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.

 

[Lord Ets]

And this has vent. Agitator weight is 5tons also.

 

[Lord Ets]

This is a rafters for dome. But this is for reference only. I'm design for cone roof.

As you can see, there vertical I section outside the tank shell.

I already design roof framing for steel tank and it is locate inside the tank.

But now, it is stainless steel tank. The client wants the roof framing is outside the roof shell.

 

[IFRs]

I'd also worry about sliding down the slope.

 

[Lord Ets]

My boss told me that it should be anchored. Maybe because it has slopped bottom.

Now you can see. API 650 doesn't have section or provision about agitator and slopped bottom.

Any ideas and suggestions are really appreciated.

Thank you.

 

[IFRs]

Bottoms uniformly sloped to one side, sometimes known as shovel bottoms are not that uncommon, but as you note, API 650 is silent on that configuration. For some slight guidenace regarding friction, see sections 5.3.1.2, 5.11.4, E.6.2.1.2, E.7.6 where friction is mentioned.

 

[Lord Ets]

Thank you Sir IFRs, what about roof framing? How do you design roof framing like that?

In my case, I used STAAD.Pro and check it manually. My boss always suggest that if the structure can be designed using software, then use software.

 

[HTURKAK]

Lord Ets ;

Pls find below my notes,

i= For the tank without vent ; the internal pressure ( vacuum ) shall be calculated acc. to piping arrangement and valves ..The absence of vent does not mean the vacuum pressure 6.9 kPa will develop.. The probable vacuum pressure shall be calculated considering the emptying and filling ..

ii= The sloped bottom ; the sliding shall be checked together with applicable seismic and wind loading.. and FS suggested in the code shall be provided.If necessary, provide anchorage for sliding and overturning.

iii= The radial rafters seems to be above the roof plate.. API does not address the use of supporting system above the roof plates..

iv= You are expected to comply roof to shell joint ( compression ring ) requirements for self supported dome or cone roofs..The horizontal and vertical force flow from radial rafters to compression ring and to the shell shall be justified..

v= data provided on the dwg does not give info. for the wind, seismicity, type of content..

Good luck..

 

[Lord Ets]

Sir HTURKAK

i. The calculation of internal pressure you are talking about is can be found at API 650 Annex F? If not, can you give me reference.

Using external pressure of 6.9kPa (maximum for API 650 - Annex V) is ok or I'm safe with that? Since I can't find the section or annex in API 650 that discuss it.

ii. What section in API 650 I can use? Or what reference code? I only used API 650 Annex E for seismic design, and Annex V to account wind loads.
Can you give me some reference code to use? I really appreciate it Sir.

iii. Yes Sir.

iv. What reference code or section/annex in API 650 should I use Sir?

v. I get the value for wind velocity based on our code.

V = 290 kph
W = 1.48(V/190)^2 (Annex V)
W = 3.45 kPa

I only used Annex E for seismicity

Tank content, my boss told me to use water.
Specific gravity = 1.0


Thank you for your response Sir.

 

[IFRs]

Internal and external pressures are not calculated during the tank design - they are usually given to you. It's like Gravity, atmospheric pressure, soil bearing capacty, solar heat input, insulation R-value, snow load or seismic parameters - they are things dictated to you from the environment, the customer, the process, the location, materials, etc. Choosing an arbitrary external pressure (vacuum) in the absence of a real load condition will make your tank stronger, but for no defined or required purpose other than an added safety factor for resisting that particular imaginary load condition.

Also, Annex V is not for wind loads. It is for internal vacuum represented as external pressure. Other sections of the basic standard cover wind buckling and overturning.

 

[Lord Ets]

Sir HTURKAK

Can you check again the 2nd photo I sent. That I.H 18B, is that a vent Sir?

 

[Lord Ets]

Sir lFRs

Therefore, I should told this to my boss? The he need to contact/email the client and request for the values specially for (internal pressure, external pressure, and seismic parametets).

I already know the location. That is why I calculate the wind load and some seismic paramters.

It means, my safety is not guaranteed if I used 6.9kPa as external pressure? Maybe this tank has large value for external pressure?

I thought Annex V includes wind load, since it has formula for total design external pressure (Ps), the greater of (Pe or W + 0.4Pe). Now I know, thanks for the information.

All of you, thank you.

Can you give me what section/annex I can read the wind buckling and over turning.

or Sir, can you give me the references/section/annex I should read to design this tank.

Thank you so much Sir.

 

[IFRs]

See API 650 5.2 for all loads including wind and 5.2.2 for load combination factors, see 5.9 for wind girders to resist buckling and 5.11 for resistance to overturning. Actually, you can do as I did and use the search function in your PDF reader...

 

[Lord Ets]

Sir lFRs

I didn't used section 5.9 for wind girders. When I noticed that Annex V has more detailed about buckling, specially it has detailed example calculation.

I should design the tank/s for both section 5.9 and Annex V?

 

[Lord Ets]

What about the operational and design pressure of full of water. How can I use that?

When I calculate the shell thickness, I only used the formula and the height from the top of tank shell. For example in 2nd photo, I calculate the 1st or bottom course with a height of 17.00m.

And for the atmospheric pressure Sir, when or where I should use that?

 

[IFRs]

I apologize for the following. I mean no disrespect to you, your boss or the situation you find yourself in. I'd love to help but this seems like a deep hole and for me it's time to stop digging.

After this, I'm done. You are going down a path to disaster, possibly putting the public in danger and causing professional ruin for you and your boss. Stop. Right. Now. You owe it to yourself, your boss, your customer and the public, not to mention the bad name engineering might suffer for your efforts.

You are taking a very simple tank design standard, making it complicated and starting from the beginning of Chapter 1 it seem y ou are not understanding why it is used or how it is applied.

Design for the actual operating conditions. Don't just throw numbers and wild guesses at it unless this is just some game your boss is playing and there is zero risk of it being built.

Annex V is for tanks with internal vacuum and that is all. It is to be applied in addition to the basic standard if and only if your tank meets the scope of Annex V. This is or should be very clear in the scope of each Annex. From what I can tell, you don't know if your tank will experience internal vacuum.

For some reason you decided to include a completely arbitrary internal vacuum in your design. For some other reason you decied not to apply Annex M for high temperature, or S for stainless or F for internal pressure etc. Why not apply them all with wild guesses at the criteria and mash it all together for a cool science project?

Choosing a completely arbitrary vacuum, temperature, pressure or any other design criteria is not what engineers do. It could be too high (increasing cost for no purpose) or too low (unsafe and subject to failure). You need to find out what the design parameters are from the purchaser. It is not up to you or your boss to decide the operating temperature, design specific gravity, corrosion alowance, product stored, corrosivity, flash point, etc etc unless those criterria are obvious by inspection. If you want to throw numbers at it, just make the whole tank 25mm thick duplex SS, stop wasting your time and it might still fail.

There is an entire annex devoted to design data to be supplied by the purchaser. Get it filled out. If no one will tell you the truth and you need to make assumptions, have good reasons for them and then write it all down including how and why you chose each one in a very explicit letter to your boss explaining why the tank design is stupid, dangerous, costly and generally useless.

If it is a water storage tank in Spain, you can get basically figure it out. But if it is at a chemical plant you probably don't have a chance in the world of guessing right. And guessing is not your job.

If the tank could be full of water, use that as a design condition. It already is if you are following API 650. Since you asked this question, we can see that you have not read or understood API 650.

Calculating the shell thickness is very straight forward and clearly outlined in API 650. You appear to be unsure of how to use the 1-foot method. Since you asked this question, we can see that you have not read or understood this part of the standard.

Atmospheric pressure is not a load to be considered unless the tank is completely sealed and purchaser is going to pull a vacuum inside. Which is one of those design conditions the purchaser needs to tell you.

Again I mean no disrespect and have probably gone way over the line here. My apologies and I hope you can get all the design criteria, find someone who knows API 650 and can show you how relatively simple it actually is for what it does, and then help you recognize the things you need that are not covered in the standard and can help you with them.

I will probably continue to foloow this thread but will only get back involved if it seems like you are going in a good direction and just need a little push here or there.

Goodbye and good luck.

 

[HTURKAK]

Dear Lord Ets ;

I will try to answer to your questions which are explicitly mentioning my name and I hope my respond will not encourage you to attempt to design of the subject tanks. Your previous thread was for tank foundation design and that could be acceptable with background of a one year of structural engineering experience . However, the tank design is totally different subject and not only finding the shell thickness with simple hydrostatic hoop force such as in one-foot method. I am still at the same point that you shall ask the guidance of an experienced engineer or better perform all the tank design ..


Pls read the scope of annex V ; (appendix provides minimum requirements that may be specified by the Purchaser for tanks that are designed to operate with external pressure (vacuum) loading as a normal operating condition. This appendix is intended to apply to tanks for which the normal operating external pressure exceeds 0.25 kPa (0.036 lbf/in.2) but does not exceed 6.9 kPa (1.0 lbf/in.2).
The tank data sheet ( which also the basic design data should be included ) normally provided by the purchaser. In the absence of some data ,the first step is, qualifying the absent data with some calculations and assumptions , and asking the approval of the purchaser. If the internal (in this case vacuum ) pressure is absent, if you know the process and piping ( filling and emptying rates, PV valves,..) the vacuum pressure which may develop could be estimated by an experienced engineer. In this case , the proposed vacuum pressure shall be dictated with a suitable breathing valve (PV valve)..



The sliding and OT check is required as per app. E.7.6 and 5.11 . Regarding the tank with sloped bottom, the slope will have negative impact for sliding..

The compression ring req. is stated at 5.10.5.2 for self supporting cone roofs. Although external radial rafters provided, the roof still self supported ..moreover, the radial rafters more complicate the tension ring required.


Wind velocity 290 kph is too high...could be syclonic region ? You are attempting to design the the tank and still you do know the content ?

Apparently there is a roof nozzle and could not be interpreted as a roof vent.

Good luck..

 

[HTURKAK]

I read in detail the last post of IFR after looking to Mr MJCronin 's respond.. English is not my first language . He explained and nailed the case with his own words.. Not only the content but syntax of his comment excellent..

I tried to give him three pink stars but not possible....


We, the commenters did beat to death ..

 

[Lord Ets]

Sir lFRs,

It's ok, I understand. I'm just feel nervous when the time I found out that my tank design is still not ok. Since there's alot of design criteria I have to consider. Lack of design criteria is my problem from the very start, I know it.

I tried to tell this to my boss before, but it seems he don't have interest to email/contact our client to request the other design criteria. He always do nothing. For how many times. It also happen last time, when the client didn't give soil report.

Well that's him, not me.

Before you sent your last reply, I made a call to my boss. I told him that we need to request the other design criteria (internal, external pressure, and seicmic parameters).

Still, it seems he don't have interest or maybe he is shy to ask. And it seems he don't believe me that we need the complete data and the design criteria he gave to me is not enough.

Again, because their past designers can design a tank with only known dimension and location. Maybe he compare. But they're not me, I want more detailed.

Until I told him that I have some adviser from other country that gives me advice and told me that the tanks has lack of design criteria. Thankfully, he listen to me.

Sir maybe yes, maybe I'm not sure if the tank will experience internal vacuum. My basic criteria is, if it has vent then no internal vacuum. If no vent, internal vacuum will occur.

I'm sorry Sir, this is very very very completely different from what I dreamed for. I fell inlove in structural engineering when I was a college student and until now. But not for tanks, no disrespect for tank designers. Designing a tank is awesome but I love more to design buildings structures and that's makes me very happy.

API 650 is completely different from what I have learn in college Sir. I believe that every civil engineer will agree if they read this. Every sentence, every terms are completely different. I feel like a little bit of thermodynamics (basic mechanical engineering).

Again it's pandemic. I just keep fighting for my family. I'm just wait for the right time and look for other company.

Just like what I have said Sir. I only know about 1 foot method, variable point method, bottom plate, roof plate, rafter spacing, Annex A, B, E, K, S, V of API 650. I'm very sure in every value in my calculation. But I'm not sure if it's ok to use a certain annex for this tank. Yes Sir, I only used Annex S and V.

I'm not asking how to use 1 foot method Sir, I'm just telling how I used it. That is misunderstanding. I read some thread about full of water and that's confused me about 1 foot method. (

https://www.eng-tips.com/viewthread.cfm?qid=165346)

Yes I know Sir. 1 foot method is very simple. I understand it, even how formula derived. It is from engineering mechanics - pressure vessels.

I'm a newbie that willing to learn and to be train. I'm sorry Sir, and I understand you. It's ok.

Thank you.

 

[Lord Ets]

Sir HTURKAK,

Thank you for your response. I really appreciate it. I will read those sections/annex you referred.

Wind velocity is 290kph. Yes sir.

The tank content is water Sir.

 

[Lord Ets]

MJCronin,

What's wrong with you. I did nothing to you.

Karma will take care of you.

Goodluck.