## ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## ASME Section VIII Div 2: Load Case Combinations for thermal gradient

(OP)

Hi all,

In Table 5.5 for Elastic-Plastic Analysis:

2.1(P+Ps+D+T)+2.7L+0.8Ss

where (Table 5.2):

T - Is the self-restraining load case (i.e.

This load case does not typically affect the collapse load, but should be

considered in cases where elastic follow-up causes stresses that do not relax

sufficiently to redistribute the load without excessive deformation.

In my vessel there is temperature gradient which cause plastic strain (temperature gradient is from 50 C deg to 500 C deg).

My questions are:

1. Thermal loads - what is that mean? Is it temperature?

2. If T is not a temperature, how can I include it in my FEA analysis?

Regards

Rafal

In Table 5.5 for Elastic-Plastic Analysis:

2.1(P+Ps+D+T)+2.7L+0.8Ss

where (Table 5.2):

T - Is the self-restraining load case (i.e.

**thermal loads**, applied displacements).This load case does not typically affect the collapse load, but should be

considered in cases where elastic follow-up causes stresses that do not relax

sufficiently to redistribute the load without excessive deformation.

In my vessel there is temperature gradient which cause plastic strain (temperature gradient is from 50 C deg to 500 C deg).

My questions are:

1. Thermal loads - what is that mean? Is it temperature?

2. If T is not a temperature, how can I include it in my FEA analysis?

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

2. I think you have already established that T is thermal loads (caused by temperature of course), or applied displacements. If you have already calculated the plastic strain from thermal loads then it sounds like you have already included it in your analysis.

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Out of curiosity, how are you implementing the 0.88*Beta factor on the thermal loads?

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

1. To be sure, I need to multiply the gradient temperature by 2.1 like internal pressure or own weight (eg 500C*2.1)?

2. If so, should I apply a material curve (epsilon-sigma from ASME II-D) for the base tempature or multiply by factor 2.1?

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Thank you for the good advice.

I have another question about welds:

1. In the case of welded joint analysis, better to do Elastic Stress Analysis (SLC as ASME VIII DIV2 5.2.1) or as shown in the article: http://journal-dl.com/item/591088713fbb6e13744158c... ?

2. It is acceptable to perform Elastic-Plastic analysis for the whole model (5.2.4; 5.3.3) and SCL for welds?

Paper Details

DOI: 10.1115/PVP2016-63759

Authors: Seipp, Trevor G.

Publish Date: 2016

ISBN: 978-0-7918-5039-8

"ELASTIC-PLASTIC ANALYSIS METHOD

The next incremental expansion of this concept is for

the elastic-plastic analysis method. The sole question is:

how to de-rate the strength of an elastic-plastic material?

We propose that, identical to the Limit-Load Analysis

Method, the weld volume plus 1*t adjacent to the weld be

modeled as a weaker material. That weaker material is

calculated in the same manner as the non-weld material:

using Appendix 3-D, however, both the yield strength and

the ultimate tensile strength shall be multiplied by the weld

joint efficiency factor for that weld."

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

(However, that method is permitted in API 579-1/ASME FFS-1, but only for fitness-for-service situations.)

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Thanks for the clarification.

2. It is acceptable to perform Elastic-Plastic analysis for the whole model (5.2.4; 5.3.3) and SCL for welds?

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

I think that it is possible to show what are the stresses in the cross section of the weld.

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Which section (point) of the Elastic-Plastic analysis can be considered as leading in the evaluation of the weld joint?

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Could you tell me where exactly this is "It's handled in the definition of the reduced strength assigned to the weld material" (which section (point) in ASME VIII Div2).

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Thank you very much for your answer.

I have another question: Does asme provide/describe creep FEA analysis?

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient

Hi,

In Table 5.5 of ASME VIII Div2 the Local Criteria is:

1.7(P+Ps+D), no T (thermal loads) but in "Design Method Combining API and ASME Codes for Subsea Equipment for HP/HT Conditions up to 25,000-psi Pressure and 400°F Temperature", they recommend taking into account the thermal load:

"When temperatures greater than 250°F are considered, thermal loads also need to be considered when evaluating for protection against local collapse."

https://www.spe.org/media/filer_public/5c/2e/5c2e5...

My question:

Should I take into account thermal load in Local Failure?

Thank you in advance

Regards

Rafal

## RE: ASME Section VIII Div 2: Load Case Combinations for thermal gradient