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7 CONSIDERATIONS WHEN DESIGNING STORAGE TANKS

Aboveground storage tanks (AST) are storage containers located above the earth’s surface and have a wide range of applications. In industrial settings, storage tanks hold various materials, including petroleum or oil, waste matter, chemicals, fuel and even hazardous materials.

Storage tanks or Storage Containers play a vital role in the operation of refineries, plants in the oil and gas industry, airports for aviation fuel storage and more. They are used to store and transport oil and gas products from the production site to the refinery or other locations. The design of these tanks is critical to ensure the safety and efficiency of operations.

This blog will discuss seven key points to consider when designing storage tanks:

1Tank Diameter / Tank Height:

  • Tank diameter and height are the most critical parameters in storage tank design as they are defined according to space availability and volume of product to be stored; defining these parameters is named "Tank Sizing", usually done by the process department.
  • These parameters play a vital role in the thickness evaluation of shell courses also various tank calculations (for example, Wind, Seismic, External pressure calculation, and more).

2Corrosion Allowance:

  • Corrosion allowance indicates an extra plate thickness to be added to the required thickness to allow for in-service corrosion. While designing a storage tank, corrosion allowance ensures extra safety above the minimum calculated thickness by accommodating corrosion effects.
  • The client evaluates corrosion allowance with the help of the process department and mentions it in the Mechanical/Process datasheet. Then, the same corrosion allowance should be added above the required thickness.

3Material Selection:

  • Materials used in storage tanks play a vital role in the thickness evaluation of storage tank components (Ex. Shell, Bottom and Roof plates). Plate Materials are classified and mentioned in API 650 code according to their strength (Refer below table).

  • Table 1

    Table 2

    Table 3

4Design Specific Gravity:

  • Specific gravity is a unitless quantity primarily defined as the ratio of working fluid density to water density.
  • Design Specific gravity indicates the Maximum specific Gravity of a stored liquid at a defined temperature considered for storage tank thickness evaluation.
  • The higher specific gravity also plays a significant role in resisting weight during storage tank overturning caused by wind and seismic effects.

5Design Internal / External pressure:

  • Design Internal / External pressure indicates the maximum pressure in which the storage tank is to be designed to sustain. Internal / External pressure plays a vital role in storage tank design; it also significantly impacts the required thickness of roof and shell courses.
  • These parameters are considered carefully while designing a storage tank as it causes significant life hazards during unfavourable situations.

6Design temperature:

  • Design temperature indicates the maximum temperature at which the storage tank is to be designed & sustain. Design temperature plays a vital role in storage tank design as it also affects the strength of the roof, shell, and bottom plate design.
  • API 650 suggests a reduction of the material's modulus of elasticity at higher temperatures, as mentioned in the table below.

    Table 4

7Wind Girder:

  • A wind girder is an arrangement located on the circumference of the tank that plays a significant role while designing the storage tank as it prevents wind-induced & vacuum-induced buckling of the storage tank due to wind pressure.
  • Typically, Standard and Plate fabricated type wind girders (as mentioned in the below images) are used according to the strength requirement.

    Table 5

  • At PMT Tank, our team prioritizes developing and perfecting a design focused on improving tank performance and increasing tank longevity and safety by following API 650 Code Guidelines. We have the expertise and capabilities to design premium storage tanks for various applications.
  • We ensure that every API 650 Storage Tank we design seamlessly fits our customers' specific design requirements.
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