difference between class and schedule of pipes?

"pipe classes" = Piping Line Class Specification This has to do with all pipe, fittings, flanges, bolts, gaskets and other data related to one specific commodity/pressure range/temperature range. May also handle a family or grouping of related commodities. (see additional information below)

"schedule" = Relates to Pipe and specifically the wall thickness thereof

Additional information on the subject of Line Class Specifications
I think you are asking about "Piping Specification for Line Class Material" or it may be called "Piping Line Class Material Specification" or it may have some other combination of words that mean the same thing. But it is a very specific "pipe spec" out of a very big family of piping specifications.

Now to your question as it relates to "this" pipe spec.
How to make pipe spec?

"Piping Material Line Class Specification"

This document would have a cover sheet and a written section which would include the following:
- Document Title
- Document Control Number
- Table of Contents
- Statement of Purpose and or Function
- General Notes
- A listing of all the Codes that apply to the material included here-in
- A list of all the Line Classes with basic data such as Commodity, Material, Flange Rating, etc.
- Each of the individual Line Class sheets
- Branch Tables (one or more tables as required)
- The common vent, drain, and other misc. connection details
- Name of Originator (Responsible person), Date created
- Name and date of checker
- Table of Approval for Issue, (Piping Department, Project, Client)
- Table of Issue History listing Revision, date, what was revised, by who, approval sign-off

All of this would then be issued as a single document.

The second part of your question
What is basic need/data for that?

Data Requirements
There are two sides to this question. There is the up front data requirements needed to produce the Line Class Specification. Then there is the output data or, what does each line class need to include?

So, first what is required to start? You need, as a minimum the following information:
• A list of every commodity that will be a part of the project. This means the feed, all products, all waste streams, all utilities and all additives.
• For each commodity you need the complete chemistry including Toxic classifications and reactions to changes in temperature. Here in the U.S.A. we have a document called a "MSDS" (Material Safety Data Sheet). These have all the chemical, toxic, medical recovery and other data about a chemical be it a gas, a liquid, a powder or a solid. If these are available in your country then get a copy for your records of the MSDS for each commodity.
• For each commodity you need the maximum sustained operating pressure and temperature.
• For each you need to know of any short term or upset condition that may cause an increase or decrease in pressure or temperature.
• For each commodity you need to determine the corrosion rate for different (common or special) pipe materials.
• For each commodity you need to know the projected maximum and minimum pipe size expected for the project.
• You need to know the location of the jobsite and the full twelve month weather/temperature profile.

When you have collected all this information then you need to spend a great deal of time reading and studying so you can answer every question that will come up. Don't try to memorize it just remember where to find the material on that issue.
This is just a start. Now you need to know what Piping Code will be the basis for the project.
Will the project governing Code be:
• ASME B31.1
• ASME B31.3
• Or some other Code?

Now the next thing you need to know is the Clients preferences and or restrictions. Things like does the client want to use "Lapp-Joint Stub-End" flanges in certain systems. Does the client want or not want certain types of valves (and why)? What about Weld-neck vs. Slip-on flanges?

Next you need to know the "Design Life" of the plant. This means you need to know how long the plant is supposed to last before it is shut down or starts to fall apart. This issue determines the amount of corrosion allowance you will consider when selecting a wall schedule.

There is no doubt more that I have forgotten to include in this first pass. I will try to add more as I remember. I also know that by posting this here on the pipingdesigners web site others will read it and ad their wisdom.


The finished "Line Class" pipe spec.

Each of the individual Line Class sheet might be created as a spread sheet in a Microsoft Excel Work Book. One spread sheet for each Line Class.
Across you might have the following column headers:
• Item
• Nominal Pipe Size (inches) or (Metric)
• Schedule (Wall Thickness)
• End Type
• Description (This is a simple description of a piping component not a full purchase description)

Vertically the first column (Item) will be divided into "Pipe", "Fittings", "Flanges", "Gaskets", "Bolts" and "Valves"
With-in this column the "Fitting" section and the "Valve" section would be divided to cover the various items normally required based on size.
"Fittings" would include:
• 90 degree ELLs
• 45 degree ELLs
• Straight TEEs
• Reducing TEEs
• Caps
• Unions
• Etc.

"Valves" would include:
• Gates
• Globe
• Check
• Ball
• Butterfly
• Etc.

Other information that needs to be included on a line class by line class basis includes.
• Basic Construction (2" and smaller Screwed/ 3" and Larger Flanged and Butt welded, etc)
• Flange Rating (150# RF)
• Temperature Limits (Minus 50 degrees F to Plus 500 degrees

I know this is a lot to information to take in.
But do it the same way you would eat an elephant, one bite at a time.