SA 240 304H "Ultimate tensile strength at external temperature is out of range error " in 2

[manj1987]

I am working on vessels with 8 barg design pressure @ 670 Deg C and full vacuum @ 670 deg C.

1- When I use SA 240 304H, I get message in material window of Pvelite that "Ultimate tensile strength at external pressure is out of range". The same error is not coming with 304.In table U of ASME sec II, FOR 304H it is not giving any value for UTS AT 550 and onwards. Is there some relationship between UTS at external pressure temperature and Table U?
What does this means can i not use 304H with full vacuum or there is some justification. Kindly explain.

2- Even though client has specified 304, but we are proposing to use 304/304H, so to meet note G12(0.04 % minimum limit on Carbon content) of ASME SEC II. Kindly elaborate our proposal to use 304H and how it should be ordered, i mean as dual grade 304/304H or simply 304H.

3- at 670 allowable stress for SA 240 304 is based on time-dependent properties. what does this means and what further calculation or FEA, buckling analysis we need to do? Design life of vessel s 30 life, with time dependent creep range in consideration do we need to perform any further calculation. I saw somewhere Creep Analysis Using Larsen-Miller Parameter Method and some formulation in API 560 and FSS standard. Kindly clarify what actions or calculation are to be performed to satisfy full design life when in creep range

Thanks
Manj

 

[TGS4]

1. Although I cannot explain the software error message, I can tell you that 670°C (1238°F) is well into the creep regime for the 304H material, and hence your buckling assessment would be governed by Creep-Buckling. Although you didn't mention your Code of Construction, I am going to assume that it is ASME Section VIII, Division 1. In that situation, I would recommend reviewing Code Case 2964 for Creep-Buckling Rules.

2. Are you doing this for the strength-at-temperature or for corrosion resistance at temperature?

3. The allowable stresses are based on 100,000 hours at the design temperature. If you are going to operate at something less than that, then you should use Code Case 2951 to see if you can get the full life out of the design. Stay away from FEA generally - with one exception - if you do go down the FEA route, please ensure that whomever you hire is an absolute expert in design for creep. It is a very small pool of experts and most engineers who can do design-by-analysis for pressure vessels cannot do creep work.

 

[manj1987]

Noted, I will look into load cases, but since I have not worked on such high temperature vessel so my initial question are:

1 & 3- Base on 30 years life hours are 262,800. This is much more than 100,000 Hours. My question what should be my first step? what should I tell to my engineering contractor? Does he need to calculate rupture stress considering 30 years life and design temperature of 670 deg C and then based on that use that rupture stress to find thickness? IF yes then what formulas they will use. kindly elaborate what additional formulation we need to perform or what notes we need to mention on datasheet for creep range vessel (reactor of SA 240 304H). kindly also refer some book which give step by step checks which we need to do for material in creep range

2- Why in external pressure case Ultimate tensile strength is out of range. I think because table U of ASME sec II is not specifying any UTS at this temperature so that is why not in range of HA-1. Anyone faced similar issue with 304H and what does this means?

 

[TGS4]

1/3 - Code Case 2951.

2 - Code Case 2964.

Please please get an expert in creep design involved. This is likely even beyond the capability of your engineering contractor.

 

[GD2]

manji1987,
Are you working on designing Reactor? I think you should look into ASME Sec III Its a bit overwhelming but this is the right way to design Nuclear Reactors.
Division 5 Subsection HB, Subpart B covers the material design info and give the allowable stress/stress intensity value upto 800C and up to 300,000 hrs.

have a look.

GDD
Canada

 

[manj1987]

TGS4, I am working on preparing calculation sheet based on code case 2951, my one concerns is what is impact if design life is more than 100000 hours. In My case design life is 30 years.

 

[GD2]

Manj1987,
You didn’t say what you are building and the construction code?

GDD
Canada

 

[manj1987]

GD2 Column is of ASME sec VIII dIV.1 with following parameters:

Design Pressure: 8 Barg
Design Temperature: 670 Deg.C
Design Life: 30 Years
Material: SA 240 304 (We are proposing dual grade 304/304H)

 

[TGS4]

Although your design is for 262,800 hours, what will truly govern the design (as covered in CC2951) is the operating time-at-temperature.

 

[GD2]

manji1987,
Even if CC2951 allows you to design the vessel at the given design conditions under ASME Sec VIII Div 1, SA 304/304H is listed material under API Std 530 and ASME Sec III and had been used in your given design parameters. This confirms that the material had been used successfully in other Codes.
WRC 541 gives a beautiful narrative and easy examples on material strengths at creep regime. This is where you can set your design life of 30 years and calculate the allowable stress.
I haven't worked with PVElite, but you may be able to bring in the values from these standards/codes and still built the column to Div 1.
You might have to add some extra analysis as TGS4 suggested, as your vessel falls in creep regime.

GDD
Canada