Double Wall Storage Tanks

[Ossareh1352]

Dear Friends

for your information we have two storage tanks in our plant as follows:

1- Double wall tank for C3(Propane)with volume of 50,000 m3 for each tank . the operation temp. is -42c.

2-Double wall tank for C4(Butane)with volume of 22,000 m3 for each tank . the operation temp. is -8c.

At basic stage these two tanks have been proposed to make by (Steel+steel), it means that inner and outer wall making by steel.

But as you are well aware we have many storage tanks making by (Concrete+Steel)(inner wall by steel and outer wall by concrete).

I don't know what is the advantage and dis-advantage of selecting (Steel+steel) in compersion of (Concrete+steel).

I would be highly appreciated if can refer me to any paper or let me know your opinion in this regard

 

[TGS4]

It all depends on the pressure. What is the internal pressure of these "tanks"? What is the purpose of the second wall?

 

[gerhardl]

I am no expert, but: At low-temperature pressurized gas storage, there exists (varying according to country) rules for how double-walled steel-tanks should be pressure checked after a number of years in use, typical maybe 10 to 15 years.

I would start by checking out existing rules in your country for both constructions and have a look at the probable cost of pressure/other checks at start up and after first running periode.

If there is a big difference here, this will probably overwieigh the difference in building cost.

Building cost will vary according to local market conditions, and would be difficult to find exact without asking for preliminary offers from contractorsd.

Two arguments for steel construction though (I,m leaning towards steel): cost of tearing down and cleaning up after operational life is over is probably much higer for steel encased in concrete.

Secondly: Access to outer wall of inner vessel and location and repair of leaks in the outer shell cheaper if steel (? )

 

[KnutS]

Steel + concrete? -42°C (OR -8°C) Where will the dew point in this design end up? Or an I missing something here? My first reaction is like; go for the steel+steel design. But i do not know enough about steel+concrete to rule this out. There will be a requirement to witness/ inspect/ verify. Best way will be with steel and no concrete, concrete will definitely rule out inspection from two sides.

 

[civilperson]

Steel for low temperature applications are required to have Charpy impact values above 15#. This may be ignored if maximum stress is less than 0.3 Fy. Corrosion allowance for the inner wall and interstitial space must be examined.

 

[vesselguy]

Are you are talking about horizontal vessels for storage or are you talking about API-620 type storage tanks. The phrase "storage tank" is very misleading when people really mean a pressure vessel. The design basis is totally different between tanks and vessels, and when you talk tanks it almost imply less importance and lower design/NDE requirements.

If you are talking about storage bullets then from the ones that I have worked on, I have not seen double wall design for LPG drums. Just design the vessel to Section VIII, Div. 1 and you're done.

If you talk about concrete as secondary containment, then it usually mean a rectangular concrete sump or concrete berm to contain a spill. Wow, it would be interesting to see a concrete shell like you mentioned though.

Like the other people have said, read your local governmental boards' requirement for butane and propane storage. Perhaps standard on this subject such as CAN/CSA-B149.2, "Propane storage and handling code" and from US'OHS is a better source to help you.

 

[jdarco]

Some above ground fuel storage tanks are encased in concrete to protect against vehicle impact, ballistics, etc...Check out

http://www.convault.com

But I agree with vesselguy about this application.

 

[vesselguy]

Ossareh1352,

After I posted my response to your question, I kept thinking about the subject matter. I know, I'm just a tech geek. I did some talking to the process engineer on my project and got info which I never knew before about LNG and NGL plants. I normally work only on refinery and upstream oil and gas. With some more digging, I can share the following info with you.

In LNG plants, the tankage which you might be talking about, have 3 kinds of secondary protection: steel inner shell and steel outer shell with insulation in between, steel shell with concrete wall, and steel shell with concrete shell. I'm told that you decide which design to use based on plant location to inhabitant and seismic zone. You can read more about this kind of plant if you do a google search for LNG or NGL plant design. I found this book and it looks good. Hope this helped you.

http://books.google.ca/books?id=lcL...ig=tnbaMkAOT8l40Zk0Ea0ifxt2Apk&hl=en#PPP28,M1

 

[JoeTank]

Vesselguy
API is now writing a new document to address such facilities. It will be API Standard 625.


Joe Tank

 

[vesselguy]

joe tank,

Thanks for the heads up. I reviewed their draft on their web site and it looks interesting.