AST Aboveground Storage Tank Forum RSS Welcome the aboveground storage tank forum, a bulletin board dedicated to tanks, fuel tanks, plastic tanks, fuel storage tanks, and above ground storage tanks for engineers, tank operators, maintenance personnel, and technicians who work on or around these aboveground storage tanks (AST) and chemical plastic tanks. 5/24/2017 4:03:23 AM Earl at AST Aboveground Storage Tank Forum RSS 180 150 tank shell replacement procedure - By: Ali [409] What is the weld sequence of shell plate replacement? Vertical seams should be welded first or horizontal? When first horizontal seam is welded the second seam should be tack welded or not? Tue, 23 May 2017 00:18:00 -0300 Re: Dynamic Liquid Hoop Forces from Seismic Event - By: ITS [1678] I meant to say acceleration of the weight and not plain weight. Mon, 22 May 2017 16:25:00 -0300 Re: Dynamic Liquid Hoop Forces from Seismic Event - By: ITS [1678] This is a difficult subject, but I hope it is simple for others to understand to issues.<br /><br />So the dynamic liquid hoop forces or hydrodynamic pressures from a seismic event must be taken into consideration through out tank to include the first shell course to the highest shell course. <br /><br />The horizontal acceleration influences the sloshing of the upper two thirds of the tank -worse case full tank - shell course that puts pressure against the shell courses on the side of the slosh and needs to be thicker because of this. <br /><br />The lower third is trickier for the critical zone where the shell and annular plate meets gets highly stressed. So the pressure from sloshing against the shell courses in the lower third requires additional thickness to over come that pressure from the added liquid level and weight of the slosh. <br /><br />The floor gets additional pressure too from the added liquid height from the slosh. This also means the ground under half of the tank will be highly pressurized and the other half will be under pressurized trying to cause over turning. So, the ring wall foundation must be robust enough to handle this dynamic shift of the mass above and maybe a concrete floor is under the tank steel floor to stiffen the structure. <br /><br />So, you should take into account the thickness of the first course and more. Mon, 22 May 2017 16:22:00 -0300 Re: Acceptance Criteria for Shelll Plumbness - By: ITS [1678] You are welcome. Thu, 18 May 2017 18:43:00 -0300 Dynamic Liquid Hoop Forces - By: ADI HAR-SHOSHAN [93] When claculating shell courses thickness as per 1 foot method ,does the Dynamic Liquid Hoop Forces or stresses that created during seimic event should be taken into account for the thickness of the first course? Thu, 18 May 2017 10:32:00 -0300 Re: Acceptance Criteria for Shelll Plumbness - By: Orlando Costa [201] ITS, I understood your explanation. I was thinking that I could use the item 10.5.2 to measure one localized deformation in one tank wall, how I showed at my sketch.<br /> Your sketch is clear like good words. I so glad with your attention. Thanks! Wed, 17 May 2017 21:59:00 -0300 Re: Acceptance Criteria for Shelll Plumbness - By: ITS [1678] The sketch is crude but it give a basis for the tank shell plumbness problem when it is experienced with tank tilting and shell out of roundness. As a good rule the 1/100 is very reasonable and gives a benchmark for unsightly tanks that look distressed. So, the 1/100 is for API 653 reconstructed tanks. Wed, 17 May 2017 15:42:00 -0300 Re: Acceptance Criteria for Shelll Plumbness - By: Orlando Costa [201] OK ITS, I understood your interpretation. <br />I would like understand better, what API 653 tell about The maximum out-of-plumbness of the top of the shell relative to the bottom of the shell shall not exceed 1/100 of the total tank height, with a maximum of 5 in. If I can consider 5in in the vertical position.<br /> Mon, 15 May 2017 19:46:00 -0300 Re: Acceptance Criteria for Shelll Plumbness - By: ITS [1678] The sketch reminds me of a shell plate ripple or wrinkle from a fabrication and tank erection issue that is not going away. Maybe you have a unique problem. I think of tank shell wall plumbness as being more akin to tank being out of round, but tilting instead of being out of round. Mon, 15 May 2017 17:22:00 -0300 Acceptance Criteria for Wall Plumbing - By: Orlando Costa [201] Hello everybody,<br /><br />According to item 10.5.2 of API 653 I am sure to consider the reference value 5 in the vertical or horizontal position. See figure.<br /><br />10.5.2 Plumbness<br /> The maximum out-of-plumbness of the top of the shell relative to the bottom of the shell shall not exceed l/ioo<br />of the total tank height, with a maximum of 5 in. The l/ioo criteria, with a maximum of 5 in., shall also apply to fixed roof columns. For tanks with internal floating roofs, apply the criteria of this section or API Std 650, Appendix H, whichever<br />is more stringent.<br /> The out-of-plumbness in one shell course shall not exceed the values specified for mill tolerances in ASTM A 6 or A 20, whichever is applicable.<br /> Sun, 14 May 2017 20:44:00 -0300 Re: Annular ring welding - By: ITS [1678] How about some pictures of what you are talking about on welding your annular ring? Tue, 9 May 2017 09:49:00 -0300 Re: Annular ring welding - By: [39] This is a basic tank construction question that suggests a lack of experience on your or your contractors part. Advice from the internet will be limited at best and without knowing all the particulars of tank erection may lead you astray. Your best bet is to find and contract with an experienced tank installer. For a general introduction, acquire a copy of the Boilermaker Manual, it will have a good basic introduction to tank construction practices. Mon, 8 May 2017 13:51:00 -0300 Re: IMPACT TEST - By: ITS [1678] Maybe a bit more clearer is needed so if the engineered design temperature is say -40F to 240F, then the Impact Testing needs to be done at -40F and when I mean ready to place in the anvil, then I mean not a minute or so later, but immediately then release the hammer. Sorry about the confusion. Fri, 5 May 2017 15:22:00 -0300 Re: IMPACT TEST - By: ITS [1678] When Impact Testing is required then the Impact Test needs to be done at those design temperatures required by the code or standard, which are at the engineers design temperatures, to ASME Section 9 or API 650. This is done by either heating or refrigerating the machined specimen, and saw cutting the notch will produce unacceptable results, so dont saw cut. For very cold temperature service a special deep freeze refrigeration will be needed. Once the Charpy Impact Tester or if you are using an Izod Impact Tester are readied the test specimen is removed, after a soaking period to ensure uniform temperature throughout the specimen, quickly into the anvil support or vice support then the hammer is released. Fri, 5 May 2017 09:36:00 -0300 Annular ring welding - By: Antonio Nadal [1857] Hi everyone,<br /><br />Sour water tank, 2500 m3, API650 on a concrete-ring foundation. I have just installed the annular ring plates and my question is, should I weld the butt joints from inner to outer or the other way around? Which is the best way to avoid annular ring shrinking? <br /><br />Thanks a million in advance for your comments! Fri, 5 May 2017 09:35:00 -0300 IMPACT TEST - By: ADI HAR-SHOSHAN [93] What should be the actual testing temprature of the steel when impact test is executed ? Fri, 5 May 2017 04:32:00 -0300 Re: 10000 gallon aluminum Hydrogen peroxide Tank - By: [1856] Please provide more details, photos, etc. of the tank. We might be interested in buying it.<br />Thanks,<br />Peter W Tue, 25 Apr 2017 14:59:00 -0300 Re: Hydro-test Exemptions - By: [39] All is not lost however: section a, b and c give you three ways to demonstrate toughness.<br /><br />Determine that the steel is tough enough - 1 cut out the shell plate for the nozzle neck as if a repad were to be used instead of an insert plate and get this coupon tested for toughness or 2 establish the material grade from a non-destructive test and determine if the shell material is tough enough.<br /><br />Another possibility is to evaluate your tank for Figure 5.2 and if you fall into the safe for use area of the curve your steel is tough enough without any other testing.<br /><br />Another possibility is to evaluate the shell stress and see if it falls under 7,000 psi Sun, 23 Apr 2017 23:35:00 -0300 Re: Hydro-test Exemptions - By: ADI HAR-SHOSHAN [93] Thank you David . Sun, 23 Apr 2017 04:50:00 -0300 Re: Hydro-test Exemptions - By: [39] Your question: API-653 Para 3.20 a say only NPS larger than 12 is a Major repair - Read further: 3.20.c says removing or replacing a shell plate larger than 12 inches is a major repair.<br /><br />Your question: API-653 Para 9.8.6 b is confusing regarding reinforcing plates, can reinforcing plate be used or only insert plate is allowed? - My reading of this section is: if the nozzle is over 2 inches your is over 2 inches AND the shell is over 0.5 inch thick yours is over 0.5 inch thick AND it does not meet current toughness yours does not meet current toughness because it is unknown, see 3.31 then you have to use a shell insert plate this section does not distinguish between single-thick or a thickened insert, just says an insert plate must be used. <br /><br />So, no - you can not use just a reinforcing plate and must use an insert plate.<br /><br />The rest of the section describes the minimum size of the insert plate. The minimum size is the greater of penetration x 2 or penetration + 12. This would apply to a nozzle and a single thick or thickened insert plate you determine the thickness based on reinforcement requirements.<br /><br />If you use a nozzle and a reinforcing plate and a shell insert plate usually this insert plate thickness is equal to the shell thickness the minimum size of the shell insert plate is the size of the reinforcing plate plus 12 inches.<br /><br />Because you are forced into using an insert plate, and the insert plate will be larger than 12 inches in at least one direction, it is a major repair per 3.20.c and you need a hydrotest or an exemption that meets the criteria in 12.3.2.<br /><br />Again - my reading and interpretation only... Sun, 23 Apr 2017 00:47:00 -0300