Material Class and Schedule

Please repost the message in lower case letters and try to explain what you are asking.

It has no logical meaning as written.

The previous responder has made a number of points, all valid. Please consider them carefully.

I am going to make an assumption about the origin of your question. I assume that you are talking about process plant piping. Is that correct?

If so your post might have looked like this:

"I am in the Piping field and I would like to know the definition of "Material Class" and "Pipe Wall Schedule" including when to use one instead of the other."

- "Material Class" - This is also written Piping Material Line Class Specification or just plain "Piping Material Specs". Piping Material Specs are prepared for all commodities by pressure/temperature breakdown found on a process plant project. The total Piping Spec might have 20, 30 or more individual "Line Classes". Each "Line Class" might handle one or more different commodities. Each "Line Class" includes a definition of application, and a listing of all pipe, fittings, flanges, valves, gaskets, bolts, and any other object necessary to complete a piping system.

- "Pipe Wall Schedule" -This term has to do with the pipe and fittings found in the "Piping Material Specs". Pipe used in a process plant is designated by it's "Nominal" size. The "Nominal" size is NOT the actual outside diameter of pipe 12" and smaller. The "Nominal" size IS the actual outside diameter for 14" and larger sizes. The wall schedule relates to the wall thickness of the pipe. Examples of pipe wall schedule are: Sch 40, sch 80, sch 160, etc. The higher the Schedule number the thicker the pipe wall. Because the outside diameter of the pipe is fixed, the inside diameter decreases as the schedule number increases.

You may also have been confused by another term used in piping.

- Flange Class - Flange Class relates to the Pressure/Temperature Design conditions of Flanges. There are two ways flanges are designated. In the USA we use word "Class" and a number such as Class 150, Class 300, etc. In other parts of the world the "PN" (Pressure Designation) and a number is used, such as PN 25, PN 50, etc.

The cross reference of Class to PN is as follows:

• Class 150 = PN 25
• Class 300 = PN 50
• Class 400 = PN 68
• Class 600 = PN 100
• Class 900 = PN 150
• Class 1500 = PN 250
• Class 2500 = PN 420
  

I hope I have guessed right and have given you the answers you need.

Nice job.

Thanks.