API 650 Tank Top Angle Size
API 650 Tank Top Angle Size
(OP)
We have a 47 ft dia , CS tank with IFR and an Aluminum Dome Roof, Can this tank be classified as an open roof tank for top angle size determination?
As per our understanding for top angle clause 5.9.3.2 applies and we specified TOP angle as 75x75x6 mm where as client insists on using 75x75x10 mm as per clause 5.1.5.9 e
Also if client specifications call for CA for Shell, does it apply to TOP angle as well
Regards,
Aamir
As per our understanding for top angle clause 5.9.3.2 applies and we specified TOP angle as 75x75x6 mm where as client insists on using 75x75x10 mm as per clause 5.1.5.9 e
Also if client specifications call for CA for Shell, does it apply to TOP angle as well
Regards,
Aamir





RE: API 650 Tank Top Angle Size
RE: API 650 Tank Top Angle Size
RE: API 650 Tank Top Angle Size
RE: API 650 Tank Top Angle Size
No probability of corrosion + readily inspectable = no CA required.
Floor is the opposite. Corrosion is very probable, and inspections are difficult and very infrequent and hard to arrange.
RE: API 650 Tank Top Angle Size
This is what our client wrote :
In real life, vapor do exist in the space as the seal and IFR is not 100% leak tight.
And atmospheric corrosion is the minimum you need to design for.
Any comments ?
Further can someone help with this requirement, we are at the time of putting the top ring when client has sent us this,
Client has requested the check on compliance against G1.3.1 and G 4.1.4?
RE: API 650 Tank Top Angle Size
RE: API 650 Tank Top Angle Size
Can you make sure Dome Supplier is complying with G4.1.4. I see the presence of tension ring in BTE drawing, but am not sure where the relevant calculation is.
- What are the loads that will be exerted by the dome roof to the tank shell and its foundation? Have you analyzed if the tank shell and foundation are good enough for the loads?
Tk-2054 was an open-top crude tank with external floating roof. Its diameter is 47m++, i.e. close to Tk-34. An aluminum dome roof was then retrofitted onto it during MPP1 implementation. Visual check shows the roof is attached to the shell via sliding shoes (see attached PICT0119.jpg), similar to BTE design. The shoe separation distance is between 3 and 4m, BTE’s is 4.14m. At every attachment point of sliding shoe to Tk-2054 tank shell, there is some form of reinforcement/strengthening at the shell, i.e. some members welded between the top girder and the top angle (see attached PIC0121.jpg). I do not know the cause of this strengthening, but I suppose it’s related to dome roof load(s).
Top angle size of Tk-2054 is 75 x 75 x 9mm.
- Corrosion allowance. Do you see those black mats in attached DSC05622.jpg and DSC05623.jpg? They covers holes on the old Tk-34 roof. There were many of such mats on the old tank, and the remaining roof areas that were not covered, were paper-thin (as described by Husaini). Do you dare to walk on the roof?
The submerged part of the tank shell was all good. Anything above it was horrible. We are applying the lesson learned and necessitate all CS parts exposed to product (liquid and vapor) be provided with corrosion allowance. In many cases, the 1st parts of the tank that experience perforation are the tank bottom (where water accumulates) and the parts that are exposed to the product vapor (upper shell courses and roof).
One of the principles of negotiation states we refer to a fair standard if the interests of the negotiating parties differ. I therefore suggest that we refer to the clarification during tender stage which indicates shell shall have 1.6mm corrosion allowance. As at least one side of the CS top angle forms a continuous part of the CS shell, that part of the top angle shall be provided with 1.6mm corrosion allowance.
I request that Owner’s experience on the corrosiveness of product vapor be respected, and the contract be honored. A formal change authorization is needed if you insist on a change.
RE: API 650 Tank Top Angle Size
1) The above normal corrosion that has been experienced certainly mandates that some CA be used for all steel parts. The owner wants 1.6mm and this should be applied to the top angle thickness. No question here unless this information was not communicated during the bid stage. If there was not such communication, the owner should pay the difference since they would have anyway.
2) The tank needs to be determined to be suitable to handle the dome loads. For this you need the dome loads. If the dome vendor is not cooperating, the owner should tell them they will never work for them again and bad news travels fast in this industry. In my opinion, it is very unprofessional for a vendor to not provide assistance to an owner especially when it is simply supplying information that they are required to supply by code ( G.1.3.2 ). If they refuse to cooperate you will have to determine the loads yourself or with help. It is not self evident what proportion of the tension is handled internally by the dome, this will have to be determined. It is not hard to figure out the dome reactions other than circumferential tension using basic geometry. It is not hard to establish the capacity of the tank as a plain cylinder. It is not hard to project these loads to the foundation and review its capacity. Again, see G.2.3.1.
I may be oversimplifying and/or missing items, probably because of my ignorance of conditions.
Good luck!
RE: API 650 Tank Top Angle Size