Piping System

Pipe schedules relate to the pipe wall thickness, as well as the Working Pressure rating (based on Maximum Allowable internal pressure, where applicable).

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1. All pipe is to be made of a long hole, surrounded by metal centered around the hole.

2. All pipe is to be hollow throughout the entire length.

3. All pipe is to be of the very best quality, preferably tubular or pipular.

4. All acid-proof pipe is to made of acid-proof metal.

5. The O.D. (outside diameter) of the pipe MUST EXCEED the I.D. (inside diameter) otherwise the hole will be on the outside of the pipe.

6. All pipe is to be supplied with nothing inside the hole so water, steam, or other stuff can be put inside the pipe at a later date.

7. All pipe is to be supplied without rust, as this can be more readily put on at the job site.

8. All pipe is to be free of any covering such as mud, tar, barnacles or any form of manure before putting up, otherwise it will make lumps under the paint.

9. All pipe over 500 feet in length must have the words "Long Pipe" clearly painted on each end so the fitter will know it is a long pipe.

10. Pipe over two miles long must also have "Long Pipe" painted in the middle so the fitter will not have to walk the entire length of the pipe to determine if it is a long pipe or not.

11. All pipes over six inches in diameter is to have the words "Large Pipe" painted on so the fitter will not use it for a small pipe.

12. All pipe closures are to be open on one end.

13. All pipe fittings are to be made of the same stuff as the pipe.

14. Pipe specified as "Straight Pipe" shall not have fittings within its length, otherwise it becomes "Crooked Pipe."

The purpose of Scheduled ratings in pipelines are to ensure that the pipe used is able to withstand the pressure of the medium within it. You have Schedule ratings from 10, 20, 40 and 80 as the norm in the market. The basis of Schedule ratings are to increase the pipe wall thickness without increasing the external diameter. This means that for a 6" pipe , the internal diameter for Sch 80 will be less than for a Sch 10 for pipes of similar material.

When using such pipes, the method of connecting two such pieces should also comply to the welding procedures to withstand the rated pressure.

Sioneme,

Please understand that my friend Lyn's answer is entirely humor. In various trades, it is easiest to talk when we have some (sometimes arbitrary) framework of words that have definitions we can easily refer to.

That is the essence of how pipe schedules were established. Years ago someone (probably a manufacturer) published tables that said a pipe with an assigned schedule number would have a certain property (working pressure rating), based on their experience with how it performed while in use. Others then could refer to that schedule number and say their pipe was equivalent in performance to it. Over time, this then became a standard referenced in some agency's or government's rules, and became associated with a certain wall thickness for any one diameter. Until this happened, you had no reliable or easy way to compare different vendors' products with each other, in terms of their performance.

This happened long enough ago with nails that the real reason why a particular penny size has a certain length has been lost to everyone's memory. Perhaps it was because 100 of the nails in any single size would have cost the designated number of pennies to purchase.

This happened with wire sizes, where each factory had their own gauge table, and you had to look at that table to see what diameter a #10 (or any other #) wire actually was. In the USA the standard was then given as AWG (American Wire Gage), and was based on the gauge table most commonly used up to then. It didn't get rid of the other tables as such, but because it was a convenient and easily used size table, the rules in different laws and standards started specifying it, so the other gauge tables disappeared.

This is true in lumber, with established lumber grading standards for dimensional lumber (#2, #1, etc), as well as various ratings for span and deflection usage for plywood or similar manufactured products.

OK? --JMM