Seamless & Welded Pipe

Stocking Program

  • Size Range | 1/4″ – 36″ NPS (Larger sizes available upon request)

  • Schedules | 10, 10s, 40, 40s, 80, 80s, 120, 160 (Custom wall thicknesses available upon request)

  • Stainless Steel Grades | 304, 304L, 316, 316L, 316L, 317L, 321 , 347, *

  • Special Alloys | 2205, 254SMo, Monel, Inconel, *

  • Chrome Moly | P5, P9, P11, P22, P91, *

  • Standards | ASTM / ASME

*-Not all grades available are listed or have a full inventory managed

General information

Pipe comes in a very wide range of sizes in which with Power and Process piping, designers utilize standards controlled by organizations such as ASTM and ASME. Unified Alloys readily stocks various alloys and grades in sizes up to 36” Nominal Pipe Size (NPS), which meet these standards.

The most common industry pipe sizes includes ¼” through to 12″ NPS and larger sizes typically increase in 2″ increments thereafter. The Nominal pipe size (NPS) pertains to the pipe size by name only, as the actual outside diameter or O. D. is different for the 12″ and under size range.

In piping dimensions, the inside diameter decreases as the as the wall thickness increases on all Nominal pipe sizes (NPS). The wall thicknesses are specified as ‘schedules’ which are covered within the specifications of ASTM and ASME. Pipe is offered in 20’ lengths, but can be supplied in certain sizes in double random (+/- 40’) to meet certain project needs.

Pipe is manufactured in either welded and or seamless form. Welded pipe is made by taking a flat plate (or skelp) which then is rolled into a tubular shape and further welded to finalize the form. Seamless is taking a solid bar (ingot), piercing a hole through its length and then drawing through dies to form the final size.

Unified Alloys typically supplies pipe in plain end form (PE), however requests for bevelled end (BE) and threaded end (TE) can be accommodated.

General Production Process Benefits

Advantages of Welded

  • Welded pipes are typically more cost effective than their seamless equivalents.

  • Welded pipes are usually more readily available than seamless. The longer lead time required for seamless pipes can not only make timing problematic, but it also allows more time for the price of the materials to fluctuate.

  • The wall thickness of welded pipes is generally more consistent than that of seamless pipes.

  • The internal surface of welded tubes can be checked before manufacturing, which isn’t possible with seamless.

Advantages of Seamless

  • The main perceived advantage of seamless pipes is that they don’t have a weld seam.

  • Seamless pipes provide peace of mind. Although there should be no issues with the seams of welded pipes supplied by reputable manufacturers, seamless pipes prevent any possibility of a weak seam.

  • Seamless pipes have better ovality or roundness, than welded pipes.

* Note: selection of pipe process type must always be made through consultation of piping engineers.

Technical data below:

Stainless Steel Pipe Chart PDF Download