×
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

Overturning Stability - Floating Roof Tanks

Overturning Stability - Floating Roof Tanks

Overturning Stability - Floating Roof Tanks

(OP)
Hello All,

I have an External floating roof tank design (Pontoon Type with single center deck) that i am looking to do overturning stability calcs for. Looking at API 650 11th Edition, Addendum 3: June2011.

Clause 5.11.2 states the tank must satisy both the uplift criterias....

0.6Mw + Mpi < MDL/1.5 + MDLR
Mw + Fp(Mpi) < (MDL + MF)/2 + MDLR

I would appreciate any feedback on the below queries....

1) I would expect that for an Atmospheric Tank with an External Floating Roof the value for Mpi = zero?

2) Are the formulas shown above only relevant to Cone Roof Tanks? If not how do we add the weight of the Floating roof with regards to MDL and MDLR, as these values in the code seem to be referring to weights associated with tanks that have fixed roof structures?

3) Why does the code not take into account any weight from the tank bottom plates with regards to wind loading/overturning stability?

Thanks in advance!

RE: Overturning Stability - Floating Roof Tanks

I would assume that Mpi= zero, and neglect the weight of the floating roof, just check the tank like it was an open top tank.
A great deal of the overturning moment with the current methods is due to wind uplift on the roof, and eliminating that ought to add a great deal of calculated stability.

RE: Overturning Stability - Floating Roof Tanks

(OP)
Thanks jStephen,

Any thoughts on why the code does not include the weight of the floor for the overturning?

RE: Overturning Stability - Floating Roof Tanks

My guess would be, that without significant movement of the tank, you'd only get uplift resistance from the foot or two of bottom nearest the shell, and that was just considered a negligible amount.

RE: Overturning Stability - Floating Roof Tanks

(OP)
Hmmm yes i see.....

This would also reinforce the theory to NOT include the weight of the floating roof in the stability calc, as it is supported/sat on the floor away from the shell and hence would not contribute to resisting any uplift.

Thanks for your comments and thoughts.

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