Vertical Storage tank shell erection

Align the inside diameters. The 1 mm OD offset can be bridged by the weld. Depending on diameter there is an allowable misalignment. 1mm is acceptable on the thickness you inquire about. The OD could be aligned but unless there is access to the vessel interior to insure a full penetration weld or backwelding and blending of the weld edges to the respective shell courses you are better off aligning the ID.

ability@ameritech.net

There are 3 options for that design and approved by any of codes and standards:

1^st The tow centerlines of both shell thicknesses are aligned, is the optimum from loading's point of view if there is no need for 2^nd or 3^rd.

2^nd External shell side (OD) kept constant, and is preferred for good appearance.

3^rd Internal shell side (ID) kept constant, and is necessary when there is an internal floating roof with sealing between floating roof and interior of tank shell.

For our tank with shell thickness 6 mm and 8 mm, all options are acceptable and you can select the easier case.

the shell courses are aligned internally. The ID of tank is kept constant. This helps when the tank is calibrated. Volume per inch of height remains constant through out the tank.

lashsd@yahoo.com

"Volume per inch of height remains constant through out the tank"

This is not true at all tanks, especially for large storage tanks which characterized by its invisible and light buckling through and around the tank peripheral.

i'm studying about storage tanks, and i need help.i'm not familier even with some basic concepts.what is course,shell course and why do we need it?

The interior surfaces should align, but that is also a function of the welding procedure. The welds will likely have to meet radiographic criteria. You should also check for appropriate industry codes for the tank, which will depend on the product stored and locality. For example, in the US, American Petroleum Institute (API) codes govern petroleum product tank design and fabrication. These codes are API 620 or 650 depending on the pressure. For water tanks in the US, the American Water Works Association (AWWA) has a code D100-96. I am not sure if other codes apply for other types of materila being stored, but th is should be researched. Often other materials are referenced to an API or AWWA standard. Before finalizing the design, the appropriate code should be consulted.