Pi is the design internal pressure in inches of water. The net uplift due to design pressure formula from Table 5.21b in API 650 12th Edition, Addendum 2 is as follows: There are several other uplift formulas in Tables 5.21a (metric) and 5.21b (imperial), which must also be considered. The basic internal pressure case is just one example. If the net force is upward in any case or condition, the tank must be held down by anchor bolts. This positive upward force is countered by the weight of the tank and roof (if not column-supported). This force pulls upward on the tank wall.
In addition to causing hoop stress and longitudinal stress in the tank wall, the slight internal pressure causes a tensile force (pressure × area) to be produced. As a result, the required wall thickness increases in a linear fashion when using the 1-foot method and in a slightly non-linear fashion when using the variable point method. For these higher temperature designs, the allowable stress of the material decreases. S is the tank wall material allowable tensile stress for the operating or test condition.ĪPI 650 storage tanks are often designed to work at temperatures of up to 500✯ (260✬). G is the specific gravity of the contents. The variable point equation in US units is as follows: The variable point method is an alternative to the 1-foot method and can be used for tanks in excess of 200ft in diameter. The basic equation in US customary units looks something like this: The 1-foot method computes the required plate thickness at a distance of one foot above the bottom of each shell course and is applicable to tanks 200ft (61m) and less in diameter.
Api 650 Tank Calculation Spreadsheet update#
These tanks have historically been used to house petroleum for use by chemical plants and power production facilities, as well as basic and strategic reserves.Ī group of dedicated individuals meet on a regular basis to maintain and update the 650 code.
Api 650 Tank Calculation Spreadsheet code#
This code can be used for designs where the internal pressure is less than or equal to 2.5 psig. At the time of this, the latest edition is the 12th, addendum 2, January 2016. The API 650 code is entitled Welded Steel Tanks for Oil Storage. Using these standards helps to ensure that tanks will be able to stand the rigours of the elements and conditions to which they are subjected. Tank design codes reflect the culmination of decades of work by many dedicated individuals. They ultimately lie in the pages of the following codes and standards: The answers to these questions are readily available.