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. 8/21/2017 4:20:02 AM Earl at AST Aboveground Storage Tank Forum RSS 180 150 Re: Secondary seal damage - By: Dunedin [37] Impossible to provide a definative answer without an on site inspection. However things to look at would be<br /><br />you say that there is a gap between the seal tip and the tank shell - has the seal tip been damaged?<br /><br />since there are at least five locations it could indicate a problem with the tank shell - are there any obvious shell plate deformations?<br /><br />what type of Primary Seal is there and how do you know that it has not been damaged?<br /><br />have you observed the roof rise and fall and if so did you note the gap at all levels of the roof position or just when it was resting on the legs? Sun, 20 Aug 2017 03:41:00 -0300 Secondary seal damage - By: sameer [387] Dear Sirs,<br /><br />In one of crude storage tank EFR : 110 diameter x 16.9 meter Ht Five locations were found with secondary seal gap opening and Skid Plates was observed deformed or straightened. However no indication of primary seal damage was found during inspection. Please advise me what is the reason for this damage and how to fix it? <br /><br />Thank you,<br /><br />Regards,<br />sameer Sun, 20 Aug 2017 00:12:00 -0300 Re: Figure 5.19----API-650 - By: Tankee [235] I always fall back to this definition in API 650: <br /> full-fillet weld A fillet weld whose size is equal to the thickness of the thinner joined member. Fri, 18 Aug 2017 08:07:00 -0300 Re: Local Stresses - By: [39] API 650 does not offer specific design guidelines on this that I know of but conscientious tank designers will evaluate the upper shell course for these stresses. Wed, 16 Aug 2017 16:30:00 -0300 Local Stresses - By: Javed Nasir [1566] Rafters supportes cone roof at the locations where they are attached with upper shell course indyce locallized stresses. Any guidelines in API 650 on this aspect? Wed, 16 Aug 2017 16:01:00 -0300 Re: API 650 - By: ITS [1678] I dont know about watching the laying down of every weld bead pass, but the ASME Section XI seem clear and has historical been clear that the WPS or weld procedure specification requires a cross section of the joint that depicts the sequence of the weld beads. Although this is a non-essential variable it is still required. After all the WPS is a welders instruction that was based on the weld coupon qualification. Now, a non-essential variable doesnt require re-qualification of the weld coupon. <br /><br />So, the WPS should never be ignored for the weld engineer had purposely made out the PQR to ensure the weld coupon was strong and practical for the application and spun off multiple Weld Procedures Specifications WPS. Mon, 14 Aug 2017 11:19:00 -0300 Re: Aluminum Dome - By: Dunedin [37] And now we may have to add CTS to this list!!! Mon, 14 Aug 2017 10:42:00 -0300 Re: Figure 5.19----API-650 - By: [39] In general, when the leg length is not included I assume the intent is a full-size fillet weld and I would use full-fillet welds if there will be piping attached to the nozzle. If the flange is not used for piping, but used only for instruments, smaller welds would be OK in my opinion, and some owners specify an outside weld only. For a gauge hatch I think owners would accept a 1/4 inch weld inside and outside. Mon, 14 Aug 2017 07:20:00 -0300 Figure 5.19----API-650 - By: Javed Nasir [1566] <br />What is the minimum fillet weld size requirement for welding the roof nozzles with Slip On Flanges as per Figure 5.19?<br /> Mon, 14 Aug 2017 02:23:00 -0300 Re: Clause - By: [39] Only for plates over half inch thick. <br />.<br />PWHT is also required for shell plates in API groups III and below when the steel is over 1 inch and the nozzle of over 12 NPS. PWHT is also required for all flush type nozzles and flush cleanouts. Sun, 13 Aug 2017 13:22:00 -0300 Re: API 650 - By: Javed Nasir [1566] As per ASME Section IX Edition 2015, following are the important definitions to make an argument of API 650 multi pass phrase:<br />These definitions are contained under QG-109<br /><br />Pass: a single progression of a welding or surfacing opera-<br />tion along a joint, weld deposit, or substrate. The result of<br />a pass is a weld bead or layer.<br /><br />Cover Pass: a final or cap passes on the face of a weld.<br /><br />Wash Pass: pass to correct minor surface aberrations<br />and/or prepare the surface for nondestructive testing.<br /><br />Weld Bead: a weld deposit resulting from a pass<br /><br />Layer: a stratum of weld metal consisting of one or more<br />beads.<br /><br />Your fabricator is correct in case where one pass results one bead and one layer. He will apply two passes, and results will be two layers . Say, the weld is completed in two passes/two layers, It will be a multi pass weld.From the top, you cannot make a judgement if the weld is multi pass or single pass. Only through cross section, you can verify. <br /><br />If bevel is wide enough or weld is long enough and welding process is manual, visually you can see multi passes in this case.<br /><br />Best Regards<br />Javed Nasir Sun, 13 Aug 2017 10:22:00 -0300 Re: Clause - By: Javed Nasir [1566] Thanks David. I was reading also the same way as you do. <br />So shortly, any nozzle assembly over NPS 2 requires PWHT if shell MOC is either from IV, IVA, V or VI. Right? Sun, 13 Aug 2017 10:05:00 -0300 API 650 - By: Tankee [235] I have always considered the multipass phrase in API 650 to mean multiple passes that are visible after welding is completed. I have a tank foreman arguing that multipass can mean 1 bead over another and only one showing. My reasoning is that an inspector cannot watch every inch of welding being performed on a tank bottom, so the end result needs to be a minimum of two beads being visible. Also, if documentation is lost, or not available, to inspection years later and they see only one bead, they are going to assume that it is not multipass. I appreciate any comments or clarifications on my way of thinking. Sat, 12 Aug 2017 11:18:00 -0300 Re: Clause - By: [39] That sentence is not ambiguous to me. It refers to all openings that require reinforcement which is defined in previous sections.<br />.<br />Arent the two references in your post essentially the same?<br />.<br />Table 5.6 tells us that fittings smaller than NPS 2 do not require reinforcing plates but they may be used if desired.<br />.<br />The first sentence of says opening larger than NPS 2 require reinforcing.<br />.<br />I read these as saying the same thing, do you?<br /> Thu, 10 Aug 2017 18:16:00 -0300 Re: ERV SET PRESSURE - By: ITS [1678] The reason you are not getting a straight-forward-answer is there is a lot engineering judgement that has to be applied. The weight of the roof is a reasonable start, but having the tank un-anchored is very-troublesome, for in catastrophic event the bottom of the tank will separate from the shell while the shell and roof lift off together or intact. I think yo already know this... Without it anchored the tank at a minimum will get a rounded bottom like is wants to tip over. Ugh! The frangible roof is a lesser of 2 evils and will damage the tank, for sure, but prevent over pressurization from boiling-liquid with massive vapor production and minimize the calamity.<br /><br />So, the basis of thought is as follows - 1- set pressure might be better understood by determining the strength of what the tank floor near the shell annular plate can resist before tearing -fillet welds of floor plates- at elevated temperatures. Then consider a number less than the weight of the roof and take the lessor of the two. Then give a margin of safety. 2- The relieving capacity of your emergency relief valve or ERV must be greater than the saturated vapor created on a full boil or rolling boil. You may have to think about superheated vapor if your ERV are marginal in size. I think you know how to do that too.<br /><br />I am thinking of multiple large rupture -disk- square diaphragms. They will require maintenance.<br /> Wed, 9 Aug 2017 14:16:00 -0300 Re: ERV SET PRESSURE - By: ADI HAR-SHOSHAN [93] My question is to what pressure the emergecy roof vent should be set in the case that the roof in a non fringible type and in order to satified API-650 5.8.5 we have to install ERV. <br />Now, API-650 1.1.1 state that that the internal pressure should not exceed the roof plates in the case of an atmosphric tank basic design , on the other hand and api-650 state that relife pressure should not exceed the calculated pressure of F.4.1 &amp; F.4.2.<br />I hope that clear my question and please correct me if Iam wrong <br /> Wed, 9 Aug 2017 09:19:00 -0300 Re: ERV SET PRESSURE - By: [39] In general, your emergency pressure / vacuum settings need to prevent over stressing the tank and its components. Note that we are not sizing normal vents since your question is for ERV Emergency Relief Vents.<br />.<br />The device should have pressure vs flow curves from the manufacturer.<br />.<br />Size the vent so it flows the required CFM or CMH calculated per API 2000 at a pressure / vacuum that will not damage the tank.<br />.<br />The set pressure is always less than this pressure because most vents dont flow much at the set pressure when they just start to open. You may need multiple vents.<br />.<br />It can get complicated if the set pressure for these vents is close to another system such as Nitrogen blanketing. Sometimes you cant get a vent with a high enough set pressure to not affect the other systems yet flow enough at the design pressure. You may need pilot operated vents, etc.<br />.<br />For a non-frangible tank, the shell-to-roof joint will likely and should be your weakest point. You use Annex F to calculate its failure pressure. Your vents should not exceed this pressure at the required flow rate. Your customer may want some factor of safety applied, or some head room to this failure pressure. Each tank is different, look for roof appurtenances or design details that may introduce a weaker area, or artificially strengthen the roof-to-shell joint piping, hand rails, etc .<br />.<br />Note that these tanks are usually anchored and you dont want to exceed the capacity of the anchors. Tue, 8 Aug 2017 21:13:00 -0300 Re: ERV SET PRESSURE - By: ITS [1678] Okay, I think API-650 Appendix F should be used for guidance, but consider API Standard 2000 Venting Atmospheric and Low Pressure Storage Tanks as well as NFPA-30. <br /><br />Do you have a photo of what is being used now? Tue, 8 Aug 2017 15:45:00 -0300 Clause - By: Javed Nasir [1566] Dear Experts,<br /><br />The phrase all opening connections requiring reinforcement in first sentence of means:<br /><br />1- All openings where reinforcing plate is used per Table 5.6a? OR<br />2- All openings NPS 2 when 5.7.2 is selected as an alternative design procedure? OR<br /><br />Best Regards<br />Javed Nasir Tue, 8 Aug 2017 00:43:00 -0300 Re: Aluminum Dome - By: Dunedin [37] Yes, based in Rheinfelden in Germany and trade under the name of VACONO. Mon, 7 Aug 2017 10:40:00 -0300