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2 minutes reading time (306 words)

Do I Have to Replace My Bulged Pressure Vessel?

Figure1-Bulged_Shape_of_Vessel-cover Need to replace bulged pressure vessel?

There are a variety of conditions an in-service component (e.g. vessel, tank, piping) can be found in.  The purpose of Fitness-for-Service (FFS) is to evaluate the integrity of an in-service component given a certain degraded condition and rate it for future service considering potential for any additional degradation.  A degraded condition does not have to just be based on corrosion. Sometimes a component can experience a large deformation due to unexpected one-time loads resulting in stresses greater than yield.  When such a large deformation event occurs it is important to inspect the vessel to make sure no cracking occurred during the deformation event.  If it is found that the impacted area is defect-free then the next step is to determine if the component can operate in the deformed shape.

One example of a non-corrosion related degraded condition is a bulged tank.  Figure 1 shows an example of a tank that bulged due to an over-pressure event.  This tank was modeled using the FEA program Abaqus.  The general bulged shape in the model can be seen in Figure 2.  An elastic-plastic analysis was performed with the mesh shown in Figure 3.  The global model used shell elements to save on computational time without sacrificing accuracy for the tank shell while the sub-model on the critical nozzle was created using 3D brick elements for maximum fidelity.  This analysis was able to demonstrate that the tank was qualified for continued operation - even with an additional corrosion allowance.     

Significant schedule and cost savings can be realized if analysis is performed to demonstrate the current and future integrity of components that otherwise would be replaced based on differences from their installed condition.

  

Have a question or would like more information?  You may post to this blog (below) or click the link below for more help.

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Figure1 Bulged Shape of Vessel

 

Figure2 Abaqus ModelFigure3 Mesh in Abaqus

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Comments 11

Guest - Mariana on Wednesday, 16 January 2019 17:12
The more you know about pressure vessel testing

Very informative and not heavy on technical jargon, which is greatly appreciated. Well done!

Very informative and not heavy on technical jargon, which is greatly appreciated. Well done! :D
Guest - C A Sterling on Thursday, 11 April 2019 15:46
Legitimate alteration?

Given that 'alterations' need to meet requirements of both the original and current code of construction, justifying the 'new' strain hardened material and irregular cylinder would be an interesting exercise. Is / was this an ASME pressure vessel? In what jurisdiction is the vessel installed?

Given that 'alterations' need to meet requirements of both the original and current code of construction, justifying the 'new' strain hardened material and irregular cylinder would be an interesting exercise. Is / was this an ASME pressure vessel? In what jurisdiction is the vessel installed?
Charles Becht V on Thursday, 11 April 2019 17:19
Not an alteration

This pressure vessel was an ASME vessel, specifically Section VIII Division 1 stamped. The bulge occurred during an over-pressure event and therefore is not an alteration but rather a degraded condition. The two primary reference codes for pressure vessel post construction lifecycle are NBIC & API-510, both of these Codes refer to API 579-1/ASME FFS-1 [NBIC under Part 2 - Section 4.4, & API-510 under Section 7.5] for the evaluation of a degraded condition to determine inspection intervals and if the condition is acceptable for continued operation even if the condition does not explicitly meet all of the original Code of Construction requirements. Within the USA I'm not aware of a single state which does not accept a properly performed API 579-1/ASME FFS-1 evaluation.

This pressure vessel was an ASME vessel, specifically Section VIII Division 1 stamped. The bulge occurred during an over-pressure event and therefore is not an alteration but rather a degraded condition. The two primary reference codes for pressure vessel post construction lifecycle are NBIC & API-510, both of these Codes refer to API 579-1/ASME FFS-1 [NBIC under Part 2 - Section 4.4, & API-510 under Section 7.5] for the evaluation of a degraded condition to determine inspection intervals and if the condition is acceptable for continued operation even if the condition does not explicitly meet all of the original Code of Construction requirements. Within the USA I'm not aware of a single state which does not accept a properly performed API 579-1/ASME FFS-1 evaluation.
Guest - C A Sterling on Thursday, 11 April 2019 18:06
Degredation resulting in an alteration.

Any 'degraded condition', if exceeding what original design parameters permit, necessitates supplemental calculations pursuant to an alteration of the original design. Requirements for alterations need to meet mandated safety requirements. From your response, it's understood that this vessel is located in the USA.

Any 'degraded condition', if exceeding what original design parameters permit, necessitates supplemental calculations pursuant to an alteration of the original design. Requirements for alterations need to meet mandated safety requirements. From your response, it's understood that this vessel is located in the USA.
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Thursday, 25 April 2019

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