Why should you inspect new tubular goods?
New oilfield tubular goods are not always perfect. In any manufacturing process, defects can escape the best efforts of quality control of the mill or the pipe can become damaged in handling or transit. Defects can cause failures – failures cost money.
NEW TUBULAR GOODS INSPECTION
WHY SHOULD YOU INSPECT NEW TUBULAR GOODS?
New oilfield tubular goods are not always perfect. In any manufacturing process, defects can escape the best efforts of quality control at the mill or the pipe can become damaged in handling or transit. Defects can cause failures – failures cost money.
WHAT TO LOOK FOR
Most flaws and defects which occur in the manufacture of new tubing and casing are defined in an API bulletin on non-destructive testing terminology. Typical defects which are potentially dangerous and critical to service are as follows:
Seams Overlaps
These are fissure type defects which characteristically are oriented nearly parallel to the long axis of the tube. They may occur on either the inside or outside surface of the pipe. In the overlap, one face of the crevice extends over at the surface of the tube while in the seam; the two faces meet parallel without overlapping.
Rolled-in Slugs & Pits
These defects result from the embedding of foreign matter into the tube wall during manufacture. They may exist on either the inside or outside surface of the tube wall and may be oriented either transversely or longitudinally with the length of the pipe. A pit is formed if the foreign matter subsequently falls from the pipe wall.
Longitudinal Cracks
Cracks, especially those located in the bottom of plug scores (gouges on the inside surface of the pipe produced in the piercing operation) occur often enough to be of serious concern. These defects usually result from residual stresses left in the pipe by the manufacturing process.
Transverse Cracks
Transverse cracks are produced primarily in the end areas of the tube during the upsetting operation, but can occasionally occur in the body of the pipe. These cracks may occur in either the inside or outside surface. High-strength or special upset tubular goods are particularly subject to this type of defect.
Eccentricity
In the manufacture of seamless pipe, the inside diameter is not always concentric with the outside diameter. In some cases this so pronounced that the thin portion of the tube fails to meet API minimum wall thickness specifications.
Hardness Variations
Non-uniform heat treating of the tube can result in serious anomalies in the hardness of the steel throughout the body of the pipe. These variations, not visible to the naked eye, can result in premature failures while the tube is in service.
