SHELL FINAL THICKNESS 5

[Lord Ets]

Good day, Engineers!

For example, I already designed the tank with 1 foot method and Annex V at API 650. The thickness are 12mm, 10mm, 8mm, and 8mm. The tank has roof frame without column and has agitator at the center. Is there any other computation for additional thickness for shell plates or to check if the shell plates can carry the vertical loads like roof frame without column, and an agitator at the center.

Thank you, Engineers! God bless.

 

[HTURKAK]

Appendix V is for the tanks external pressure (vacuum) loading between 0.25 kPa to 6.9 kPa . How did you decide the vacuum pressure? specified by the Purchaser ?

What about the shell stiffeners ?

You may look at the worked example at appendix V 10 .

How did you design the roof for the supported agitator?

If you provide the operation weight, frequency, and torque of the agitator with a descriptive sketch you may get better responds.

 

[MJCronin]

Lord Ets ... HTURTAK makes good sense ..

Is this the first tank you have ever designed ?

Are you an engineer or someone that just substitutes in numbers in equations .... What is your background ?

Where is your calculation for an agitator of unknown weight ?.... Agitators are designed based on a STIFFNESS not a stress criteria

What about the effects of wind and earthquake loadings on the shell thickness ?

.... or will you come running to this forum five minutes from now to ask about this ....

Show ALL of your work, assumptions, design criteria etc ..... not a half-assed preliminary result

MJCronin
Sr. Process Engineer

 

[HTURKAK]

The OP is too busy and hardly ever responds or , to read the posts..

Dear LORD ets, we are waiting with sanguine hope that you will raise new questions.. we are always online and waiting to jump with a respond to your new questions since being retired engineer, we have a lot of free time ...

 

[Lord Ets]

I'm very thankful for your response Sir HTURKAK and Sir MJCronin.

The purchaser did not specify the external pressure. Simple drawing with dimensions only. I ask my boss for external pressure but he don't know. I just choose 6.9kPa. I'm sorry to say this but my intention is to over design the tank.

Over design for my safety.

I'm really sorry Sir, but structural design is my contract to them. Designing large tanks is so awesome but since I don't have any experience on it even in my college days, I'm hoping they will teach me or advice me how to design it.

I always ask my boss with few things with tanks but his response is always he don't know. And also, sometimes no soil data. Our last conversion is all about the soil test, but he has no plan to take soil test.

In my first months in my job is ok, I design steel structure. He just ask me to design the thickness of tank (just thickness). Until he told me to design the whole tank.

I used to design the tank/s with Annex V to credit the wind load and external pressure. To add stiffener and to increase the thickness of the tank. With 1 foot method and Annex V, I'm confident with my design with those reference. But I'm still thinking if I need to add or check if the shell plate thickness can carry the roof framing and agitator.

Givens in drawing
Dimesions
Design height
Operational height
Rafters
Sloped bottom
Roof slope

Givens in the table
Specific gravity of content
Design volume
Operational volume
Design pressure full of water
Design temperature
Operating temperature

Agitator weight 5tons

I compute the rafters spacing using API 650 5.10.4.4. And I use STAAD to design it, since my boss told me to use software. But I check it manually.

 

[Lord Ets]

Sir, the agitator weight is 5 tons. The torque, etc. is unknown.

 

[Lord Ets]

Yes I used Annex V.10 as reference, Sir HTURKAK.

 

[Lord Ets]

Sir MJCronin, I'm a civil engineer. With less than 1yr experience. My specialty is analysis and design of steel frame, concrete frame, etc. but not for tanks. Tanks are special structure. I'm struggling because I don't have senior to ask. In our department, we have electrical and mechanical engineer, architect, and draftman. My boss is civil engineer, but he don't know have any idea how to design any structure. That's why I need to study with myself, but not all of answers for my questions can be found at API 650. Like, is there any other calculations to increase/check the thickness of tank shell since there is roof framing and additional dead load of 5tons due to agitator.

Sir HTURKAK, your right about torque of agitator. The client should be provide that? Base on API 650 Annex L, there's alot of data to be consider and should be provided by the purchaser. I think they give us incomplete data.

 

[Lord Ets]

Based on your replies Sir HTURKAK and Sir MJCronin. There's alot be consider when designing of tank. Yes, I agree. To be honest, my boss give me an old design of tank. It is already operating since 2008. The design is very simple. The pass designer used 1 foot method only, and that's it. A very very low budget design. For example the calculated thickness is 7mm point something, he rounded up to 8mm. That's it, a less than 1mm allowance. He didn't compute the spacing of rafters. He use minimum thickness of 5mm for roof plates. Channel section for rafters without calculation, he just used an old reference book with tables of minimum sections and numbers of rafters. Minimum for bottom plates, 6mm + 3mm (corrsion allowance). Minimum top stiffener. Above all he assume the allowable soil bearing capacity of 96MPa. The old tank dimesions are dia 12.57m and 7.8m height.

I didn't used his design as reference. Because I just want to compute the values, I just don't want to rely on minimum without calculations.

I hope you can give me some advice how to design it correctly. Thank you so much. God bless.

 

[HTURKAK]

Lord Ets (Civil/Environmental); if you do not provide necessary info, the responds which you will get will only be guessing..

If you want helpful responds; provide some data ( dimensions, material ,properties of the content , wind , seismicity, temperature, design pressure, agitator loads...)

In past , having worked for phosphoric acid ( reactors and storage ) tanks, there are two possible supporting systems for roof type center-mounted tank agitators,

i = agitators mounted on two beams ( for open roof tanks or flat roof tanks ) running parallel to diameter of the tank,

ii = agitators mounted on reinforced nozzle for cone roof (or dished roof for small tanks )

For your case, with cone roof, the radial rafters shall be designed to support the roof loads and the loads that will be supplied by the agitator vendor...

Your replies imply , it is better for you to ask consultancy of an experienced engineer to get safe, economical design...

Good luck..

 

[IFRs]

My suggestion is to use API 650 for the tank, include 1 ro 2 mm for corrosion allowance based on the product's corrosivity to steel, include open vents sized using API 2000 then ignore extrenal pressure (vacuum), include wind and seismic for the tank buckling, overturning and compression, use local ice and snow loads for the roof but include no equipment loads, assume soil capacity equal to the full height liquid load (product or water whichever is greater). Use API minumum roof plate thickness and rafter quantity, basic structural analysis for the roof support structure. For the agitator include horizontal beams that span the tank to support the agitator, assume a torque based on the motor used, run vertical beams down the outside of the tank down to 300mm below the first round seam encountered. For vertical loads on the shell from rafters and the agitator, you'll find that the tank shell is quite strong but check using FEA, Roark's or anchor bolt chair type analysis. Also search this site for previous questions that include the key words agitator and tank.

 

[MJCronin]

IFRs gives good advice .... but this tank should be designed by a third-party consultant with experience .... The Consultant cost is relatively small part of the total design and installation cost and, more importantly IT IS A SHIFT OF CURRENT AND FUTURE REPONSIBILITY TO AN EXPERIENCED THIRD PARTY !

The environmental cost of a massive liquid spill in terms of possible lives lost and environmental damage pales when the services of an experienced tank designer are considered.

You claim to be a civil engineer (concrete)but are doing the best you can "learning on the fly".... Let us ask you, would you enter and occupy a multi level concrete building with NO REBAR designed by a geologist that was " learning on the fly" ????

Your sleazebag boss practices "MBA thinking" (Anyone can do any job in any amount of time") and is someone that will never take any responsibility for anything...

Always remember, a boss like yours have will take ZERO RESPONSIBLITY if there is any accident or design failure ..... He will always point to you as the tank designer, experienced or not. .... Remember, this tank could fail YEARS from now for reasons we have not even yet considered and the authorities could come looking for you !!!

Does your company require the PE stamping or sealing of documents ?.... Will you be the one certifying the tank design and safety ?

Here in the USA , we are trying to get a similar irresponsible MBA reptile out of the White House right now ....... He has caused death and destruction of many institutions and environmental programs, yet he take responsibility for anything ..... He is borderline delusional and belongs in a place where he can no longer harm others

In what country are you located ? ...... What is the liquid stored ????

MJCronin
Sr. Process Engineer

 

[Lord Ets]

Mr. MJCronin, concrete and steel frame. How about you, are you going to do that? Because I won't. If you don't know something just study and get some advice with person/s have experience on it. I thought anyone can ask some professionals here?

I'm just asking some advice, I'm not asking you to design it for me. That's learning on fly you are talking about.

I am willing to learn and to be trained. But who will train me in our company? Nothing, I'm lucking of support. To be honest, a small idea coming from my colleagues is very helpful. But also, they don't have idea.

Yes, you're right. The problem here is my boss. He already know that I don't have any idea how to design tanks.

At first, he gave me an excel file with formula of 1 foot method. Oh god it's very easy. That's why he thought this is a very easy job.

Again, our pass designer always design a tank with 1 foot method only and he didn't consider anything. He get some minimum values of tank parts. And thats it.
I don't have trust with his designs. That's why I'm here to ask you because I trusted you guys.

Tank design is not on my contract. We have mechanical engineers in our office and wondering why I'm the one who design it. I think mechanical engineers has more idea to design it.

Before. My company has two designer, mechanical and civil. The mechanical engineer only used 1 foot method. Base on his designs, he always added 5mm to his computed thickness (let say 7mm with corrosion allowance, +5mm. His final thickness is 12mm) thats it, no other computation. And his report is summary only.

I already told how the civil engineer design tanks.

Again the boss is the problem here. He is like a child as what like told me by my colleagues.

Mr. HTURKAK is right about his advice on my other thread. "If you don't like where you are, move. You are not a tree."

But again, we are facing pandemic right now. I need money to support my family that's why I accepted the work he gave. And since pandemic, it's very difficult to apply to other company. That's why I'm enduring these circumstances.

 

[r13]

I feel your anxiety on lack of support from your office, but you are not alone, as there are many locations like that. You are lucky to have that many information (as you have provided) and a previous design example to follow, or compare. Relax, start review the relevant code, and do the best you are aware/capable of. The additional information will be dripping in, as the design progress forward. Industry design is usually done through iterations/cycles, as many information are not known before hand. And lastly, for the know nothing boss, unfortunately he's the one ultimately to sign off your design, and be responsible for it. I don't think he will say "I don't know" to his boss then.

 

[Lord Ets]

I'm waiting until the pandemic is gone, and look for another company.

I'm aware that these should be design with someone with experience.

Again, maybe this is so rude but I don't have a choice. My intention is to over design and over price the tank/s.
Over design for my safety and over price to make sure that these tanks construction will not be awarded to my boss.

Yes, it is so rude. But he don't care about me, he don't care about my professional license. Then we're the same.

My colleagues also complaining about his mindset. By the way, he is not the ceo/president of our company. He is just trained to be the next ceo because his uncle (the ceo) is already old.

Even if my intention is to over design and over price the tank/s, I'm still wanted to be learn how to design it.

Even if it is over design/price. There's still computations, I can show or send to my boss. By the way, I'm work from home right now. The another goal is to have reports to sent to my boss.

For example I designed it with API 650 Annex V even if there's vent. So this is over design. It is ok for me, my boss don't have idea with that.

But still I want to learn how to design it properly. I'm interested.

I only know about 1foot method, variable point method, bottom, roof, rafter spacing, Annex A, B, E, K, S, V of API 650.

That's why I'm here to ask some advice.

Thank you.

 

[Lord Ets]

Yes Sir r13, thank you. I'm trying my best, that's why I'm here to gather some informations.

All of you, thank so much.

 

[Lord Ets]

Sir IFRs, yes. I will add vertical beam outside the tank shell.

That's the problem, no info for agitator motor to be use.

For example, I already know the agitator torque. Is there any other formula to be consider. Or a fomula with relation between tank/shell and the agitator torque?

If mild steel, I always used 3mm corossion allowance.

If stainless steel what is the good value for corrosion allowance? Because I used 3mm also for my safety.

Finite element analysis. Ok ok, I get it.

Thank you.

 

[IFRs]

You are in a tough spot, as is your customer who buys the tank, and the public that lives nearby. Fortunately, tanks are not too complicated. From what I have read, you are OK with the basic tank design using much of API 650, perhaps understand the theory behind their cookbook equations and methods such that you can derive the API equations and understand where the constants come from; and might have read other background and footnoted sources. It seems like you are now looking at the agitator. For the agitator you know the weight and torque. You can therefore design the bridge beams, I would keep them around a meter apart, include corrosion allowancees. Include all loads - wind, seismic, personnel, etc. Don't forget the connections, welds, bolts, etc. The verticals you can design for the same loads, the same way. Their impact on the tank depends on how they are attached. I would start with assuming they are welded to the upper portion of the tank and the lower ends of the verticals using 300mm square doubler plates equal to the shell plate thicknesses. this will simplify the analysis of the vertical beams. Avoid shell seams if possible. I think you'll find that the additional loads they put in to the shell plates can be determined using basic structural analysis methods, possibly confirmed with FEA. Combine load using appropriate load combination factors and look for areas of maximum stress. Stay conservative and continue to look for experts that can review your work.

 

[Lord Ets]

This is 1 example of the tank, stainless steel. As you can see, no vent.

The agitator weight is 5tons.

Sir HTURKAK, these are the datas you are looking for.

 

[IFRs]

You may have overturning issues from seismic for a tank taller than wide and a huge weight on top. Shell anchors may be needed.