Pipe thread defects

Pipe thread defects are as follows:

1, Tear (cracked): Mainly tooth side, addendum (round thread) geometry (including roughness) is damaged. Early thread processing with a single-knife picks easily lead to tear, blunt tool, lubrication is not good and other reasons are also likely to cause tearing, the general was scaly, ubiquitous thread side; thread oil in impurities such as sand, Will also cause torn; gauges have tumor on the flanks, the rules can easily lead to pipe thread surface torn.

2, The knife marks (trembling): Tooth top, side of the tooth due to the amount of feed, the tool beating or blunt tool wear caused.  

3, Wear marks: Tooth top grinding very smooth into a flat top, the surface of the tube defects such as cracks, pits, etc. after grinding (wall thickness allowed to grind 12.5%), processing thread caused.

4, Shoulder: There are two forms: (1) after the disappearance of the male thread male buckle, due to the tube is not round, eccentric and other caused, and some called "white neck", partial trapezoid because no L4 regulations, along the tube direction Free to disappear, so there is no shoulder. (2) appears on top of the tooth, mostly due to lack of a piece of tool wear.

5, Black buckle: Round buckle outside the thread LC is not allowed; partial buckle outside the thread LC allows 2 buckle, no more than 1/4 circumference. 

6, Incision: Formerly called broken buckle, the thread is not continuous. Processing generally does not appear, is generally caused by external forces (such as chisel chisel bit) is sometimes caused by lack of body tube, FRP thread snap a lot, may be caused by the bubble.

7, Damage: A lot of shape, appear in the tooth top, tooth side. The general principle is that the geometry is damaged. Longitudinal, a flat trace. Mechanical damage, protective wire by external impact, can be seen when removed, and some are in the handling, transport caused by the collision. Before the factory found the tooth top damage, after grinding, the geometry does not change can be considered as qualified; on-site inspection of those obvious thread top flat side of the tooth to produce significant protrusions will scratch the thread coating, and sentenced unqualified.

8, Velcro: Seized in seldom found, the scene downhole operation due to excessive torque, wrong buckle, poor lubrication, high-speed on the buckle caused. Material soft and easy to stick, 5B provisions of the tubing after four times on the shackle buckle should not appear; 5C5 provisions of the pipe nine times on the buckle buckle non-slip buckle, casing on the second shackle buckle. 

9, Deformed buckle: Bizarre buckle, inspection found in relatively small, such as crooked, ripple, flat buckle, double top buckle and other defects. Crooked, ripple is caused by the machine. Flat button, double top button is caused by the tool. 

10, Rust: Mainly after the water pressure is not treated on the smear smear oil. 

11. Knife edge: A thin tip portion of a thread crest, usually formed by the disappearance of the initial thread on a round or even trapezoidal thread, rather than on a chamfer, at the end of the tube. 

12, Cutting edge: As the outer chamfer is too small or chamfered surface caused by the oblique side of the pipe is not only the sharp edge. 

13, No initial thread: the thread disappears in the tube end. 

14, Within the chamfer or incomplete edges and corners have burrs: All sentenced to failure. 88 years ago 5B did not make the request for chamfering, only after 88 years showed the arrow, requiring chamfering.