API 653 Shell Thickness

[ronfrend]

If I have a calculation regarding hydrotest and the material is unknown, to find the max allowable the stress do I use 0.429 of the UTS, 0.8 of the Yield strength (which for unknown are given as 55,000 and 30,000 respectively) or do I use the value given in Table 4-1?

This is for a tank which has been in service for some time - not a new tank.

Thanks

Ron Frend

Ron Frend

http://www.predicon.net

 

[JoeTank]

If you are to hydrotest an existing tank built with an unknown grade of material, take the allowable stress from Table 4-1. About two-thirds of the way down the table you will see an entry for material grade that says "Unknown". The last two columns of this table give the allowable stresses for hydrotest conditions. One column is for the lower two shell courses and the other column is for the upper courses.

Joe Tank