Allowable stress and wt for ASTM A-519 Grade 4130 tube 1

[DSGPDE]

What is allowable stress for ASTM A-519 Grade 4130 tube per B31.3?
It is 15000 psi service, room temperature, Tensile ultimate strength is 105000, yield 85000.
Is it 56667 psi?
Can I use K304.1.2 eq 34a for wall thickness calculations?

 

[XL83NL]

You have some issues here, and Im not sure if you understand the intent of B31.3.
- A519 4130 isnt listed in B31.3, so you have an unlisted material.
- What design code is specified in the engineering spec?
- What is the service youre using the piping for?
- You're referencing chapter IX. Has chapter IX been specified by your customer? Chapter IX is not that straightfoward as the base Code, and requires a more thorough analysis.
- The rules for using unlisted materials are different in chapter IX compared to the base code.
- What makes you come to 56667 psi?

 

[DSGPDE]

A519 4130 isnt listed in B31.3, so you have an unlisted material

Therefore I have a question about allowable stress for this material. It is not listed in table K-1.

What design code is specified in the engineering spec?

As I have stated above, B31.3.

What is the service youre using the piping for?

OBM, WBM, Brine

You're referencing chapter IX. Has chapter IX been specified by your customer? Chapter IX is not that straightfoward as the base Code, and requires a more thorough analysis.

No, I use Chapter IX due to high pressure service.

The rules for using unlisted materials are different in chapter IX compared to the base code.

Right. For allowable stress as well.

What makes you come to 56667 psi?

K302.3

 

[DSGPDE]

According to Chapter II the allowable stress will be 35,000 psi. Is it an overkill? No advantage for high pressure and thick wall thickness?

 

[GD2]

DSGPDE,
First you need the specify application of this pipe/tube A519.
1) if inside a furnace, B31.3 do not apply. By looking at the room service temp it's surely not inside a furnace.
2) If in a piping system outside equipment (see B31.3 scope diagram Fig. 300.1.1), it will be accepatable to use.
First have a look what the code says about 'Unlisted Materials":
Quote
323.1.2 Unlisted Materials. Unlisted materials may
be used provided they conform to a published specification
covering chemistry, physical and mechanical properties,
method and process of manufacture, heat
treatment, and quality control, and otherwise meet the
requirements of this Code. Allowable stresses shall be
determined in accordance with the applicable allowable
stress basis of this Code or a more conservative basis.
Unquote
Now let's go line by line.
A. Does it have a published Specification covering ......? - yes. ASTM A519 Gr. 4130. It will give you all the details.
B. You said that the design temp is room temperature (I am not sure if you meant this temperature as Operating or Design. even if it is operating at room temp (which I am assuming 21C, your design temp. can be assumed as 31C with a 10C margin).
C. You will need to determine the basic allowable stress in tension by para 302.3. it's not easy to determine the lowest value by para 302.3.2. Because, your application is below creep range and your room temperature and design temp is below 38C, you will calculate the basic allowable stress in tensions as the lowest of the following conditions:
i) 1/3 of the specified minimum tesile strength = 105000/3 = 35,000
ii) 2/3 of the specified minimum yeild strength = 2/3 of 85000 = 56,600
The answer is 35000 psi which you guessed right.

Bottom line: You can use A519 in B31.3 and start your calc using 35,000 psi as basic allowbale stress in tension.

Hope it helps.




Ganga D. Deka, P. Eng
Canada

 

[DSGPDE]

GD2, Thank you. Appreciated for such a detailed response.
The application is a piping system outside the equipment. WT calculations and Hoop stress analysis (due to WT>D/6) were done many years ago and repeated multiple times. Piping systems were built many times and we have no complains.
I reviewing the calcs and trying to optimize it. I have modeled the system in Ansys and not happy with results. I see stress exceed the allowable stress. Maybe the model is too simplified, I still working on it.
The room temperature is 40C, Design temperature is 50C.
According to 31.3 Chapter IX is applicable for High pressure systems (pressure in excess of B16.5 PN 420 (Class 2500)). Which is 6170 psi. The allowable stress requirements are way different as per that Chapter. Basically, it is 2/3 of yield strength at temperature. WT calculations are also differ from Chapter II. Am I missing something?

 

[GD2]

DSGPDE,
35ksi allwable stress won't work now because the design temp is 50C. It most likely be a little less than 35ksi.
Are you are somewhere in the Middle East? The room temp is pretty high.
We will need to find Ry in order to calculate the YS at temp. I will work on it over the weekend.

Ganga D. Deka, P. Eng
Canada

 

[DSGPDE]

GD2, it is an offshore platform which can operate in the Middle East.
Does the same allowable stress rules apply for normal Sch and a WT like 1 1/4"?

 

[GD2]

DSGPSE,
I have looked into the rules.
Take the Basic Allowable Stress at design temp of 50C as = 0.9 x 35 = 31.5 ksi , where Ry = 0.9
And yes, you need to follow the WT calc using the equation 34a in Chapter IX.

Ganga D. Deka, P. Eng
Canada

 

[XL83NL]

No, I use Chapter IX due to high pressure service.

If the customer (/owner) did not specify chapter IX, then Im not sure what the rationale is to use chapter IX. You seem to fail understand that - read K300(a);

K300 GENERAL STATEMENTS
(a) Applicability. This Chapter pertains to piping designated
by the owner as being in High Pressure Fluid Service.

Read my 1st post again.

 

[DSGPDE]

GD2,Thanks, but it is still not clear for me. Both Chapter II and Chapter IX have both, allowable stress and WT requirements. Why you use Chapter II in one case and Chapter IX in other?

XL83NL, we do specify the Design code. Not the owner. Of cause we will follow the owner requirements if they have such. But usually the owner just agree with our Construction Specification. My goal is to find an optimal solution and do not over-margin WT.

According to 31.3 Chapter IX is applicable for High pressure systems (pressure in excess of B16.5 PN 420 (Class 2500)). Which is 6170 psi. Read K300 (a).

Let's just assume that I'm the owner. Which Chapter I should choose and why? For sure I'm going to keep allowable stress from original design without proofs that adjusted (per Chapter IX) allowable stress is reasonable.

 

[GD2]

DSGPE,
Most of the time, the Owner depends on the designer to specify the construction codes. Usually, the project produces a document called 'DBM or EDS' that is written by the designer and approved by the Owner. Look for this document for any luck.
On the calc on Basic allowable stress value, my calc was wrong. I mixed up the bases in Chapter II and IX. Follow Chapter IX, take Ry as 0.9 and find the allowable stress and WT.

Ganga D. Deka, P. Eng
Canada

 

[XL83NL]

According to 31.3 Chapter IX is applicable for High pressure systems (pressure in excess of B16.5 PN 420 (Class 2500)). Which is 6170 psi.

Not it's not. First of all, there's no hard limit in B31.3 when ch. IX (or High Pressure Fluid Service, which is what its really called) kicks in. And certainly not at just any number like 6170 psi. Second, B16.5 doesnt specify PN-based ratings, it's 100% all the way Class-rated, but that a-side.

I dont have experience with B31.3 chapter IX, but do know it's not just a matter of cherry picking which formula suits best for your application. There's more in ch IX than just a wall thickness formula.
- Have you considered fatigue analysis for example?
- Do you have all information necessary to perform the analyses and tests required by ch IX (review K300(b)(1)), provided by the owner?
- Are you experienced in ch IX design?

Here are some more hints for review;
-

https://becht.com/blog/when-should-the-high-pressure-rules-in-chapter-ix-of-asme-b31-3-be-used

-

http://www.eng-tips.com/search.cfm?q=B31.3+high+pressure&action=search

-

http://www.eng-tips.com/search.cfm?q=B31.3+chapter+IX&action=search

Something tells me your not really understanding the Code's intent, and should be looking for expert help on this subject:

Why you use Chapter II in one case and Chapter IX in other?

 

[DSGPDE]

Thanks, GD2, looks like now we are on the same page.

Not it's not. First of all, there's no hard limit in B31.3 when ch. IX (or High Pressure Fluid Service, which is what its really called) kicks in. And certainly not at just any number like 6170 psi. Second, B16.5 doesnt specify PN-based ratings, it's 100% all the way Class-rated, but that a-side.

So, 15000 psi is not a high pressure. I got it.

- Have you considered fatigue analysis for example?

It is not required on Basic Design stage. However if I have some spare time I plan to look into it.

- Do you have all information necessary to perform the analyses and tests required by ch IX (review K300(b)(1)), provided by the owner?

Not sure if you read my posts. Usually owner agree with our choice. I'm also not well familiar with Chapter IX therefor I ask my questions. I was wondered if I can utilize Section IX and decrease WT. Looks like you do not know.

- Are you experienced in ch IX design?

No. Our design was done according to Chapter II. And it is way too conservative.

Something tells me your not really understanding the Code's intent, and should be looking for expert help on this subject

I came to forum to ask a question. What is an allowable stress for a pipe/which Chapter to use for WT calcs and I have provided all requested information like material, service, temperature, pressure. Looks like you also do not know the answer. What is you point? Trolling?

Appreciated for the links. Your links are useful and also have same as mine concerns. WT is way too thick and can be reduced for high pressure service. There is a huge difference in allowable stress requirements in between these Chapters.

Owner is even less experienced in this question due to this pipe system is a tiny peace in the project.

Maybe I'm wrong and a really unexpirienced engineer but I see the following:
If I utilize Chapter IX than it decrease WT, weight and cost of the pipes. Downsides - extra tests are required. I do not do procurement, so I do not know what will be an economical effect. However, the system itself will have an advantage in weight and in inner bore (reduced friction losses).