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Pipe Sizes and Pipe Schedule – A Complete Guide For Piping Factory

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Table of Contents

Steel pipe is a long, hollow cylinder made of steel. The length of a steel pipe is much greater than its diameter or circumference. Steel pipes are classified by their cross-sectional shape, material, purpose, and production process.

galvanized steel pipes

By cross-sectional shape, steel pipes are divided into round, square, rectangular, and other shapes.

By material, steel pipes are divided into carbon steel structural pipes, low-alloy structural steel pipes, alloy steel pipes, and composite steel pipes.

By purpose, steel pipes are divided into pipes for conveying pipelines, engineering structures, thermal equipment, petroleum and chemical industries, mechanical manufacturing, geological drilling, and high-pressure equipment.

By production process, steel pipes are divided into seamless pipes and welded pipes. Seamless pipes are further divided into hot-rolled and cold-drawn (drawn) pipes. Welded pipes are further divided into straight-seam welded pipes and spiral-seam welded pipes.

Welcome to the tytsteel.com~
In this blog, you will learn about Pipe Sizes and Pipe Schedules.
If you ever get confused between them, watch this video till the end and you will never get confused ever.

You will also learn about different terms.
such as NPS, DN, NB, schedule number and may others that associated with Pipe Sizes and Pipe Schedules.

Let’s start!

What is Nominal Pipe Size?

Nominal pipe size or NPS is the number that define the size of the pipe.
For example, when you say 6” pipe, the 6” is the nominal size of pipe.

But there is some catch here.

From 1/8” to 12” pipe, NPS is neither OD or ID of the pipe.
Check this example of 4” Schedule 80 pipe.
For 4” schedule 80 pipe, OD is 4.5”.
Thickness is 0.337”.
So, the Nominal 4” is somewhere in-betweens.

However, for pipe sizes NPS 14 and above Outside Diameter is same as nominal pipe size.

What is Nominal Bore?

NPS is frequently referred as a NB or Nominal Bore.
As such there is no difference between NB and NPS. (NB is also an American way to refer pipe dimensions. I have also seen that people used NB and DN interchangeably.


What is DN?

DN or Diameter Nominal is International designation,
you can say it is SI or Matric Designator and also a European equivalent of NPS to show
pipe sizes.

Here, you have to note that DN shows pipe sizes differently than NPS.

2” pipe is simply mentioned as DN 50.
8” NPS as DN 200.
You can convert NPS to DN by multiplying NPS with 25.

What is DN Pipe Size?

NPS½¾11 ½234681012
Check the table for easy understanding.

There is no change in other dimensions such as thickness and OD when you us DN.

Second point that use to define pipe size is pipe schedule.

Previously we shared: galvanized pipe sizing measurements you can learn too.

galvanized pipe sizing measurements

What is Pipe Schedule?

Schedule for pipe wall thickness

Early pipes had only one wall thickness for each size, which was later referred to as the Standard Wall Thickness STD. The outside diameter of the pipe was also standardized.
As industry developed to handle high-pressure fluids, thicker pipes began to be manufactured.
Gradually, XS (or XH) and XXS (or XXH) were introduced, but the standard pipe OD did not change.
In March 1927, the American Standards Committee surveyed the industry and added smaller grades between the two classes of pipe wall thicknesses, i.e., SCH to indicate the nominal thickness of the pipe.
These thickness grades include: SCH5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS.

schedule is the standard method to define the thickness and pressure rating of pipe and is different to the nominal.
the higher the schedule number is the thicker the pipe is and the more.
pressure it can handle it is also worthwhile to note the outside diameter of the pipe doesn’t change only the wall thickness and the inside diameter.

Schedule 40 Pipe vs Schedule 80 Pipe

for example, at 50 nominal ball schedule 40 and schedule 80 both have an od of 60.33 millimeters but schedule 80 has thicker walls and a smaller internal diameter .

If you have any questions about schedule part please get in touch with the TYTSTEEL because we make buying galvanized steel easy.

what does schedule 40 means?

Schedule 40 Steel Pipe is nothing but a pipe thickness designator. Schedule 40 pipe has a wall thickness of 40% of the inside diameter and is typically used in applications where normal pressures or temperatures need to be withstood.
In simple word you can say that for given material, sch 40 pipe can withstand certain amount of pressure.

Schedule 40 Steel Pipe

what is schedule 80 pipe?

Schedule 80 pipe wall thickness is 80% of the inside diameter. Typically used in applications requiring high pressure or temperature.

schedule 80 pipe

Now, can you tell me which is thicker?-schedule 40 pipe or schedule 80 pipe.

Schedule 80 pipe is thicker than schedule 40 pipe. Look at the formula of schedule number, allowable stress for material at given temperature is fixed. That means with increase in service pressure schedule number will increase which is nothing. but pipe wall thickness designator.

And in general, Schedule 80 pipe lasts longer than Schedule 40 pipe because Schedule 80 pipe has a thicker wall thickness and can therefore withstand greater pressure and stress.
Schedule 80 pipe typically lasts twice as long as Schedule 40 pipe, given the same materials and usage environment.

How pipe schedules are used to measure pipe?

Measuring metal is typically pretty simple. For bar stock, generally all you need is a tape measure. But when it comes to measuring pipe, things get a little trickier.

The best way to see the relationship between pipe size, schedules and wall thicknesses is:you need a conversion chart.

  1. outside diameter reading 1.050
  2. wall thickness reading 0.113
  3. I then go to my pipe schedule chart. I find that outside diameter of 1.050; The wall thickness of 0.113.
    that tells me that this is a 3/4″ schedule 40 pipe.

Hope fully this has given you a better understanding of pipe schedules and how to measure pipe.

If you need steel pipe for your next project.

TYTSTEEL is a professional manufacturer of galvanized steel pipes in China. All the pipes are high-frequency welded. You can find galvanized steel pipes in all sizes (custom diameters, thicknesses, lengths) and materials.

Please get in touch with the TYTSTEEL because we make buying galvanized steel easy.

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