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 5.1.5.9(e), they have revised the angle size slightly. In 5.5.1 they changed 172 MPa to be 171 MPa. In 5.6.3.1 they changed the limit for using the 1-foot method for shell design to 61 m. Revised the angle size in 5.9.3.1 and 5.9.3.2.
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 5.6.1.3 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) 5.10.2.9 now states that the purchaser can specify that lateral loads be imposed on the roof supporting columns.
9) 5.10.3.2 has been revised to reduce the minimum thickness for roof support columns from 0.25" to 0.236".
10) 5.10.4.4 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.

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.

3 Bay Rafters

I would like to annouce that we just released an update to ITSdesign that includes 3-bay rafter systems. This applies to API-650 and AWWA D-100 tanks. In this update we also corrected some calculations related to SI units including the change from using 0.785 as the factor for pressure in the anchorage calculations to using 785. This change may possibly appear in Addendum 1 when it is released (still no proof copy yet). We continue to expand the capabilities of ITSdesign in both US and SI units. Also, we continue to verify that it is up to the latest edition of the code. If you have not tried ITSdesign, you can download a trial copy at www.innovativetanksolution.com. You will find the program easy to use. If you do have questions, we are here to answer them. You can contact us at its@innovativetanksolution.com or by calling 651-480-0258.

API-650 Table 5-21

I received a reply on my concern with the formulas in Table 5-21a for SI units and it is agreed that the formula is wrong when pressure is included in the calculations. They are now trying to determine what is the easiest and fastest way to make the corrections. In my program, ITSdesign, I will use the factor of 785 instead of 0.785 for the pressure. This revision will be included in the release I will do this weekend. There is a possibility this change could make it into Addendum 1 but I kind of doubt it. Maybe they will release an errata sometime soon after Addendum 1 is released. I have not seen the proof copy of Addendum 1 so am still wondering when it will end up being released. I will keep you informed on this.

API-650 Table 5-21 Uplift Loads for Anchorage

After returning from the API committee meeting I began looking at revising ITSdesign to conform to the changes approved to Table 5-21, Uplift Loads for anchorage. I had reviewed the changes proposed and agree with the changes being made. However, as I began rewriting the program and checking the output, it appears to me that the factor in Table 5-21a (SI units) is wrong. In looking back at even the 10th Edition, Addendum 3, it has a value of 0.785 for the factor when working with pressure. However, the pressure is in kPa while the result is to be in N. When checking the units we are off by a factor of 1000. I have written a note to the person who handled the agenda item and requested a claification. I will let you know what his response is once I receive it. In the meantime, I am revising ITSdesign for the SI units to use a factor of 785 instead of 0.785. I will also be incorporating the changes as approved by the committee for the agenda item.

API meeting in New Orleans

I attended the API meetings in New Orleans. There were some things addressed. Here is a brief summary.

1) Addendum 1 to the 11th Edition of API-650 should be released by the end of May. The proof copy we received was incomplete and they have not resent the complete proof copy yet. I will let you know when that occurs.
2) All of the agenda items approved at last falls meeting and this spring meeting are supposed to be coming out in addendums by the end of the year.
3) Table 5-21 was revised to conform to the combination loadings. This should be in Addendum 2.
4) Self-supporting roof calculations are changing that would use the strength of the material. This could reduce the compression ring area when highe strength materials are used. This should be in Addendum 2.
5) Clarification of the API-620 references in F.7 are still being worked on.
6) Shell nozzles larger than 48" is still being worked on.
7) Several minor items were approved and several are being reworked or reballoted.

Inquiries that had been submitted for review were not considered due to some timing problems. Hopefully this will be resolved by the next meeting.

Not much came out of this meeting. I will keep you informed as to when Addendum 1 is ready to release.

API meeting

I am currently at the API meeting in New Orleans. The day has been very disappointing. I found out that Addendum 1 for API-650 now will probably not be released until at least June. In fact the draft I have is incomplete. When released it should include new appendices X and SC. We shall see.

The other disappointment was that they did not review design or fabrication inquiries. They were scheduled to take place. However, it seems that all those inquiries we sent to API staff never made it to the heads of the committees in time to be sent out to the other committee members to review. Therefore, none of them are being reviewed at this meeting.

We will see if tomorrow is any more productive. We will continue to add to and update ITSdesign. We will also keep you updated on what is happening here at the committee meetings.