Finite Element Analysis (FEA) of Storage Tanks as Per API Standards

Introduction

The structural integrity of storage tanks used in industries like oil and gas, chemicals, and power generation is of utmost importance to ensure operational safety and reliability. As per API (American Petroleum Institute) standards, storage tanks must withstand a variety of loading conditions, including internal pressure, wind, seismic events, and hydrostatic testing. Finite Element Analysis (FEA) serves as a powerful tool to validate designs against these rigorous requirements.

 

Key Considerations for FEA of Storage
Tanks

1. Modeling Parameters

The FEA model of the storage tank includes detailed geometry and material properties to ensure accurate stress distribution and deformation predictions. Wall thickness, weld elements, and skirt-to-bottom head joints are critical areas modeled with precision to reflect real-world conditions.

2. Loading Scenarios

Different loading scenarios are analyzed to simulate the tank’s response under various operational and testing conditions:

Case Details

Mass (kg)

Internal
Pressure (psi)

Wind Force
(kN)

Seismc Force
(kN)

Notes

Case 1: Empty
Tank with Wind Loading

330,700

–

70.9

–

No internal
pressure, CG adjusted for empty condition

Case 2:
Operating Condition with Internal Pressure and Wind Loading

337,800

1,311

70.9

–

–

Case 3:
Operating Condition with Seismic Loading

337,800

1,311

–

414.1

–

Case 4 & 5:
Hydrostatic Testing

539,100

1,868.8

23.4

–

Reduced wind
force

 Each case ensures that the tank design can withstand worst-case scenarios without structural failure.

 

3. Boundary Conditions

The bottom surface of the tank base is
constrained in all degrees of freedom (DOF) to simulate real-life anchoring
conditions, ensuring stability during analysis.

4. Material Properties

Materials used for storage tanks, such as
SA 516 Gr 70 steel, are considered for their weldability, toughness, and
strength. The weld elements are treated as the base metal to replicate the actual
behavior of the structure.

API Compliance and FEA

API standards specify guidelines for the
design and operation of storage tanks, emphasizing safety, durability, and
resilience. FEA allows engineers to:

  ->  Validate tank designs under
API-recommended load combinations.

  ->  Assess stress concentration at
critical areas, such as skirt joints and weld seams.

  ->  Optimize material usage to balance
cost and performance.

 

  ->  Identify potential failure points
under extreme conditions.

 Why FEA is Crucial
 

FEA empowers engineers to make informed decisions by providing a detailed visualization of stress and deformation patterns. It eliminates guesswork, enhances design efficiency, and ensures compliance with industry standards.

Conclusion

By integrating FEA into the design process, storage tanks can achieve API compliance while maintaining high safety standards. This methodology highlights the importance of simulating real-world conditions to prevent structural failures and ensure longevity in demanding industrial environments.

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