(1) the outlet part of the compressor and pump;
(2) Compensator, three-way, elbow (bend), size head, branch connection and dead Angle of medium flow;
(3) The pipe components and welded joints near the damaged part of the hanger rack;
(4) Where there have been problems affecting the safe operation of pipelines;
(5) The pipe section in the crucial part of the production process and the pipe segment connected with the important device or equipment;
(6) The working conditions are harsh or bearing the pipe section of the alternating load.