tank shell evaluation 1

[blawn]

Hi,

API 653 Section a paragraph 4.3.3.1 a)when determining the minimum acceptable thickness for an entire shell course,t min is calculated as follows:

t min = 2.6(H-1)DG/SE

S=maximum allowable stress, E=joint efficiency, G=specific gravity of contents, H=height of the course in consideration

API 653 Table 4.1 gives the allowable stress for each course,allowable product stress and allowable hydro-static test stress(to be used if tank is subject for hydro test)

My tank is a water storage. Referring to the given formula,which allowable stress should be used in the formula?.Since the product is water,I used the maximum allowable for hydro-test and not the allowable product stress.Please comment if ever you found my judgement wrong or if Im missing something.I truly appreciate any reply.

best regards,
blawn

 

[IFRs]

Use product stress for long term service. Use hydrotstatic stress for short term testing using water. In your case you should use product stress with SG=1.0 ( or slightly higher if sea water ). You could also use ADDA D-100 as your design code.

 

[IFRs]

Sorry - AWWA, not ADDA in previous post.

You are using a out-of-date version of the code. The shell thickness equation is in 5.6.3.2. Don't forget to add corrosion allowance.