Non-destructive Testing of Straight Seam Steel Pipes

1. Appearance inspection of straight seam steel pipe welds
Before the non-destructive testing of straight seam steel pipes, the weld appearance inspection shall meet the requirements. The welded joints used for pipe joints generally require the appearance and surface quality of straight welds as follows:

The welding profile should be good, and both sides of the groove should be covered with a width of 2mm. The height of the welded joint of the fillet weld shall conform to the design specification, and the shape shall be smoothly transitioned.

Surface of welded joint:
(1) No cracks, no melting, slag inclusion, and splashing are allowed.
(2) The weld surface of steel pipes with a design temperature lower than -29 degrees and stainless steel pipes with a greater tendency to harden shall not be undercut. The bite depth of the weld of other related materials should be greater than 0.5 mm, the length of the continuous edge should not exceed 100 mm, and the total length of the undercut on both sides of the weld should not exceed 10% of the total length of the weld.
(3) The weld surface shall not be lower than the pipe surface. The high welding residue is not more than 3mm.
(4) The wrong side of the welded joint should not exceed 10% of the wall thickness and should not exceed 2mm.

2. Surface non-destructive testing
The selection principle of the non-destructive testing method for the surface of the straight seam steel pipe: the ferromagnetic steel pipe is selected for magnetic particle testing, and the non-ferromagnetic steel pipe is used for the penetration test.

For welded joints that are prone to hot cracks, an important surface non-destructive test shall be carried out after welding and heat treatment. For welded joints with a tendency to delay cracks, the surface non-destructive analysis test should be carried out after different welding systems have cooled for a period of working time.

The application of surface non-destructive testing is implemented in accordance with the requirements of the standard. The objects and applications of surface non-destructive testing are generally as follows:
(1) Quality inspection of the outer surface of the pipe.
(2) Detect important butt welds for surface defects.
(3) Important fillet welds shall be inspected for surface defects.
(4) Inspection of surface defects of important socket welding and jumper tee branch pipe welding joints.
(5) Groove detection of welded joints with high hardening tendency.
(6) Check the grooves of non-austenitic stainless steel pipes whose design temperature is lower than or equal to -29°C.
(7) Inspection of double-sided welds after cleaning.

3. X-ray and ultrasound examination
The main purpose of X-ray inspection and ultrasonic inspection is the butt joint of longitudinally welded steel pipe and the butt joint of welded pipe fittings.

After delayed welding, the weld is easy to crack. After cooling for a period of time, X-ray inspection and ultrasonic inspection should be performed. When the main pipe in the casing has a circumferential seam weld, the weld should be 100% X-ray inspected, and the concealed operation can only be carried out after the test pressure is qualified.

Welded joints on pipes that can be covered with reinforcing rings or support pads should undergo 100% radiographic qualification inspection, and the reuse range can only be expanded after passing the test. The NDT is arranged in the middle of the weld, and after inspecting the appearance of the radiation, ultrasonic inspection is performed on the back side. The welding can only be continued after the welding is qualified.

The above is to share with you the relevant content of the non-destructive testing of straight seam steel pipes. Hope that through the above content, everyone has a better understanding and understanding of the non-destructive testing of straight seam steel pipes.

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