How to Avoid “Crack Damage” of Steel Pipe in Use?

The term “crack” refers to one type of damages that occurs primarily in rigid piping, whereby distinction is made between three main forms which can be the precursors for the pipe break and, finally, for the collapse of the sewer.
•Longitudinal cracks;
•Lateral cracks;
•Cracks originating at a point (in some cases also with pipe fracture).

In most cases, failure of an operating gas pipeline is a rare event. However, it can not be denied that it is very necessary that care must be exercised to prevent damages to the fracture area in good time to extend the service life of pipeline in use.

The techniques for cleaning debris and corrosion products from pipeline fractures include washing with a mild detergent and bristle brush, solvent cleaning and degreasing in an ultrasonic cleaner, replica stripping, and chemical or electrochemical etching in mild or inhibited alkaline or acid solutions.

Causes Of Pipeline Failures

Over half of pipeline failures result from some externally applied mechanical force. There are several typical failures of steel pipe in use.
1) fatigue crack damage during pipe shipment, particularly in rail and sea shipment. This damage, sometimes called transit fatigue, results from flexing the pipe during load movement. Transit fatigue in seamless pipe and the base metal of welded pipe results from concentrated stresses where the pipe contacts a protrusion, such as a rivet or bolt, the weld of an adjacent pipe, or bearing strips of insufficient size. In submerged-arc welded pipe, transit fatigue crack can develop at the toe of the weld even in the absence point contact.
2) Corrosion can cause failures by thinning the wall over a large area or localized pitting. Both external and internal corrosion can easily lead to failures.
3) Another form of corrosion, stress-corrosion cracking, can also lead to failures. External stress-corrosion crack results from the accumulation of moisture on the pipe surface at imperfections in the pipe coating. Certain corrosives in the moisture in conjunction with normal operating stresses cause cracking.
4) Material defects are not common causes of service failures because they are usually found before the pipe is placed in service, either during inspection of the pipe or during hydrostatic testing. The few failures that do result typically originate at longitudinal weld seams or at laminations in seamless pipe.

In short, crack damage of steel pipe is a very common phenomenon in a couple of applications, though most professional steel pipe manufacturers have done a good job in manufacturing, testing, or inspection of steel products in a mill. Based on different type of fatigue cracking, it is very important for you to take protective measures to extend the service life of pipeline in use.

For any further information, you can refer to the previous article of corrosion protection for steel pipe on our official website later.