×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

4C900 PVC Pipe Buckling during Testing

4C900 PVC Pipe Buckling during Testing

4C900 PVC Pipe Buckling during Testing

(OP)
Hi Gents,
I’m a machinery designer for the PVC Pipe Industry, few months ago I was involved to design a Hydrostatic Pipe Tester according to AWWA C900/5 or FM Standard. One of the special features requested by my customer was “Quick-Burst” capability using a whole pipe -6.1m / 20ft long- as a sample instead of using short pipe samples as the standard said.
The machine is capable to test from 4C900 to 12C900, and hasn’t any problem performing Hydrostatic regular test or quick-burst test -according to the DR- in all the size from 6C900 up to 12C900
Few weeks ago I was testing 4C900 DR18 at quick burst pressures -740 psi- during time required by the standard -60sec-and something strange to me started happening, the pipe itself buckled…as you shown below.
As a mechanical engineer I’m trying to relate the behavior of the pipe itself with Euler Column Effect, with no much success…
What I’m to intent is to simulate by FEA what’s happening, I don’t know exactly if I’m clamping too much the pipe or maybe I’m adding extra support “points” to it….

Do you guys have seen this kind of buckling before on a pvc pipe during a test?
Any suggestion will be helpful!
Regards
LPUS

http://files.engineering.com/getfile.aspx?folder=4...

http://files.engineering.com/getfile.aspx?folder=6...

http://files.engineering.com/getfile.aspx?folder=6...

RE: 4C900 PVC Pipe Buckling during Testing

Are the ends restrained? I would suspect that has and effect.
In metal tubing people will sometimes clamp against the ends, in high pressure tests this causes very strange failures as the tube length will change with applied pressure.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: 4C900 PVC Pipe Buckling during Testing

I will second the "fixed ends" causing a axial thrust theory -> That led to a buckling failure at the weakest point. Were you pushing the two end covers onto the pipe to maintain pressure and prevent leaks?
Do you normally test larger diameter or smaller diameter pipes at this length?
Have you tested this diameter pipe before at this wall thickness at this length?

The pipe buckled "up" (lifted up off of the supports). Was that it's failure position, or did it rotate or move after the failure and before the picture? Did it fail in place, then lift up as the water was drained and weight removed?

RE: 4C900 PVC Pipe Buckling during Testing

I'll third the "fixed ends" as the problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

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!


Resources