Strength & Properties of ASTM A36 Steel at -40F 5

• Apr 20, 2007

1
• #2

metengr

Materials

Oct 2, 2003

15,478

Inconsistent notch toughness on thicker plate sections.

 

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• Apr 20, 2007

1
• Thread starter
• #3

SamCheung

Mechanical

Apr 20, 2007

42

Please elaborate.

The situation is: I have a fabricator who is supposed to U stamp an aqua ammonia tank which is specified at -40F ambient temperature operations. There is no doubt I will reject the design. I understand that ASTM AS36 is OK down to -20F but I don't know how bad it is at -40F with shell thickness 3/8" and heads thickness 5/16"

Thanks for further explanation.

 

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• Apr 20, 2007

1
• #4

doct9960

Mechanical

Aug 15, 2006

618

SamCheung,

What is the design MDMT of the tank? What are the rated MDMT of the shell and head?

 

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• Apr 20, 2007

• #5

MJCronin

Mechanical

Apr 9, 2001

5,097

Sam...

Metengr gave you the correct answer....you just do not understand it.

Do you know what these terms mean ?

Where is your tank located ?

Has that area ever experienced -40F ?

API-650 contains a section about the selection of materials based on the geographic area. Materials are grouped base on thier notch-toughness.

Are you aware of the fact that tank shell temperature never mimic the instantaeuos air temperatures ?

Is this the first tank material you have ever evalated ?

-MJC

 

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• Apr 20, 2007

• Thread starter
• #6

SamCheung

Mechanical

Apr 20, 2007

42

Thanks for responding.

Vender: 110F; MDMT: -20F At 25 PSI
Specified: 110F; MDMT: -40F at 30 PSI

My main concern is how bad is it from -20F to -40F if the tank were put into service. What will be the result and any documentation or real experience to put the tank in prolong period of -40F ambient temperature operation.

 

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• Apr 20, 2007

• #7

metengr

Materials

Oct 2, 2003

15,478

SamCheung;
You need to Review ASME B&PV Code, Section VIII, Div 1, Part UCS. There are materials listed, and impact curves, and material that is not permitted.

You need to familiarize your self with Section VIII for pressure retaining items.

 

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• Apr 20, 2007

• Thread starter
• #8

SamCheung

Mechanical

Apr 20, 2007

42

@ MJCronin,

1. You are right I have no idea at all. Can you explain in real layman terms.

2. The tank will experience -40F.

3. What is the notch toughness at -20F and what is the notch toughness at -40F for SA36? Why notch toughness at -40F is not acceptable?

Thanks for any further elaboration.

 

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• Apr 20, 2007

• Thread starter
• #9

SamCheung

Mechanical

Apr 20, 2007

42

@ metengr,

I have 2 copies of ASME besides me. I read the ASME 2 days ago. I am a bit dum, but that does not address my question how bad it is at -40F or what is bad about the SA36 at -40F.

Will you please elaborate?

Thanks

 

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• Apr 20, 2007

• Thread starter
• #10

SamCheung

Mechanical

Apr 20, 2007

42

@mentengr,

How thick is thick? > 0.394" on CD curves? That was for impact testing exemption, right?

 

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• Apr 20, 2007

• #11

metengr

Materials

Oct 2, 2003

15,478

SamCheung;
A36 is typically not used as pressure retaining material for low temperature service, for the reason I stated above in my first response. ASME Sa 36 is permitted under strict limitations. You are not dumb, you just don't have the experience to understand Code rules. Please review the specific sections below;

ASME Section VIII, Div 1, Part UCS

UCS-6 Steel Plates . Your answer is there for using A 36 plate in a pressure vessel service.

UCS-65 and UCS-66.

 

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• Apr 20, 2007

• Thread starter
• #12

SamCheung

Mechanical

Apr 20, 2007

42

I guess now I understand that SA36 is on curve A and is not even good for -20F tank design temperatures, so impact test is required.

 

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• Apr 20, 2007

• #13

doct9960

Mechanical

Aug 15, 2006

618

SamCheung,

Vender: 110F; MDMT: -20F At 25 PSI
Specified: 110F; MDMT: -40F at 30 PSI

Click to expand...

The vendor did not meet the specified design conditions.

I don't know if your specified conditions are correct or not. Correct me if I am wrong, you mentioned the following design conditions:
Design Pressure = 30 psig
Design Temperature = 110 [°]F
MDMT = -40 [°]F
Then you mentioned that the ambient (surrounding area) temperature is -40 [°]F.

You must understand that the MDMT is not always the same as the ambient temperature. Assuming your vessel is operating at 100 [°]F and insulated (heat conservation), your MDMT would be warmer than the ambient.

So check again if the vessel MDMT is truly -40 [°]F.

 

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• Apr 20, 2007

• Thread starter
• #14

SamCheung

Mechanical

Apr 20, 2007

42

@doct9960,

Thanks. Our specification calls for freeze protection but the vender proposed tank is bared with only painting, so its ambient - another reason to reject the vender without providing insulation and heat tracing.

 

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• Apr 20, 2007

• Thread starter
• #15

SamCheung

Mechanical

Apr 20, 2007

42

Any quick answer to at what temperature 29% Aqua Ammonia will freeze, thanks.

 

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• Apr 20, 2007

• Thread starter
• #16

SamCheung

Mechanical

Apr 20, 2007

42

OK, I found it, the freezing point of 29% aqua ammonia is about -110F. So no insulation and heat tracing is required!

 

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• Apr 20, 2007

• Thread starter
• #17

SamCheung

Mechanical

Apr 20, 2007

42

Please point me to which part of the ASME applicable to pressure tank impact testing, thanks.

 

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• Apr 20, 2007

• #18

metengr

Materials

Oct 2, 2003

15,478

SamCheung;
Please see my response above

UCS-65

 

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• Apr 23, 2007

• Thread starter
• #19

SamCheung

Mechanical

Apr 20, 2007

42

metengr,

I have returned the 2004 version of ASME Section VIII Div 1 to our library, and I have only the 1998 edition with me. From the 1998 edition, UCS-65 is the scope. I guess my question was not cleared enough and I should have written:

"which part of the ASME code detailed the impact testing for pressure tanks and for pressure piping if ASTM SA36 were used to construct the tank and carbon steel were used for the pressure piping"

Please point me to the right direction so that I can instruct my vender what should they do to comply with the requirements of impact testing, thanks.

Sam

 

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• Apr 23, 2007

• #20

metengr

Materials

Oct 2, 2003

15,478

SamCheung;

which part of the ASME code detailed the impact testing for pressure tanks and for pressure piping if ASTM SA36 were used to construct the tank

Click to expand...

You will not be permitted to use SA 36 plate based on UCS-6. Please read this section carefully.

Regarding use of carbon steels for piping, this would probably fall under one of the ASME Piping Codes, most likely B31.4 (to convey ammonia to an aqua ammonia tank).

 

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