What Is The Difference Between Seamless And Welded Pipe?
The seamless pipes are drawn from a single billet of material whereas the welded pipes are welded end to end from a sheet, plat, strip or coil of the same material. The materials can range as ferritic, austenitic, duplex and other high alloy materials. The seamless pipes are more dimensionally accurate than the welded tubes. The wall thicknesses are even and the absolute roughness is less for the seamless tubes and pipes. The welded pipes have the seam or joints and the absolute roughness is higher than the seamless pipes.
Price Difference Between Seamless And Welded Pipe
Depending on the fully worked or as welded type of the production, the welded pipe and seamless pipe prices can vary. The fully welded pipes are expensive than the as welded pipes and the seamless pipes. Sometimes, the material is hard to weld. In high alloys that need special procedures for welding, the welded pipes are expensive than the seamless pipes. If the material is easy to weld such as the 304 and 316 materials, the drawing procedure is more expensive than the welding procedure.
Also, these materials do not require preheating for welding. So the seamless pipes are expensive in such material grades than the welded pipes. The preheating and post weld heat treatment requirements can also make the price difference between the seamless and welded pipe types.
Seamless And Welded Pipe Manufacturing Process
The seamless pipes can be cold drawn. Meaning, these pipes are extruded from a single billet of material at room temperatures. The lack of heating also reduces the expansion and deformation of the material. This allows for precision in the dimensions. The welded pipes are welded from plates, strips and sheets. These strips or pieces of sheets are curved and welded from end to end. While welding, the heat generated by welding can cause smaller deformations in the pipe dimensions.
Some materials require preheating before welding. Some material grades also require post weld heat treatments to make sure that the welded joints are properly bonded. The seamless tubes and pipes are equally strong at any given point. The welded tubes and pipes however can be weak at the welded joints. So the minimum tensile strength and the minimum yield strength of the material is retained in the seamless pipes. The strength values are slightly lower for the welded pipes and the maximum strength is limited by the strength at the welded joints.
Seamless And Welded Pipe Application
The seamless pipes are used in precise applications. Applications such as tools, equipment, sensitive measuring units and high temperature, high pressure units such as medical equipment, hydraulic applications, power plant, nuclear power station, chemical and pharmaceutical applications prefer the seamless pipes. The welded pipes and tubes can be used in most industrial applications without the need for uniform strength of precision in dimensions.
Applications include water lines, water purification, sea water, marine, construction, petroleum, oil and gas, heat exchangers, aircraft exhaust components and so on. It has to be noted that bot seamless and welded pipes could be used in similar applications depending on the application requirement for precision and uniform strength. Also, the seamless pipes can only be produced up to a certain diameter; usually up to 60 inches. The welded pipes can be produced up to 100 inches in diameters. This dimensional choice also makes the welded pipes picked up for certain applications over the seamless pipes.
Seamless vs Welded Pipe
Relatively shorter in length due to manufacturing difficulties.
Can be manufactured in long continuous lengths.
Ready to withstand more weight and burden as there is no feeble crease.
Because of welding they are accepted to withstand 20% less weight and burden when contrasted with consistent line.
Manufactured for nominal size 24 inch or less.
No such size restriction on production.
Rough due to extrusion process
Smooth high quality surface as compared to seamless pipe.
Less prone to corrosion, means more corrosion resistant.
Weld areas are more prone to corrosion attacks, means less corrosion resistance.
Seamless pipes does not require testing for weld integrity.
Must be tested before use.
Complex, long procurement lead time
Simpler, short procurement lead time.
Better ovality, roundness
Poor ovality and roundness as compared to seamless counterpart.
Less available, limited material types, longer delivery time
Readily available for various different materials; shorter delivery time
Suitable for high presure temperature and corrosive environment
Normally used for less corrosive and low pressure environment.
Inconsistent wall thickness across length, thicker so heavier
Wall thickness more consistent than seamless ones, thinner
Internal surface check
Checking not possible
Internal surface can be checked before manufacturing