Monday, July 28, 2008

New Revisions to ITSdesign

I have just posted a revision to ITSdesign. In this revision I added new data entries for shell and roof appurtenance weights in the corroded condition. This allows you to have a different weight for the new and corroded condition. I also added a new data entry for the percentage of the roof appurtenances that is transferred to the shell. For column supported roofs this allows you to specify how much of the weight is transferred to the shell for resistance to overturning. The appurtenace weights have also been added to the resistance to uplift when internal pressure is present. For wind girder required section modulus I have added the 'm' factor to account for increased loading per I also added to check whether Appendix F calculations need to performed based on the weight of the roof and appurtenances as compared to the uplift due to internal pressure.

For those who are using ITSdesign, see the Revision block for other minor revisions to ITSdesign. We continue to strive to make ITSdesign as accurate and complete as possible. Suggestions for additions and corrections are always welcome.

Thursday, July 17, 2008

API-650 Appendix J Material

I have been debating about what to do with the material requirements for an Appendix J tank. What is specified in J.2 is that the material must meet the requirements of Section 4. This would mean that if you use A36 material in a shop built tank with a design metal temperature of -10 degrees F, you would have to impact test the material. What is strange to me is that if I built that same tank to Appendix A the material does not have to be impact tested per A.2. I plan on presenting the question to the API committee at the next meeting. In the meantime, I have added a checkbox to the design page of our software where you can select to use the material limitations of Appendix A. Each user will have to determine whether their customer will allow them to use the material as specified in Appendix A instead of the requirements of Section 4.

We have made some additional modifications and corrections to ITSdesign. Be sure to read the revision notes to see what we have done.

API-650, 11th Edition, Addendum 1

I am continuing to review Addendum 1 to the 11th Edition of API-650. Here are some comments on what I have found so far.

1) There are many slight modifications in the values used for SI units. Places that used to specify 12.5 mm now use 13 mm. In the table for, they have revised the angle size slightly. In 5.5.1 they changed 172 MPa to be 171 MPa. In they changed the limit for using the 1-foot method for shell design to 61 m. Revised the angle size in and
2) In 5.2.1 (loadings) they revised the external pressures so that tanks with internal floating roofs with circulation vents do not require a minimum external pressure.
3) In 5.2.1 they also added loading requirements for internal floating roofs.
4) In they added additional rules when using a lower allowable stress material in the upper courses. You now can do an elastic analysis or the lower course must be no thinner than the required thickness for product design or hydrotest design of the upper course.
5) They have revised some of the tables for manway neck thicknesses, nozzle reinforcement, cover plate thicknesses, and flush cleanouts.
6) For intermediate wind girders, the shell course thickness is now to be based on the thinnest shell course which may not be the top shell course.
7) An expanded design for frangible roofs has been added.
8) now states that the purchaser can specify that lateral loads be imposed on the roof supporting columns.
9) has been revised to reduce the minimum thickness for roof support columns from 0.25" to 0.236".
10) has been revised to provide calculations for the maximum spacing of the roof rafters. It also set the maximum spacing at 84". These limits apply to both inner and outer rafters.
11) 5.11.2 has been revised to add a limit on the value of wL for the wind condition. It also now specifies that tb is in the corroded condition. A calculation of the minimum annular ring width for wind has been added.

This covers most of the changes I see in the design section (Section 5). Next time I will give you information on the changes to the various appendices and which new appendices have been added.

To keep our software, ITSdesign, current, we are already working on the revisions to incorporated these changes into ITSdesign.

Monday, July 7, 2008

API-650 11th Edition Addendum 1

Can you believe it! I have finally received a proof copy of Addendum 1 to the 11th Edition of API-650! Yes, Addendum 1 will be finally released in the next 4 to 6 weeks. I will be working my way through this addendum to see what changes have been made. It looks like Appendix E has been corrected. Also, duplex stainless, aluminum, and mixed material appendices have been added. There is a change in Appendix V on how loadings are calculated combined for wind and vacuum. It appears there are some minimum thicknesses that are changing slightly. There is also a change in the determination of the maximum spacing of rafters (both inner and outer). The calculations for anchor bolts has changed as well. Appendix F has revised formulas for calculating the internal pressure. Appendix S has specific requirements for the use of "seamed" stainless steel.

This is just a quick overview of what I see in my first glance through the addendum. I will be posting more on the specific changes as I begin a more complete reading of the addendum. Be sure to come back for more information.