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Does API 650 allow for different length shell plates on the same course. ie could you use 4 plates of equal length and then one small piece of less than a meter to form the shell?

Many thanks.. As this is not directly addressed in API 650 is there any other storage tank standard that specifically states that 2 shell courses can be of different grade steels?

Is there any problem with having 2 different grade steels on an API 650 Storage Tank? We want to weld a bottom course of A537 and all other courses of A283 and want to know if there could be any detrimental effects caused by this? I understand that they may distort at slightly different rates...

Duwe6... Many thanks again and one final question. You have stated that "If it looks good, it is good" is only applicable to thinner plates but not plates above 1/2". Why is that the case? Could residual stresses still be in these plates even though there is no significant distortion?

Duwe6... Many thanks for your informative, very helpful answer. So essentially if the distortion (deviation) is within the limits set by API 650 then it has to be assumed that the residual stress in the shell plates would be considered acceptable?

I would like to ask for some advice on welding sequence on API 650 storage tanks which I know is not covered in the standard. When erecting a storage tank with a crane we have typically fully welded the verticals of one shell course before welding the verticals of the course above and then the...

Thanks JStephen.... That makes more sense.

In API 650 section F.7.5 states that; "The counterbalancing weight, in addition to the requirements in 5.12, shall be designed so that the resistance to uplift at the bottom of the shell will be the greatest of the following: a. The uplift produced by 1.5 times the design pressure of the tank...

I would like some help in sizing a curb angle due to the tension caused by the rafters. I have the attached as a sample which is a rafter roof for a 9m Dia tank using an IPE 160 as the rafters with a 1:5 slope. 1) I would initially like to ask a seemingly simple question as to how the...

Does anyone have any guidance on how a machine shop could become a certified machine shop by API. We are in the middle of Africa where there are currently no certified machine shops and very little information to pull from on how to go about becoming certified. We are in particular targeting...

In the past we have always earthed storage tanks into a "earthing pit" right next to the tank... We have just come across a consultant who is insisting that all earthing should be done outside of the bund wall as when it rains the whole bund area will become charged. What are your opinions on this?

Thanks for the reply... Sorry please could you explain "because the bottom has no strength in that direction". If the pressure is acting in all directions it would surely be pushing the bottom plates down just as much as creating uplift on the roof.

Probably a simple one.... As per API 650 why does the internal design pressure of a tank have any bearing on the overturning moment? Why is only the uplift taken into account whereas the pressure would act equally in all directions so the downward pressure would cancel out the uplift.

Thanks for your reply Duwe6... The particular tanks we have are Diesel Storage tanks which are to be open vented. Judging by your comments I assume that you can assume 0 mbar internal pressure if the tank is open vented with a simple swan neck breather? Please confirm

Dear All, If you have an open vented tank how would you go about ascertaining the internal design pressure of your tank when calculating the overturning moments? I do not want the maximum design pressure as per Appendix F but the actual design pressure. I would guess that it is just an...

I need to design a floating suction and want to establish how buoyant the float should be. We are designing for a tank of 5.9m Dia x 7.5m High with only one single swivel elbow. This will mean that the when the tank is filled to the top the float will be submerged so I do not want to make the...

Is it acceptable to have a bottom plate joint at the centre of the storage tank. This would mean that a portion of the joint would be cut out for the sump. Would this constitute a 3 plate lap joint?

What is the maximum deflection in a beam in bending according to AISC Steel Construction Manual 13th edition. I have the manual but cannot find where this is defined? I have heard L/360 but want to be sure. I want to design roof rafters for a storage tank and want to know the allowable...

Dear All, When calculating the uplift loads in API 650 it refers to P = deign pressure (see Appendix F). If you calculate P in Appendix F and the tank is small the maximum design pressure could be very high. This would mean that a large number of anchors are required even if my "actual design...

I know this is quite frowned upon however I would really like someone to be able to assist me in my query for emergency venting capacity based on the calculation below. CFH = 1,667*Cf*A*?(Pt-Pa) Where; Cf = Flow coefficient of valve A = Area of manhole or area of manhole lift Pt = Absolute...