API 650 Roof Structure Standard Drawing 2

[takiyasamsama]

Dear All,

Basically, our client had their own standard drawing for self-supporting roof meeting EN 14015. However, the client decided to design this new tank as per API 650 which they don't have the standard drawing for the roofing structure.

My question, can the API 650 roof structure design use EN14015 roofing structure drawing? However, in EN14015 roof slope is limited to 1:5 to meet frangibility while API limit the slope to 2:12. Is this compatible?

If not, where can one find a standard drawing for roof framing detail (rafter, truss, and framing detail) available? Does API have standard drawing for this?

 

[JStephen]

In API-650, a "self supporting" cone roof is one that does not have any structural members supporting it, just the plate. If you have rafters, trusses, etc., it wouldn't be a self-supporting roof as used there.

For API-650 self-supporting cone roofs, minimum slope is 2:12, maximum slope is 9:12. For a structurally supported cone roof, minimum slope is 1:16 and there is no maximum slope.

I am not aware of any standard drawings for roofs. There are some general arrangement diagrams for column-supported cone roofs in some of the tank publications.

 

[takiyasamsama]

JStephen,

I think I may have misunderstood the codes, so does that make cone roof with truss and rafter under self-supporting roof or considered supported cone roof? My current understanding is self-supported are the one that does not have column, and supported are the one with column.

That means, cone roof supported by rafter and truss are classified under "Supported Cone Roof" correct? I think I may have overlook this somewhere in the API.

Thanks for pointing this out JStephen.

 

[JAS]

Self supporting Roof - Only the Roof
Supported Roof - With Rafter/Truss/Column etc.,

 

[IFRs]

API 650

5.10.1.a "A supported cone roof is a roof formed to approximately the surface of a right cone that is supported principally either by rafters on girders and columns or by rafters on trusses with or without columns.

Self supporting roofs are supported only at the periphery and are made from formed plate.

5.10.2.8 Alternate Designs: These rules cannot cover all details of tank roof design and construction. With the approval of the Purchaser, the roof need not comply with 5.10.4, 5.10.5, 5.10.6, and 5.10.7. The Manufacturer shall provide a roof designed and constructed to be as safe as otherwise provided for in this standard. In the roof design, particular attention should be given to preventing failure through instability