Insulation thickness added to ITSdesign

We have just released a new version of ITSdesign that includes entries for insulation thickness and weights. You have the option of having insulation on just the shell, just the roof, or both. The insulation thickness and weight can be different for the shell and the roof. You can also specify as to whether the insulation weight is to be used in the resistance to overturning for wind and seismic calculations. The addition of insulation thickness affects the area of the tank exposed to wind. In the printouts for wind you will see a different value for the tank diameter and height when detemining the area exposed when the tank is insulated. This increases the overturning moment and the sliding forces. For seismic you will see an increase in the weights. Insulation thicknesses and weights are also shown in the printouts including in the loadings page.

Frangible roof design of anchored tanks

At the API committee meeting in November I brought up the subject of the frangible roof design requirements. In particular I asked about the requirement if 5.10.2.6.d which says "For anchored tanks of any diameter, the tank shall meet the requirements of 5.10.2.6.a and the anchorage and counterweight shall be designed for 3 times the failure pressure calculated by F.6 as specified in 5.12." One of the requirements is in 5.10.2.6.a.5 which gives the maximum area of the compression ring that you can have and still be considered frangible. I asked if this requirement can be removed when the tank is anchored since we have to design the anchorage for 3 times the failure pressure which is based on the actual area of the compression area. After some discussion the committee as a group decided that you still must meet the area requirement of 5.10.2.6.a.5. What this means is that for smaller diameter tanks meeting the frangibility requirements is very difficult. For shop built tanks built to Appendix J meeting the frangibility requirements is next to impossible.

What is next in ITSdesign

We are currently working on adding Appendix P.2 calculations to our ITSdesign software. It has turned out to be a bigger challenge than first anticipated and so is taking longer than expected to program. I will keep you informed as to the progress on this. With regard to Appendix P.3 that was deleted from the standard, the committee is still working on the review of the equations in relation to the charts. That work has not been completed and so we do not have a timetable for when this section will be put back into the standard. Since it is not ready for balloting as yet, it will be at least a year.

It is a New Year!

Welcome to the New Year! My first post for 2011 will be about Addendum3 of API 650. Where is it? It is still in the process. I know it should have been released in November but it wasn't. In fact we have not seen the final draft of it to review. The last word is that it should be released in February or March. I am looking forward to its release as there are some changes in it to help with reducing anchorage on some tanks due to wind. As soon as I know it is being released, I will let you know and have the changes ready to release in our ITSdesign software program.