to uneven or irregular problems, which will affect the seal after installation.

3、Lined plastic pipes flange hole welding at both ends of the flange eye is not against, this will lead to increased labour intensity when installing the pipe, because it needs to turn the pipe to hold the flange eye.

4、The flanges at both ends of the pipe are not leveled when riveted, so that the flange of the pipe is tilted after welding, and the whole pipeline will be crooked after installation.