Time dependent properties for SA-516 Gr.70 2

[Digitall]

We have the strength calculation at fractionator column (operating temperature 475C) for 200,000 hours of operation, but manufacturer use table 1a from ASME II D maximum allowable stress values for SA-516 Gr.70 - 45.5. (Don't include time dependent properties such as creep fatigue and creep rupture)
We think this value should be lower.
Сould you provide a calculation method or a graph of time dependence at such temperatures for this material?

 

[TGS4]

We're missing too much information to provide a reasonable response. What are you trying to accomplish here? What is your Code of Construction?

Assuming ASME Section VIII, Division 1 construction, the allowable stresses above a temperature of 400°C are governed by time-dependent properties (they are in italics in Table 1A - Also noted by Note T2). Refer to Mandatory Appendix 1 of ASME Section II, Part D for how the allowable stresses are developed.

I would also bring your attention to Note G10

G10 Upon prolonged exposure to temperatures above 425°C, the carbide phase of carbon steel may be converted to graphite. See Nonmandatory Appendix A, A–201 and A–202.

Operating at a temperature of 475°C with SA-516 GR. 70 is ill-advised, at best.

 

[GD2]

OP,
I completely agree with TGS4.
There are couple of design issues involved here:
1. Operating/Design Temp (operating at creep)
2. Design/rupture life (200,000 hrs.)
ASME sec II part D Table 1A provides allowable stress value for a rupture life of 100,000 hrs. Even if many ASME Sec VIII vessels are designed with this life, there are many research papers/reports that report that vessels have run up to 300,000 hrs. without failure.
Other viable options will be to:
3. Line/clad the CS vessel
4. Use allowable stress values from other Code Division (example: ASME Sec III Div 1 Subsection NH). It provides stress values up to 300,000 hrs. or calculate from WRC 541.



GDD
Canada

 

[Digitall]

Dear
1. Design preassure code ASME VIII Div.1 2021
2. Сladding layer 410S.
3. Design temperature is 475C, sorry for misleading you.
4. We think that the specified calculation with the specified parameters corresponds to a service life of 100,000 hours (approximately 13 years). For devices with a service life of 20 years, the permissible stresses will be less, since the influence of the parameters of the long-term strength limit and the creep limit is taken into account.
5. We want to understand whether such a calculation is worth agreeing on, but we cannot find anything to refer to to prove to the manufacturer that the permissible stresses will be lower than he presented.

 

[Digitall]

At table 1-100 (Appendix 1 ASME Mandatory Appendix 1 of ASME Section II) we see average stress to cause rupture at the end of 100,000 hr.
Our design/rupture life (200,000 hrs.) We can find values for SA-516 Gr.70.
At ASME Sec III Div 1 Subsection NH (ASME Sec III Div 5) we can't find values to our material.

 

[weldstan]

Has this vessel been operating at the 475 or 450 temps or is this the proposed design for a new vessel? If the latter, change the design material to 1 1/4 Cr - 1/2 Mo low alloy steel. SA 516 is the wrong choice. It is much more susceptible to graphitization and has actually lower creep strength than SA 515 and neither of these materials should be contemplated.

 

[GD2]

OP,
You are all over the place. If your vessel is cladded with 410S, you won't see 475C on the base metal (SA516 Gr.70)

GDD
Canada

 

[TGS4]

Perhaps you need to refer to Code Case 2951. But, the important part is using the Operating Temperature (time at temperature), as opposed to the Design Temperature.