Schedule Numbers and Pipes

Here's a start:
Standard Pipe Schedules and Sizes - Engineers Edge

As Lyn's chart shows it is an expression of pipe wall thickness.

Schedule = 1000 * service pressure / allowable stress

as per the original concept (ref piping handbook)

Also schedules 4 or 8 are not recognised by ANSi (the standard 11 schedules are 5,10,20,30,40,60,80,100,120,140 and 160) now of course there are some special schedules offerred too.

Engineers who work with pipe makers and boiler makers have arrived at a way to specify the piping for a system of a certain pressure. These are called pipe schedules, and they deal with various pressures, various fluids and timescales.

The simplest would be iron pipe in low pressure water service. The schedule will tell you what wall thickness pipe to buy for what water pressure and what degree of corrosion in the water is used and what is the expected sevice life and frequency of inspections for the system.

Special schedules for stainless steel, acids, glass, etc are listed.

This allows a designer to specify pipe and installers around the world can go to standard pipe makers for that schedule of pipe and make a safe installation for that application.

It is sort of like nuts and bolts. Where would we be if all machine makers made their own bolts and thread sizes. Well, in the 1800's there was so much abuse with machinery makers and special threaded parts you could only get from them, that assorted thread standards emerged. Similarly with pipe, and boiler makers and explosions and insurance companies, there emerged a body of standards called pipe schedules and a body of people who enforced them. Also if you install piping that holds pressure, your insurance company will insist it be built to the proper schedule and inspected annually to ensure public safety. There were some huge boiler explosions that killed many people in the 1800's as these standards emerged

generally Schedule represents pressure holding capacity in bar.

means sch 40 pipe can withstand approx. 40 bar pressure.

generally as schedule increases the thickness of pipe increases & ID will decreases.

For example 4" sch 40 pipe is having OD=114.3mm Thk=6mm

4" sch 80 pipe is having OD=114.3mm Thk=8.6mm

♣ Please refer to the following CR4 Threads:

• Pipe schedule calculation

• Pipe Schedule Formula??

• ASA Pipe Schedule

• How to confirm the Pipe Class?

♣ Example demonstrates how we calculate the pipe wall thickness and how we find the Schedule No. of pipe: High Pressure Steam Pipe

Dear Experts

What is PN rating for pipes and fittings?

PN is pressure Number.This is flange rating used in European code.Pipe or pipe fitting on particular pipeline are called as per flange rating.

In ASME flange rating decided as per ASME B16.5 based on Design pressure , Design Temp. and material.

In ASME std.flange rating denoted by class like150......2500.Flange rating also denoted as 150#,300#......2500#.

The schedule number refers to the (nominal) wall thickness of the pipe

Example:

4" schedule 40 pipe has a wall thickness of .237"

4" schedule 80 pipe has a wall thickness of . .337"

However

6" schedule 40 pipe has a wall thickness of .280

6" schedule 80 pipe has a wall thickness of .432"

It is actually sch. 80 and sch 40 and there is really so many good explanations already posted I will not say more other than supply you with a link to order a very good book that spec. most carbon steel fittings, pipe and so on. if you go here they will send you out a catalog that is very useful and it is also free.

http://weldbend.com/catalogform.htm