Example: Select a Conical Roof carbon steel tank to store 40,000 barrels (bbl) of crude oil, using the API 650 standard.
OBSERVATION: The 40,000 barrels of crude represent the Net Work Capacity of the Tank.
Steps to follow:
1- According to figure 5.4 shown, establish:
The Net Capacity of the Tank Work: 40,000 bbl for this example.
The Liquid Design Level: 1 foot is usually set below the top of the tank. This value may be subject to increase once the seismic analysis of the tank is performed.
The Minimum Level of Filling of the Tank: normally one foot is established above the top of the tube (TOP) of liquid exit from the tank. Below this Minimum Level is the Liquid Exit Nozzle at a distance HN (see Table 5.6b shown below) from the bottom of the tank to the center of the Nozzle.
Minimum Volume of Remnant of Operation in the Tank: it is the volume comprised between the bottom of the tank and the Minimum Level of Filling of the Tank.
2- The diameter of the nozzle of the tank liquid is determined according to the pumping requirements of the liquid stored in it. For this example, it is established that the outlet diameter of the liquid is 16 ".
3- The minimum distance (HN), from the bottom of the tank to the center line of the liquid nozzle (set as 16 "), is selected from the following table:
4- Preselect from table A.3b, at least 2 tanks, with a capacity (C) greater than 40,000 bbl.
For this example, two (2) tanks with the following dimensions are preselected:
Tank 1:
Diameter (D1): 100 feet
Height (H1) = 32 feet
Capacity (C1) = 44,800 bbl
Tank 2:
Diameter (D2): 90 feet
Height (H2) = 40 feet
Capacity (C2) = 45,360 bbl
5- Calculate the Dead or Unused Volume of the preselected tanks, using the following formula:
C = 0.14xD2xH
Where:
C = Nominal Capacity, in bbl
D = Tank Nominal Diameter, standing
H = Tank Nominal Height, standing
To Calculate the Dead or Unused Volume of the preselected tanks, the Height of the Dead Volume (h) must be subtracted from the Nominal Height (H) of the Preselected Tanks, that is, the H to be used in the formula will be equal to:
H = Nominal Height of the Preselected Tank - h (Dead Volume in the Tank)
Where:
For this example we have:
h = (1 foot associated with the Liquid Design Level + 1 foot associated with the Minimum Tank Filling Level + Minimum Distance (16" according to table 5.6b), from the bottom of the tank to the center line of the nozzle discharge + 8 "from the center of the nozzle to the TOP of the 16" tube).
NOTE:
- 1 foot equals 12 ".
- For this example: 16 "+8" = 24 ", Then: 24" = 2 feet.
Finally, the height of the Dead Volume (h) = 1 foot + 1 foot + 2 foot = 4 foot
6- Finally, from the table "NET WORK CAPACITY OF PRE-SELECTED TANKS", choose the tank whose capacity (bbl) is immediately higher than the volume to be stored, resulting in this example Tank 2 mentioned above.
NOTE: The thickness of the bottom, cylinder or body and roof sheets; As well as the weights (empty and in operation) of the tank, existing programs can be calculated for that purpose, such as the TANK program.