×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Retiring thickness of piping system
3

Retiring thickness of piping system

Retiring thickness of piping system

(OP)
The required thickness is described in ASME B31.3. This can be calculated from internal pressure of piping system. However, the result (especially in Class 150# piping system) is very far from the thickness of comercial pipe. Do we have other factors to be considered? Please comment about the method to specify the practical retiring thickness of piping system.

RE: Retiring thickness of piping system

Two other major factors additive to pressure design (but others exist):
-sustained loads and support span
-corrosion allowance
Most codes specify also minimum thicknesses to insure minimum general robustness of system.

prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design

RE: Retiring thickness of piping system

2
Pan, hi again. Prex have the reason, when you calculate the required thickness you need to estimate a STRUCTURAL THICKNESS also, is refer to the minimun thickness neccesary resist the weight of the pipe distance between supports, the weight of valves and the weight of the fluid.
Genereally, in 150# systems, the pressure it's too low, my recomendation is began with 0.125" (normal corrosion allowance) plus the required thickness per B31.3 (involve Material, pressure and temperature) equation,  e.g .085" (is't looked like to the value that made you writte the question? )and get a round value 0.125 + .085" = 0.235.
Now you have a value similar to commercial pipe.
Example:

                T-Min Calculation  

       Design: B31.3                       PIPE
Material Code: A106B                                   Design Temp: 150.0 °F
MSpec: A106       GR: B       P No: 1    Cl/Type:        Notes:

    T-Min has been calculated using the variables listed below.
  t  = Pressure design wall thickness, in
  P  = Internal design gauge pressure (150 lb/in²)
  S  = Applicable allowable stress (20000 lb/in²)
  E  = Quality Factor, long weld joint factor (1.00)
  y  = Temperature Factor (0.40)
  D  = Outside Diameter (6.625 in)

          P * D                    150 * 6.625
  t = ------------- =  ----------------------------= 0.025 in
     2 * (SE + Py)     2 * [(20000 * 1.00) + (150 *0.40)]

As you can see 0.025 it's too low, but the corrosion allowance, the weight of the pipe etc. where is?

Are here: (this is an example)

Structural T-Min has been calculated using the variables listed below.

 Ro = Outer Radius of Pipe (3.313 in)
 Ri = Inner Radius of Pipe (3.000 in)
 SG = Specific Gravity of Fluid in Pipe (1.000)
  D = Pipe Support Spacing (25.00 ft = 300.0 in)
  L = Max Center Load on Pipe (250.00 Lb)
  S = Material Stress of Pipe (20000.00 lb/in²)
  A = Additional Corrosion Allowance for Pipe (0.125 in)

 WP = Pipe Weight / in = ((Ro*Ro)-(Ri*Ri))*Pi*0.2833 = (1.7557 lb/in)
 WF = Fluid Weight / in = Pi * Ri * Ri * SG * 0.03613 = (1.0215 lb/in)
 WL = Load Bending Moment = L * D / 4 = (18750.00 in-lb)
  X = Max Bending Moment = WL + (WP + WF)*D*D/8 = (49993 in-lb)

                          X * Ro * 4
  t = A + Ro - ((Ro**4) - ----------- )**(0.25) = 0.200 in
                            S * Pi

and now .200" looks comercial? I hope this help you.
   

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close