DOUBLE DECK FLOATING ROOF DETAILS 3

[gerrytt]

Meyers only has a cross section and a vague picture. Does anyone have CAD drawings or PDF files for a DDFR showing details for tank of diameter 300 ft (say), eg pontoon layout, location of support legs, etc, any information will be appreciated. The principle of design as per appendix C of 650 is understood, however looking forward to any advise, guidance or experiences.

 

[IFRs]

For what purpose do you need this information? What do you need guidance and advice for? Repairs? Performance? Replacement? I have some powerpoint slides that may help visualize the basic arrangement, but you seem to already have that information. Leg spacing and specific structural details were usually vendor specific. Do you know the manufacturer and the date of installatioin?

 

[gerrytt]

Preparing a preliminary design for tender for 300ft diameter tank. This is a new one for the company I work for and seeking information as per original thread.
Thanks

 

[IFRs]

If you like, post your email and I will send you a set of specifications.

 

[gerrytt]

I would like,
gmahadeo@tstt.net.tt or gmadadeo@damusgroup.com
thanks

 

[umesh15374]

Hi IFRs

I am a Mechanical Engineer mainly in the design of Distillation tower and tower internals. But can you send me you power point slides (on double deck floating roof tanks) to me on the below mentioned email id for the sake of academic interest.

Thanks in advance

my email chennaidevan1974@yahoo.com

 

[mech8]

Hi IFR
I do appreciate , if you could send me the specification
for floating roof.

I thank you in advance.
magi_n@hotmail.com
maji@safineh.net

 

[kunali]

Hi IFR
I do appreciate , if you could send me the specification
for floating roof.

I thank you in advance.
nkumaresan@technip-coflexip.com

 

[fracontr]

Hey please send me the information ...

THX in advance.

fracontr@hotmail.com

 

[ludan]

hi, i am new member.
i would like also if you could send those specifications for floating roof

thanks in advance

aviv @ludan.co.il

 

[roca]

Hi IFRs (Petroleum)
I too would be gratefull if you could send me your specs.
My e-mail address is as follows:
joseph.ortega@clough.com.au

Additionally I am at present involved with some tank issues and have the following questions:

For a floating roof tank what are the tolerances prescribed with respect to tank shell verticallity and plumbness. The API tank code and the British code BS 2654 state that the tolerance can be a max of 1 in 200 over the tank shell height. This means that at the top of a 15m tall tank the allowable tolerance would be +/- 150 mm. Would a floating roof seal be able to accomoate sucha tolerance - or am I mis reading the codes?

I was also advised of the following experience by a colleague:
Whilst hydro-testing a tank with a floating roof tank the floating roof actually buckled (if thats the correct word to use here) due to the difference in temperature between the tank and hydrotest water. The tank was in a hot climate (ambient temp 40 degrees C +) and the shell was quite hot and the sea water was at about 20-25 degrees C.
Has anyone had similar experiences?

 

[IFRs]

roca -

I will be happy to send you what I have, though I fear you will be disappointed as it is just a simple drawing. If you need more details, please ask.

Wouldn't the 1/200 criteria yield
15M = 15,000MM / 200 = 75MM tolerance, not 150MM?

I read that to say that the tank can be +75MM in one place and -75MM in another place but not +75MM and -75MM in the same vertical slice. In that case, most seals should be OK.

API 650 section 5 gives the 1/200 criteria but also says that for tanks with internal floating roofs, apply the criteria of this section or Appendix H, whichever is more stringent.

API 650 appendix H (internal floating roofs) calls for the seal to be able to accommodate a +/- 100MM [4"] of local deviation between the floating roof and the shell. Appendix H also calls for the columns, ladders and other appurtenances to be plumb within a tolerance of +/-75mm (+/-3in.).

API 650 appendix C (external floating roofs) is less specific, calling for seals to provide a reasonably close fit to the shell surfaces, and that an adequate but minimum number of expansion joints shall be provided.

If your tank is worse than a standard seal can deal with, ask your seal vendor for a special seal. Allentech (sales@allentech.com) has designed floating roof seals for tanks that are more than 12" out of plumb.

I'm not surprised that steel floating roofs change shape when they are floated or when their temperature changes rapidly. A stiffer floating roof (pontoon or double deck) would suffer much less than a "frying pan" type.

What was the damage like?

Note that API 650 appendix H has footnotes on pan type floating roofs, one of which I have copied here:

These designs contain no closed buoyancy compartments, and are subject to flooding during sloshing or during application of fire
fighting foam/water solution. Also, without bracing of the rim being provided by the pontoon top plate, design to resist buckling of the rim must be evaluated. These types are considered a fixed roof tank (i.e., having no internal floating roof) for the siting requirements of NFPA 30.

Was this any help?

 

[roca]

Hi IFRs
Thanks for the reply
And your correct - 1/200 of 15m is 75 mm - I must brush up on my maths....!!
Regards
joe

 

[laikin]

Hi IFRs,

I am new member here. I would very appreciate if you could send me a set of the spec. of external floading roof.

my email: lee@protank.com.my

Thank you and best regards,
Laikin

 

[georginr]

IFR, do you have any info on a rule of thumb about the fill rates? We have a 222" diamenter, 32" height tank with a floating roof, and we are using mechanical shoe seals. The product is oil.

 

[IFRs]

The liquid velocity through the inlet pipe is generally not more than 25 feet per second, more typically 15 feet per second. Inside the tank, the liquid velocity as it exits the inlet pipe must be reduced to 3 feet per second or less (per NFPA and API).

What is the size of your inlet pipe?

If you are concerned about the maximum speed that your floating roof can handle, start with 1 inch per minute and see where that gets you. That would be about 34,500 barrels per hour.

 

[georginr]

IFRs
Thank you for your time, the pipe size we use at the inlet and outlet is 24". I compared the rate you gave me with what we use, 25 bbl/hr, and we have a much lower rate which tells me that is not the cause of the problem.

Oil is getting on top of the floating roof, after several inspections, our best guess is that the roof is binding somewhere on the columns making the roof hang from one side and after a while it releases itself splashing the product out. The columns have seals, but no guiding system which makes the roof free to move horizontally and to rotate. Another observation is the probability of some friction involved with the mechanical shoe seal around the shell.

What do you think it is the problem? any suggestions/comments?

 

[IFRs]

Is the floating roof internal or external, aluminum or steel? DO you know the original manufacturer? If steel is it a pan, bulkhead, pontoon, center pontoon or double deck? What brand perimeter seal and when was it installed?

Would you like us to visit, inspect and report?

 

[georginr]

It is an internal, pan steel decks floating in contact with the product. It was installed in the late 70's and the original perimeter seal were double wiper seals, but we changed them to mechanical shoe seals 10 yrs ago. I do not know the brand of the seals but they were fabricated by Tank SEal Technologies.

 

[IFRs]

Well, it could be a lot of things. We have seen many reasons for oil to be on floating roofs. It could be an overloaded area, corrosion, deformed rim plate, leaky weld, a damaged sump, a damaged leg sleeve, seal friction, tank deformations, etc. etc. etc.

If you have a substantial amount of oil on the roof, I'd treat it as a potential emergency and get a definitive answer and remediation plan put together ASAP.

Where and how much oil is on the roof? When was it first noticed? Does it go away and come back? How active is your tank? Is there evidence that the oil seeped up from below or ran down the rim or column wells? Do you have pictures?

While I will continue to try to help here, this forum may not be the best method for determining your problem and avoiding a major "event". If you would like to discuss setting up an inspection trip, send me a note at Sales@Allentech.Com and I will call you.