AS 1210 - FEA x Analytical calculation 1

[IvanKFC]

Dear Sir

We designed a vertical vessel with big diameter and low pressure acc AS 1210 . This vessel have a high diameter nozzle with a relation nozzle diameter to shell diameter of 0,8.

We follow a criteria of using in the first place the analitical approach to determine shell thickness and discontinuity analysis cited in AS1210 and ASME code and other analitical papers Watts & Lang method for conical head using alpha angle lower than 30 degrees mentioned by ASME as well as the limitis of WRC Bull 107 . We have used the ASME code in this situation because the AS 1210 recommends to use it when is out of its limits or there is not any analitycal method within AS1210

In other to check the selected thickness we made a FEA analysis to check the stress . The FEA was not used in the first place to determine thickness but just to check the stress envolved .WE believe to have done what recommends the AS 1210 on its Appendix on FEA method for pressure vessel.

On other hand an australian engineer used just the FEA analysis to determine the thickness and analyse the discontinuity of nozzles and mentions that is common practice to use such approach in Australian for pressure vessels as its is an economical approach and results on lighter vessels. The selected thickness by the australian engineer using only FEA analysis was 30 % thinner than our calculations.

We have read the AS 1210 Appendix on FEA and it seams to me that AS 1210 does not put in the first place the FEA and second plan the traditional analytical approach and other analytical papers on PV.

Anyway we would like to hear from the australian standard expert what its a recommendation of using FEA x Analytical approach on PV. What is the priority ?


Ivan Nogueira
KFC Projetos & Consultoria
Av Marechal Floriano 38 sala 409 Brazil
Tel / fax 55 21 22 23 31 56

 

[bogu]

I have designed many pressure vessels in Australia and in my experience FEA is only used along with other methods ie AS code requirements to supplement them and perhaps used on a component that cannot be readily calculated by another available method. It is quite usual to take the thickness calculated by AS1210. Appendix B AS1210 states that FEA should never be done in isolation and should be conducted with other established methods. Appendix B also states that FEA should not be used as a primary design tool. I hope this helps.

 

[IvanKFC]

Our client in Australia is convinced that FEA is the best thing in the world give to them thin thickness and light vessel for heavy steel work application .
Our design using analytical approach on safe side and check the stress with FEA do not satisfy our client who prefer to believe on results of others who give to them light vessel .

Can you recommend any australian expert engineer on pressure vessels who we can suggest to be consulted by our client .

Do you know any specific software on FEA using AS 1210 ??

Ivan

 

[IvanKFC]

Please reply Renata question

 

[bogu]

Renata
If you give me a contact email I can supply you with an engineering co.

Bogu.

 

[IvanKFC]

BOGU

My e:mail is kfc@terra.com.br
Country : Brazil

 

[gramya]

I agree that the FEA is the choice when you do not have a proven design and stress analysis theoretical methods. FEA assumes lot of conditions and then arrives to the best stress distribution in the area of concern. However, it is prudent that we cross check such FEA with experimental stress analysis of the area during loaded conditions of the vessel preferably during hydrotests. this will ensure the provenness of FEA for subsequent design. We did that way for a tall tower design for area near the discountinuity stress point at the joint of dished end to the skirt support area, some 20 years earlier on our actual vessels erected at site, hydrotested and experimental stress analysed using ER strain gages ( some 40 numbers of them suitably located and monitored for strains). This was again adopted for a spherical vessel supported on columns at the attachment region falling near equatorial shell course. We improved the theoretical stress analysis using the test data and that was followed in subsequent designs. Yes it resulted in material savings but with a confidence.

Narendra K. Roy
Gramya Research Analysis Institute,
PO box 4016, Vadodara 390015, India
Website:

http://www.gramya.com

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http://www.charismaglobal.com