Standards for leg-supported vertical atmospheric conical bottom tanks

[andrew_]

Hello,
I've been through may posts on this forum and am still struggling with a particular topic.
I am looking for the relevant design standards for leg-supported vertical atmospheric conical bottom tanks.
These tanks are to contain media such as water, mineral oil, caustic etc.

As far as I understand (please correct me if I am mistaken)
1) there are standards for pressurised vessels (ASME VIII, PED 2014/68/EU, EN 13445, AD2000)
2) there are standards for flat bottom atmospheric tanks only (API 620, BS EN 14015:2004)
3) there are standards for flat bottom atmospheric tanks with no restrictions for "non flat bottom" (API 650, BS EN 1993-4-1 and 2)

Is one of these actually applicable here?
Would it be "best practice" to design to pressurised vessel standards but with atmospheric design pressure?
I ask because I have seen many tanks as I described according to ASME VIII-1.

Same question for the same type of tank with -0.5 to +0.5 barg design pressure. Would that have to follow the standard for pressurised vessels?

Same question for the same type of tank with a design for full vacuum. Would that have to follow the standard for pressurised vessels?

 

[HTURKAK]

Dear Andrew_ (Mechanical),

Your quote 'As far as I understand (please correct me if I am mistaken)'

1) there are standards for pressurised vessels (ASME VIII, PED 2014/68/EU, EN 13445, AD2000) .OK. TRUE ..
2) there are standards for flat bottom atmospheric tanks only (API 620, BS EN 14015:2004)..NO!..API 620 FOR LOW PRESSURE STORAGE TANKS!!!
3) there are standards for flat bottom atmospheric tanks with no restrictions for "non flat bottom" (API 650, BS EN 1993-4-1 and 2). TRUE BUT ENTIRE BOTTOM IS UNIFORMLY SUPPORTED, AND THE SLOPE FOR DRAW OFF TO CENTRAL PIT,ESSENTIALLY FLAT BOTTOM.

Your quote 'Is one of these actually applicable here?' NO!!!
Your approach should be HYBRID.. Regarding Liquid-Filled Elevated Tanks , for dimensions ,piping etc pls look AWWA, For the design of shell =You may look AWWA D100 + API 650, For the design of conical bottom and roof = pls look any handbook for design of shell and plate structures applicable formulas WOZNIAK (E.g)

You may look also=Eurocode 3 — Design of steel structures —Part 4-1: Silos

In case of -0.5 to +0.5 barg design pressure or full vacuum , pls look ASME codes.

 

[andrew_]

Thank you for your response, this opens up an interesting topic.
Would it be fair to say that even if a tank is set for atmospheric use, it may not be wise to design it to atmospheric only?
I'm thinking that the tanks I describe need to go through Cleaning In Place for instance.
For this there will be various temperature media being used infrequently - this could potentially lead to short fluctuations in pressure.
Hence perhaps a more "safe" approach for atmospheric tanks that are going to go through CIP is to design according to ASME VIII - with a design pressure of -0.5 to +0.5 for instance?
For sure there is tank instrumentation that can react to changes in pressure (pressure or vacuum relief, bursting disk) but I am not sure this is enough to be safe for a simple atmospheric tank.

 

[HTURKAK]

Dear ANDREW,

API 650 is valid for internal pressures not more than 17.2 kPa (2.5 Psi) and API 620 is valid for pressures not more than 15 lbf/in.2 gauge.
Design of atmospheric tank (API 650 tank) for vacuum pressure more than2.5 Psi is not wise and in this case, will not be API 650 Tank.. API 650 tanks are very flexible and prone to vacuum collapse. We can say , soda can is more rigid for vacuum pressure than API 650 tank .

More over, if the size of the tank is large, total cost will be very very high...

You must thrust to pressure or vacuum relief valves...

If the pressure is more than 15 lbf/in.2 , ASME pressure vessel code is applicable..

 

[MJCronin]

Andrew,

You have pointed out an important gap in our tankage rules and standards.

This small low-pressure, coned bottom container is common and very important to industry.

It does not fit within any commonly used code, standard or industry guideline

If designed improperly, it can fail catastrophically and threaten lives and property.

There should be a dedicated standard, similar to API-650, showing rules, recommendations and examples of safe designs. There should be a section on leg design and selection as well as supporting ring analysis.

Do our European friends have such a standard ?..... I would like to know...

Can anybody add to this discussion ???

Regards

MJCronin
Sr. Process Engineer

 

[andrew_]

Thank you both for your responses,
I am indeed thinking about small-ish tanks here, for instance sizes of 1-5-15-30m3.

 

[HTURKAK]

..........Do our European friends have such a standard ?..... I would like to know...

Your European friends have such a dedicated standard : pls look Eurocode 3 — Design of steel structures —Part 4-1: Silos