Seamless pipe is made from a round steel billet (solid cylindrical hunk of steel that is cast from raw steel). This billet is then heated, stretched out and pushed or pulled over a form. It is then pierced through the center with a die and mandrel which increases the inside diameter and reduces the outside diameter.
Welded pipe is made by cold forming flat strip, sheet or plates into a round or circular shape by a roller or plate bending machine. The pipe is then welded with or without filler material using a high energy source.
From the above introduction,we could see the difference between seamless and welded pipe:
|Sr. No||Parameter||Seamless Pipe||Welded Pipe|
|1||Strength||Able to withstand more pressure and load as there is no weak seam.||Due to welding they are believed to withstand 20% less pressure and load as compared to seamless pipe.|
|2||Length||Relatively shorter in length due to manufacturing difficulties.||Can be manufactured in long continuous lengths.|
|3||Size||Manufactured for nominal size 24 inch or less.||No such size restriction on production.|
|4||Corrosion Resistance||Less prone to corrosion, means more corrosion resistant.||Weld areas are more prone to corrosion attacks, means less corrosion resistance.|
|5||Surface Quality||Rough due to extrusion process||Smooth high quality surface as compared to seamless pipe.|
|7||Production Process||Complex, long procurement lead time||Simpler, short procurement lead time.|
|8||Tests||Seamless pipes does not require testing for weld integrity.||Must be tested before use.|
|9||Application||Suitable for high presure temperature and corrosive environment||Normally used for less corrosive and low pressure environment.|
|10||Availability||Less available, limited material types, longer delivery time||Readily available for various different materials; shorter delivery time|
|11||Wall Thickness||Inconsistent wall thickness across length, thicker so heavier||Wall thickness more consistent than seamless ones, thinner|
|12||Ovality||Better ovality, roundness||Poor ovality and roundness as compared to seamless counterpart.|
|13||Internal surface check||Checking not possible||Internal surface can be checked before manufacturing|