ASME Section 1 Boiler Superheater Tmin 3

[jvhandle]

Hi,

I a new to this but I thought I would ask a question.

I am working on calculating the Tmin of a superheater tube bend. I was wondering if I should use the original code of construction or the current edition of the ASME code?

Thanks

 

[Duwe6]

Have to use the original Code year, and it's associated Allowable Stress for the materials. There was a MAJOR change in 1999.

 

[metengr]

IF this is an in-service item, you can use the edition and year that results in the safest or most conservative condition. In other words, you are NOT locked into using the code of construction year and addendum, only that you use the original code of construction - ASME B&PV Code.

 

[jvhandle]

Thanks for the information. This is an in-service boiler which was constructed in 1970. I am having problems determining the allowable stress valves at 850F for SA 178 A and SA 178 C at 880F because I do not have a copy of the 1971 ASME code. That’s why I was wondering if I need to use code of construction or current code.

 

[metengr]

You can use a more current code of construction (ASME Section I) for allowable stress values.

 

[jvhandle]

Metengr

Where does ASME section 1 allow you to use a more current code for allowable stress values?

Thanks

 

[metengr]

jvhandle;
For in-service components, the NBIC or API codes and standards are used for inspection, repair and alteration activities. The NBIC and API refer you to a construction code for specific requirements related to design calcs, NDT requirements and allowable stress values.

Since construciton codes, like ASME B&PV Code, Section I, are updated, one should be aware that the year and addenda selected for stress values should be the one to provide the most conservative or safest approach. So, you do not have to go back to the specific year and addendum for a construction code.

 

[Duwe6]

Conflicting statements above: The current edition of Sect-1 is less conservative that any original code year prior to 1999. Thus you are bound by original year for any equipment oldar than 1999.

SA-516 Gr 70 pre-1999 17.5 kips at 600°F
SA-516 Gr 70 today 20 kips at 600°F

 

[metengr]

You are not bound to go to any specific year and addendum, period. There is an NBIC interpretation on this.

Once again, I will repeat, original code of construction means code of construction used in design. It is up to the owner/user and repair organization to determine, which addition and addendum they would use. In some cases, a repair can become an alteration. I don;t know where this information originated with having to be locked into a specific year and addendum.

 

[metengr]

INTERPRETATION 95-19
Subject: RC-1000 General Requirements
1995 Edition
Question: When the NBIC references “the original code of construction,” is it
required to use the edition and addenda of that code as used for
construction?
Reply: No. The term “original code of construction” refers to the document itself,
not the edition/addenda of the document. Repairs and alterations may be
performed to the edition/addenda used for the original construction or a
later edition/addenda most applicable to the work.

 

[jvhandle]

What about for fitness for service? In my situation, I am trying to determine if existing bends need to be replaced. Does ASME in this scenario (calculating Tmin), distinguish year/edition of ASME Section 1 between repairs and alterations from fitness for service?

 

[metengr]

jvhandle;
Your in-service inspection, repair and alteration code for boilers is the National Board Inspection Code (NBIC). Are you familiar with this document? Do you have a copy of this document? I can tell you are new because of the continued questions surrounding ASME and it's application.

Please contact the National Board at the web site below and talk to one of their staff engineers. They will provide assistance over the phone versus the internet. You need more help than I can provide in writing.

You will use ASME Section I formula to calculate a Tmin to compare with the thickness you measured on an actual boiler tube. The Edition and addendum for this calculation can be what is most applicable to your situation. Do you understand this?

Once you have calculated T min using Section I and compared with your measured thickness in service, here are your options plain and simple - weld build-up to restore the eroded/corroded wall back to the calculated T min or replace the tube.

If you want to perform a fitness for service, this is more complex and well over your head. The document for this is ASME/API FFS-1.

http://www.nationalboard.org/default.aspx

 

[GenB]

Metengr Great advise.
There is every one looking for Earlier versions Ed & Add's of the ASME Code
and at the end it was not necessary.
and that is because of the miss-interpretation of the NBIC.

 

[davefitz]

all the above sounds correct. 2 points to add

I recall that for several years there was a debate regarding the required wall thickness at the extrados of bent tubing , and that the older section I code did not provide an easy out for the boiler mfr . Use of torroidal equations , plus credit for work hardening, normally shows that some wall thinning should be acceptable at the extrados, but many clients are not convinced.

Also, although it might not yet apply to section I, other codes have been revised in the last 10 yrs to both increase the allowable stress of some alloys plus lower the hyddrotest pressure. For theose codes, the 2 are interrelated, and it might not be appropriate to use the newer stresses plus to continue to use the older hydrotest value.