double walled tank API 650 qualification
double walled tank API 650 qualification
(OP)
thread809-204059: Double Wall Tanks
Why is it that there is no reference of a double-wall arrangement in the API STD, even as a reference, committee interpretations so far? Will it not need a qualification for a double-walled arrangement wherein say an 80 m steel tank is enclosed by another steel tank offset radially by approx 3 m. There are aspects that need to be addressed such as the nozzle penetrations through the outside wall. The common bottom plate. The hydro test, operations and maintenance. Moreover having a dyke wall or earthen compacted bund overlayed with concrete offers a more reliable containment. Some thoughts on this is welcome.
Why is it that there is no reference of a double-wall arrangement in the API STD, even as a reference, committee interpretations so far? Will it not need a qualification for a double-walled arrangement wherein say an 80 m steel tank is enclosed by another steel tank offset radially by approx 3 m. There are aspects that need to be addressed such as the nozzle penetrations through the outside wall. The common bottom plate. The hydro test, operations and maintenance. Moreover having a dyke wall or earthen compacted bund overlayed with concrete offers a more reliable containment. Some thoughts on this is welcome.
RE: double walled tank API 650 qualification
Double wall arrangement is foreseen in API 620 and 625 for low pressure storage tanks for refrigerated and liquefied products.
If the question is for API 650 ( i assume ), API 650 suggests the use of dikes etc. for containment.
You may look EN 1993-4-2: 2007 ..Double wall arrangement is foreseen if the primary tank contains toxic or dangerous fluids and may look EN 14015 for containment requirements.
RE: double walled tank API 650 qualification
RE: double walled tank API 650 qualification
so long as the bund wall can take the entire contents of the tank without overflowing, you can make it from whatever you want.
What you refer to is very odd and therefore not addressed in a design code intended for more normal installations.
Usually you find other factors such as fire precautions and separation distances mean you don't need such a tank or that it wouldn't be permitted.
I've never seen anything like that in API 650.
I would avoid a common bottom plate with the tank to separate tank from bund.
Also the zone in between becomes a zone 0 or Zone 1 and becomes horrendous to get any access into it, never mind filling with rubbish, sand, animals etc etc.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: double walled tank API 650 qualification
API 650 does not specify double shell . If there is a space problem for containment, ( if the liquid content is petroleum, petroleum product , etc ), you should consider dike wall ( may be RC wall with height suitable for the space constraints..)
I have seen RC dike wall with 7.0 m but not double shell for API 650 tanks..IMO, it is not matter to design the double shell but the increased safety and fire risks could be the main concern..
I will suggest you, consider posting this thread at Storage Tank Engineering forum to get better responds..
RE: double walled tank API 650 qualification
I certainly hope that we are not having this insane third-world conversation "because the client said so" ....
I also certainly hope that this is not the type of client who, when he learns of the massive double shell tank Capital costs, will simply say "Never mind ... Do it the old way"
It is important to remember that a double walled tank this large increases various types of Capital costs dramatically. This due to much higher costs for foundations, paint and coatings as well as leak detection systems.
If this huge tank is subject to foundation settlement (as many large tanks are)the double shelled tank design may put the inner shell at risk.
MJCronin
Sr. Process Engineer
RE: double walled tank API 650 qualification
RE: double walled tank API 650 qualification
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: double walled tank API 650 qualification
These are outside Philadelphia, PA.
The inner tanks are 150 foot diameter. The outer tanks have large windgirders on the inside of the tank shell.
RE: double walled tank API 650 qualification
IFRs: Good picture and post. Curious to know about the floating roof for the annulus.
This is the same that I wanted to say that these configurations are in use around the world. Is it not time for API 650 to acknowledge to include. Agree that secondary containment is not scope but here the containment is another tank. There should be clarity in the STD to say that such configurations are acceptable with the corresponding provisions and considerations.
LittleInch: Incidentally there were 3 tanks at an Island tank farm that had this configuration. The tanks are now due for refurbishment. This calls for a major re-investment. Many of the tanks are to be re-built. The current effort is to re-locate some of them so as to create the safety intertank spacing required by the current NFPA. Possibly to meet the insurance requirement. There were shortfalls and not meeting the safety spacing requirement. At the outset, It was the intent to do away with the double-walled ones. However in the process of layout, based on the number of tanks / operational storage needs and the limited plot space availability on the island, it has again driven the selection to the double-walled design.
Yes, the space between the shells is a confined space that needs inspection access. It cannot be filled up with anything. The nozzles from the inner wall penetrate the outer wall with a bellow sealing. This includes the foam and fire water
MjCronin: My common sense says not to. I intend to bring some sanity into the selection. Nevertheless, it needs something as the tank STD to negate it. I do not know how the original double-walled tanks (30 year+) came into being and what were the design considerations. The operational driver is the experience with the existing double-walled tanks over this time. Double-walled tanks do not seem to be uncommon from Many a tank design person says that they go by the premise as if they are designing 2 tanks and therefore justified by the requirements in the API 650. I am driven to think this isn't so and want to know why there has never been a request for an interpretation. I did raise one now. But would not know when or what response will that be.
HTURKAK: I took the cue from an earlier thread in this group. besides cross-posting is to be avoided.
RE: double walled tank API 650 qualification
Dear svi,
The subject tanks having dia 80 m and the ht should be in the range of 18.0 m . The roof should be EFR ..The picture posted by MR. IFR has diameter 45.0 m with fixed roofs and the radial space between exterior dike wall should be in the range of 12.0 m.. and apparently these are not double wall tanks..I have the opinion that API 650 does not address double wall tanks ..
If the available plot space is limited , you may consider to increase the height ( of course if soil conditions allows ). In past, i have designed 22m ( h) tanks and saw 25.0 m ( h ) at northern Europe. This option will allow more space between the tanks and more space..
I will suggest you ;
- Consider the option of increasing the ht.
- Consider dike walls ( not double wall )
- In case of double wall , provide fixed roof for the annular space..
These are my thoughts based on 40+ years experience.. and remember, this is WORLD WILD WEB ..
P.S. Have ever seen an when oil storage tank in fire ?
Good Luck ..
-
RE: double walled tank API 650 qualification
svi - the outer floating roof was similar in construction to the nromal inner one, but it had seals on both inner and outer edges. Not hard to do or build.
The outer tank is a dike wall, I don't think NFPA limits the spacing between dike walls but I don't remember what they say about this situation regarding tank to tank spacing if the dike is tall enought to contain the proper volume.
RE: double walled tank API 650 qualification
I've never worked in tanks so bare with me here. For my own curiosity
I looked at the linked photo and got a chilling image of an operator being in-between the tanks when a failure occurs. Specifically someone attempting mitigation or the like during the initial phases of failure. IE; tank's leaking! Lets drain it! Then a burst.
Is there a method of retreat for the operator in this case? Or is there an SOP not to go between the tanks? Or is the simplest answer that this a non-issue that an early coffee fed morning has conjured up in my head.
RE: double walled tank API 650 qualification
RE: double walled tank API 650 qualification
The annular floating roof, that must be for liquid filling on both sides. Will that be double wall?
will you have a shot. This one must be from a drone?
RE: double walled tank API 650 qualification
NFPA provides the minimum inter-tank spacing of the regular tank. Wall to to wall spacing so as to minimize radiation effect to an adjacent tank. With the additional wall that acts as a shield. If both tanks are using an outer wall for secondary containment, The inter-tank distance is between the inner wall of one tank to the outer wall of the adjacent tank. The adjacent outer wall being without content may need consideration. Is this not a consideration in the case of tank in the picture?
When the annulus space is used for storage. Or during testing of the outer shell. The external pressure loading onto the outside of the inner wall needs consideration.
These and other considerations need to be addressed by API, NFPA entities.