Hello,

I am working on the redesign of a steam turbine to a temperature of 1050F. I have looked thru the code requirements and it appears that I have to use division 1 for 217-wc6 or wc9 material. Division 2 limits the temperature to 900F for Max allowable stress and limits to 1000F for yield stress. So the temperature is exceeded for division 2. Are there any code cases on this subject that allow higher temperatures for div 2?

Table 1A is based on the creep rate at 1050F. At this high temperature the yield, tensile and rupture do not govern the design. This is given in App 1 where it explained how the values for Table 1A are obtained.

I am wanting to know if the 1.5 * Sa in bending was taken into account when the Sa was established for table 1A? I am sure the FEA maximum equivalent stress would be a good indicator of the overall stress. I also think that this overall stress when it exceeds the creep stress will indeed creep. It just isn’t the same as the part bending and yielding and relieving its’ self. Is it?

I would like to plug an allowable value into the Inventor FEA program so I can get a Factor Safety plot based on the allowable. I plan on using 1.5Sa and I would like to know your opinion on this.

Thanks

Please note that Sect.VIII (any Div.) does not cover pressure containers which are integral parts or components of rotating or reciprocating mech.devices such as pumps, compressors, turbines.....
Mauro

Well that may be true but I have always used the ASME code to design the pressure boundary for pumps. A designer has to start somewhere and the ASME code does have some basic formulas, methods and allowable stress levels that can be used. I worked for Ingersoll-Rand making boiler feed pumps for 18 years. It was our standard to use the ASME code for design. Many customers would require this in there specifications. Design to ASME code but no code stamp required.

Barrel pumps are pretty much round and straight forward as far as pressure vessel design goes. Some of these pumps get to 8000psi. We also had boiler circulating pumps that operated at 650F and 3000psi. Now those were a different story as the housing was a dual discharge volute and did not lend itself to basic calculations for circles.

This all gets more interesting for me in my present job. The agencies that have to approve this new design use the words “other proven design methods” to qualify the design. So in my book the ASME code is a good place to start. Of course the hydro test pressure is the final qualifier.

Hi,
Sorry, I am not the real design expert, but if I remember correctly, the S values in Table 1A are primary membrane stresses to be used in the design formulas of Section VIII Division 1. Bending is considered in the formulas, e.g. for the flat heads.

The Sm values in table 2A are for the same purpose, just with the formulas of Div. 2. The Division 2 up to Edition 04 Addenda 06 was developed before numeric methods were used in the design. If you read the text of Div. 2 you will find that a stress classification is required into primary, secondary membrane and bending, etc. This relates to the 50s when engineers were using paper and pencil.

In the 2007 Edition new methods were implemented, and I have not reviewed it accordingly, but the plan was to make it more suitable for numeric methods. This should also suit your demands.

DK