EFW and ERW pipes comparison 1

[khalidkhattak]

I need to know about strength wise comparison of EFW and ERW pipes... which pipe to be used where?... Some where i studied that welded pipes have 25% lesser yeild strength than seamless pipes.. but i do nee comparison of ERW VS EFW.. thnx

 

[DrillerNic]

ERW/EFW pipe is fully normalised etc, so has the same mechanical properties as seamless pipe. If you need pipe bigger than about 12/14" NPS, you have to use ERW or SAW pipe. ERW used to have a 'cheap & cheerful' reputation against SAW pipe, but I believe that with increased QA/QC processes in the mill, most of the problems of the longitudinal weld 'unstitching' have been solved, but a materials engineer would give a truly authoritative answer.

 

[NozzleTwister]

Assuming your EFW or ERW pipe is fabricated from equivalent plate materials your base yeild strength will be the same. Your loss of strength comes as the result of the Joint Efficiency Factor for the Welded Seam. This is only applicable for Pressure Design (Hoop Stress). Refer to the code you are using to find these values. If you are using ASME B31.3, refer to table 302.3.4.

With ERW pipe, all of the quality control and inspection in the world won't improve the Joint Efficiency Factor.

With EFW pipe, the Efficiency Factor can be improved up to 1.0 (100%) depending on the amount of additional radiography you specify above and beyond what is required per the pipe specification for your material.

For longitudinal bending stresses the Joint Efficiency is ignored.

NozzleTwister
Houston, Texas