Calculating t/min on economizer tubes.

[Stone Jordan]

Guys I can't seem to find a correct answer after digging and searching for t-min on SA-178/A economizer tubes. I have the calculation from 2023 ASME SEC I (PG-27.2.1).
This is what I have so far and I'm stuck.
(P) Pressure=850PSIG
(D) Diameter=2.00" OD
(S) Stress=13,400 (According to ASME SEC II Part D Table 1A
(E) Efficiency= ??
(W) Weld joint reduction factor=??

I'm stuck on figuring out exactly what E and W would be? When I scroll down to see it says (W) would be in PG-26 of ASME SEC 1 when I look at the table in the notes it says PG-26 nor Table PG-26 is not required for carbon steels so would I just take it out of the equation?
When looking for E on PG 27.4.1 it starts talking about cylinders and heads, nothing to do with boiler tubes so I'm completely lost on this one. Any help is greatly appreciated.

 

[GinBread]

Where does E come into play? I'm looking at the equations provided by PG-27.2.1 and I see lowercase e, which is the thickness factor for expanded tube ends, but not uppercase E, efficiency.

You are correct with note 3 and PG-26's applicability to carbon steels. W would just be 1. Remember, this is a factor, so to not apply it in this case would be setting it equal to 1.

Let me know if this helps, and feel free to correct me if I've missed something.

 

[Stone Jordan]

Okay so how would I use "e" in my equation? I'm dealing with trying to get t/min for economizer tubes. How does PG-27.4.4 apply to figuring this? Also I've learned the "w" refers to weld efficiency which would be .85 according to ASME SEC II Part D Table 1A Notes for SA 178/A tubes.. Thanks for the response and any help is appreciated.

 

[Stone Jordan]

Where does E come into play? I'm looking at the equations provided by PG-27.2.1 and I see lowercase e, which is the thickness factor for expanded tube ends, but not uppercase E, efficiency.

You are correct with note 3 and PG-26's applicability to carbon steels. W would just be 1. Remember, this is a factor, so to not apply it in this case would be setting it equal to 1.

Let me know if this helps, and feel free to correct me if I've missed something.

Also if you look at PG-27.4.4 "e"=0 for strength welded tubes which is what I'm doing. So in my equation I have "e" as "0"

 

[GinBread]

Okay so how would I use "e" in my equation? I'm dealing with trying to get t/min for economizer tubes. How does PG-27.4.4 apply to figuring this? Also I've learned the "w" refers to weld efficiency which would be .85 according to ASME SEC II Part D Table 1A Notes for SA 178/A tubes.. Thanks for the response and any help is appreciated.

The symbols used in the equations provided in PG-27.2.1 are defined in PG-27.3. I do not see where the definition for "w" refers to the notes in Section II Table 1A. I did see note G4 listed in that table for SA-178/A, but to me, that reads as if they are baking the 0.85 factor into the stresses that they are providing in the table itself. If you set w to 0.85, you would likely err on the conservative side, which in my opinion is the best way to err, but it may impact your quotations and design.

It sounds as though you have read and understand how to apply "e" in the equations.

 

[Stone Jordan]

I get the "w" from w being weld strength reduction factor in ASME SEC 1 PG-27.3. That exact tube being ERW sense its seam welded with no heat treatment nor 100% rt going by the MTR the reduction factor would be .85. In ASME SEC 2 Part D in the notes for that material G3 would call for that to be .85. Any better explanation for "w" or more exact words to figure this equation will be greatly appreciated.

 

[Stone Jordan]

The symbols used in the equations provided in PG-27.2.1 are defined in PG-27.3. I do not see where the definition for "w" refers to the notes in Section II Table 1A. I did see note G4 listed in that table for SA-178/A, but to me, that reads as if they are baking the 0.85 factor into the stresses that they are providing in the table itself. If you set w to 0.85, you would likely err on the conservative side, which in my opinion is the best way to err, but it may impact your quotations and design.

It sounds as though you have read and understand how to apply "e" in the equations.

Thinking about it again. Since in Table PG-26 in ASME SEC I says carbon steels are exempt from this table should I leave "w" at 1?

 

[GinBread]

Did you read the plain language of note G3? I just read it, and it seems fairly straightforward to me where the 0.85 is being factored in, and I do not believe it is intended to be used as "w" in the equations provided to you in PG-27.2.1.

 

[Stone Jordan]

Okay the what would the w represent and where would I find that for the equation?

 

[GinBread]

See PG-

Okay the what would the w represent and where would I find that for the equation?

I feel we've covered this at this point, have we not?

 

[Stone Jordan]

So go off of PG-26 and represent this as 1 correct? Since its not required for carbon steels? I'm sorry if I sound repeating I'm just trying to find the exact answer.