API-650 11th Edition

It has been too long since I posted information concerning changes about the 11th Edition of API-650. Here is the next part having to do with changes in Section 5, which is design. This used to be Section 3.

5.1.3.6.1 specifies that multipass welding is required for manual welding processes on fillet weld legs or groove depths greater than ¼”. For semi-automatic and automatic welding processes multipass welding is required for welds greater than 3/8”. This applies to bottom plate welds, roof plate welds, and shell-to-bottom welds for Groups I, II, III and IIIA materials.

5.1.3.7 specifies that all attachments to the tank exterior shall be completely seal welded (intermittent welding is not permitted) except as specified in 5.1.5.8 for wind girders.

5.1.3.8 says permanent backing strips are not permitted (unless approved by the purchaser) except as permitted in 5.1.5.5 and 5.1.5.6 which is for butt-welded bottom plates.

5.1.5.1.b specifies that the top surfaces of bottom welds shall be ground flush where they will contact the bottoms of the shell, insert plates, or reinforcing plates.

5.1.5.8.b requires all horizontal bottom-side joints of wind girders shall be seal-welded unless specified otherwise by the purchaser. (Previously seal welding of the underside was only required if specified by the purchaser.)

5.1.5.9.c adds tension rings and compression rings to top-angle sections that require butt-welds shall have complete penetration and fusion.

5.2.3.d adds localized loads resulting from such items as ladders, stairs, platforms, etc., shall be considered.

5.3.1.2 specifies that sliding friction resistance shall be verified for tanks subject to lateral wind loads or seismic loads.

5.3.2 provides how corrosion allowances are to be applied. (Many of these had been scattered throughout the code or not specifically defined.)

5.4.4 specifies that unless otherwise specified, tank bottoms requiring sloping shall have a minimum slope of 1:120 upwards toward center of tank.

5.4.5 adds requirements for foundation drip rings if specified by the purchaser.

5.5.3 requires that if the product height times the specific gravity of the product exceeds 75 feet, then you must perform an elastic analysis to determine the annular plate thickness.

5.6.1.1 note 4 says that for diameters from 10.5 feet to 50 feet, the minimum thickness of the lowest shell course only is increased to ¼”. (The question is does this apply to field erected tanks or was this a note related to Appendix J tanks??)

5.6.1.5 adds that isolated radial loads on the tank shell, such as those caused by heavy loads on platforms and elevated walkways between tanks, shall be distributed by rolled structural sections, plate ribs, or built up members.

5.8.5 has been added to address the limitations for roof venting. Normal and emergency vents shall prevent the internal pressure from exceeding the pressure calculated in F.4.1 with some other limitations as well. Screen sizes are specified as being ½” nominal opening.

5.8.10 specifies platform, walkway, and stairway requirements. They have added that unless declined on the data sheet, a roof edge landing or gaugers platform shall be provided at the top of all tanks.

5.10.4.7 provides requirements for column bases. A ¼” wear plate seal welded to the floor is required or you can provided a thickened bottom plate that also distributes the load. Guides for the column to allow vertical movement of at least 3” are required and cannot be welded to the tank bottom. Several possible methods are given in Figure 5-26.

I will posting more soon. Also we will be releasing a revision to ITSdesign which will bring it into compliance with the 11th edition.

API-650 Wind Design with I > 1 or Exposure D

API-650 provides the formulas for designing a tank for wind. However, the formulas are all based on a importance factor (I) = 1.0 and an exposure = C. If your requirements are for exposure D or an importance factor greater than 1.0, you have to modify all of the calculations. For the wind loadings you need to calculate a new horizontal load and a new vertical load using ASCE-7. For this you have to determine values for Kz, Kzt, Kd, G, Cf, and GCp from ASCE-7. From these values you can then calculate your new loadings. You also have to calculate a new horizontal loading based on the base wind velocity. To this you have to add the internal drag pressure specified in 3.9.7.1 and compare that to the base value used in the calculations for maximum wind girder spacing as well as for sizing requirements for wind girders.

The effect on your wind calculations is greatly dependent upon the height of your tank. The API-650 formulas are based on Kz = 1.04. For a short tank with exposure C, Kz could be equal to 0.85 which will give a lower horizontal wind load depending upon the importance factor. The vertical uplift from wind might increase depending upon the tank height. If you have a higher tank or a tank with exposure D these values will increase and will probably result in higher loadings on the tank.

The effect on the wind girder requirements for a short tank probably will not change as you cannot use a factor less than 1. The values will change for taller tanks, tanks with higher importance factors, and tanks in exposure D.

Because there is becoming more of a requirement for importance factors greater than 1.0 and the possibility of clients requiring exposure D, we have just released our new version of ITSdesign to include calculations based on ASCE-7 for these conditions. If you enter either a importance factor greater than 1.0 or exposure D, ITSdesign will automatically provide the calculations based on ASCE-7 requirements.

API-650 11th Edition

There are changes from the API-650, 10th edition to the 11th edition. I will be reviewing some of these changes over the next several postings. So here goes!

Added new paragraphs 1.1.4 and 1.1.5 and revised 1.1.6 and 1.1.18 to specify that Appendix L data sheets are mandatory unless waived by the purchaser, all tanks and appurtenances shall comply with the data sheet and attachments, field tanks shall be furnished completely erected, tested, and ready for service connections unless specified otherwise, and shop tanks shall be furnish tested and ready for installation.

Added Appendix W providing recommendations covering commercial and documentation issues.

Added section 1.3 to outline the responsibilities of the parties involved.

Added section 1.4 to specify documentation requirements.

References was moved to section 2 instead of being a part of section 1.

Added section 3 to provide definitions.

Material are now in section 4 and have the following changes:
1) Rimmed or capped steels are not permitted.
2) Cast iron for pressure parts or for attachment by welding to the tank is prohibited.
3) Cadmium-plated components shall not be used without the consent of the purchaser.
4) Added section 4.7 on bolting stating that (unless otherwise specified on the data sheet) flange bolting shall be A193-B7, anchors shall be threaded A36 round bar with heavy hex nuts and shall be galvanized, and all other bolting shall be A307 or A193, and A325 may be used for structural purposes only.
5) Added section 4.8 on welding electrodes.
6) Added section 4.9 stating gasket material is to be specified on the data sheet and shall not contain asbestos unless specified by the purchaser. Gaskets shall be made with integral centering or positioning device. No sealing compound, adhesive, or lubricant shall be used unless specifically allowed by the purchaser. Spare gaskets are not required unless specified on the data sheet.
7) Test gaskets must have comparable dimensions and compressibility characteristics as service gaskets. Descriptions of gaskets for temporary use only as test gaskets shall be submitted for purchaser’s approval.
8) The test gasket for joints that will not be disassembled after testing must be the specified service gasket.
9) Flange bolts and nuts used for testing are acceptable for use in the completed tank except for stainless steel bolting.

This takes us through section 4. Next time we will continue our look at the changes in the 11th edition.

AWWA D-100-05 is now in ITSdesign

Finally! Yes, we are finally releasing our newest update to ITSdesign! It now includes AWWA D-100-05 designs in addition to API-650 Addendum 4 designs. The new release has shell designs per the standard and per Section 14, wind designs, seismic designs per Section 13, self-supporting cone and dome roofs, single span rafters and center columns, anchor bolts, and anchor chairs. Current users of ITSdesign will automatically receive the update. A trial copy of ITSdesign can be obtained by going to www.innovativetanksolution.com and clicking on ITSdesign download. We are continually expanding the capabilities of ITSdesign and look forward to your comments concerning what you would like to see added or changed. ITSdesign is a design program for designing steel tanks to the API-650 Addendum 4 code and now also the AWWA D-100-05 code.

Email notification

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API-650 meeting

It has been too long since I did the first post. I need to catch you up on what is coming with regards to API-650.

An errata was issued in April following the committee meetings in Seattle. Most of the changes did not have an affect on our ITSdesign program as they were more notation in nature.
1) The changes to Equations E-18 and E-21 did affect the program and have been changed. They actually reduce the seismic load.
2) We had changed Equation E-20 and E.6.2.2.3 (second equation and fourth equation) quite a while ago.
3) There still seems to be a problem with what they have shown for Equation E-23a and E-23b. It would seem that E-23a should have a factor of 196 not 1.96 and that E-23b should either be 1.28 or 1.25 but not 1.96.
4) Equation E.6.2.2.3 (third equation) should still have a factor of 83 not 8 as shown.
5) Equation E.7.2 (second and fourth equations) where corrected to remove the I and replace it with 1.
6) There seems to be a problem with the equation changes in V.7.3.3, V.7.3.4, V.8.2.1.3 and V.8.2.1.4. For the first two equations, if the factor for the US units is correct then the factor for the SI units should be 19.0 and 13.4 respectively. The 13.4 factor corresponds to what is used elsewhere in the save appendix and elsewhere in the code. The latter two equations do not make any sense as they did not even show the original equation correctly to begin with. As such we have currently left all of these equations as in the orginal Addendum 4.
7) The change in V.8.2.3 from 32tb to 16tb was in our original program change as we did not feel this was correct to begin with.
8) The change in the example equation of V.10.2 corresponds to what we have built into our program except that according to the definition of fc, it does not have to be less than 15000 psi.

The 11th Edition of API-650 is about to be released. I just received an email stating that the final review was completed today and it will be released (I assume to the printers). I would expect to see something in the next few weeks. At the meeting they indicated it would be released sometime in June and it appears that is going to happen. Once that is released we will see what changes they have made. Along with that I would expect an addendum to the 11th Edition to be coming out by the end of the year.

There were many interesting things discussed at the meeting in Seattle. Some where just for discussion and some are going to be coming sometime in the near (??) future. A few of the items being discussed are:
1) They are looking at adding 201 and 201LN material to Appendix S.
2) They are working on an appendix that would add duplex stainless to the code.
3) They are workng on an appendix that would add mixed materials (carbon steel, duplex stainless, and austenitic stainless). You would then be able to use these materials in various combinations in one tank. You could then have a duplex stainless bottom and first ring and the rest carbon steel or other combinations.
4) There are modifications to the safety factors for Appendix V being worked on.
5) The problem of using narrow plates shop welded to make shell plates is being addressed along with the extent and location of x-rays required.
6) Shell nozzles larger than 48" are being worked on.

It will be interesting to see how much of this is included in the 11th Edition or the first addendum when it comes out. I will keep you posted.

API-650 Addendum 4

When API issued Addendum 4 to the API-650 Storage Tank specification many aspects of the code were affected. The wind and seismic designs were change to try to bring them more into line with ASCE7, a new section for vacuum design was added, and a new section specifying load criteria was added. Sometimes the changes are difficult to interpret and time consuming to perform.

ITSdesign is a software program developed by Innovative Tank Solutions, LLC, to address these problems and to assist designers in meeting the requirements of the Addendum 4 of API-650. We are continuing to develop this program to meet the requirements of the code and the needs of the users of this design software.

Our goal is to help our users better understand what the code is requiring and how ITSdesign helps them meet those requirements. We want our users to better understand how to work with ITSdesign. To this end we are going to be posting questions and answers about both the API-650 code and the ITSdesign software.

We are working on adding AWWA D100-05 designs to ITSdesign and will be keeping you posted as to the progress on that part of the software. We will also be dealing with questions concerning this design code as there have been many changes to it as well.