Stainless steel seamless pipes are made from solid steel that is either in sheet or bar form. The steel is molded into a solid circular shape known as “billets,” which is then heated and cast over a form, such as a penetrating rod, to make a hollow tube or a shell.
These kinds of lines are notable for their ability to deal with pressure all the more proficiently when contrasted with different strategies of line creation methodology, just as for being both quick and cost-effective to manufacture. Gas lines, as well as pipelines that transport liquids are often constructed using seamless pipes. For a perfect pipe, seamless pipe manufacturers should stay cautious.
Because seamless pipes have the ability to sustain high pressures, they are also commonly employed in high-pressure applications such as refineries, hydraulic cylinders, hydrocarbon industries, and oil and gas pipelines, among other things.
Defects in the Manufacturing Process
There are several variances in wall thickness that may be found in seamless pipe, particularly earlier designs. A maximum of 12.5 percent decrease in wall thickness is permitted by specifications such as API 5 L for seamless pipe.
In the case of differences in wall thickness, the operator must determine whether these fluctuations are acceptable.
Variations in the Thickness of the Walls
The term “inclusion” refers to a discontinuity (for example, a patch of manganese sulfide) in the microstructure of the steel. When operating under sour working conditions, they have the potential to produce cracking if atomic hydrogen diffuses into these locations, resulting in hydrogen-induced cracking. Repeat inspections of the pipeline should be performed while it is functioning under these conditions.
Various Manufacturing Techniques
It is possible to construct the pipe using one of the following processes:
Seamless (SMLS) pipe is manufactured using a technique that does not include welding at any point throughout the manufacturing process.
During the welding process, weldable (WLD) pipe is formed by employing an automated welding procedure, with no filler being added during the welding process.
Before final annealing, heavy cold-worked pipe (HCW) is formed by applying cold working to a welded pipe that results in at least a 35% reduction in wall and weld thickness. There is no filler utilized in the fabrication of the weld.
Design Principles and Values
Conforming to ANSI/ASME, the allowable stresses for the materials specifications provided in the pipe class have been determined.
As a result of the weld joint factor E=0.95 (as defined by American National Standard Institute/American Society of Mechanical Engineers), an important distinction between seamless pipe and the welded pipe has been created for API 5L Grade B.
The selection of pipe wall thickness for all other materials is based on internal pressure estimates for seamless pipe only, and not on other materials’ internal pressure calculations. A weld joint factor of one should thus be assured when welded tubing is utilized in a structural application.
According to ANSI/ASME, when calculating the nominal wall thickness of but welding fittings, no more than 87.5 percent of the nominal wall thickness should be taken into consideration. The seamless pipe manufacturers have to have full knowledge about these.
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