INTRODUCTION

Quick Opening Closure(QOC) is a door in pressure vessel & boilers, which also serves as ahead. It is locked at its position by locking mechanism. QOC’s always comes under the influence of mechanical static & fatigue loadings.

FEA gives a better understanding of the actual behavior of assembly due to various static & fatigue loadings. Main door structure, hub, locking ring are critical components of QOC assembly, which can be analyzed by FEA. Due to the asymmetric nature of static loadings, a structure may result in higher localized stresses; while fatigue loading is dangerous than other loadings as the structure will experience sudden failure without any prior indication.

Process equipment manufacturer from India & Abroad approached ANALYZER to seek assistance in evaluating the design of their newly developed QOC’s to multiple loading conditions using simulation techniques & provide the solution in case of any observed stress failure.

FEA WORKFLOW

• Design parameters & material properties extraction for Complete QOC’s FEA
• Preparing FEA Model for three different cases – Door, Hub & Locking pins.
• Deciding analysis techniques for all three cases.
• Solving all three models separately in order to calculate stresses in structure for various loading conditions.
• Results extractions & combining the results with other loadings in order to get the desired combinations.–For fatigue analysis, Performing the Fatigue calculations as per ASME Sec. VIII Div. 2 Part 5 & Annexure 3.F

  –For Static analyses, comparing stresses with allowable stress limits

• Report the results for client’s reference.

CHALLENGES

• Preparing complete structural Hexahedral mesh for a door which has holes at different depths & without losing small geometrical details such as fillets & weld chamfers.
• Deciding element types for different analysis cases.
• Simplifying FEA model of locking ring & hub for axisymmetric analysis.
• Identifying the critical locations & carrying out stress linearization at those locations

THE SOLUTION

Ø Fatigue Analysis:

The QOC was analyzed using Finite Element Method to determine the induced stresses due to  various cyclic loadings. In order to assess fatigue strength for the QOC, guidelines from ASME Section VIII Div. 2 part 5 & Annexure 3.F were utilized. The fatigue calculations were performed & fatigue damage factor is found much below unit value. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

Ø Static & Dynamic Analysis:

The QOC was analyzed using Finite Element Method to determine the induced stresses due to  various loading conditions. In order to assess strength of complete QOC, guidelines from ASME Section VIII Div. 2 Ed. 2013 was utilized. Stress Linearization has been carried out at various locations. The results showed that the induced stresses were well within the acceptable limits as per guidelines even for optimized thickness. Hence, the structure’s design was predicted to behave safely during operation without premature failure.

BENEFITS

• Better insights on design modifications for alternate applications
• Optimized design with reduced material cost
• Reduced manufacturing time