Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Pipe wall thickness, barlow equation problem

  1. Apr 23, 2015 #1
    Hi guys
    I am working on some project that involves pipe wall thickness calculation, and I have one problem.
    here is the explanation of the example:

    http://pokit.org/get/?24c6e34b...4662402372ce5fc7.jpg

    Please, can some one tell me what means tf/m2 (ton force/square meter ???) and how to do conversion as shown on picture.

    Thank you very much.
     
  2. jcsd
  3. Apr 23, 2015 #2

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Fresh water has a density of 1000 kg / m3 (in round numbers) or a weight of 1000 kg-force for each cubic meter.

    1 tonne-force = 1000 kg-force, therefore 1 m3 of fresh water weighs 1 tonne-force (tf).

    Since the acceleration due to gravity is approximately 10 m/s2, 1 kg-f = 10 N approximately; thus 1 m3 of fresh water weighs 10 kN.

    Each meter of depth of fresh water produces a pressure of 10 kN/m2,
    so a head of 110.585 m = 110.585 tf/m2 = 110.585 tf/m2 × 10 kN/tf = 1105.85 kN/m2

    1 m2 = 1,000,000 mm2, so a pressure of 1105.85 kN/m2 / 1,000,000 = 1.106 N/mm2

    so it appears the value of 11.06 kN/mm2 is off by a few decimal places. :frown:

    http://en.wikipedia.org/wiki/Ton-force

    I'm not familiar with the equation shown for calculating the wall thickness of the pipe, but it is not the Barlow formula.

    http://www.engineeringtoolbox.com/barlow-d_1003.html
     
  4. Apr 23, 2015 #3

    stewartcs

    User Avatar
    Science Advisor

    Can you describe the application a little bit? Are you using any particular codes (API, ASME, etc.)? Pipe burst pressures are determined using widely different safety factors depending on the code you're using and the application.

    Regardless, I don't recommend copying an example to perform engineering calculations if you're not 100% sure of how it was derived! Start with stating the application, figure out your loading conditions (i.e., static internal pressure vs. cyclical, any external loading, etc.) then you can just pick one of the many industry standards/codes that cover your application.

    CS
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook