I. Pipe / tube fabrication:

  1. Seamless Pipe:

•Strongest amongst all pipes.

•Homogenous structure throughout pipe length.

•Available in wide range of size.

•Restriction on large size

•Used in manufacturing of bends, elbow, tee.

Seamless pipe are manufacture by following methods:

seamless 1

seamless 2

seamless 3

seamless 4* For seamless tube ( threaded ): continue from step 20 above processing.

seamless a

seamless b.PNG2) For other pipe:

seamless c.PNG3) Welded pipe: ( refer above processing )

•Pipe are manufactured from Plate or Coil

•Plate or coil rolled in circular section to weld

•Can be welded with or without filler material

•No restriction on large size

•Used in manufacturing of bends, elbow

•Weak in compare to seamless pipe due to joint

* Welded:

  • Longitudinal seam: single seam & double seam ( NPS >= 36 inch )
  • Helical ( spiral ) seam: NPS >= 4 1/2 inch, submerged arc welding, 0.8 OD<= skelp width <= 3.0 OD

*Welding process:

  • Without filler metal: electric welding & continuous welding
  • With filler metal: SAW & GMAW

4) Pipe / tube classification:


pipe 1.PNG

pipe 2


pipe 3.PNG

5) Pipe standard:

pipe STD

6) Pipe marking:

•Following shall be marked on pipe:

−Manufacturer logo
−ASTM material code
−Material Grade
−Heat No
−Special marking WR or NH,

Ex: VP 8” Sch 80 A106 XYZ123 10.2m

•Marking can be by paint or by Hard punching

•For stainless steel stenciling can be used:

−For carbon steel no hard punching below 6 mm thickness
−For stainless steel no hard punching below 12 mm thickness

II. Pipe & tube: what is difference?

Tube and Pipe are two remarkably similar cylindrical “materials” that are used for a wide variety of applications. People often confuse the two, and the terms are used interchangeably at times, but they do exhibit different characteristics. As a general rule, a tube has higher engineering specifications and manufacturing requirements than a pipe.

There are 5 basic differences between pipe & tube.


  • Pipe Size Specified in Nominal Pipe Size (NPS) or Nominal Bore (NB) or Diameter Nominal (DN). The purpose with a pipe is the transport of a fluid like water, oil or similar, and the most import property is the capacity or the inside diameter.

    NPS DN pipes

  • Tubes sized are specified in millimeter or in inches by outside diameter. The nominal dimensions of tubes are based on the outside diameter.

    NPS DN tubes


  • Pipe Wall thickness is expressed in schedule number
  • Tube Wall thickness is expressed in millimeter, or inches, or BWG (Birmingham wire gauge.)


  • The outside diameter of pipe up to size 12” are numerically larger than corresponding pipe size
  • Outside diameter of tubes is numerically equal to the corresponding size.


  • Used in all process & utility lines
  • Generally used in tracing lines, tubes for heat exchanger & fired heater & in instrument connection.


  • Pipe Available in the small bore as well as the big bore.
  • Normally small-bore tube is used in process piping. For structural use, tubes are available in custom sizes.



Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s