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. 9/24/2018 4:31:50 AM Earl at AST Aboveground Storage Tank Forum RSS 180 150 Re: Bottom plate in welded steel petroleum storage tan - By: Karsadi [652] Dear Sir,<br /><br />Maybe other ways can be considered as follows<br />To change the slope of the existing bottom tank, it can be done by installing a new bottom plate above it, without dismantling the old bottom plate and installing a new bottom plate above it by making the bottom slope in accordance with the plan by implementing Double Steel Bottom Construction<br />If a double steel bottom is used, the details of construction shall provide for the proper support of the primary bottom and shell for all operating conditions. The design shall be evaluated to verify that the primary bottom and shell are not overstressed. The evaluation shall consider all anticipated operating conditions such as design metal temperature, maximum design temperature, fill height, hydrostatic testing, seismic conditions, and tank settlement.<br /><br />The evaluation is not required if the primary bottom is uniformly supported on both sides of the shell and is not structurally attached to the secondary bottom or primary bottom support.<br /><br />For double steel bottom systems that use steel members such as grating, structural shapes, or wire mesh to separate the bottoms, ingress of water between the bottoms will result in local accelerated corrosion rates. If the perimeter of the bottoms is not sealed, corrosion protection of the tank bottoms shall be provided. <br /><br />Thus hopefully it provides an overview of the benefits.<br /><br />Best Regards<br /> Sun, 23 Sep 2018 02:37:00 -0300 Re: IFR with double wiper secondary seal. - By: Karsadi [652] Dear Mr. Orlando Costa,<br /><br />Sorry, maybe my last posting are unclear and I repeat, as follows<br /><br />The main objective of this storage tank design is to accommodate Naphtha products and in an effort to overcome due to evaporation losses due to emissions, an IFRT tank is planned with Al IFR HC full liquid contact type as per API 650 annex H, because of tank operation is equipped with N2 blanketing , then I need to maintain the N2 pressure in the tank, so it is chosen with the addition of the fix. Al Geodesic Dome with tight vapor type as per API 650, annex G. and for completeness, I plan to install primary seals with mechanical shoe type and above it is installed with a single wiper secondary seal.<br /><br />For alternative of tank construction with the same functions, I intend to change the HC design. IFR from liquid full contact becomes a vapor contact, in this construction a double Wiper Seal will be installed over the primary Mechanical Shoe type.<br /><br />if Al IFR vapor contacts are planned, does it need to be equipped with pressure / vacuum vent as presuure balance between below and above the skin deck.<br /><br />According to my understanding, this is best and challenges others how and please argue.<br /><br />Best Regards<br />Karsadi<br /> Sun, 23 Sep 2018 01:07:00 -0300 Re: IFR with double wiper secondary seal. - By: Karsadi [652] Dear, Sir<br /><br />If you think of a secondary seal as weather seal, then it is enough to plan EFRT with the weather secondary seal only and do not need to consider being IFRT.<br /><br />With technological advancements to reduce emissions and leaks due to evaporation, the EFRT is installed vapor tight secondary seal,<br /><br />Many ways to overcome losses due to emissions and leaks due to evaporation among them I planned to Fix Geodesic roof using N2 gas blanketing method, to maintain the N2 in the tank, then the construction of the vapor tight fix roof tank and using the standard API 650 annex G.<br /><br />To make the vapor tight Aluminum Dome fix roof to maintain the expected operating life it is not easy and not many vendors can carry out according to API 650 annex G.<br />to overcome the above, emissions and leaks due to evaporation, <br />My opinion of design with combining EFRT construction with Mechanical Shoe and IFRT with double wiper seal.<br /><br />That is the meaning of my post and I am waiting for comments and suggestions.<br /><br />Best Regards<br />Karsadi Sat, 22 Sep 2018 20:32:00 -0300 Re: IFR with double wiper secondary seal. - By: Orlando Costa [201] From what I understand in your text, you have a tank with an external EFRT floating roof with a aluminum dome Aluminum Geodesic Dome.<br /><br />And you want to install another seal on the EFRT or replace the existing one. I see no reason for this. As Dunedin said a secondary seal is not necessary because the dome already serves as a protection against the weather.<br />I just recommend using a consecrated and approved stamp template, checking who they used. You can see more in API 650 Appendix H. Wed, 19 Sep 2018 08:00:00 -0300 Re: IFR with double wiper secondary seal. - By: Dunedin [1843] Since this tank is a CFRT, i.e. Fixed Roof with Aluminum Dome, I do not consider a Secondary Seal absolutely necessary. <br /><br />The main purpose of a Secondary Seal is to protect the Primary Seal from the elements, wind, rain, snow, etc. but as you have a roof on the tank, this will protect the Primary Seal.<br /><br />A Mechanical Shoe type of Primary Seal is ideal. Wed, 19 Sep 2018 03:57:00 -0300 IFR with double wiper secondary seal. - By: Karsadi [652] Greetings for all friends.<br /><br />To plan for the perfection operations of storage tank with Naphtha content.<br /> I will design an Internal Aluminum Floating Roof Tank with a vapor mounted type, which is equipped with a Fix. Aluminum Geodesic Dome.<br />To determining of Internal Floating Seal will be install the combination of Mechanical shoe primary seal which is equipped with a Secondary seal where the secondary seal is planned to be installed with double wiper seal or using a secondary seal which is equipped with two sets of wiper seal.<br />The question is? For my confidence and to increase my knowledge, hopefully from friends can share knowledge and information as your comment.<br />Is my design still permissible by API 650 standards and habits in Internal Floating planning, is it a common design or special design?<br />Hopefully somebody will be give opinions and explanations as comments.<br />It is wrong design or correct design? and if allowed by standard,<br />what the benefits and disadvantages if compared with secondary seal type with single Wiper.<br />Previously we thank you very much for the attention and knowledge that you can share.<br />Best Regards<br />Karsadi<br /> Fri, 14 Sep 2018 09:00:00 -0300 Re: Bottom plate in welded steel petroleum storage tan - By: Orlando Costa [201] Depending on the dimensions as the angle of inclination of the existing bottom and others details of your tank you can use API-653 - to - Replacement of entire Tank Botton. <br /><br />I worked on a similar case in the past. See an attached sketch. Wed, 5 Sep 2018 18:47:00 -0300 Re: Nozzle minimum thickness. - By: ADI HAR-SHOSHAN [93] I can recommend you the following:<br /><br />1. The rejection limit of the remaining THK at the next out of service inspection of a nozzle neck with respect to uniform corrosion should be 50% of the nominal THK, or 2.54 mm which ever is bigger.<br /><br />2.The rejection limit of the remaining THK at the next out of service inspection of a nozzle neck with respect to pitting corrosion should be 2.54 mm.<br /><br /> Wed, 5 Sep 2018 12:35:00 -0300 Re: Nozzle minimum thickness. - By: BABRTs973 [53] Depends on the nozzle size. API 650 Table 5.6 a for SI units or 5.6b for USC units gives the required thickness for tanks built to API 650. If your are inspecting a 12C tanks, you need to refer to that standard for required thickness used for those tanks. IF the 12C tank has been repaired and new nozzles installed they should have met API 650 requirements. Wed, 5 Sep 2018 08:08:00 -0300 Nozzle minimum thickness. - By: Jose [1721] Dear folks,<br />I&#194;&#180;m looking for some information about the subject in order to inspect as per API 653, some people is talking about 0,1 but nothing like this is stated in API 653, as per API 650 new connections are minimum 1/2.<br />Thanks in advance for any information on the subject. Tue, 4 Sep 2018 13:41:00 -0300 Re: Roof beam twisted - By: Jose [1721] I am talkimg about main beams. Tue, 4 Sep 2018 13:34:00 -0300 Re: Bottom plate in welded steel petroleum storage tan - By: BABRTs973 [53] Was this tank built with a cone up, cone down or flat profile. If it is a cone up or flat you may have to raise the nozzles to slot the shell for new sketch plates allowing drainage away from the shell. <br /><br />Not knowing the size diameter and height also makes for a shot in the dark. <br />If it is a cone roof less than 10 meters diameter you may be able to lift the tank and reprofile the base material for drainage to the center then set the tank back on the foundation.<br /> <br />But never in any circumstance should plates be laid on the existing floor and filet welded to the shell. The shell needs to be notched and the sketch plates inserted through the shell and welded on both sides. <br /> Mon, 3 Sep 2018 11:33:00 -0300 Re: Bottom plate in welded steel petroleum storage tan - By: Orlando Costa [201] However, the plates to correct the problem would be welded over top the existing bottom. Fri, 31 Aug 2018 06:30:00 -0300 Re: Bottom plate in welded steel petroleum storage tan - By: Orlando Costa [201] You mean you have the suggestion of soldering plates under the existing plates bottom. Thats right?<br /><br />I would think about another suggestion: depending on the diameter of the tank, it would weld plates to compensate for the inclination required using API 653, see itens 9.10 and 9.9.2 as a reference.<br /><br />Of course, a project correction document signed by an Engineer certified by API 653 will be required. Considering details such as nozzle level, need to fill the space between the plates, dimensions required of the new plates to avoid tensions and others. Thu, 30 Aug 2018 22:46:00 -0300 Re: Erection Procedure for tank over 140 ft HEIGHT - By: ITS [1678] I cannot say much about using guy wires for the purpose of comfort when building a 140 foot vertical tank that is about 130 foot in diameter. But, this note might guide you. <br /><br />The purpose of using guyed wires on a vessel or tank is to restrain the tank or vessel. Bare with me. Guyed wires essentially reduces the size of the foundation including reducing the number of anchor bolts and their size. This is because the guyed anchorage is now consider. But, there are trade off for the wire are a nuisance to say the least. <br /><br />Using guyed wires for anchorage seems impractical during the building process of the tank. <br />The idea that the tank is 140 feet tall is not as important as the slenderness ratio of the vessel or tank. <br /><br />So, how is the soil? Is the soil and foundation supportive enough and are their other structures around the tank to help manage the live loads like wind. Do these other surrounding foundations influence or stabilize the ground where your tank foot print will be located?<br /><br />Good luck. Thu, 30 Aug 2018 10:52:00 -0300 Erection Procedure for tank over 140 ft HEIGHT - By: TankCons [1946] Does anyone know of any special procedures from safety perspective for erection of a tank of 140 in height? We are planning to use jack-up method and wanted to know if any temporary guy ropes would be needed for each shell course to ensure stability during jack-up? Something else as well?<br /><br />Any thoughts on this?<br /><br />Yes, I agree this is a seriously abnormal height for a tank. But this is a Thermal Energy Storage tank and there are severe space restrictions. The tank dia is going to be close to 130 ft, but the height is critical here. Going by OSHA, the tallest TES tank in the world was constructed by CBI and its 150 tall. So, this is going to be pretty close. Anyone here knows if CBI did the erection using jack-up or conventional?<br /><br />Any other concerns that you feel would need to be addressed? FYI, we are in seismic Zone 2B. <br /><br />Thanks in advance for your thoughts and comments. Wed, 29 Aug 2018 11:55:00 -0300 Bottom plate in welded steel petroleum storage tan - By: [1945] In a newly constructed ATF tank due to settlement the slope of bottom tank is towards annular plate. Due to this water settles around critical zone in tank bottom.<br /><br />This is not allowed in ATF tank to overcome this another plate is welded from shell to bottom so that slop is toward the center of the tank.<br /><br />My query is whether this welding will have effect on load on bottom plate and if so what else is suggested to correct the slope of bottom plate from outward to center.<br /><br />Thanks Wed, 29 Aug 2018 05:39:00 -0300 Re: Tank shell thickness - By: Orlando Costa [201] .... correcting: I meant API-650 Tue, 28 Aug 2018 21:26:00 -0300 Re: Tank shell thickness - By: ITS [1678] Orlando, good point! Your detail description of the tanks upper most shell course thicknesses of necassary details seems to bring the question in better focus. Mon, 27 Aug 2018 19:27:00 -0300 Re: Tank shell thickness - By: Orlando Costa [201] Excuse me, but I think that ganesh is referring to Appendix F - Figure F-2-Permissible Details of Compression Rings API 650. Possibly confusing with item API-650 . <br /> Mon, 27 Aug 2018 16:14:00 -0300