About the roof of an API 650 tank

[T2ioTD]

I have difficulties understanding technical matters regarding a self supported (no middle columns) roof for an API water tank.

1. The excel sheet on the right shows 6mm thickness for the roof. I assume it is because no rafter are being used, otherwise thickness would be around 2mm. Am I right?

2. On the photo on the right, the rafters appear to resting on some rod extending to the bottom. Is it something similar to 2cm x 2cm square hollow section? Or am I erroneously understanding the image?

Regards

 

[1503-44]

Probably. The tank wall is put in tension due to the compression load of the roof intersecting the rim. With rafters the roof plate would not have to carry the compressive load to the tank wall, which can become quite high at low angles a d larger diameters. There is an API Tank forum that you might want to post this question there and delete this on here.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Roof thickness seems to say 5mm, but 2mm seems very thin to me.

You also need to consider what the weight of the roof is as this normally sets the max overpressure in the tank to avoid roof damage / lift off.

difficult to know what those are in the tank from a single photo or if the ring at the top is thicker than the rest of the tank to take some of the load.
They seem rather small to be of any use.

As mr 44 says, there is a dedicated storage tank frum under mechanical Engineers and this might be better placed there, but you need to get some better photos if possible.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Thickness of a supported roof plate probably depends more on rafter spacing.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."