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Dear venkatesh,
If your weld joint for tube to tubesheet is just a Seal weld and there is no special requirements from your client, then you can propose your client to use the existing pqr.
Check your client spec for any Mockups required as per ASME IX Qw193.
Is this for U stamp Project?
If yes, then you write a WPS based on existing 10 mm PQR , once it is confirmed as Seal Weld in your fab. Dwg
Seal weld is nothing but a fillet weld.
Read ASME QW 288 also for tube to tubewelds.
Regards
Sarav.
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QW-193 TUBE
‐TO‐TUBE SHEET TESTSWhen the applicable Code Section requires the use of this paragraph for tube‐to‐tube sheet demonstration mockup qualification, QW-193.1 through QW-193.1.3 shall apply.
QW-193.1 Procedure Qualification Specimens. Ten mockup welds are required to qualify each procedure. The mockup assembly shall essentially duplicate the tube hole configuration and tube-to-tube sheet joint design within the limits of the essential variables of QW-288. The thickness of the tubesheet in the mockup test assembly shall be at least as thick as the production tubesheet, except it is not required to be thicker than 2 in. (50 mm). The mockup welds shall be submittedto the following tests sequentially and must meet the applicable acceptance criteria.
QW-193.1.1 Acceptance Criteria
— Visual Examination.QW-193.1.2 Acceptance Criteria
— Liquid Penetrant.QW-193.1.3 Acceptance Criteria
— Macro‐ExaminationNo. Untold thousands (hundreds of thousands?) of heat exchangers have been built without problem without mockup qualification.
Section VIII, Division 1, does not require qualification by mock-up. Costly and generally unnecessary.
Section VIII Div 2 design is the only ASME Code section that requires this. Division 2 transferred responsibility for qualification from VIII-Div. 2 Article F3 to Section IX, which created QW-193 etc to support Div 2 construction.
NONMANDATORY APPENDIX K:- GUIDANCE ON INVOKING SECTION IX REQUIREMENTS IN OTHER CODES, STANDARDS, SPECIFICATIONS, AND CONTRACT DOCUMENTS
K-302 RECOMMENDED WORDING — TUBE-TO- TUBESHEET WELDING:- When invoking Section IX for qualification of tube-totubesheet welding procedures and personnel, and qualification by use of mock-ups is desired, the following wording is recommended. “Welding procedures, welders, and welding operators shall be qualified using mock-ups in accordance with Section IX.”
Note that if qualification using mock-ups is not specified but qualification to Section IX is, tube-to-tubesheet welding procedures and personnel may also be qualified following the standard groove welding rules.
QW-288 TUBE‐TO‐TUBESHEET QUALIFICATION ESSENTIAL VARIABLES
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I have been involved in making heat exchangers for many years. Have been involved in both automatic and manual welding of, typically, J-groove strength welds. The basic lesson for manual welding is to never hurry the root pass. The root pass should be made with small diameter wire, 1/16 in. This will assure penetration to the root and prevent bridging that occurs with larger diameter wires.
Qualification (performance or procedure) by mock-up in no way guarantees that the t-ts weld will be good. Having been burned by vendors has amply demonstrated that. It is most problematic in shops where welders are paid on a piece work/pounds deposited basis. In the remainder of shops, there can also be problems when management is pushing to hard for quick completion. This is when excessive fill causes bridging of the root and almost guarantees premature failure.
Mock-up demonstration is expensive and unwarranted. A review of welding procedures, shop practices, and previous history does more to assure a quality product then such qualification.
Certainly, if exotic materials are required, the media is lethal or unusually corrosive it may behoove the purchaser to
pay extra for special qualification. Surprising how many demanding customers don't want to do that.
I will agree that if the these type welds are to be welded by automatic/machine processes, then a mock up qualification makes sense. It is, as you point out, necessary to establish the correct parameters as there is only limited in process adaptability.
Please also note, that ScIX qualification does not require the tube sheet pitch and spacing be used. The tube holes may be in linear string - Interpretation is on the way.
Sec. VIII Div. 1 does not stipulate as a mandatory requirement to apply QW-193, it is manufacturer’s option to choose between QW-193 otherwise normal procedure qualification in accordance with QW-250 tables.
However, in case of Sec. VIII Div. 2, application of QW-193 is mandatory in accordance with para. 6.3.4.
Hope my understanding is right Gentlemen.
Regards,
Saravanan
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